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Thermal Power Sensors (C-Series)


  • Power Ranges Covering 10 µW to 200 W
  • Wavelength Ranges Covering 190 nm to 20 µm
  • Broadband Coatings with High Damage Thresholds
  • Sensors Designed for Microscopes and Pulsed Lasers

S425C-L

Featuring Removable
Heat Sink and Shown
with a Fiber Adapter
(Sold Below) and
Fiber Patch Cable

S350C

For Excimer Lasers

S401C

High Sensitivity
Down to 10 µW

S175C

18 mm x 18 mm Aperture Size
for Use with Microscopes

Related Items


Please Wait

Internal SM05 (0.535"-40) threading on the S405C's aperture (left) accepts the included external SM05 to SM1 (1.035"-40) thread adapter (right). Most sensors include an SM1 externally threaded adapter that allows accessories like fiber adapters to be mounted.


Click to Enlarge
S401C Connected to the PM100D Console

Features

  • Broad Spectral Ranges with Relatively Flat Spectral Responses (See Plots Below)
  • Individually Calibrated with NIST- and PTB-Traceable Certificate of Calibration 
  • Free-Space and Fiber-Based Applications Supported
    • All Sensors Accept Free Space Input
    • Majority Accept Fiber Adapter (Available Below) for Fiber-Based Input
  • C-Series Connector
    • Enables Quick Sensor Connection to Our Power Meter Consoles
    • Embedded EEPROM Contains Sensor and Calibration Data
  • Ten Models Feature Over-Temperature-Alert Sensor (See Specs Tab for Details)

Thorlabs' C-Series Thermal Power Sensors are collectively able to detect power ranges from 10 µW to 200 W and wavelength ranges from 190 nm to 20 µm. These thermopile-based sensors are ideal choices for measuring broadband spectra from amplified spontaneous emission (ASE) sources, light emitting diodes (LEDs), filament lamps, swept-wavelength lasers, and other sources. In addition, thermal power sensors do not saturate, which makes them well suited to measuring pulsed sources with high pulse peak powers or long-duration pulses. These thermal power sensors also exhibit low dependency on the angle and position of the incident light beam. They are preferred for applications that cannot tolerate the strong wavelength dependencies and/or saturation thresholds of photodiode sensors. However, thermal power sensors generally have lower power resolutions and longer response times. We offer a wide range of thermal power sensors, with each including different design features.

Mounting
The sensors sold here (except the S175C) can be mounted on our Ø1/2" Posts using an 8-32, M4, or M6 tap. A 60 mm or 75 mm tall post is included with select sensors. Additionally, many of our thermal sensors are compatible with 30 mm cage systems, Ø1" lens tube systems, and our fiber adapters (sold below). Please refer to the Specs tab for more information.

Calibration
Each sensor head is individually calibrated and is shipped with a NIST- and PTB-Traceable Calibration Certificate. The calibration and identification data is stored in the electrically erasable programmable read-only memory (EEPROM) built into the connector of the sensor and is downloaded automatically to the connected power meter console. The EEPROM also contains sensor model and serial numbers, wavelength range, information on the built-in thermistor (when present), and the calibration date. For more information on sensor calibration, please see the Calibration tab on our Power Meter and Sensor Tutorial.

Power Meter Compatibility
All sensors are connected to the power meter console via the C-Series connector, which offers quick sensor exchange. These sensors are compatible with our current power meter console offering but cannot be used with our previous generation of consoles. For our sensors with natural response times greater than 1 second, these power meters can use the data stored in the connector to predict the incident power after a single time constant of the sensor. Please see the Operation tab for more information.

Recalibration Services
Thorlabs offers recalibration services for our thermal power sensors. To ensure accurate measurements, we recommend recalibrating the sensors annually. This service can be ordered below (see Item # CAL-S200).

Sensor Upgrade and Service
All C-Series Sensors are incompatible with former generation power meter consoles with non-C-Series connectors. We offer a sensor upgrade service if you want to use your existing sensors with a new power meter console with a C-Series connector. Note: upgraded sensors will be incompatible with old power meter consoles with non-C-Series connectors. Please contact our Tech Support team for details.

Thermal Power Sensors Selection Guide
Type High Resolution Max Power: 10 W  Max Power: 40 W to 200 W High Max Power Density
for Pulsed Lasers
Microscope Slide Thermal Sensor
Wavelength Rangea 190 nm - 20 µm 190 nm - 20 µm 190 nm - 20 µm 250 nm - 10.6 µm 300 nm - 10.6 µm
Optical Power Rangea 10 µW - 5 W 2 mW - 10 W 10 mW - 200 W 100 µW - 10 W 100 µW - 2 W
Max Optical Power Densitya 500 - 1500 W/cm² (Avg.) 1500 W/cm² (Avg.) 2 - 4 kW/cm² (Avg.) 35 W/cm² (Avg.);
100 GW/cm² (Peak, 1 ns Pulse)
200 W/cm²
Resolutiona 1 µW - 5 µW 100 µW 100 µW - 5 mW 10 µW - 250 µW 10 µW
  • Combined Range for All Sensors in the Respective Category

Thorlabs' Thermal Power Sensors (C-Series)

Click on the links in the following list or Selection Guide to move to the inicated specification tables.

 

High Resolution

Item # S401C S405C
Detection Specifications
Detector Type Thermal Surface Absorber 
with Background Compensation
(Axial Thermopile)
Thermal Surface Absorber
(Axial Thermopile)
Wavelength Range 190 nm - 20 µm 190 nm - 20 µm
Optical Power Range 10 µW - 1 W 100 µW - 5 W
Max Average Optical Power Density 500 W/cm² 1.5 kW/cm²
Max Pulse Energy Density 0.2 J/cm² (1 µs Pulse),
2 J/cm² (1 ms Pulse)
0.3 J/cm² (1 ns Pulse),
5 J/cm² (1 ms Pulse)
Max Intermittent Powera 3 W -
Linearity ±0.5% ±0.5%
Resolutionb 1 µW 5 µW
Measurement Uncertaintyc
(Calibration Uncertainty)
±3% @ 1064 nm
±5% @ 190 nm - 10.6 µm
±3% @ 1064 nm
±5% @ 250 nm - 17 µm
Response Timed 1.1 s 1.1 s
General Information
Suggested Application Low Power Lasers and LEDs Low Power Lasers and LEDs
Absorber High-Power Broadband Coating High-Power Broadband Coating
Cooling Convection (Passive)
Temperature Sensor (In Sensor Head) NTC Thermistor NTC Thermistor
Console Compatibility PM400, PM200, PM100D, PM100A, PM320E, and PM100USB
Mechanical Specs
Housing Dimensions
(Without Adapter)
33.0 m x 43.0 mm x 15.0 mm
(1.30" x 1.69" x 0.59") 
40.6 mm x 40.6 mm x 16.0 mm
(1.60" x 1.60" x 0.63")
Sensor Input Aperture Ø10 mm Ø10 mm
Active Detector Area 10 mm x 10 mm 10 mm x 10 mm
Distance to Detectore 3 mm 5 mm
Cable Length 1.5 m
Connector D-Sub 9 Pin Male
Weight 0.05 kg (0.11 lb) 0.11 kg (0.24 lb)
Mounting and Accessories
Post Ø1/2" Post via Universal 8-32 & M4 Tap
(Post Not Included)
Ø1/2" Post via Universal 8-32 & M4 Tap
(Post Not Included)
Cage System Mounting N/A 30 mm Cage Systems via Two 4-40 Tapped Holes;
Two Ø6 mm Through Holes for ER Series Rods
Aperture Thread Externally SM1-Threaded Adapter for
Ø1" Lens Tubes and Fiber Adapters
Internally SM05-Threaded Aperture
Externally SM1-Threaded Adapter for 
 Ø1" Lens Tubes and Fiber Adapters
Fiber Adapters (Available Below) S120 Series Fiber Adapters
  • Twenty-minute maximum exposure time for the S401C. The S405C saturates for optical input powers >5 W.
  • Measurement taken with the PM200 console for the S401C and the PM400 console for the S405C. In both cases, the acceleration circuit was switched off. Resolution performance will be similar with our other power meter consoles.
  • Measurement uncertainty during calibration at the specified wavelengths for a beam diameter > 1 mm. The ±3% specification was determined by laser calibration, and the ±5% specification was determined through spectral calibration, in which values were interpolated using the laser calibration data and the absorption curve for the absorber. Calibration can be performed at 10.6 µm upon request.
  • Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <1 s). See the Operation tab for additional information. 
  • Distance is measured from the detector to the front face of the housing.

 

Max Power: 10 W

Item # S415C S425C
Detection Specifications
Detector Type Thermal Surface Absorber
(Axial Thermopile)
Thermal Surface Absorber
(Axial Thermopile)
Wavelength Range 190 nm - 20 µm 190 nm - 20 µm
Optical Power Range 2 mW - 10 W 2 mW - 10 W
Max Average Optical Power Density 1.5 kW/cm² 1.5 kW/cm²
Max Pulse Energy Density 0.3 J/cm² (1 ns Pulse),
5 J/cm² (1 ms Pulse)
0.3 J/cm² (1 ns Pulse),
5 J/cm² (1 ms Pulse)
Max Intermittent Powera 20 W 20 W
Linearity ±0.5% ±0.5%
Resolutionb 100 µW 100 µW
Measurement Uncertaintyc
(Calibration Uncertainty)
±3% @ 1064 nm
±5% @ 250 nm - 17 µm
±3% @ 1064 nm
±5% @ 250 nm - 17 µm
Response Timed 0.6 s 0.6 s
General Information
Suggested Application Low and Mid-Power Lasers & LEDs Low and Mid-Power Lasers & LEDs
Absorber High-Power Broadband Coating High-Power Broadband Coating
Cooling Convection (Passive)
Temperature Sensor
(In Sensor Head)
NTC Thermistor
Console Compatibility PM400, PM200, PM100D, PM100A, PM320E, and PM100USB
Mechanical Specs
Housing Dimensions
(Without Adapter)
50.8 mm x 50.8 mm x 35.0 mm
(2.00" x 2.00" x 1.38") 
50.8 mm x 50.8 mm x 35.0 mm
(2.00" x 2.00" x 1.38")
Sensor Input Aperture Ø15 mm Ø25.4 mm
Active Detector Area Ø15 mm Ø27 mm
Distance to Detectore 5 mm 4.6 mm
Cable Length 1.5 m
Connector D-Sub 9-Pin Male
Weight 0.22 kg (0.49 lb) 0.22 kg (0.49 lb)
Mounting and Accessories
Post Ø1/2" Post via Universal 8-32 & M4 Tap (Post Not Included) Ø1/2" Post via Universal 8-32 & M4 Tap (Post Not Included)
Cage System Mounting N/A N/A
Aperture Thread Internally SM1-Threaded Aperture
 External SM1-Threaded Adapter for Ø1" Lens Tubes
and Fiber Adapters
Internally SM1-Threaded (1.035"-40) with External SM1-Threaded Adapter for Ø1" Lens Tubes
and Fiber Adapters
Fiber Adapters (Available Below) S120 Series Fiber Adapters
  • Two Minute Maximum Exposure Time
  • Measurement taken with the PM400 with the acceleration circuit switched off. Resolution performance will be similar with our other power meter consoles.
  • Measurement uncertainty during calibration at the specified wavelengths for a beam diameter > 1 mm. The ±3% specification was determined by laser calibration, and the ±5% specification was determined through spectral calibration, in which values were interpolated using the laser calibration data and the absorption curve for the absorber. Calibration can be performed at 10.6 µm upon request.
  • Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <1 s). As the natural response times of the S415C and S425C are fast, these do not benefit from accelerated measurements and this function cannot be enabled. See the Operation tab for additional information.
  • Distance is measured from the detector to the front face of the housing.

 

Max Power: 40 W to 200 W

Item # S350C S425C-L S322C
Detection Specifications
Detector Type Thermal Surface Absorber
(Radial Thermopile)
Thermal Surface Absorber
(Axial Thermopile)
Thermal Surface Absorber
(Radial Thermopile)
Wavelength Range 190 nm - 1.1 µm, 10.6 µm 190 nm - 20 µm 250 nm - 11 µm
Optical Power Range 10 mW - 40 W 2 mW - 50 W 100 mW - 200 W
Max Average Optical Power Density 2 kW/cm² 1.5 kW/cm² 4 kW/cm²
Max Pulse Energy Density 0.7 J/cm² (1 ns Pulse),
10 J/cm² (1 ms Pulse)
0.3 J/cm² (1 ns Pulse),
5 J/cm² (1 ms Pulse)
0.5 J/cm² (1 ns Pulse),
10 J/cm² (1 ms Pulse)
Max Intermittent Powera
(2 Minute Max)
60 W 75 W 250 W
Linearity ±1% ±0.5% ±1%
Resolutionb 1 mW 100 µW 5 mW
Measurement Uncertaintyc
(Calibration Uncertainty)
±3% @ 351 nm
±5% @ 190 nm - 1100 nm
±3% @ 1064 nm
±5% @ 250 nm - 17 µm
±3% @ 1064 nm
±5% @ 266 nm - 1064 nm
Response Timed 9 s
(1 s from 0 to 90%)
0.6 s 5 s
(1 s from 0 to 90%)
General Information
Suggested Application High Power Excimer Lasers Mid-Power Lasers Mid-Power Lasers
Absorber Excimer Coating High-Power Broadband Coating High-Power Broadband Coating
Cooling Convection (Passive) Forced Air with Fane
Temperature Sensor
(In Sensor Head)
NTC Thermistor
Console Compatibility PM400, PM200, PM100D, PM100A, PM320E, and PM100USB
Mechanical Specs
Housing Dimensions
(Without Adapter, if Applicable)
100 mm x 100 mm x 54.2 mm
(3.94" x 3.94" x 2.13") 
100.0 mm x 100.0 mm x 58.0 mm
(3.94" x 3.94" x 2.28") 
100 mm x 100 mm x 86.7 mm
(3.94" x 3.94" x 3.41")
Sensor Input Aperture Ø40 mm Ø25.4 mm Ø25 mm
Active Detector Area Ø40 mm Ø27 mm Ø25 mm
Distance to Detectorf 13 mm 4.6 mm 15 mm
Cable Length 1.5 m
Connector D-Sub 9-Pin Male
Weight 1 kg (2.20 lb) 0.71 kg (1.57 lb) 0.75 kg (1.65 lb)
Mounting and Accessories
Post M6, 75 mm Long Ø1/2" Post Included Ø1/2" Post via Universal 8-32 & M4 Tap (Post Not Included) M6, 75 mm Long Ø1/2" Post Included
Cage System Mounting N/A N/A 30 mm Cage Systems via Four 4-40 Tapped Holes
Aperture Thread Unthreaded Internally SM1-Threaded Aperture with External SM1-Threaded Adapter for Ø1" Lens Tubes
and Fiber Adapters
Externally SM1-Threaded Adapter for Ø1" Lens Tubes 
and Fiber Adapters
Fiber Adapters (Available Below) S120 Series Fiber Adapters
  • Two Minute Maximum Exposure Time
  • Measurement taken with the PM100D console, except for the S425C-L in which the PM400 was used. In all cases, the acceleration circuit was switched off. Resolution performance will be similar with our other power meter consoles.
  • Measurement uncertainty during calibration at the specified wavelengths for a beam diameter > 1 mm. The ±3% specification was determined by laser calibration, and the ±5% specification was determined through spectral calibration, in which values were interpolated using the laser calibration data and the absorption curve for the absorber. Calibration can be performed at 10.6 µm upon request.
  • Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <1 s) for the S350C and S322C. As the natural response time of the S425C-L is fast, the S425C-L does not benefit from acceleration and this function cannot be enabled. See the Operation tab for additional information.
  • 12 VDC power supply included.
  • Distance is measured from the detector to the front face of the housing.

 

High Max Power Density for Pulsed Lasers

Item # S370C S470C
Detection Specifications
Detector Type Thermal Volume Absorber
(Axial Thermopile)
Thermal Volume Absorber
(Axial Thermopile)
Wavelength Range 0.4 - 5.2 µm 0.25 - 10.6 µm
Optical Power Range 10 mW - 10 W 100 µW - 5 W
Max Power Density 35 W/cm² (Avg);
100 GW/cm² (Peak, 1 ns Pulse)
35 W/cm² (Avg);
100 GW/cm² (Peak, 1 ns Pulse)
Max Pulse Energy Density 1 J/cm² (1 ns pulse)
10 J/cm² (1 ms pulse)
1 J/cm² (1 ns Pulse)
Max Intermittent Powera 15 W -
Linearity ±1%  ±0.5%
Resolutionb 250 µW 10 µW
Measurement Uncertaintyc
(Calibration Uncertainty)
±3% @ 1064 nm
±5% @ 400 - 1064 nm
±3% @ 1064 nm
±5% @ 250 nm - 10.6 µm
Response Timed 45 s
(3 s from 0 to 90%)
6.5 s
(<2 s from 0 to 90%)
General Information
Suggested Application High Peak Power Lasers High Peak Power,
Low Average
Power Lasers
Absorber Broadband Volume Absorber
(Schott NG1 Filter)
Broadband Volume Absorber
(Schott NG1 Filter)
Cooling Convection Convection
Temperature Sensor
(In Sensor Head)
N/A N/A
Console Compatibility PM400, PM200, PM100D, PM100A, PM320E, and PM100USB PM400, PM200, PM100D, PM100A, PM320E, and PM100USB
Mechanical Specs
Housing Dimensions
(Without Adapter, if Applicable)
75 mm x 75 mm x 51.2 mm
(2.95" x 2.95" x 2.02") 
45.0 mm x 45.0 mm x 18.0 mm
(1.77" x 1.77" x 0.71")
Input Aperture Size Ø25 mm Ø15 mm
Active Detector Areae Ø25 mm >Ø15 mm
Distance to Detectorf 13 mm 5.1 mm
Cable Length 1.5 m 1.5 m
Connector Sub-D 9-Pin Male Sub-D 9-Pin Male
Weight 0.5 kg (1.10 lb) 0.1 kg (0.22 lb)
Mounting and Accessories
Post M6, 75 mm Long Post Included Universal 8-32 / M4 Tap,
Post Not Included
Cage System Mounting 4 x 4-40 Threads for
30 mm Cage Compatibility
N/A
Aperture Thread Externally SM1-Threaded Adapter
for Ø1" Lens Tubes
and Fiber Adapters
External SM1-Threaded Aperture
for Ø1" Lens Tubes
and Fiber Adapters
Fiber Adapters (Available Below) S120 Series Fiber Adapters S120 Series Fiber Adapters
  • Two Minute Maximum Exposure Time
  • Measurement taken with the PM100D console for the S370C and with the PM200 for the S470C. In all cases, the acceleration circuit was switched off. Resolution performance will be similar with our other power meter consoles.
  • Measurement uncertainty during calibration at the specified wavelengths for a beam diameter > 1 mm. The ±3% specification was determined by laser calibration, and the ±5% specification was determined through spectral calibration, in which values were interpolated using the laser calibration data and the absorption curve for the absorber. Calibration can be performed at 10.6 µm upon request.
  • Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <2 s). See the Operation tab for additional information.
  • Input aperture size is the same as the active sensor area for the S370C. The S470C uses a Schott glass volume absorber that is designed to be slightly larger than the entrance aperture to make it easier to detect a beam that is entering the sensor at an angle.
  • Distance is measured from the detector to the front face of the housing.

Microscope Slide Thermal Sensor

Item # S175C
Detection Specifications
Detector Type Thermal Absorber
(Axial Thermopile)
Wavelength Range 0.3 - 10.6 µm
Optical Power Range 100 µW - 2 W
Max Power Density 200 W/cm2
Max Pulse Energy Density 0.1 J/cm² (1 µs pulse)
1 J/cm² (1 ms pulse)
Max Intermittent Power -
Linearity ±0.5%
Resolutiona 10 µW
Measurement Uncertaintyb
(Calibration Uncertainty)
±3% @ 1064 nm
±5% @ 300 nm - 10.6 µm
Response Timec 3 s
(<2 s from 0 to 90%)
General Information
Suggested Application Light Measurement on
the Microscope
Objective Plane
Absorber Broadband Coating
Cooling Convection
Temperature Sensor
(In Sensor Head)
N/A
Console Compatibility PM400, PM200, PM100D, PM100A, PM320E, and PM100USB
Mechanical Specs
Housing Dimensions 76 mm x 25.2 mm x 4.8 mm
(2.99" x 0.99" x 0.19")
Input Aperture Size 18 mm x 18 mm
Active Detector Area 18 mm x 18 mm
Distance to Detectord 1.1 mm
Cable Length 1.5 m
Connector Sub-D 9-Pin Male
Weight 0.05 kg (0.11 lb)
Mounting and Accessories
Post N/A
Cage System Mounting N/A
Aperture Thread N/A
Fiber Adapters (Available Below) N/A
  • Measurement taken with the PM200 console with the acceleration circuit switched off. Resolution performance will be similar with our other power meter consoles.
  • Measurement uncertainty during calibration at the specified wavelengths for a beam diameter > 1 mm. The ±3% specification was determined by laser calibration, and the ±5% specification was determined through spectral calibration, in which values were interpolated using the laser calibration data and the absorption curve for the absorber. Calibration can be performed at 10.6 µm upon request.
  • Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <1 s). See the Operation tab for additional information.
  • Distance is measured from the detector to the front face of the housing.

C-Series Sensor Connector

D-Type Male

DB9 Male

PinConnection
1 Not Used
2 EEPROM Data
3 Sensor and NTC Ground
4 Not Used
5 Not Used
6 EEPROM Ground
7 NTC
8 Sensor Signal
9 Not Used

Operational Principle

Radial Thermopile Configuration
Click to Enlarge

Figure 1: A thermal sensor with radially configured thermocouples, which is depicted as seen from the top. Light is incident on the absorbing layer at the center, and heat flows through the thermocouples to the heat sink.
Axial Thermopile Configuration
Click to Enlarge

Figure 2: A thermal sensor with axially configured thermocouples, which is depicted as seen from the side. Light is incident on the top, and heat flows down through the thermocouple layer and dissipates in the heat sink below.

Thorlabs' Thermal Power Sensors are based on thermopiles. The top layer of the sensor consists of a light-absorbing material. A region filled with multiple thermocouples, which are connected in series, is immediately adjacent to the absorber. Thermocouples are made by bringing two dissimilar metals into contact, and their point of contact is called a junction. On the other side of the thermocouples is a heat sink. The thermocouples are connected in series, and the placement of the junctions alternates from being in close proximity to the absorber to being in close proximity to the heat sink.

The absorber converts incident light energy into heat. The heat flows from the absorber, across the thermocouples, and to the heat sink, where it dissipates. The temperatures of the thermocouple junctions placed close to the absorber are higher than those the adjacent junctions placed close to the heat sink. This arrangement takes advantage of the thermoelectric (Seebeck) effect, in which a temperature difference between the adjacent junctions generates a proportional voltage difference. By connecting multiple thermocouples in series, the magnitude of the generated voltage is increased. The thermocouples are often arranged in a radial (also called a disk) configuration, as illustrated in Figure 1, or in an axial (also called a matrix) configuration, which is diagrammed in Figure 2. Thermal power sensors with both types of configurations are available from Thorlabs.

Radial Configuration of Thermocouples
A diagram of a thermal power sensor with a radial thermopile is shown in Figure 1, viewed from the top. This construction places the light absorber at the center. It is surrounded by a concentric ring of thermocouples connected in series, which are surrounded by a concentric heat sink. Light incident on the absorber generates heat that flows in a radial direction through the thermocouples and towards the heat sink. The heat sink must be specially designed so that it is in good mechanical contact with the outer ring of thermocouple junctions, without being in thermal contact with the light absorber or the inner ring of thermocouple junctions. The area behind the absorber cannot be in thermal contact with anything that will divert the heat flow from its intended radial path of flow. 

A benefit of the radial construction is that sensors can be designed to measure power levels as high as kilowatts. This high upper limit is made possible both by the thickness of the sensor disk and by displacing the thermocouples from the absorber, which protects them from the conditions in the laser impact area. Disadvantages of the radial thermopiles include the use of a heat sink with a special design, which adds complexity when customizing the sensor head, and a sensor head which is generally a least twice the diameter of the active detector area. Resolution for radial thermal power sensors is typically limited to around 10 mW.

Thorlabs' thermal power sensors featuring a radial configuration include the S350C and S322C, which are all designed for mid-power range applications.

Axial Configuration of Thermocouples
A diagram of a thermal power sensor with an axial configuration of thermocouples is shown in Figure 2. In this design, the thermocouples are arranged between two flat layers. One layer is the light absorber, and the other is the heat sink. As the heat flows directly from the front surface to the back side, the dimensions of these sensor packages can be made compact. The sensor housing can be approximately the same size as the active detector area.

The new generation of axially-designed sensors achieves high resolutions in the microwatt range while providing relatively fast response times. These sensors detect optical powers up to several Watts, which limited mostly by the thickness of the absorbing material. The performance of the newly designed sensors, which includes the S401C and S405C, contrasts with sensors of previous generations, which have slower response times.

Heat sink shapes and dimensions are much less constrained for axially, as compared with radially, configured thermopiles. Heat sinks for axial designs can be as simple as a block of aluminum attached with thermal glue, or as sophisticated as a metal-core PCB that is soldered to the sensor. Our S415C, S425C, and S425C-L thermal power sensors have heat sinks can be easily removed and replaced. This enables the user to upgrade the heat sink, potentially to one with fans or water cooling, or to integrate the sensor into a custom setup. Please note that the heat sink must provide heat dissipation adequate for the application.

Volume Absorbers for Pulsed Lasers
Volume absorbers are alternatives to surface absorbers, which sustain damage when subjected to highly energetic and short pulses of nanosecond duration. Unlike surface absorbers, which suffer damage as a consequence of absorbing the pulse energy within a localized region, volume absorbers collect the heat from the light pulse and distribute it throughout a volume. Heat generated throughout the volume flows across the thermocouples and dissipates in the heat sink. Thorlabs offers two thermal power sensors with volume absorbers, S370C and S470C, which are both designed for the detection of Nd:YAG laser pulses, among other applications. In these axially-constructed sensors, the Schott glass volume absorber replaces the surface absorber of the other axial sensors. The response times of sensors with volume absorbers are slower than those with surface absorbers, as the thermal mass of the volume absorber is larger. The S470C is faster than the S370C, as its glass volume is smaller and other design changes have resulted in a faster response of the axial thermopile.

Natural Response of the S415C
Click to Enlarge

Figure 3: Natural response of the S415C with the dotted line at 99% and the red square indicating the point on the curve corresponding to a single sensor time constant.

Natural Responses, the Sensor Time Constant, and Power Measurement Predictions

The typical natural response of the S415C thermal sensor to an instantaneous transition from darkness to being steadily illuminated is shown in Figure 3. This step function illumination stimulus produces a response that can be modeled using an exponential function and is similar to the function describing the rate at which a capacitor charges.

The sensor time constant is defined in terms of how long it takes for the sensor response to reach 99% of its maximum response. When the sensor has reached the 99% level, a time period equal to five sensor time constants has elapsed. In Figure 3, the dotted line corresponds to the 99% level and the red square to the response after a single sensor time constant has elapsed.

When the sensor's natural response characteristic function is known, it is possible to use it to model and predict the final power reading well before the sensor reading has stabilized. Thorlabs' power meter consoles calculate and display predictions of the stabilized power reading when Thorlabs sensors with sensor time constants ≥0.5 s (natural response times >1 s) are connected. Prediction is implemented using the sensor information stored in the EEPROM built into the C-Series connectors. The S415C, S425C, and S425C-L are fast enough, with sensor time constants <0.2 s (natural response times <0.6 s), that prediction is not necessary and is not enabled. Prediction is enabled for the other sensors.

When prediction is active, the first prediction is made after a time duration equal to a single sensor time constant, and this prediction is updated at time intervals of one sensor time constant until a total time duration of seven sensor time constants has elapsed. Prediction is then turned off; the power reading after seven time constants is 99.9% of the final reading. As there is uncertainty associated with the predicted measurements, they can exhibit some ripple. The faster the sensor, the less the uncertainty. After prediction is turned off, the gradient of the power reading is monitored, and prediction is re-enabled if an increase is detected which exceeds a defined threshold. 

Protect Thermal Power Sensors from Thermal Disturbances

For the most accurate results, thermal power sensors should be protected from air flow and other thermal disturbances during operation. Otherwise, measurements will drift. This is of particular importance for low power sensors with high resolution. Handheld use is not recommended for any of the thermal power sensors, as body heat transferred to the sensor or heat sink can negatively impact the accuracy of the measurements.

Thermal power sensors operate by measuring a temperature differential, which is converted to a voltage signal. The sensor design assumes that heat generated in the absorber flows towards the heat sink. If the operator is in contact with the sensor housing during operation, body heat may transfer to the sensor and make spurious contributions to the power measurement. For example, if the sensor is held by the heat sink, heat transferred from the hand to the heat sink will flow towards the absorber. If no light is incident on the absorber, this will result in a negative power reading. If there is light incident on the absorber, it will result in an inaccurate power reading.

Thorlabs offers a wide selection of power and energy meter consoles, ranging from the touch screen PM400 to the analog PM100A. Key specifications of all of our power meter consoles are presented below to help you decide which device is best for your application. We also offer self-contained wireless power meters.

When used with our C-series sensors, Thorlabs' power meter consoles recognize the type of connected sensor and measure the current or voltage as appropriate. Our C-series sensors have responsivity calibration data stored in their connectors. The console will read out the responsivity value for the user-entered wavelength and calculate a power or energy reading.

  • Photodiode sensors deliver a current that depends on the input optical power and the wavelength. The current is fed into a transimpedance amplifier, which outputs a voltage proportional to the input current. The photodiode's responsivity is wavelength dependent, so the correct wavelength must be entered into the console for an accurate power reading. The console reads out the responsivity for this wavelength from the connected sensor and calculates the optical power from the measured photocurrent.
  • Thermal sensors deliver a voltage proportional to the input optical power. Based on the measured sensor output voltage and the sensor's responsivity, the console will calculate the incident optical power.
  • Energy sensors are based on the pyroelectric effect. They deliver a voltage peak proportional to the pulse energy. If an energy sensor is recognized, the console will use a peak voltage detector and the pulse energy will be calculated from the sensor's responsivity.

The sensors are also capable of displaying the current or voltage delivered by the sensor. Alternatively, a current or voltage equivalent to the measured value is provided at the analog output.

Item # PM100A PM100D PM100USB PM200 PM400 PM320E
(Click Photo to Enlarge) PM100A PM100D PM100USB PM200 PM400 PM320E
Description Analog Power Meter Console Digital Power and Energy Meter Console USB Power and Energy Meter Interface Touchscreen Power and Energy Meter Console Touchscreen Power and Energy Meter Console with Multi-Touch Dual-Channel Benchtop Power and Energy Meter Console
Compatible Sensors Photodiode and Thermal Photodiode, Thermal, and Pyroelectric
Housing Dimensions
(H x W x D)
7.24" x 4.29" x 1.61"
(184 mm x 109 mm x 41 mm)
7.09" x 4.13" x 1.50"
(180 mm x 105 mm x 38 mm)
3.67" x 2.38 " x 1.13"
(93.1 mm x 60.4 mm x 28.7 mm)
6.70" x 4.93" x 1.48"
(170.2 mm x 125.1 mm x 37.5 mm)
5.35" x 3.78" x 1.16"
(136.0 mm x 96.0 mm x 29.5 mm)
4.8" x 8.7" x 12.8"
(122 mm x 220 mm x 325 mm)
Channels 1 2
External Temperature Sensor Input
(Sensor not Included)
- - - - Instantaneous Readout and Record Temperature Over Time -
External Humidity Sensor Input (Sensor not Included) - - - - Instantaneous Readout and  Record Humidity Over Time -
GPIO Ports - 4, Programmable 4, Programmable -
Source Spectral Correction - - - Yes! Yes! -
Attenuation Correction - - - Yes! Yes! -
External Trigger Input - - -  yes -  yes
Display
Type Mechanical Needle and LCD Display with Digital Readout 320 x 240 Pixel Backlit Graphical LCD Display No Built-In Display
Controlled via GUI for PC
Resistive Touchscreen with Color Display Protected Capacitive Touchscreen with Color Display 240 x 128 Pixels
Graphical LCD Display
Dimensions Digital: 1.9" x 0.5"
(48.2 mm x 13.2 mm)
Analog: 3.54" x 1.65"
(90.0 mm x 42.0 mm)
3.17" x 2.36"
(81.4 mm x 61.0 mm)
- 4.65" x 3.48"
(118.0 mm x 88.5 mm)
3.7" x 2.1"
(95 mm x 54 mm)
3.7" x 2.4"
(94.0 mm x 61.0 mm)
Refresh Rate 20 Hz Dependent on PC and Settingsa 100 Hz 10 Hz (Numerical)
25 Hz (Analog Simulation)
20 Hz
Measurement Viewsb
Numerical yes yes Requires PCc yes yes
Mechanical Analog Needle yes - - - - -
Simulated Analog Needle - yes Requires PCc yes Yes! yes
Bar Graph - yes Requires PCc yes Yes! yes
Trend Graph - yes Requires PCc yes Yes! Yes!
Histogram - yes Requires PCc - - Yes!
Statistics Yes! yes Requires PCc yes Yes! yes
Memory
Type - SD Card - NAND Flash NAND Flash -
Size - 2 GB - 128 MB 4 GB -
Power
Battery LiPo 3.7 V 1300 mAh - LiPo 3.7 V 2600 mAh LiPo 3.7 V 2600 mAh -
External 5 VDC via USB or Included AC Adapter 5 VDC via USB 5 VDC via Included Power Supply 5 VDC via USB Selectable Line Voltage: 100 V, 115 V, 230 V (±10%)
  • Up to 300 Hz. The refresh rate is limited by the PC used to operate the PM100USB power meter interface, as it does not have a built in display.
  • These are the measurement views built into the unit. All of our power meter consoles except the PM320E can be controlled using the Optical Power Monitor software package. The PM320E has its own software package.
  • The PM100USB power meter interface does not have a built-in monitor, so all data must be displayed through a PC running the Optical Power Meter Software.

Posted Comments:
cwong3  (posted 2017-01-16 18:00:18.07)
Hi there. Can you tell me what the max energy density would be for a 30 fs pulse? I'm mostly interested in the S470C and S310C. Thanks.
wskopalik  (posted 2017-01-17 05:13:38.0)
This is a response from Wolfgang at Thorlabs. Thank you very much for your inquiry. Unfortunately, we don't have specifications for the maximum energy density for fs pulses. Depending on the exact laser parameters (wavelength, pulse energy, repetition rate, etc.) one of our sensors might however still be suitable. I have contacted you directly to further discuss your requirements and to look for a suitable sensor.
arkke.eskola  (posted 2016-10-27 12:06:48.73)
Hi, I am searching a (thermal) sensor, which would work both with excimer laser (193, 248, and 351 nm) and Nd:YAG laser (213, 266, 355, and 532 nm). I am thinking your S350C sensor due to its large aperture size and wide wavelenght range. Could you please comment its suitability for this purpose; especially I would like to know whether there might appear any issue(s) to use S305C to measure (short) Nd:YAG laser pulse energies. Or should I think about pyroelectric energy sensors? Thanks, Arkke Eskola
wskopalik  (posted 2016-10-28 05:19:58.0)
This is a response from Wolfgang at Thorlabs. Thank you for your inquiry. Thermal sensors are generally a good choice to measure the average power of pulsed lasers. It depends on the exact laser parameters which sensor model is the most suited (i.e. wavelength, pulse energy, pulse width, repetition rate, beam diameter). These parameters are necessary to make sure that the sensor can handle the power levels of the laser and will not be damaged by it. I will contact you directly to further discuss your requirements.
kedves  (posted 2016-04-13 18:29:51.247)
Hello, I am looking for a power meter for a femtosecond laser of about 25 mJ pulse energy, 10 Hz repetition rate (i.e. 250 mW average power), and 40 fs pulse duration (i.e. 625 GW pulse peak power) and 15 mm pulse diameter. Which of your products would you recommend that can tolerate this high peak power too?
shallwig  (posted 2016-04-14 10:34:42.0)
This is a response from Stefan at Thorlabs. Thank you very much for your inquiry. At the moment we have no sensor available which is specified to stand 625 GW peak power and 353,7 GW/cm2 peak power density. I will contact you directly to discuss if there is a special solution we can offer.
mastron  (posted 2016-02-24 19:42:46.833)
I am looking into power meters and sensors for measurements of ultrafast pulsed lasers (pulses <250fs at 1khz). Would the S470C be appropriate for this kind of measurement? I wouldn't need shot-to-shot resolution; just to be able to measure pulse energies in several ranges: low uJ (so at 1 khz, low mW range), ~500mW, and ~2W without damaging the power sensor. Also, are calibration options available for multiple wavelength regions? I'd like to be able to measure visible, 800 nm, and near to mid-IR (so around 1.5, 2, 5, and 6 um) accurately.
shallwig  (posted 2016-02-25 10:16:16.0)
This is a response from Stefan at Thorlabs. Thank you very much for your inquiry due to its long response time (<2s) as typical for thermal sensors average power measurements of pulsed sources are possible. The calibration and measurement uncertainty of this sensor are specified from 250nm – 10,6µm. More information about the calibration of our thermal heads can be found in the power meter tutorial in the “calibration “ Tab here: http://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=6188 I will contact you directly to discuss your application and your parameters in more detail.
user  (posted 2015-12-16 15:42:00.627)
In addition to my question below, would you please advice me if you conducted calibration with any emmersion oil? How would it be calibrated with angled beam?
shallwig  (posted 2015-12-16 05:09:11.0)
This is a response from Stefan from Thorlabs. Thank you again for your for your inquiry. We calibrate the sensor S175C at 1064nm with a collimated laser at 100mW, the beam hits the sensors surface perpendicular. Apart from the calibration at 1064nm we do perform a reflectivity measurement were the reflectivity of the coating gets measured from 266 – 1064nm . In our power meter tutorial the whole process gets described in detail: http://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=6188 We have a NIST traceable reference built in a integrating sphere and measure the spectral intensity distribution. Afterwards we put the sensor under test in and measure the spectral reflectivity again. The difference between both curves tells us about the reflectivity of the sensors absorber surface. This is the calibration curve you also get delivered with the sensor. But there is no NIST standard available which allows to calibrate the sensors with angled beams so far. Therefore we cannot specify any measurement accuracy for this measurement task.
user  (posted 2015-12-16 13:57:56.547)
I am interested in you S175C sensor to measure oure Ti:Sa laser under 20X objective(oil emmersion). We can't know about real power under the objective as we have not had any sensor. But guessing it would be 500mW-less than 1W. Can we use your S175C for our measurment?
shallwig  (posted 2015-12-16 04:37:05.0)
This is a response from Stefan at Thorlabs. Thank you very much for your inquiry. For estimation how suitable this sensor is for power measurement of your Ti:Sa I would need further information about the beam. We specify for the sensor a maximum average power density of 200W/cm2 and for µs Pulses and a max pulse energy density of 0.1J/cm2 and 1J/cm2 for 1ms pulses. You can find these information in the spec sheet: http://www.thorlabs.de/thorcat/MTN/S175C-SpecSheet.pdf The measurement accuracy we specify is only valid for parallel beams with diameter >1mm. I would like to discuss your application in more detail with you directly, unfortunately you left no email address. Please feel free to contact me at europe@thorlabs.com
hsynvnvural  (posted 2015-11-20 09:55:12.33)
Is there any difference between CW/Pulsed Laser average power measurement for thermopile sensors? Is the uncertainty same for both measurement for S350C and S470C sensors?
shallwig  (posted 2015-11-20 10:09:03.0)
This is a response from Stefan at Thorlabs. Thank you very much for your inquiry. In general Thermopile sensors have a very slow response time, for the S470C we specify <2s. Depending on the repetition rate of your pulsed source multiple of pulses will hit the active surface before a measurement point is taken. The measurement uncertainty for the S350C and S470C can be found in the specs table: ±3% @ 351 nm; ±5% @ 190 - 1100 nm (S350C) and ±3% @ 1064 nm; ±5% @ 250 nm - 10.6 µm (S470C) A main difference apart from the power range is the detector type. The S350C is a thermal surface absorber while the S470C is a thermal volume absorber. Thermal volume absorbers have significantly higher responsivities, which allow them to detect very low power levels and short (ns) pulses. However, this improvement usually comes at the expense of response time. I will contact you directly to check which sensor is suited for your application.
Paul.taylor  (posted 2015-03-20 11:12:45.53)
Can you read the voltage direct from the head via a Plc analog input card? If so - what rough calibration V/W is it?
shallwig  (posted 2015-03-23 06:13:37.0)
This is a response from Stefan at Thorlabs. Thank you very much for your inquiry. You can use a PLC analog input card to read out the voltage directly by taking the generated thermo voltage from Pin 3 and 8 of the D-Sub connector. Please take a look into the “Pin Diagrams” Tab on the website http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=3333 With the sensor head you will get a calibration certificate where the sensitivity at our calibration sources (1062nm) is listed with an uncertainty of +/-3%. Depending on which sensor you are interested in the sensitivity is between 0,1mV/W and about 100mV/W. Thus you have to deal with very small voltages. Further information about how our thermal sensors get calibrated can be also found in the power meter tutorial on our website: http://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=6188 in the “calibration” tab. I will contact you directly to discuss your application in more detail.
tonyhongxp  (posted 2015-02-10 22:20:54.77)
would the thermal power meter work below 190 nm? The absorption curve does not seem to fall at wavelength below 190 nm.
tschalk  (posted 2015-02-11 08:03:01.0)
This is a response from Thomas at Thorlabs. Thank you very much for your inquiry. You can use the sensor below 190nm but we dont have specific informaiton about the sensitivity and we dont have the possibility to calibrate the sensor below that wavelength. I will contact you directly to discuss your application.
user  (posted 2011-11-28 09:07:26.0)
A response from Tyler at Thorlabs: Hello Krister, The thermal power meter sensors that Thorlabs sells use a thermopile sensor to measure the incident power. These sensors would not be an out-of-the-box solution for a non-contact temperature sensor. We will contact you to discuss your application and possible solutions.
krister.magnusson  (posted 2011-11-28 05:57:45.0)
This product measures light intensity. Does it also include a laser which send out a detection signal wich is analyzed? That is, how does it operate? I am looking for a non-contact temperature sensor (not pyrometer). Best regards, Krister Magnusson
jjurado  (posted 2011-07-08 15:18:00.0)
Javier Jurado: Response from Javier at Thorlabs to last poster: We do offer a cap that you can use to cover the entrance port of the S302C sensor. The part number is SM1CP1: http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=3519 Please do not hesitate to contact us at techsupport@thorlabs,com if you have any further questions.
user  (posted 2011-07-08 15:50:53.0)
I ordered S302C and I would like protect its window. Do you sell a cap for it?
jjurado  (posted 2011-06-02 11:34:00.0)
Response from Javier at Thorlabs to halverso: Thank you very much for contacting us. With a maximum incident power density spec of 200W/cm^2, the S302C should work for your application. However, other parameters such as wavelength range, minimum incident power, and beam diameter are important, as well, in order to determine the most suitable sensor. I will contact you directly to discuss these details.
halverso  (posted 2011-06-02 09:18:06.0)
I want to measure power on a stable solar simulator. Expected value is 100mW/cm2. The S302C appears to be ideal for my purpose, but I wanted to confirm. Thanks.
apalmentieri  (posted 2010-02-22 22:55:57.0)
A response from Adam at Thorlabs to malayk: The S302C sensors are not compatible with the old PM100 power meters. They are compatible with the new PM100D power meter. I will contact you directly to help provide you with the best possible solution that suits your needs.
malayk  (posted 2010-02-22 22:00:52.0)
Is the S302C sensor compatible with the old PM100 power meter?
Handheld Power Meter with iPad
Click to Enlarge

The PM160 wireless power meter, shown here with an iPad mini (not included), can be remotely operated using Apple mobile devices.

This tab outlines the full selection of Thorlabs' Power and Energy Sensors. Our photodiode and thermal sensors are compatible with all of Thorlabs' current line of power meter consoles, while our pyroelectric sensors are compatible with all of our current power meter consoles except for the PM100A Analog Power Meter Console. In addition to the power and energy sensors listed below, Thorlabs also offers all-in-one, wireless, handheld power meters and compact USB power meter interfaces that contain either a photodiode or a thermal sensor, as well as power meter bundles that include a console, sensor head, and post mounting accessories.

Thorlabs offers three types of sensors:

  • Photodiode Sensors: These sensors are designed for power measurements of monochromatic or near-monochromatic sources, as they have a wavelength dependent responsivity. These sensors deliver a current that depends on the input optical power and the wavelength. The current is fed into a transimpedance amplifier, which outputs a voltage proportional to the input current.
  • Thermal Sensors:  Constructed from material with a relatively flat response function across a wide range of wavelengths, these thermopile sensors are suitable for power measurements of broadband sources such as LEDs and SLDs. Thermal sensors deliver a voltage proportional to the input optical power.
  • Pyroelectric Energy Sensors: Our pyroelectric sensors produce an output voltage through the pyroelectric effect and are suitable for measuring pulsed sources, with a repetition rate limited by the time constant of the detector. These sensors will output a peak voltage proportional to the incident pulse energy.

Power and Energy Sensor Selection Guide

There are two options for comparing the specifications of our Power and Energy Sensors. The expandable table below sorts our sensors by type (e.g., photodiode, thermal, or pyroelectric) and provides key specifications.

Alternatively, the selection guide graphic further below arranges our entire selection of photodiode and thermal power sensors by wavelength (left) or optical power range (right). Each box contains the item # and specified range of the sensor. These graphs allow for easy identification of the sensor heads available for a specific wavelength or power range. 

Photodiode Power Sensors
Thermal Power Sensors
Pyroelectric Power Sensors (Not Compatible with PM100A)
  • The response time of the photodiode sensor. The actual response time of a power meter using these sensors will be limited by the update rate of your power meter console.
  • Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <1 s) when the natual response time is approximately 1 s or greater. As the natural response times of the S415C, S425C, and S425C-L are fast, these do not benefit from accelerated measurements and this function cannot be enabled. For more information, see the Operation tab here.
  • With intermittent use: maximum exposure time of 20 minutes for the S401C, otherwise maximum exposure time is 2 minutes.
  • All pyroelectric sensors have a 20 ms thermal time constant, τ. This value indicates how long it takes the sensor to recover from a single pulse. To detect the correct energy levels, pulses must be shorter than 0.1τ and the repetition rate of your source must be well below 1/τ.

Sensor Options
(Arranged by Wavelength Range)

Sensor Options
(Arranged by Power Range)

High Resolution

Item #a S401C S405C
Sensor Image
(Click the Image to Enlarge)
S401C S405C
Wavelength Range 190 nm - 20 µm 190 nm - 20 µm
Optical Power Range 10 µW - 1 W (3 Wb) 100 µW - 5 W
Input Aperture Size Ø10 mm Ø10 mm
Active Detector Area
10 mm x 10 mm 10 mm x 10 mm
Max Optical Power Density 500 W/cm² (Avg.) 1.5 kW/cm² (Avg.)
Detector Type Thermal Surface Absorber (Thermopile)
with Background Compensation
Thermal Surface Absorber (Thermopile)
Linearity ±0.5% ±0.5%
Resolutionc 1 µW 5 µW
Measurement Uncertaintyd ±3% @ 1064 nm
±5% @ 190 nm - 10.6 µm
±3% @ 1064 nm
±5% @ 250 nm - 17 µm
Response Timee 1.1 s 1.1 s
Cooling Convection (Passive)
Housing Dimensions
(Without Adapter)
33.0 m x 43.0 mm x 15.0 mm
(1.30" x 1.69" x 0.59")
40.6 mm x 40.6 mm x 16.0 mm
(1.60" x 1.60" x 0.63")
Temperature Sensor
(In Sensor Head)
NTC Thermistor NTC Thermistor
Cable Length 1.5 m
Post Mounting Universal 8-32 / M4 Taps
(Post Not Included)
Universal 8-32 / M4 Taps
(Post Not Included)
30 mm Cage Mounting - Two 4-40 Tapped Holes &
Two Ø6 mm Through Holes
Aperture Threads - Internal SM05
Accessories Externally SM1-Threaded Adapter
Light Shield with Internal SM05 Threading
Externally SM1-Threaded Adapter
Compatible Consoles PM400, PM200, PM100D, PM100A, PM100USB, and PM320E
  • For complete specifications, please see the Specs tab.
  • For conditions of intermittent use, with a maximum exposure time of 20 minutes for the S401C. The S405C saturates for optical input powers >5 W.
  • Measurement taken with the PM200 console for the S401C and the PM400 console for the S405C. In all cases, the acceleration circuit was switched off. Resolution performance will be similar with our other power meter consoles.
  • Defined as the measurement uncertainty during calibration at the specified wavelengths for a beam diameter > 1 mm. The ±3% specification was determined by laser calibration, and the ±5% specification was determined through spectral calibration, in which values were interpolated using the laser calibration data and the absorption curve for the absorber. Calibration can be performed at 10.6 µm upon request.
  • Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <1 s). See the Operation tab for additional information.
  • High Resolution of 1 μW or 5 μW
  • S401C and S405C Have Thermistors Used to Monitor Temperature of Sensor Head
  • S401C: Background Compensation for Low-Drift Measurements
  • S405C: Accommodates Average Optical Power Densities up to 1.5 kW/cm²

Click to Enlarge

S401C Thermal Sensor with Included Light Shield

The S370C and S470C Thermal Sensors are designed to measure short and highly energetic laser pulses. All of these units are post-mountable for free-space applications and feature NIST-traceable data stored in the sensor connector.

These thermal power sensors are unique in that they have thermal volume absorbers, where our other thermal power sensors have thermal surface absorbers. The volume absorber consists of a Schott glass filter. Incident pulses are absorbed and the heat is distributed throughout the volume. In this way, pulses that would have damaged the absorption coating of a thermal surface absorber are safely measured by these thermal volume absorbers.

The S370C features a large Ø25 mm aperture ideal for large-spot-size beams, and it is compatible with average powers from 10 mW to 10 W (CW).

In comparison, the S470C is faster, as the glass absorber volume is reduced and other design parameters have been optimized for speed. This results in a different optical power range, with the ability to measure powers down to 100 µW. The Ø15 mm aperture is of the S470C is smaller, and it has a lower max average power of 5 W. Its 10 µW resolution is better than the 250 µW resolution of the S370C.

Thorlabs offers a recalibration service for these sensors, which can be ordered below (see Item # CAL-S200).

Low Power High Resolution Thermal Sensor Absorption
Click to Enlarge

Raw Data: S401C, S405C
The S405 shares the same absorption curve with the S415C, S425C, and S245C-L. (All are sold below.)
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
S401C Support Documentation
S401CThermal Power Sensor Head, Surface Absorber, 0.19 - 20 µm, 1 W, Ø10 mm
$740.52
Lead Time
S405C Support Documentation
S405CThermal Power Sensor Head, Surface Absorber, 0.19 - 20 µm, 5 W, Ø10 mm
$704.00
Today

Max Power: 10 W

Item #a S415C S425C
Sensor Image
(Click Image to Enlarge)
S415C S425C
Wavelength Range 190 nm - 20 µm 190 nm - 20 µm
Optical Power Range 2 mW - 10 W (20 Wb) 2 mW - 10 W (20 Wb)
Input Aperture Size Ø15 mm Ø25.4 mm
Active Detector Area
Ø15 mm Ø27 mm
Max Optical
Power Density
1.5 kW/cm² (Avg.) 1.5 kW/cm² (Avg.)
Detector Type Thermal Surface Absorber (Thermopile)
Linearity ±0.5% ±0.5%
Resolutionc 100 µW 100 µW
Measurement
Uncertaintyd
±3% @ 1064 nm
±5% @ 250 nm - 17 µm
±3% @ 1064 nm
±5% @ 250 nm - 17 µm
Response Timee 0.6 s 0.6 s
Cooling Convection (Passive)
Housing Dimensions
(Without Adapter)
50.8 mm x 50.8 mm x 35.0 mm
(2.00" x 2.00" x 1.38")
50.8 mm x 50.8 mm x 35.0 mm
(2.00" x 2.00" x 1.38")
Temperature Sensor
(In Sensor Head)
NTC Thermistor
Cable Length 1.5 m
Post Mounting Universal 8-32 / M4 Taps
(Post Not Included)
Universal 8-32 / M4 Taps
(Post Not Included)
30 mm Cage Mounting - -
Aperture Threads Internal SM1 Internal SM1
Removable Heatsink Yes Yes
Accessories Externally SM1-Threaded Adapter Externally SM1-Threaded Adapter
Compatible Consoles PM400, PM200, PM100D, PM100USB, PM100A, and PM320E
  • For complete specifications, please see the Specs tab.
  • Two Minute Maximum Exposure Time
  • Measurement taken with the PM400 with the acceleration circuit switched off. Resolution performance will be similar with our other power meter consoles.
  • Defined as the measurement uncertainty during calibration at the specified wavelengths for a beam diameter > 1 mm. The ±3% specification was determined by laser calibration, and the ±5% specification was determined through spectral calibration, in which values were interpolated using the laser calibration data and the absorption curve for the absorber. Calibration can be performed at 10.6 µm upon request.
  • Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <1 s). As the natural response times of the S415C and S425C are fast, these do not benefit from accelerated measurements and this function cannot be enabled. See the Operation tab for additional information.
  • 100 µW Optical Power Resolution
  • Thermistors Used to Monitor Temperature of Sensor Head
  • Removable Heat Sinks Included

These thermal power sensors are designed for general broadband power measurements of low and medium power light sources. All include an externally SM1-threaded (1.035"-40) adapter, with threading concentric with the input aperture. The adapters are useful for mounting Ø1" Lens Tubes and Fiber Adapters (available below). The apertures of the S415C and S425C have internal SM1 threading.

These sensors operate with fast (<0.6 s) natural response times, and their removable heat sinks provide a high degree of flexibility to those interested in integrating them into custom setups or replacing the included heat sink with one that is water or fan cooled. If replacing the heat sink, please note that the replacement must provide heat dissipation adequate for the application.

Thorlabs offers a recalibration service for these sensors, which can be ordered below (see Item # CAL-S200).

Thermal Sensor Absorption Mid-Power Thermal
Click to Enlarge

Click Here for Raw Data
The absorption curves of each of the thermal power sensors designed for use with low and medium power optical sources.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
S415C Support Documentation
S415CThermal Power Sensor Head, Surface Absorber, 0.19 - 20 µm, 10 W, Ø15 mm
$726.00
Today
S425C Support Documentation
S425CThermal Power Sensor Head, Surface Absorber, 0.19 - 20 µm, 10 W, Ø25.4 mm
$792.00
3-5 Days

Max Power: 40 W to 200 W

Thermal Sensor Absorption Mid-Power Thermal
Click to Enlarge

Raw Data: S350C, S425C-L, S322C
The absorption curves of each of the thermal power sensors designed for use with low and medium power optical sources.
  • Thermistors Used to Monitor Temperature of Sensor Head
  • S322C Has 4-40 Taps for Use with Our 30 mm Cage Systems
  • S350C Has Ø40 mm Aperture Well Suited to Excimer and Other Lasers with Large Spot Sizes
  • S425C-L Features Removable Heat Sink
  • S322C is Fan Cooled with an Optical Power Range up to 200 W

These thermal power sensors are designed for general broadband power measurements of low and medium power light sources. With the exception of the S350C, all include an adapter with external SM1 (1.035"-40) threading concentric with the input aperture. This allows the sensors to be integrated into existing Ø1" lens tube systems in addition to being compatible with fiber adapters (available below). The aperture of the S425C-L has internal SM1 threading.

The S425C-L operates with a fast (<0.6 s) natural response time and has a removable heat sink, which provides a high degree of flexibility to those interested in integrating them into custom setups or replacing the included heat sink with one that is water or fan cooled. If replacing the heat sink, please note that the replacement must provide heat dissipation adequate for the application.

Thorlabs offers a recalibration service for these sensors, which can be ordered below (see Item # CAL-S200).


Item #a S350C S425C-L S322C
Sensor Image
(Click Image to Enlarge)
S350C S425C-L S322C
Wavelength Range 190 nm- 1.1 µm, 10.6 µm 190 nm - 20 µm 250 nm - 11 µm
Optical Power Range 10 mW - 40 W (60 Wb) 2 mW - 50 W (75 Wb) 100 mW - 200 W (250 Wb)
Input Aperture Size Ø40 mm Ø25.4 mm Ø25 mm
Active Detector Area
Ø40 mm Ø27 mm Ø25 mm
Max Optical Power Density 2 kW/cm² (Avg.) 1.5 kW/cm² (Avg.) 4 kW/cm² (Avg., CO2)
Detector Type Thermal Surface Absorber (Thermopile)
Linearity ±1% ±0.5% ±1%
Resolutionc 1 mW 100 µW 5 mW
Measurement Uncertaintyd ±3% @ 351 nm
±5% @ 190 nm - 1100 nm
±3% @ 1064 nm
±5% @ 250 nm - 17 µm
±3% @ 1064 nm
±5% @ 266 nm - 1064 nm
Response Timee 9 s
(1 s from 0 to 90%)
0.6 s 5 s
(1 s from 0 to 90%)
Cooling Convection (Passive) Forced Air with Fanf
Housing Dimensions
(Without Adapter, if Applicable)
100 mm x 100 mm x 54.2 mm
(3.94" x 3.94" x 2.13")
100.0 mm x 100.0 mm x 58.0 mm
(3.94" x 3.94" x 2.28")
100 mm x 100 mm x 86.7 mm
(3.94" x 3.94" x 3.41")
Temperature Sensor
(In Sensor Head)
NTC Thermistor
Cable Length 1.5 m
Post Mounting M6 Threaded Taps, Includes
Ø1/2" Post, 75 mm Long
Universal 8-32 / M4 Taps
(Post Not Included)
M6 Threaded Taps, Includes
Ø1/2" Post, 75 mm Long
30 mm Cage Mounting - - Four 4-40 Tapped Holes
Aperture Threads - Internal SM1 -
Removable Heatsink - Yes -
Accessories - Externally SM1-Threaded Adapter Externally SM1-Threaded Adapter
Compatible Consoles PM400, PM200, PM100D, PM100USB, PM100A, and PM320E
  • For complete specifications, please see the Specs tab.
  • Two Minute Maximum Exposure Time
  • Measurement taken with the PM100D console, except for the S425C-L in which the PM400 was used. In all cases, the acceleration circuit was switched off. Resolution performance will be similar with our other power meter consoles.
  • Defined as the measurement uncertainty during calibration at the specified wavelengths for a beam diameter > 1 mm. The ±3% specification was determined by laser calibration, and the ±5% specification was determined through spectral calibration, in which values were interpolated using the laser calibration data and the absorption curve for the absorber. Calibration can be performed at 10.6 µm upon request.
  • Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <1 s) for the S350C and S322C. As the natural response time of the S425C-L is fast, the S425C-L does not benefit from acceleration and this function cannot be enabled. See the Operation tab for additional information.
  • 12 VDC power supply is included.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
S350C Support Documentation
S350CThermal Power Sensor Head, Surface Absorber, 0.19 - 1.1 µm and 10.6 µm, 40 W, Ø40 mm
$1,095.48
Today
S425C-L Support Documentation
S425C-LThermal Power Sensor Head, Surface Absorber, 0.19 - 20 µm, 50 W, Ø25.4 mm
$858.00
3-5 Days
S322C Support Documentation
S322CThermal Power Sensor Head, Surface Absorber, 0.25 - 11 µm, 200 W, Ø25 mm, Fan Cooled
$1,356.60
Today

High Max Power Density for Pulsed Lasers

Item #a S370C S470C
Sensor Image
(Click Image
to Enlarge)
S370C S470C
Wavelength Range 400 nm - 5.2 µm 250 nm - 10.6 µm
Optical Power Range 10 mW - 10 W (15 Wb) 100 µW - 5 W
(Pulsed and CW)
Input Aperture Size Ø25 mm Ø15 mm
Active Detector Area
Ø25 mm Ø16 mm
Max Optical Power Density 35 W/cm² (Avg.); 100 GW/cm² (Peak)
Detector Type Thermal Volume Absorber (Thermopile)
Linearity ±1% ±0.5%
Resolutionc 250 µW 10 µW
Measurement Uncertaintyd ±3% @ 1064 nm
±5% @ 400 nm - 1064 nm
±3% @ 1064 nm
±5% @ 250 nm - 10.6 µm
Response Timee 45 s (3 s from 0 to 90%) 6.5 s (<2 s from 0 to 90%)
Cooling Convection (Passive)
Housing Dimensions
(Without Adapter, if Applicable)
75 mm x 75 mm x 51.2 mm
(2.95" x 2.95" x 2.02")
45.0 mm x 45.0 mm x 18.0 mm
(1.77" x 1.77" x 0.71")
Temperature Sensor
(In Sensor Head)
N/A N/A
Cable Length 1.5 m
Post Mounting M6 Threaded Taps, Includes
Ø1/2" Post, 75 mm Long
Universal 8-32 / M4 Tap
(Post Not Included)
30 mm Cage Mounting Four 4-40 Tapped Holes -
Aperture Threads - External SM1
Accessories Externally SM1-Threaded Adapter -
Compatible Consoles PM400, PM200, PM100D, PM100A, PM100USB, and PM320E
  • For complete specifications, please see the Specs tab.
  • Two Minute Maximum Exposure Time
  • Measurement taken with the PM100D console for the S370C and with the PM200 for the S470C. In all cases, the acceleration circuit was switched off. Resolution performance will be similar with our other power meter consoles.
  • Defined as the measurement uncertainty during calibration at the specified wavelengths for a beam diameter > 1 mm. The ±3% specification was determined by laser calibration, and the ±5% specification was determined through spectral calibration, in which values were interpolated using the laser calibration data and the absorption curve for the absorber. Calibration can be performed at 10.6 µm upon request.
  • Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <2 s). See the Operation tab for additional information.
  • Designed for Optical Power Measurements of Nd:YAG Lasers
  • Ideal for Applications with High Peak Pulse Powers
  • S370C: Ø25 mm Aperture for Large-Spot-Size Beams
  • S470C: High-Sensitivity for High-Peak-Power Pulses with Low Average Power

The S370C and S470C Thermal Sensors are designed to measure short and highly energetic laser pulses. All of these units are post-mountable for free-space applications and feature NIST-traceable data stored in the sensor connector.

These thermal power sensors are unique in that they have thermal volume absorbers, where our other thermal power sensors have thermal surface absorbers. The volume absorber consists of a Schott glass filter. Incident pulses are absorbed and the heat is distributed throughout the volume. In this way, pulses that would have damaged the absorption coating of a thermal surface absorber are safely measured by these thermal volume absorbers.

The S370C features a large Ø25 mm aperture ideal for large-spot-size beams, and it is compatible with average powers from 10 mW to 10 W (CW).

In comparison, the S470C is faster, as the glass absorber volume is reduced and other design parameters have been optimized for speed. This results in a different optical power range, with the ability to measure powers down to 100 µW. The Ø15 mm aperture is of the S470C is smaller, and it has a lower max average power of 5 W. Its 10 µW resolution is better than the 250 µW resolution of the S370C.

For high-power, pulsed-lasers the S370C and S470C Thermal Sensors can withstand high average and peak power densities. However, for sensors with a broader spectral range or shorter response time, consider one of our  Pyroelectric Energy Sensors.

Thorlabs offers a recalibration service for these sensors, which can be ordered below (see Item # CAL-S200).

Thermal Sensor Absorption Pulsed Lasers
Click to Enlarge

Click Here for Raw Data
This absorption curve is shown over a broader wavelength range than the sensors' operating ranges. See the table for the operating wavelength range of each sensor.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
S370C Support Documentation
S370CThermal Power Sensor Head, Volume Absorber, 0.4 - 5.2 µm, 10 W, Ø25 mm
$1,137.30
Today
S470C Support Documentation
S470CThermal Power Sensor Head, Volume Absorber, 0.25 - 10.6 µm, 0.1mW - 5W, Ø15 mm
$1,157.70
Today

Microscope Slide Thermal Sensor

Item #a S175C
Sensor Image
(Click Image to Enlarge)
Microscope Thermal Sensor
Wavelength Range 0.3 - 10.6 µm
Power Range 100 µW - 2 W
Input Aperture Size 18 mm x 18 mm
Active Detector Area 18 mm x 18 mm
Max Optical Power Density 200 W/cm2
Detector Type Thermal Surface Absorber (Thermopile)
Linearity ±0.5%
Resolutionb 10 µW
Measurement Uncertaintyc ±3% @ 1064 nm;
±5% @ 300 nm - 10.6 µm
Response Timed 3 s (<2 s from 0 to 90%)
Housing Dimensions 76 mm x 25.2 mm x 4.8 mm
(2.99" x 0.99" x 0.19")
Temperature Sensor
(In Sensor Head)
N/A
Cable Length 1.5 m
Housing Features Integrated Glass Cover
Engraved Laser Target on Back
Compatible Consoles PM400, PM200, PM100D, PM100USB, PM100A, and PM320E
  • For complete specifications, please see the Specs tab.
  • Measured with PM200 Touch Screen Console
  • Defined as the measurement uncertainty during calibration at the specified wavelengths for a beam diameter > 1 mm. The ±3% specification was determined by laser calibration, and the ±5% specification was determined through spectral calibration, in which values were interpolated using the laser calibration data and the absorption curve for the absorber. Calibration can be performed at 10.6 µm upon request.
  • Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <1 s). See the Operation tab for additional information.
Microscope Thermal Sensor
Click to Enlarge

The back of the S175C housing is engraved with the sensor specifications and a target for centering the beam on the sensor.
  • Designed to Measure Optical Power at the Sample Plane of a Microscope
  • 76.0 mm x 25.2 mm Footprint Matches Standard Microscope Slides
  • Wavelength Range: 300 nm - 10.6 µm
  • Sensitive to Optical Powers from 100 µW to 2 W
  • Information Stored in Connector
    • Sensor Data
    • NIST- and PTB-Traceable Calibration Data

The S175C Microscope Slide Thermal Power Sensor Head is designed to measure the power at the sample in microscopy setups. The thermal sensor can detect wavelengths between 300 nm and 10.6 µm at optical powers between 100 µW and 2 W. The sensor head's 76.0 mm x 25.2 mm footprint matches that of a standard microscope slide and is compatible with most standard upright and inverted microscopes.

The thermal sensor has an 18 mm x 18 mm active area and is contained in a sealed housing behind a glass cover. An immersion medium (water, glycerol, oil) may be placed over the glass cover plate.

As seen in the image to the right, the bottom of the sensor housing features a laser-engraved target to aid in aligning and focusing the beam. In standard microscopes, the target can be used for beam alignment before flipping the sensor head to face the objective for power measurements. In inverted microscopes, turn on the trans-illumination lamp and align the target on the detector housing with the beam; this will center the sensor in front of the objective.


Click to Enlarge

Click Here for Raw Data
Typical absorption curve for the S175C (glass and absorber). Note that this curve is representative, and the actual absorption across the spectrum will vary from unit to unit.

Sensor specifications and the NIST- and PTB-traceable calibration data are stored in non-volatile memory in the sensor connector and can be read out by the latest generation of Thorlabs power meters. We recommend yearly recalibration to ensure accuracy and performance. Calibration may be ordered using the CAL-S200 recalibration service available below. Please contact Tech Support for more information.

The complete set of specifications are presented on the Specs tab above. Thorlabs also offers a Microscope Slide Sensor Head with a photodiode sensor for low-power, high-resolution measurements; the full presentation may be found here.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
S175C Support Documentation
S175CCustomer Inspired! Microscope Slide Thermal Power Sensor, 300 nm - 10.6 µm, 2 W
$1,137.30
Today

Internally SM1-Threaded Fiber Adapters

These internally SM1-threaded (1.035"-40) adapters mate connectorized fiber to any of our externally SM1-threaded components, including our photodiode power sensors, our thermal power sensors, and our photodetectors.

    Please contact Tech Support if you are unsure if the adapter is mechanically compatible.

    Item #S120-FCS120-SMAS120-STS120-SCS120-LC
    Click Image to Enlarge S120-FC S120-SMA S120-ST S120-SC S120-LC
    Fiber Connector Typea FC/PCb SMA ST SC LC
    Thread Internal SM1 (1.035"-40)
    • Other Connector Types Available upon Request
    • In certain angle-independent applications, this adapter may also be used with FC/APC connectors.
    Based on your currency / country selection, your order will ship from Newton, New Jersey  
    +1 Qty Docs Part Number - Universal Price Available / Ships
    S120-FC Support Documentation
    S120-FCFC/PC Fiber Adapter Cap with Internal SM1 (1.035"-40) Thread
    $39.78
    Today
    S120-SMA Support Documentation
    S120-SMASMA Fiber Adapter Cap with Internal SM1 (1.035"-40) Thread
    $39.78
    Today
    S120-ST Support Documentation
    S120-STST/PC Fiber Adapter Cap with Internal SM1 (1.035"-40) Thread
    $39.78
    Today
    S120-SC Support Documentation
    S120-SCSC/PC Fiber Adapter Cap with Internal SM1 (1.035"-40) Thread
    $49.98
    Today
    S120-LC Support Documentation
    S120-LCLC/PC Fiber Adapter Cap with Internal SM1 (1.035"-40) Thread
    $49.98
    Today

    Recalibration Service for Thermal Power and Pyroelectric Energy Sensors

    Sensor Type Sensor Item #s
    Thermal Power S175C, S302Ca, S305Ca, S310Ca, S314Ca, S322C, S350C, S370C, S401C, S405C, S415C, S425C, S425C-L, S470C
    Pyroelectric Energy ES111C, ES120C, ES145C, ES220C, ES245C
    • This former catalog item is now offered as a special.

    Thorlabs offers recalibration services for our thermal power and pyroelectric energy sensors. To ensure accurate measurements, we recommend recalibrating the sensors annually. Recalibration of the console is included with the recalibration of a sensor at no additional cost. If you wish to recalibrate only your power meter console, please contact Tech Support for details.

    The table to the right lists the sensors for which this calibration service is available. Please enter the Part # and Serial # of the sensor that requires recalibration prior to selecting Add to Cart.

    Based on your currency / country selection, your order will ship from Newton, New Jersey  
    +1 Qty Docs Part Number - Universal Price Available / Ships
    CAL-S200 Support Documentation
    CAL-S200Recalibration Service for Thermal Power and Pyroelectric Energy Sensors
    Part Number:  Serial Number:
    $182.58
    Lead Time

    * A member of our team will contact you with an RMA Number and return instructions. Please do not ship your item prior to being contacted.

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