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Thermal Power Sensors (C-Series)![]()
S425C-L Featuring Removable S350C For Excimer Lasers S401C High Sensitivity S175C 18 mm x 18 mm Aperture Size 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
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 Calibration Power Meter Compatibility Recalibration Services Sensor Upgrade and Service
Thorlabs' Thermal Power Sensors (C-Series)Click on the links in the following list or Selection Guide to move to the indicated specification tables.
High Resolution
Max Power: 10 W
Max Power: 40 W to 200 W
High Max Power Density for Pulsed Lasers
Microscope Slide Thermal Sensor
C-Series Sensor ConnectorD-Type Male
Operational Principle![]() 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. ![]() 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 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 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 ![]() 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 PredictionsThe 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 DisturbancesFor 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 and interfaces for operating our power and energy sensors. Key specifications of all of our power meter consoles and interfaces are presented below to help you decide which device is best for your application. We also offer self-contained wireless power meters and compact USB power meters. When used with our C-series sensors, Thorlabs' power meter consoles and interfaces 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.
The consoles and interfaces are also capable of providing a readout of the current or voltage delivered by the sensor. Select models also feature an analog output. Consoles
Interfaces
Pulsed Laser Emission: Power and Energy CalculationsDetermining whether emission from a pulsed laser is compatible with a device or application can require referencing parameters that are not supplied by the laser's manufacturer. When this is the case, the necessary parameters can typically be calculated from the available information. Calculating peak pulse power, average power, pulse energy, and related parameters can be necessary to achieve desired outcomes including:
Pulsed laser radiation parameters are illustrated in Figure 1 and described in the table. For quick reference, a list of equations are provided below. The document available for download provides this information, as well as an introduction to pulsed laser emission, an overview of relationships among the different parameters, and guidance for applying the calculations.
![]() Click to Enlarge Figure 1: Parameters used to describe pulsed laser emission are indicated in the plot (above) and described in the table (below). Pulse energy (E) is the shaded area under the pulse curve. Pulse energy is, equivalently, the area of the diagonally hashed region.
Example Calculation: Is it safe to use a detector with a specified maximum peak optical input power of 75 mW to measure the following pulsed laser emission?
The energy per pulse: seems low, but the peak pulse power is: It is not safe to use the detector to measure this pulsed laser emission, since the peak power of the pulses is >5 orders of magnitude higher than the detector's maximum peak optical input power. ![]() 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. Refer to the lower right table for power meter console and interface compatibility information. 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 four types of sensors:
Power and Energy Sensor Selection GuideThere 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.
Sensor Options
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Posted Comments: | |
Ronald Sipkema
 (posted 2020-07-14 09:06:51.93) L.S.,
I'm interested in using the S425C in combination with either a PM101 or PM100USB for OEM use / integration into a machine. Is it possible to order the sensor with a different cable length or alternatively shorten or lengthen the fixed cable attached to the sensor head ourselves? What would be practical limits on the cable length from sensor to meter?
Similarly the PM16-425 might also be an interesting solution, except for the fixed cable length and the fact that the combined electronics / USB plug probably won't fit through a cable carrier or cable hose. Are there options for changing cable length on those sensors? dpossin
 (posted 2020-07-16 08:23:45.0) Dear Ronald,
Thank you for your feedback. We did not test at what length the data transfer does not work any more but up to 3m works for sure. We can either offer special power heads with longer cables or you lengthen the cable yourself. The cable of the USB powermeter PM16-425 can be easily extended by a USB to USB extension cable. Alp Ucak
 (posted 2020-06-26 12:09:54.14) Hello, at our laboratory, we are using S350C to measure power. Our beam diameter is about 3mm fwhm and the average power is 25W with 350fs laser pulses. At our measurements, we observe an initial rise and we suspect of the powermeter heating problems. It is getting about 45 celsius degrees. Does that create a problem? Should we use a fan or is there another solution? dpossin
 (posted 2020-07-02 10:02:19.0) Dear Alp,
Thank you for your feedback. Most probably the average power of your laser is too high which leads to the fact that the heat sink is not able to dissipate all the heat. I am reaching out to you in order to provide further help. Joseph Donovan
 (posted 2019-09-18 08:11:55.98) Hi,
I was wondering if the surface of the S425C-L can tolerate short pulsed sources well (the S370C doesn't have enough power handling for our needs).
The laser we're using is 1035 nm, max. power 60W (though will be mostly used around 20W), ~300fs pulses at 1MHz, ~3mm beam diameter. dpossin
 (posted 2019-09-20 02:49:18.0) Dear Joseph,
Thank you for your feedback. We do not tested this but we have at least one customer who uses our high power thermal sensors in the fs regime at a pulse peak power of 0.1 MW. At the repetition rate you would like to use the laser, the operating mode can be seen as quasi CW (continues wave). In case you want to use the laser at a average power of 20W you will get a pulse peak power of about 67 MW. At 20W, the heat dissipation should be no problem but I am a bit concerned if the absorption layer on the detector surface can survive the high peak power. Andrey Kuznetsov
 (posted 2019-04-11 21:31:28.367) What are the noise figures for all the products in units of Watts? This would help to choose a meter based on how sensitive the measurement can be while not being overpowered by the noise. nreusch
 (posted 2019-04-18 05:04:50.0) This is a response from Nicola at Thorlabs. Thank you for your suggestion! The optical power range specification in combination with the resolution (both specified in Watts) should allow you to determine whether your optical signal can be detected. These features contain all limiting factors including noise. gizem.alpakut
 (posted 2019-01-22 08:00:48.627) Hi, I have a question regarding S425C-L and S121C pwoermeter sensors. Whenever I measure a specific power value using both of them, I always get different results. S425C-L always gives 50% less power value than S121C does. I am well aware that S425C-L is a thermal power sensor and other is a photodiode, I used PM100D and PM100USB as power meter consoles, which automatically recognize the console type. What can be the resson for that difference? Is there a way to fix this problem? Thanks in advance. nreusch
 (posted 2019-01-23 10:50:02.0) This is a response from Nicola at Thorlabs. Thank you very much for your inquiry. You are right about the fact that such differences are mostly due to the different nature of both sensors. This is especially the case for e.g. broadband sources, for larger angles of incidence (relevant for the photodiode sensor) or for pulsed sources. I will get back to you directly to discuss your specific application. spanna
 (posted 2018-12-30 14:08:20.63) Dear Thorlabs, I have two questions regarding the S425C-L model:
1. Below what power I can safely remove the heatsink, my laser provides 6mJ (6W @ 1kHz rep.rate) 35fs pulses with 11mm full width 1/e2 spot size?
2. Does the heatsink removal affect the detector calibration or its reading in any way?
Thanks in advance swick
 (posted 2019-01-08 04:00:56.0) This is a response from Sebastian at Thorlabs. Thank you for the inquiry.
1. When measuring low optical powers we recommend for stability reasons to use thermal detectors with heat-sinks.
Removing the heat sink provides the option to use other type of heat-sinks like water-cooling.
2. Calibration should not be affected if heat-sink is replaced with an other appropriate one.
I contacted you directly for further discussion. 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? |
Item #a | S401C | S405C |
---|---|---|
Sensor Image (Click the Image to Enlarge) |
![]() |
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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) |
(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, PM100D, PM100A, PM100USB, PM101A, and PM320E |
Thorlabs offers two broadband thermal power sensors designed to measure low optical power sources with high resolution. Both thermal sensor's broadband coating has a flat spectral response over a wide wavelength range, as shown in the plot below. The aperture size of Ø10 mm allows for easy alignment and measurement of large-spot-size laser sources. For easy integration with Thorlabs' lens tube systems and SM1-threaded (1.035"-40) fiber adapters (available below), both sensors include an externally SM1-threaded adapter.
The S401C uses active thermal background compensation to provide low-drift power measurements. This is implemented through the use of two sensor circuits to measure heat flow between the light absorber and heat sink in both directions. The measurements of the two sensor circuits are then subtracted, which minimizes the effect of thermal drift on the laser power measurement. (For information about how external thermal disturbances can affect thermal power sensor readings, please see the Operation tab.) The S401C's broadband coating offers high absorption at wavelengths between 0.19 and 20 µm (shown in the graph below), which makes it ideal for use with aligning and measuring Mid-IR Quantum Cascade Lasers (QCLs). The included, internally SM05-threaded (0.535"-40) light shield is shown in the photo above.
The S405C has internal SM05 (0.535"-40) threading that is directly compatible with our SM05 lens tubes, and it can also connect directly to Thorlabs' 30 mm Cage Systems.
Thorlabs offers a recalibration service for these sensors, which can be ordered below (see Item # CAL-THPY).
Item #a | S415C | S425C |
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Sensor Image (Click Image to Enlarge) |
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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) |
(2.00" x 2.00" x 1.38") |
(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, PM100D, PM100USB, PM100A, PM101A, and PM320E |
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-THPY).
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-THPY).
Item #a | S350C | S425C-L | S322C |
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Sensor Image (Click Image to Enlarge) |
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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, PM100D, PM100USB, PM100A, PM101A, and PM320E |
Item #a | S370C | S470C |
---|---|---|
Sensor Image (Click Image to Enlarge) |
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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) |
(2.95" x 2.95" x 2.02") |
(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 | - | |
Compatible Consoles | PM400, PM100D, PM100USB, PM100A, PM101A, and PM320E |
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-THPY).
Item #a | S175C |
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Sensor Image (Click Image to Enlarge) |
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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, PM100D, PM100USB, PM100A, PM101A, and PM320E |
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.
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-THPY 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.
These internally SM1-threaded (1.035"-40) adapters mate terminated fiber to any of our externally SM1-threaded components, including a selection of our photodiode power sensors, our thermal power sensors, and our photodetectors.
The APC adapters have two dimples in the front surface that allow them to be tightened with the SPW909 or SPW801 spanner wrench. The dimples do not go all the way through the disk so that the adapter can be used in light-tight applications when paired with SM1 lens tubes.
For details on narrow versus wide key connectors, please see our Intro to Fiber tutorial. Please contact Tech Support if you are unsure if the adapter is mechanically compatible.
Sensor Type | Sensor Item #s |
---|---|
Thermal Power | S175C, S302Ca, S305Ca, S310Ca, S314Ca,S322C, S350C, S370C, S401C, S405C, S415C, S425C, S425C-L, S470C, PM160T, PM160T-HP, PM16-401, PM16-405 |
Pyroelectric Energy | ES111C, ES120C, ES145C, ES220C, ES245C |
Thorlabs offers recalibration services for our Thermal Power and Pyroelectric Energy Sensors. To ensure accurate measurements, we recommend recalibrating the sensors annually. Recalibration of a single-channel power and/or energy meter console or interface is included with the recalibration of a sensor at no additional cost. If you would like to have the PM320E Dual-Channel Power and Energy Meter Console calibrated with a sensor or sensors, please contact Tech Support for ordering information.
Please note that the CAL-THPY recalibration service cannot be used for our Thermal Position & Power Sensors; recalibration for these sensors can be requested by contacting Tech Support.
The table to the upper right lists the sensors for which the CAL-THPY recalibration service is available. Please enter the Part # and Serial # of the sensor that requires recalibration prior to selecting Add to Cart.
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