General Information - THORLABS RSB1 Operation Manual

Raman Spectroscopy Bundle Chapter 1: General Information

1 General Information

This manual describes the use of the Thorlabs components for Raman Spectroscopy, a spec-
trograph and different front ends, suitable for varying applications.
Raman spectroscopy is a technique that detects and analyzes inelastic photon scattering,
known as Raman scattering. Because Raman scattering is material specific and provides a mo-
lecular fingerprint, Raman spectroscopy can be used to identify specific chemicals or mo-
lecules.
One challenge in Raman spectroscopy has long been the low signal-to-noise ratio (SNR) due to
the very weak Raman scattering signal. The low SNR can be overcome with the use of Coded-
Aperture (CODA) technology: The CODA technology uses a two dimensional matrix with a
defined pattern of multiple slits instead of a single slit input aperture. This coded input aperture
with multiple slits allows data acquisition from a larger sampling volume than a single slit input
aperture. This in turn, enables higher sampling rates and an increased SNR. Please find more
general information on Raman spectroscopy and background on Coded-Aperture systems in
the chapter Operating Principle .
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RSB1(/M) Raman Spectrograph
The Thorlabs RSB1(/M) Raman Spectroscopy Base Unit features such a highly optimized spec-
trograph based on the CODA technology with a pseudo Hadamard mask of order 64 and an at-
tached CMOS camera. The geometric size of the coded-aperture's active area is 3.159 mm x
2.304 mm. Due to the coded-aperture technology and the spatial averaging in the analysis, the
Thorlabs Raman spectrograph RSB1(/M) is superior in the analysis of complex mixtures.
Beyond the Coded-Aperture technology, the RSB1(/M) Raman Spectroscopy Base Unit is de-
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signed for 785 nm excitation and a detection range of 500 cm to 1800 cm . The RSB1(/M)
Base Unit can be purchased in an imperial (RSB1) or metric version (RSB1/M). For the purpose
of this manual, RSB1(/M) refers to both versions.
To assemble a full Raman spectroscopy system, the RSB1(/M) needs to be equipped with a
front end which collects the scattered Raman signal for detection and analysis, an excitation
light source at 785 nm, and a PC.
Front Ends RSBR1(/M) and RSBC1(/M)
Thorlabs offers different front ends for variable applications:
The RSBR1(/M) reflective front end is designed to examine powder and solid samples. It
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carries the optical modules which guide the laser light to the sample and collect back-scattered
Raman signal from the sample and focus it onto the RSB1(/M) input aperture. For laser light in-
put, the RSBR1(/M) features an FC/PC connector. A sample table is provided to place a speci-
men at the optimal focal plane. The RSBR1(/M) even allows to analyze samples that are trans-
parently wrapped. The wrapping component can be eliminated from the output spectrum
provided that the focal volume is located within the sample.
The RSBC1(/M) cuvette front end for 10 mm cuvettes is designed to examine transparent,
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translucent, or semi-transparent materials, since Raman scattered light is collected in a 90°
geometry with respect to excitation. Compared to the reflective front end, due to the 90° geo-
metry, this reduces the amount of scattered laser light or Rayleigh scattering that enters the
spectrograph. As for the RSBR1(/M), the laser is connected via a FC/PC connector.
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