Modular Raman Spectroscopy Kit


  • 2.3 mm x 3.2 mm Coded Input Aperture
  • 7.8 cm-1 to 9.7 cm-1 Spectral Resolution
  • Typical Signal-to-Noise Ratio: 700:1
  • Modular Design for Easy Customization

Application Idea

The RSB1(/M) Base Unit mounted to the included MB1824 (MB4560/M) breadboard.

RSBR1(/M)

Reflective Front End Shown with the RSB1(/M) Base Unit (Items Sold Separately; Breadboard Not Shown)

RSBC1(/M)

Cuvette Front End Shown with the RSB1(/M) Base Unit (Items Sold Separately; Breadboard Not Shown)

Related Items


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Building a Complete System from the Thorlabs Raman Spectroscopy Kit

A complete Raman spectroscopy system must include:

  • 1 RSB1(/M) Spectrograph Base Unit
  • 1 Front End for Collecting Raman Signal
    • RSBR1(/M) Reflective Front End
    • RSBC1(/M) Cuvette Front End
    • Custom-Built Front End
  • 785 nm Excitation Source (See Laser Requirements tab; Sold Separately)
  • PC for Running the Thorlabs OSA Raman Software (User Supplied)

Note: Do not mix imperial base units with metric front ends or vice versa. The input aperture height between imperial and metric units differs slightly due to the mounting posts.

Key Specificationsa
Input Aperture Size 2.3 mm x 3.2 mm
Wavelength Detection Range
at 785 nm Excitation
500 cm-1 to 1800 cm-1
Spectral Resolution <9.7 cm-1 at 500 cm-1
<7.8 cm-1 at 1800 cm-1
Spectral Accuracy <2.3 cm-1 at 500 cm-1
<1.8 cm-1 at 1800 cm-1
Exposure Time 1000 ms to 20 s
Signal-to-Noise Ratio (SNR) 700:1 (Typical)
>300:1 (Min)
Maximum Excitation Power SM-Fiber: 250 mW
MM-Fiber with Ø105 µm Core: 600 mW
  • See the Specs tab for complete specifications.
Raman System Webinar

Features

  • Modular, Large Field-of-View Raman Spectroscopy Kit with a Coded-Aperture Input
  • Designed for 785 nm Excitation and an 815 nm to 915 nm Detection Wavelength Range
  • Attached CMOS Monochrome Camera for Room Temperature Measurements
  • Wavelength and Amplitude Calibrated for Comparison to Spectral Data Bases
  • Optional Adapter for Compatibility with 60 mm Cage System
  • Spectra Recorded with the Included Thorlabs OSA Raman Software

Applications

  • Quantitative Analysis of Chemical Mixtures
  • Identification of Illegal or Dangerous Substances
  • Quality Inspection (Pharmaceuticals, Food, etc.)
  • Monitoring Chemical Processes at Production Sites

The Thorlabs Raman Spectroscopy Kit is a modular spectroscopy system that features a large (2.3 mm x 3.2 mm) coded aperture at the spectrograph input instead of a traditional slit to achieve a high signal-to-noise ratio (700:1), a low power density (at the sample), and room temperature operation. A pseudo-Hadamard mask of order 64, i.e., a defined pattern of elements for intensity modulation, is used at the input to increase the total light throughput of the system while maintaining high spectral resolution; please see the Coded Aperture tab for more information on coded-aperture (CODA) technology. This kit is designed for 785 nm excitation and an 815 nm to 915 nm (500 cm-1 to 1800 cm-1) detection range. A full list of specifications can be found on the Specs tab.

In comparison to traditional slit spectrographs, this kit averages Raman photons from a larger sampling volume, making it ideal for analyzing complex mixtures. The resulting output spectrum is a linear combination of the Raman fingerprints from the various molecules in the sampling volume, which can be identified through comparison to spectral databases.

A complete Raman spectroscopy system must include an RSB1(/M) base unit and a front end for collecting the scattered Raman signal; RSBR1(/M) and RSBC1(/M) front end are sold below. A 785 nm excitation source, as well as a PC for running the Thorlabs OSA Raman software, must be supplied by the user.

Base Units
The RSB1(/M) Base Unit, the core of Thorlabs' Raman spectroscopy system, is a volume-holographic grating imaging spectrograph that includes a coded input aperture and an attached Kiralux® monochrome CMOS camera. This unit is designed for 785 nm excitation; we recommend using the FPV785M VHG-Stabilized Laser or any source that meets the specifications on the Laser Requirements tab. For easy comparison to spectral databases, the base unit is wavelength calibrated, as well as amplitude corrected using a NIST-certified polynomial during factory calibration.

To get started instantly, this kit ships with the necessary accessories for mounting, including an aluminum base, mounting posts, and post clamps. The Thorlabs OSA Raman software, which is needed to acquire spectra, is available on the USB drive included with the base unit. For A full list of items shipped with each base unit, please see the Shipping List tab. Note that a polystyrene calibration sample should be used to accurately determine the laser wavelength; these calibration samples are shipped with each front end or are available for purchase separately below.

Note: The attached Kiralux camera should not be removed; disassembly of the RSB1 base unit will destroy the system calibration.

Reflective, Cuvette, and Custom Front Ends
This modular kit offers two front ends optimized for the collection of Raman-scattered photons from a variety of sample types. The RSB1(/M) reflective front end is designed to examine powder and solid samples, while the RSBC1(/M) cuvette front end is ideal for liquids. To build up a custom front end, the base unit is compatible with Thorlabs optomechanics through the SM1 (1.035"-40) and SM1.5 (1.535"-40) external threading on the aperture or our 60 mm cage system using the RSBA1 adapter (sold below).

Note that when paired with a user-supplied laser source, the front ends provide a free space beam. Necessary laser safety protocols will depend on the user's chosen laser source and the lab environment. Please consult your laser safety officer to ensure the safety of the setup before powering on any laser source.

Software
The Raman base unit ships with a USB stick that contains the Thorlabs OSA Raman Software, a folder with the camera calibration dataset, and a Microsoft Excel spreadsheet with macros for evaluating the excitation laser wavelength.

The Thorlabs OSA Raman Software is used to record Raman spectra, and the user-friendly software GUI allows the user to adjust the integration time of a single measurement, the analog gain, and the black level (pixel offset). The software also allows the user to easily change the axis units from wavelength to wavenumber, apply spectrum smoothing, and automatically correct the camera’s amplitude response with a NIST fluorescence standard for easy comparison to database spectra. For more information on the Raman software suite, please see the Software tab.

Raman Spectroscopy Kit Options

The images below show the possible setups that can be built from the Raman spectroscopy kit components. Each depicts the RSB1/M base unit mounted to an aluminum breadboard (included) with one of the available front ends. Note that the base unit and front ends are sold separately. The Raman kit does not include an excitation source (see the Laser Requirements tab) or PC for running the included software.

Note: Do not mix imperial base units with metric front ends or vice versa. The input aperture height between imperial and metric units differs slightly due to the mounting posts.

Raman Kit with Reflective Frontend
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Raman Spectroscopy Kit Setup for Solid Samples
Raman Kit with Cuvette Frontend
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Raman Spectroscopy Kit Setup for Samples in Cuvettes
Raman Kit with Custom Frontend
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Raman Spectroscopy Kit Setup for Custom Builds

Specifications

This tab describes the specifications for the base units and front ends, as well as specifications for the full kit. 

Contents

 

Raman Spectroscopy Kit Specificationsa
Exposure Time: Technical Limitations 0.036 ms (Min) to 22795 s (Maximum) in 0.022 ms Increments
Exposure Time: Typical Use-Case 1 s (Min) to 20 s (Maximum)b
Signal-to-Noise Ratio (SNR) 700:1 (Typical)
>300:1 (Minimum)c
Typical Amplitude Correction NIST Standard (NIST SRM2241)d
Maximum Excitation Power SM Fiber: 250 mW
MM Fiber with Ø105 µm Core: 600 mWe, f, g
  • These specifications are for a RSB1(/M) base unit used with either a RSBR1(/M) or RSBC1(/M) front end.
  • 1000 ms is the minimum recommended integration time to achieve a SNR of 100:1; 20 s is the maximum integration time supported by the sensor.
  • The SNR is defined as the ratio of the Raman signal intensity to the noise in an area without a peak. The specified SNR was determined from baseline-subtracted, amplitude-corrected Raman spectra of polystyrene (RPB Polysterene Sample Block), and the excitation laser had a wavelength of 785 nm and an excitation power of 300 mW. Signal is the amplitude of the main polystyrene Raman feature at 1001 cm-1. The noise is given by one standard deviation in the spectral region between 1500 and 1540 cm-1. The specified SNR is valid for an integration time of 10 seconds, independent of the camera gain.
  • Relative Intensity Correction Standard for Raman Spectroscopy at 785 nm Excitation
  • Limited by the damage threshold of the integrated filters.
  • A Ø105 µm core armored multimode fiber patch cable is strongly recommended. If a single mode fiber is to be used, the SNR may degrade due to less uniform illumination and the power has to be reduced.
  • The maximum excitation power depends on the stability of the sample. Take care with inflammable, explosive, and absorbing samples.

 

Base Unit Specifications

All technical data are valid at 23 ± 5 °C and 45 ± 15% relative humidity (non-condensing).

Item # RSB1 RSB1/M
Optical Specifications
Wavelength Detection Range 815 nm to 915 nm
Spectral Resolution (FWHM, Wavelength) <0.65 nm
Spectral Accuracy (Wavelength) <0.15 nm
Wavelength Detection Range @ 785 nm Excitation 500 cm-1 to 1800 cm-1
Spectral Resolution (FWHM, Wavenumber) <9.7 cm-1 @ 500 cm-1
<7.8 cm-1 @ 1800 cm-1
Spectral Accuracy (Wavenumber) <2.3 cm-1 @ 500 cm-1
<1.8 cm-1 @ 1800 cm-1
Beam Heighta 3.25"
(82.6 mm)
84.1 mm
(3.31")
Numerical Aperture 0.22b
Input Aperture
Type Coded Aperture (Hadamard, 64th Oder)
Aperture Material Chromium on Fused Silica
Aperture Size 2.3 mm x 3.2 mm
Single Element Size 36 µm x 36 µm
Grating
Type Transmission
Line Density 1624 Lines/cm
Center Wavelength 871 nm
Diffraction Efficiency (@ Center Wavelength, Average Polarization, and AOI = 45°) >80%
Camera/Sensor
Sensor Type Monochrome CMOS, Non-Cooled
Effective Number of Pixels (H x V) 4096 x 2160
Imaging Area (H x V) 14.131 mm x 7.452 mm (0.56" x 0.29")
Pixel Size 3.45 µm x 3.45 µm
ADCc Resolution 12 Bits
General Specifications
Interface to PC Hi-Speed USB 3.0
Dimensions (L x W x H) 6.46" x 5.20" x 1.88"
(164.2 mm x 132.0 mm x 47.6 mm)
Weight (Base Unit) 0.867 kg
Weight (Base Unit and Accessories) 1.86 kg
Ambient Operating Temperature 10 °C to 40 °C (Non-Condensing)
Storage Temperature 0 °C to 55 °C
  • The beam height is measured from the surface of the breadboard to the middle of the input aperture.
  • Design Value for Vignetting to Occur
  • Analog-to-Digital Converter

 

Reflective Front End Specifications

All technical data are valid at 23 ± 5 °C and 45 ± 15% relative humidity (non-condensing).

Item #a RSBR1 RSBR1/M
Optical Specifications
Fiber Connector FC/PC, Wide-Key
Excitation Bandpass Filter, Center Wavelength 785 nm ± 0.6 nm
Longpass Filter, Cut-on Wavelength 805 nm
Angle of Incidence 30°
Collection Geometry Back-Scatteringb
Maximum Excitation Power at Fiber Output 250 mW SM Fiber
600 mW MM Fiber with 105 µm Corec,d,e
Focal Volumef ~10 mm3
General Specifications
Interface to the RSB1(/M) Base Unit SM1 (1.035"-40) Internal Thread
Dimensions (L x W x H)g 3.00" x 3.89" x 4.36"
(76.2 mm x 98.8 mm x 110.6 mm)
75.0 mm x 99.1 mm x 114.6 mm
(2.95" x 3.90" x 4.51")
Weighth 0.5 kg
Ambient Operating Temperature 10 °C to 40 °C (Non-Condensing)
Storage Temperature 0 °C to 55 °C
  • These front ends collimate the excitation laser. When using the front ends incorrectly, a collimated (Class 4) laser beam may be emitted, which is dangerous even at large distances.
  • With Respect to the Angle of Incidence
  • Limited by the Damage Threshold of the Integrated Filters
  • A >Ø105 µm core armored multimode fiber patch cable is recommended. If a SM fiber is to be used, the SNR may degrade due to less uniform illumination and the power has to be reduced.
  • The maximum excitation power depends on the stability of the sample. Take care with inflammable, explosive, and absorbing samples.
  • A depth of focus >1 mm results in a sampling volume of <10 mm3.
  • These are the dimensions of the front end mounted to the breadboard with the sample table and light shield.
  • This weight includes the front end with the light cover and sample table.

 

Cuvette Front End Specifications

All technical data are valid at 23 ± 5 °C and 45 ± 15% relative humidity (non-condensing).

Item #a RSBC1 RSBC1/M
Optical Specifications
Fiber Connector FC/PC, Wide-Key
Excitation Bandpass Filter, Center Wavelength 785 nm ± 0.6 nm
Longpass Filter, Cut-on Wavelength 805 nm
Collection Geometry 90°b
Maximum Excitation Power at Fiber Output 250 mW SM Fiber
600 mW MM Fiber with 105 µm Corec,d,e
General Specifications
Compatible Cuvette Type 10 mm Light Path
Dimensions: 12.5 mm x 12.5 mm x 45 mm (0.49" x 0.49" x 1.77")
Optical Axis Height Above Cuvette Base: 8.5 mm (0.33")
Four Polished Sides
Interface to the RSB1(/M) Base Unit SM1 (1.035"-40) Internal Thread
Dimensions (L x W x H)f 2.66" x 4.54" x 5.19"
(67.5 mm x 115.4 mm x 131.9 mm)
69.3 mm x 115.2 mm x 133.4 mm
(2.73" x 4.54" x 5.25")
Weight 0.5 kg
Ambient Operating Temperature 10 °C to 40 °C (Non-Condensing)
Storage Temperature 0 °C to 55 °C
  • These front ends collimate the excitation laser. When using the front ends incorrectly, a collimated (Class 4) laser beam may be emitted, which is dangerous even at large distances.
  • This collection geometry is with respect to the angle of the excitation laser input orientation in the standard configuration. For changes to the configuration, please see the "Polarization Dependent Raman Spectroscopy" section in the manual.
  • Limited by the Damage Threshold of the Integrated Filters
  • A >Ø105 µm core armored multimode fiber patch cable is recommended. If a SM fiber is to be used, the SNR may degrade due to less uniform illumination and the power has to be reduced.
  • The maximum excitation power depends on the stability of the sample. Take care with inflammable, explosive, and absorbing samples.
  • These are the dimensions with the post at its lowest height, not including the clamp or screws.
Laser Requirements
Wavelength 785 nm ± 0.5 nm
Spectral Bandwidth (FWHM) <0.15 nm
Wavelength Stabilization <0.02 nm
Thermal Stabilization ±0.1 °C (Max)
(Wavelength Stability: <0.02 nm)
Output Power (Max) 600 mWa
Recommended Output Power (Approximate) 250 mW ± 150 mW
Fiber Connector FC/PC
Fiber Core Diameter Ø105 µm
Fiber NA 0.22
  • The maximum excitation power is limited by the excitation bandpass filter and is also a function of what the sample can tolerate. Take care with inflammable, explosive, and absorbing samples.

Recommended Laser for the Raman Spectroscopy System

Raman spectroscopy requires a laser source with a narrowband, stabilized output to produce spectra with clean signatures. Because the number of Raman-scattered photons is linearly proportional to the intensity of the excitation source, the laser should also have a high output power. The laser specifications required for proper operation of Thorlabs' Raman system are shown in the table to the right. Note that, as the sample needs to be illuminated homogeneously, a Ø100 μm to Ø200 μm multimode fiber should be used to guarantee a flat-top profile on the sample after collimation by the front end.

For the best system performance, we recommend using Thorlabs' FPV785M Volume-Holographic-Grating- (VHG) Stabilized Laser. This laser uses a volume holographic grating to provide narrow-linewidth operation at 785 nm, and it is pigtailed to an FC/PC-terminated multimode fiber to accommodate high-power, homogenous sample illumination. To achieve a wavelength-stable output, we also recommend using this laser with our CLD1015 Laser Driver and Temperature Controller.

The use of an armored multimode fiber patch cables with a >Ø105 µm core is strongly recommend even if the laser is fiber pigtailed. Directly connecting to the front end with a non-armored fiber increases the risk of exposure to dangerous radiation in case the fiber becomes damaged.

Note that when paired with a user-supplied laser source, the front ends provide a free space beam. Necessary laser safety protocols will depend on the user's chosen laser source and the lab environment. Please consult your laser safety officer to ensure the safety of the setup before powering on any laser source.

 

Input Fiber Requirements
Fiber Connector to RSBR1(/M) or RSBC1(/M) Front Ends FC/PC
Fiber Type Multimode Fiber
Fiber Core Diameter Ø100 µm (Minimum)
Ø105 µm (Typical)
Ø200 µm (Maximum)
Fiber NA 0.22
Recommended Fiber MR16L01 Armored Fiber Patch Cable

Fiber Specifications

The table to the right shows the specifications required for the fiber that connects the excitation laser to the reflective and cuvette front ends.

Software

Version 3.0

Includes a GUI for acquiring spectra with the RSB1(/M) Base Unit from the Raman Spectroscopy kit.

Software Download
Recommended System Requirements
Operating System Windows® 10 (64-Bit)
Processor (CPU) Intel Pentium 4 or AMD Athlon 64 3000+
Memory (RAM) 2.0 GB
Graphic Card
Resolution (Min)
800 x 600 Pixels
Hard Drive (Min) 2 GB of Available Disk Space (64-Bit)
Interface Free High-Speed USB 3.0 Port

Software for Raman Spectroscopy Kit

Thorlabs' Raman Spectroscopy Kit is controlled by our Thorlabs OSA Raman software package. This software features a straightforward, intuitive, responsive interface that exposes all functions in one or two clicks. Click the software link to the right to download the latest version of the OSA Raman Software package.

 

Cuvette Frontend Setscrews
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The integration time, analog gain, and black level can be adjusted in the settings dialog. Also in this window are the device status icons and the calibration information.
Cuvette Frontend Setscrews
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The OSA Raman software can display data on the primary and secondary vertical axes, which are on the left and right of the graph, respectively. A trace displayed on the secondary axis will have a small arrow displayed next to its icon in the Trace controls bar. The software can handle up to 26 traces.

Software Highlights

The text below summarizes several key features of the OSA Raman software. Complete details on the software are available in the manual (PDF link).

Settings Dialog
The OSA Raman software allows critical parameters for Raman spectroscopy to be adjusted, including the integration time, analog gain, and black level. Also included in the device settings are indicator buttons to show whether the camera is connected to the PC, the saturation state of the camera, and whether acquisition of a new dark image is required. Spectra units can also be set to either wavelength (nm) or wavenumbers (cm-1).

Built-In Tools for Analysis
Robust graph manipulation tools include automatic and manual scaling of the displayed portion of the trace and markers for determining exact data values and visualizing data boundaries. Automated peak and valley tracking tools identify up to 2048 peaks or valleys within a user-defined wavelength range and follow them during continuous spectrum acquisition. Statistical parameters of traces such as standard deviations, RMS values, and weighted averages are available, and a curve fit tool fits polynomial, Gaussian, and Lorentzian functions to the spectrum.

To compare acquired spectra to Raman signatures of known substances, spectra from external databases can be be imported into the software using CSV files.

Data Export
The Raman trace can be saved in the OSA Raman software spectrum file format (.spf2x) or exported into various file formats, including Matlab, Galactic SPC, JCAMP-DX, CSV, and text formats. Note that the OSA Raman software can load but not export .spf2 file formats generated with other Thorlabs OSA software.

Shipping List

The following are shipped with the RSB1(/M) Base Unit:

  • Base Unit for Raman Spectroscopy
  • USB3-MBA-118 USB 3.0 USB Cable (Micro B to A) to Connect the Camera to the PC
  • MB1824 (MB4560/M) 18" x 24" x 1/2" (450 mm x 600 mm x 12.7 mm) Aluminum Breadboard
  • BBH1 Breadboard Lifting Handles
  • 2 x RS2.5P(/M) Ø1" (Ø25.0 mm) Mounting Posts, L = 2.5" (65 mm)
  • 2 x CF125C(/M) Clamping Forks
  • USB Stick with OSA Raman Software and Coded Matrix Calibration Data
  • Quick Reference

The following are shipped with the RSBR1(/M) Front End for Reflective Measurements:

  • Front End for Reflective Measurements
  • Sample Table with a BA2F(/M) Mounting Base
  • RPC Polystyrene Calibration Chip
  • Stray Light Shield
  • Quick Reference

The following are shipped with the RSBC1(/M) Front End for Cuvette Measurements:

  • Front End for Cuvette Measurements
  • TR1.5 (TR40/M) Ø1/2" (Ø12.7 mm) Mounting Post, L = 1.5" (40 mm)
  • PH2E (PH50E/M) Ø1/2" (Ø12.7 mm) Pedestal Post Holder
  • CF125C(/M) Clamping Fork
  • 3500 µL Macro Fluorescence Fused Quartz Cuvette1
  • RBP Polystyrene Block for Calibration
  • Quick Reference

The following are shipped with the RSBA1 Adapter for 60 mm Cage Systems:

  • 2 Mounting Brackets
  • 4 8-32 (9/64" Hex) and 4 M4 (3 mm Hex) Cap Screws
  • Quick Reference

  1. The CV10Q35F Macro Fluorescence Cuvette is an equivalent replacement.
Slit Width and Spectral Resolution
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A spectrograph with a coded aperture uses a slit pattern to increase light throughput while maintaining high spectral resolution. This example shows a Hadamard mask of order 2, while the mask used in the RSB1(/M) base unit is order 64. 
Slit Width and Spectral Resolution
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Traditional imaging spectrographs require narrow slits to achieve high spectral resolution. This limits the light that can pass through the spectrograph.

Coded-Aperature (CODA) Raman Spectroscopy

The Thorlabs Raman Spectroscopy System is based on an imaging spectrograph that features a diffraction grating as the dispersive element. Traditional spectrographs of this design face a trade-off between the desired spectral resolution and the achievable light throughput. This is because the dispersive element produces spectrally separable images of the same slit image. When the slit is wider, the light throughput may be increased, but the spectra may no longer be separable, leading to loss of the spectral information.

In contrast, the Thorlabs' Raman system spectrograph replaces the single-slit input aperture of conventional systems with a defined pattern of multiple slits, which is known as a coded-aperture (CODA) input. This spatial amplitude modulation mask acts as a convolution operator with an orthogonal basis in two dimensions. The resulting mesh image from the sensor is reconstructed using the inverse transform operator. This encoding uses the complete large window of the mask for optical input, while the output spectral resolution is defined by dimensions of a single mask element.

The pure math engine of a Hadamard transform is adopted for the Raman spectroscopy application; please see the reference article for more details1. Hadamard matrices consist of elements that only take values of 1 and -1. Since the -1 element cannot be realized in a real-world mask, our pseudo-Hadamard optical mask maps the -1 to 1 values to intensity modulations from the range of 0 (light blocked) and 1 (pixel transparent). The necessary spectrum reconstruction algorithms are implemented in the supplied Thorlabs OSA Software, as well as corrections for the unavoidable optical distortions due to a large input field. Device specific calibration data for compensation of the exact instrument distortions and transmission characteristics are shipped on a USB with each RSB1(/M) base unit.


References

  1. M.E. Ghem et al., "Static Two-Dimensional Aperture Coding for Multimodal, Multiplex Spectroscopy," Applied Optics, vol. 45, no. 13, 2006.

Polarization-Dependent Raman Spectroscopy

Cuvette and Polarization Orientation
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Coordinate Axes for Polarization Orientation

Controlling the polarization of the excitation and Raman-scattered light can provide information about the symmetry of bond vibrations within a molecule. In the as-delivered configuration (90° geometry), the RSBC1(/M) cuvette front end only detects s-polarized light unless the excitation light is completely unpolarized. The signal strength of peaks resulting from symmetrical vibrational modes can be optimized by rotating the collimator or by adding polarization optics to the excitation and collection paths. Note that due to its 180° geometry, the RSBR1(/M) reflective front end is not sensitive to polarization.

When adjusting any part of the Raman spectroscopy kit, carefully follow laser safety instructions for the user-supplied laser; a collimated laser beam is emitted from the fiber port of the RSBC1 front end and collimator bundle when the user-supplied laser is connected. Any laser should be turned off before modifying the setup.

Background
The symmetry of the bond vibration behind a Raman peak is characterized by the depolarization ratio:

where I|| and I are the peak intensities for parallel and perpendicular polarization of the observed Raman scattered light with respect to the excitation light. A vibrational mode is completely symmetric and referred to as a polarized band when ρ < 0.75. When ρ ≥ 0.75, a vibrational mode is not completely symmetric and is called a depolarized band.

In this application note, excitation light propagates along the z-axis, s-polarized means light polarized in the y-direction, and p-polarized means polarization in the x-direction.

RSBC1(/M) with Polarization Optics
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Excitation and Collection Paths with Polarization Optics Included
Cuvette Frontend Setscrews
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Loosen Two 1/6" (1.5 mm) Setscrews to Rotate the Collimator

Optimizing Raman Signal via Collimator Rotation
In general, excitation light is not completely non-polarized, as the original polarization of the laser source is partially preserved even after passage through a considerable length of multimode fiber. The setup consisting of the RSB1(/M) base unit and RSBC1(/M) cuvette front end only allows for the observation of s-polarized light. The ratio of parallel and perpendicular components contributing to the measured Raman spectrum changes upon rotation of the fiber around the z-axis, which can strongly enhance or attenuate the Raman peaks.

It is not possible to rotate the fiber within the collimator FC/PC fiber port, and fiber rotation around the z-axis can only be achieved by rotating the collimator with the fiber attached to it. To rotate the collimator, loosen the two 1/16" (1.5 mm) nylon-tipped screws that secure it in the fiber input.

When adjusting any part of the Raman spectroscopy kit, carefully follow laser safety instructions for the user-supplied laser; a collimated laser beam is emitted from the fiber port of the RSBC1 front end and collimator bundle when the user-supplied laser is connected. Any laser should be turned off before modifying the setup.

Including Polarization Optics in the Excitation and Collection Path
To accurately determine depolarization ratios, polarization optics can be added to the excitation and collection paths of the Thorlabs Raman system that includes the RSB1(/M) base unit and RSBC1(/M) cuvette front end.

The excitation path can be modified by unscrewing the fiber input and collimator bundle from the front end and mounting them in an optics mount, such as CP33(/M). Then, a half-wave plate and polarizer, mounted in appropriate optics mounts, can be placed in front of the input port of the main body of the front end. The collection path can be modified by unscrewing the baffle assembly from the base unit and inserting a half-waveplate and polarizer. Note that this construction must be made light tight and samples that have increased scattering should have user-supplied baffles to help prevent unwanted straylight from entering the spectrograph.

Note: P-polarized Raman-scattered light is observable in a 180° geometry, i.e. transmission setup. While it is possible to convert the RSBC1(/M) cuvette front end into a 180° setup and observe Raman signal in this configuration, a significant amount of excitation light will reach the camera sensor. This leads to increased background and noise levels in the spectral range of the base unit. In this modified orientation, it is recommended to use additional filters, such as FEL0800 or FELH0800, to supress the excitation light in the Raman-scattered light path.

Slit Width and Spectral Resolution
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Energy Levels of Various Radiation Types

Raman Spectroscopy

Raman Spectroscopy is a well-established technique for the molecular characterization of chemical substances in solid, powder, liquid, or gas forms. It is based on the detection and analysis of Raman scattering emitted from a sample upon exposure to monochromatic light.

Raman Scattering
Atoms in a molecule are held together by chemical bonds. Depending on the strength of these bonds and the geometry of the molecule, there are different ways molecules can vibrate. Each unique mode of vibration can be excited only with a certain, well defined amount of energy. When an exciting photon passes the molecule and excites a vibration mode, the exciting photon loses or gains energy due to the interaction between material and light (Raman effect). The emitted photon becomes subject to inelastic scattering, and the resulting shift in energy and wavelength of the scattered photon due to this inelastic scattering (Raman scattering) is called the Raman shift. Raman spectroscopy measures this Raman shift. 

Raman scattering is a rather rare event and occurs in only about 1 in 1 million exciting photons. It is, therefore, critical to excite the sample with a high-power light source and to collect as much Raman-scattered light as possible for analysis. To generate sufficient Raman scattering, the sample is typically exposed to high-intensity monochromatic laser light.

Because excitation of a whole set of vibrational states of a sample with a defined amount of energy (the exciting laser light) results in material-specific Raman scattering, a measured Raman spectrum may be considered a chemical fingerprint of the substance. The vibrations detected by Raman Spectroscopy differ from those modulating the molecular dipoles, which are observable by IR spectroscopy, and make it a valuable source for material analysis and complementary to other types of vibrational spectroscopy.

Energy Shift Due to Inelastic Scattering
Raman spectroscopy analyzes the shift in energy due to inelastic scattering caused by the Raman effect. The wavelength of the inelastically scattered photon is related to the excitation wavelength through the following energy equation describing the Raman scattering event:

where Evib is the vibrational energy of the molecule affected by the exciting photon, Eout is the energy of the scattered photon, and Ein is the energy of the exciting photon.

The photon energy and molecular vibration frequency are related via the Planck-Einstein relation:

with h = 6.6260715 x 10-34 J⋅s, fin is the incoming photon frequency in Hertz.

Using equations 1 and 2, as well as λ=c/f where c is the speed of light, the wavenumbers or Raman shift of a molecular vibration can be characterized with knowledge of the precise wavelength of the excitation wavelength λin based on the following equation:

Describing Raman scattering in wavelength space is a disadvantage, as it depends on the precise excitation wavelength. However, it is fixed in the Raman-shift scale, or wavenumber scale, in units of cm-1. Therefore, in order to compare Raman spectra of a substance between different experimental setups, Raman spectra are represented as 2D plots of measured relative intensity (Y-axis) in Raman shift of the inelastic scattered light in wavenumbers (cm-1, X-axis). This unit is, in contrast to nanometer, a scale proportional to energy.


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Spectrograph Base Unit

Must be Purchased Separately

  • One of the Following Front Ends:
  • 785 nm Excitation Source (See Laser Requirements Tab)
  • PC for Running the Thorlabs OSA Raman Software

For the full list of components shipped with this base unit, please see the Shipping List tab.

  • Volume-Holographic Grating Imaging Spectrograph with a 2.3 mm x 3.2 mm Coded Aperture
  • Attached and Aligned Monochrome CMOS Camera with a USB 3.0 Interface (Item # CS895MU)*
  • Designed for 785 nm Excitation Wavelength
  • Amplitude Corrected using a NIST-Certified Polynomial (NIST SRM2241)
  • Includes USB with Software and Camera Calibration Data

The RSB1(/M) Base Unit is the core of Thorlabs' Raman Spectroscopy Kit, which is a modular system ideal for detecting low-intensity Raman signal. Designed for a 785 nm excitation laser, spectra are recorded in the 815 nm to 915 nm wavelength range, which corresponds to 500 cm-1 to 1800 cm-1 wavenumbers. Each base unit includes an imaging spectrograph with a volume-holographic grating, a large coded-aperture (CODA) input, and an attached Kiralux Monochrome CMOS Camera; the grating and camera have wavelength-dependent efficiencies that are amplitude-corrected using a certified NIST standard during factory calibration. For optimal extraction of the Raman-scattered light, this base unit uses an internal longpass 805 nm filter.

Coded Aperture Compared to Conventional Slit
Click to Enlarge

Size comparison of the coded aperture and a standard slit aperture. The coded aperture is a pseudo-Hadamard mask of order 64; the white and dark areas represent where light is transmitted through the mask or blocked, respectively.

To assemble a full Raman spectroscopy system, this base unit must be equipped with a front end (see below), a 785 nm excitation source, and a PC. We recommend using Thorlabs' FPV785M VHG-Stabilized 785 nm Laser as the excitation source; however, a full list of required specifications for alternative excitation sources can be found on the Laser Requirements tab.

Each base unit includes an MB1824 (MB4560/M) 18" x 24" x 1/2" (450 mm x 600 mm x 12.7 mm) aluminum breadboard; see the Shipping List tab for a full list of items shipped with the base unit. To mount to the breadboard, the spectrograph housing features three 1/4"-20 (M6 x 1) taps for RS2.5P(/M) mounting posts. Note that this device is isometric and can be mounted upside down using three additional mounting taps located on the top of the housing.

*Note that the attached Kiralux camera should not be removed; disassembly of the RSB1 base unit will destroy the system calibration.

Coded Input Aperture
This base unit utilizes a pseudo-Hadamard mask of order 64 as the aperture, instead of a single slit like conventional spectrographs. With an aperture size of 2.3 mm x 3.2 mm, this spatial amplitude modulation mask improves light-throughput, or the system étendue, allowing enough Raman-scattered light to reach the CMOS sensor for room temperature operation.

Increased étendue of the spectrograph's input also enables a larger spot size (Ø1 to Ø2 mm), which allows sample excitation with an unfocused laser beam. This is ideal for nonhomogeneous samples, such as powders and pills, that require an average over a large area to determine composition. An unfocused excitation beam also results in a lower power density, reducing the risk of laser-induced damage to the sample. For more information on CODA technology, please see the Coded Aperture tab.

RSB1/M with Lens Tube
Click to Enlarge

Ø1.5" Lens Tubes can be attached to the base unit to build up a custom front end.
RSB1/M with Lens Tube
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The OSA Raman Software GUI allows for easy acquisition of Raman spectra, and it includes built-in tools for analysis. Shown here is a spectrum where peak information has been identified with the peak track tool.

Mounting to Front Ends
The Raman base unit features an SM1 (1.035"-40) external thread adapter for mounting the RSBR1 and RSBC1 front ends onto the input aperture. For customer-designed front ends, the base unit also includes an SM1.5 (1.535"-40) external thread adapter, which can be used, for example, with our Ø1.5" lens tubes. Alternatively, the base unit has two 8-32 (M4 x 0.7) taps for the RSBA1 adapter sold below; this can be used to provide compatibility with Thorlabs' 60 mm cage system components.

Amplitude Correction
The components of this spectrograph, such the grating and detector, have wavelength-dependent efficiencies. To compensate for this, these spectrographs are amplitude corrected using a the NIST SRM2241 certified standard during factory calibration, which ensures compatibility with spectral databases. This standard defines a polynomial with relative, quantitative florescence intensity for the base unit detection range expected under 785 nm excitation. All information necessary for automatic amplitude correction is included within the calibration data supplied on the included USB stick; note that the software has this amplitude correction enabled by default.

Software
Each base unit is shipped with a USB stick that contains the Thorlabs OSA Raman software, which is used to record Raman spectra, a folder with the camera calibration dataset, and a Microsoft Excel spreadsheet with macros for evaluating the excitation laser wavelength. The attached Kiralux camera includes a USB interface for compatibility with most computers; see the Software tab for a list of recommended system requirements. Each base unit is shipped with a USB 3.0 cable to connect the camera to the PC.

Note: Do not mix imperial base units with metric front ends or vice versa. The input aperture height between imperial and metric units differs slightly due to the mounting posts.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
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Reflective Front End for Powder and Solid Samples

Must be Purchased Separately

  • RSB1(/M) Base Unit
  • 785 nm Excitation Source (See Laser Requirements Tab)
  • PC for Running the Thorlabs OSA Raman Software

For the full list of components shipped with this front end, please see the Shipping List tab.

RSB1/M Base Unit and RSBR1/M Frontend
Click to Enlarge

A full Raman spectroscopy system configured for solid samples. Included in the setup are a RSB1(/M) Base Unit, a RSBR1(/M) Reflective Front End (with the stray light cover), and an armored FC/PC fiber patch cable for a 785 nm source.
RSBR1(/M) Sample Stage
Click to Enlarge

Sample Stage Components
  • Designed for Use with Powder and Solid Samples
  • FC/PC Fiber-Coupled Input for the Excitation Laser
  • Height-Adjustable Sample Stage for Samples of Varying Thickness
  • Includes Polystyrene Chip Calibration Sample

The RSBR1(/M) Reflective Front End is designed to optimize collection of Raman-scattered light from powder and solid samples. Back-scattered Raman signal collected from the sample is carried through an optical baffle assembly, eliminating unwanted stray light, and then focused onto the coded input aperture of the base unit. Intended for use with a fiber-coupled excitation source, this front end features a FC/PC connector; we recommend using the Thorlabs FPV785M VHG-Stabilized 785 nm Laser. 

The main body of this front end, which includes a 785 nm bandpass filter, an 805 nm longpass filter, and collection mirror, connects to the input aperture of the base unit through the SM1 (Ø1.035"-40) internal threads on the optical baffle assembly. An SM1 locking ring is also included on the optical baffle, which has a factory-set position for ideal performance of the front end.

Each reflective front end includes the main body and attached optical baffle, a height-adjustable sample table, and a stray light cover. Also shipped with each unit is a polystyrene chip calibration sample (Item # RPC); replacement calibration samples can be purchased below. For the full list of components shipped with this front end, please see the Shipping List tab.

Sample Stage
For best performance, the sample needs to be in the focal plane of the collection mirror, which is 2.08" (52.6 mm) or 54.1 mm (2.14") above the breadboard for imperial and metric front ends, respectively. The included sample stage should be positioned directly underneath the window of the RSBR1 front end and can be mounted to the breadboard using the counterbored slots in the included BA2F(/M) mounting base; secure the mounting screws with a 0.2" (5 mm) hex key.

The sample stage is shipped with the sample table at a height optimized for the included polystyrene calibration chip, however, this height is adjustable to accommodate samples of varying thicknesses. For thinner samples, the sample table can be raised by 7.0 mm (0.27") using the locking screw in the BA2F(/M) base and a 3/16" (5 mm) hex key. Thicker samples can be evaluated by removing the 2 mm spacer and 1.5" (38 mm) mounting post and replacing them with a shorter post.

Stray Light Cover
To prevent unwanted light from entering or exiting the setup, a 2-piece stray light cover is included with the reflective front end. The U-shaped bottom piece sits underneath the sample stage and fits around the lens tube of the optical baffle assembly, while the top cover fits around the main body of the front end and sample area. The top cover is secured into place using three 8-32 (M4) cap screws.

This light cover does not fulfill laser safety standards and can only be installed when the laser input port points upward. Also note that when paired with a user-supplied laser source, the front end provides a free space beam. Necessary laser safety protocols will depend on the user's chosen laser source and the lab environment. Please consult your laser safety officer to ensure the safety of the setup before powering on any laser source.

Note: Do not mix imperial base units with metric front ends or vice versa. The input aperture height between imperial and metric units differs slightly due to the mounting posts.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available
RSBR1 Support Documentation
RSBR1NEW!Raman Spectroscopy Kit, Reflective Front End, Imperial
$4,400.00
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Cuvette Front End for Transparent, Semi-Transparent, and Translucent Samples

Must be Purchased Separately

  • RSB1(/M) Base Unit
  • 785 nm Excitation Source (See Laser Requirement Tab)
  • PC for Running Thorlabs OSA Raman Software

For the full list of components shipped with this front end, please see the Shipping List tab.

RSB1/M Base Unit and RSBC1/M Frontend
Click to Enlarge

A full Raman spectroscopy system configured for liquid samples. Included in the setup are a RSB1(/M) base unit, a RSBC1(/M) cuvette front end, and an armored FC/PC fiber for a 785 nm source.
  • Designed for Use with Transparent, Semi-Transparent, and Translucent Materials
  • Adaptable for Polarization-Dependent Raman Measurements
  • FC/PC Fiber-Coupled Input for the Excitation Laser
  • Ideal for 3500 µL Fluorescence Cuvettes with a 10 mm Transmitted Path Length
  • Polystyrene Block Calibration Sample

The RSBC1(/M) Cuvette Front End is designed for Raman spectroscopy measurements on transparent, semi-transparent, and translucent materials. Raman-scattered light is collected in a 90-degree geometry with respect to the excitation source, reducing the amount of stray laser light and Rayleigh-scattered photons that enter the spectrograph. Intended for use with a fiber-coupled excitation source, this front end features a FC/PC-terminated collimator; we recommend using the Thorlabs FPV785M VHG-Stabilized 785 nm Laser.

Each cuvette front end includes the main body, an optical baffle, a 3500 µL fused quartz cuvette, and a light-tight cover. Also shipped with each unit is a polystyrene block calibration sample (Item # RPB); replacement calibration samples can be purchased below. For the full list of components shipped with this front end, please see the Shipping List tab.

The main body of this front end, which includes a CVH100 Cuvette Holder, collimator, a 785 nm bandpass filter, and an 805 nm longpass filter, connects to the input aperture of the base unit through SM1 (Ø1.035"-40) internal threads on the optical baffle assembly.  The distance between the base unit and front end is critical for performance of the Raman kit, and an SM1 locking ring and SM1M05 connecting ring are included on the baffle to achieve the necessary 1.5 mm (0.59") separation. A detailed procedure for setting up this front end can be found in the user manual.

When paired with a user-supplied laser source, the front end collimates the laser for excitation. Necessary laser safety protocols will depend on the user's chosen laser source and the lab environment. Please consult your laser safety officer to ensure the safety of the setup before powering on any laser source.

Compatible Cuvette Specifications
Light Path 10 mm
Dimensions 12.5 mm x 12.5 mm x 45 mm
(0.49" x 0.49" x 1.77")
Optical Axis Height
Above Base
8.5 mm
Polished Sides 4

Cuvette
This front end ships with a 3500 µL UV Fused Quartz cuvette, which has four polished sides, a standard 12.5 mm square outside dimension, and a 10 mm transmitted path length through the sample. The cuvette is engraved with a letter "Q" that designates its quartz construction and the optical window axis, and it comes with a PTFE cap to prevent contamination by dust or other particles. Additional UV Fused Quartz Cuvettes are also available for purchase separately, including the CV10Q35F Macro Fluorescence Cuvette which matches the specifications shown in the table to the left.

The cuvette included with this kit should not be used with benzene, toluene, aqua regia, ethanol, corrosive solutions, or other similar substances, as they may degrade the bonds between the pieces and cause the cuvette to leak.

Polarization-Dependent Measurements
Controlling the polarization of the excitation and Raman-scattered light can provide information about the symmetry of bond vibrations within a molecule. In the as-delivered configuration (90° geometry), this front end only detects s-polarized light unless the excitation light is completely unpolarized. The signal strength of peaks resulting from symmetrical vibrational modes can be optimized by rotating the collimator, which can be done by loosening the 1/16" (1.5 mm) nylon-tipped screws that secure the collimator in the fiber input. It is also possible to include polarization optics into the excitation and collection paths; please see the Polarization tab for more information.

Please note that it is possible to remove the collimator from the front end, which presents the risk of radiation exposure when connected to a user-supplied laser. Necessary laser safety protocols will depend on the user's chosen laser source and the lab environment. Please consult your laser safety officer to ensure the safety of the setup before powering on any laser source.

Note: Do not mix imperial base units with metric front ends or vice versa. The input aperture height between imperial and metric units differs slightly due to the mounting posts.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available
RSBC1 Support Documentation
RSBC1NEW!Raman Spectroscopy Kit, Cuvette Front End, Imperial
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60 mm Cage System Adapter

RSB1/M Base Unit and RSBA1 Adapter for Custom Front End
Click to Enlarge

The RSBA1 Adapter provides compatibility with 60 mm cage system components.
  • Provides Compatibility with Thorlabs' 60 mm Cage System Components
  • Ideal for Attaching Custom-Built Front Ends to the RSB1(/M) Base Unit
  • Each Adapter Includes:
    • Two Brackets
    • Four 8-32 Cap Screws (9/64" Hex)
    • Four M4 Cap Screws (3 mm Hex)

The RSBA1 60 mm Cage System Adapter provides an option for applications that require a custom-built front end for the base unit input aperture. Each adapter consists of two brackets that can be attached to an RSB1(/M) base unit using the included cap screws. Two dowel pins on each bracket fit into holes on the base unit to aid with accurate alignment. Each bracket also features two through holes for our Ø6 mm cage system construction rods; these are spaced apart by 60 mm for compatibility with our 60 mm cage system components. The cage rods can be locked into place using a 5/64" (2 mm) hex key.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
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Replacement Calibration Samples

  • RPC: Replacement Polystyrene Block for the RSBR1(/M) Reflective Front End
  • RPB: Replacement Polystyrene Chip for the RSBC1(/M) Cuvette Front End

The RPC polystyrene chip and RSB polystyrene block are replacement calibration samples for use with the Raman spectroscopy kit front ends.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
RPC Support Documentation
RPCNEW!Polystyrene Chip, Ø25.4 mm, Raman Spectroscopy Kit Replacement Calibration Sample
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RPB Support Documentation
RPBNEW!Polystyrene Block, 12.5 mm x 12.5 mm x 47.0 mm, Raman Spectroscopy Kit Replacement Calibration Sample
$500.00
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