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Proceedings Paper

Novel narrow linewidth 785 nm diode laser with enhanced spectral purity facilitates low-frequency Raman spectroscopy
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Paper Abstract

Raman Spectroscopy enables fast, sensitive and label-free chemical analysis of a large range of materials and has become a routine analytical tool in a wide range of material science and process-control applications. As the Raman signal is weak it is critical that the illumination laser has a very high level of spectral purity, for efficient detection of the Raman signal. Most materials can be characterized by studying Raman shifts down to 100 cm-1, but in some cases, for instance for determining the crystallinity of pharmaceutical compounds, it is required to study Raman shifts in the low-frequency regime; <100 cm-1 . 785 nm is the most common illumination wavelength for Raman spectroscopy as it offers the best compromise between Raman signal strength and fluorescence background suppression. In this paper, we present a novel design for a frequencystabilized 785 nm diode laser using a highly reflective volume Bragg grating (VBG) element that offers not only a narrow spectral linewidth and low wavelength drift, but also a very high level of spectral purity. Using the VBG reflected light as output from the laser suppresses Amplified Spontaneous Emission (ASE) from the diode so that a very high level of sidemode suppression ratio (SMSR) in the laser output is reached within just a few cm-1 away from the main peak without any external spectral filtering. This enhanced spectral purity directly from the laser enables simpler, more compact and more cost-efficient detection of Raman shifts in the very low frequency range.

Paper Details

Date Published: 21 February 2020
PDF: 7 pages
Proc. SPIE 11252, Advanced Chemical Microscopy for Life Science and Translational Medicine, 112521A (21 February 2020); doi: 10.1117/12.2545875
Show Author Affiliations
Magnus Rådmark, Cobolt AB (Sweden)
Gunnar Elgcrona, Cobolt AB (Sweden)
Håkan Karlsson, Cobolt AB (Sweden)

Published in SPIE Proceedings Vol. 11252:
Advanced Chemical Microscopy for Life Science and Translational Medicine
Ji-Xin Cheng; Wei Min; Garth J. Simpson, Editor(s)

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