New Conference publication from Pittcon 2020
“Novel narrow linewidth 785 nm diode laser with enhanced spectral purity facilitates low-frequency Raman spectroscopy”
New technology for low-frequency Raman spectroscopy narrow-linewidth diode lasers facilitates pharmaceutical inspection – Read the latest editorial from Wiley’s Physics Best.
We are happy to be granted permission from Pittcon to share our poster from the March 2020 Conference.
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.
Authors: Magnus Rådmark, Gunnar Elgcrona, Håkan Karlsson
Part of Pittcon 2020 Proceedings: Vibrational Spectroscopy, 614-15P, (3 March 2020).