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31 May 2013 Miniaturized diode laser-based light sources for in-situ shifted excitation Raman difference spectroscopy
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Weak Raman bands are often covered by pronounced background signals due to fluorescence or Rayleigh scattering. Several techniques to separate Raman lines from the background are known. In this paper, diode laser based light sources will be presented suitable for shifted excitation Raman difference spectroscopy (SERDS). The two wavelengths are realized by varying the injection current, by addressing two micro-integrated ECLs or by temperature tuning. Due to the freedom of choice in the wavelengths using diode lasers, the emission wavelength can be selected with respect to the addressed application (e.g. the required penetration depth) or the plasmonic resonances of the substrates for surface enhanced Raman spectroscopy. Devices were developed for the wavelengths 488 nm, 671 nm, and 785 nm. The two emission wavelengths each were selected to have a spectral distance of 10 cm-1 according to the typical width of Raman lines of solid or liquid samples. Output powers between 20 mW for the shorter wavelength devices and 200 mW for the red emitting lasers were achieved at electrical power consumptions below 1 W. With a footprint of only 25 x 25 mm2 including all collimation and filter elements, these devices are well suited for portable applications. The diode lasers were implemented into Raman measurement systems. The SERDS signal-to-background ratio was improved by several orders of magnitude.
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Bernd Sumpf, Martin Maiwald, Kay Sowoidnich, and Heinz-Detlef Kronfeldt "Miniaturized diode laser-based light sources for in-situ shifted excitation Raman difference spectroscopy", Proc. SPIE 8718, Advanced Environmental, Chemical, and Biological Sensing Technologies X, 87180D (31 May 2013); doi: 10.1117/12.2017852;

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