Abstract

A 785 nm grating-coupled external-cavity (EC) laser was fabricated and applied as a light source for shifted-excitation Raman difference spectroscopy (SERDS) to extract Raman signal from the fluorescence background. A simple Littrow-type EC configuration with the grating lines parallel to the p–n junction was applied to narrow the linewidth of a commercially available high-power broad-area laser diode. The characteristics of the EC laser, including wavelength tuning range, output power, and emission spectra, were investigated in detail. A wavelength tuning range of more than 6 nm was realized at an injection current of 900 mA by simply changing the grating rotation angle. The output power after Raman probe coupling exceeded 40 mW and the spectral linewidth was narrowed significantly down to less than 0.1 nm from 0.9 nm (the free-running width). Then, five shifted emission lines were used for the Raman measurement with sesame oil as the target, whose Raman signal was overwhelmed in the fluorescence background. Due to the constraint relationship between the signal intensity and the spectral resolution, the best reproducibility of the Raman signal without fluorescence background was obtained when the excitation wavelength interval was fixed at around the linewidth of the Raman peak. In conclusion, the grating-coupled EC laser with flexible wavelength tunability, high output power, and narrow spectral linewidth was demonstrated to be an ideal light source for SERDS application.

© 2017 Optical Society of America

Microsystem 671 nm light source for shifted excitation Raman difference spectroscopy

Martin Maiwald, Heinar Schmidt, Bernd Sumpf, Götz Erbert, Heinz-Detlef Kronfeldt, and Günther Tränkle
Appl. Opt. 48(15) 2789-2792 (2009)

Capability of shifted excitation Raman difference spectroscopy under ambient daylight

Martin Maiwald, André Müller, Bernd Sumpf, Götz Erbert, and Günther Tränkle
Appl. Opt. 54(17) 5520-5524 (2015)

Dual-wavelength diode laser with electrically adjustable wavelength distance at 785  nm

Bernd Sumpf, Julia Kabitzke, Jörg Fricke, Peter Ressel, André Müller, Martin Maiwald, and Günther Tränkle
Opt. Lett. 41(16) 3694-3697 (2016)

Fiber-coupled high-power external-cavity semiconductor lasers for real-time Raman sensing

Ming-Wei Pan, George R. Gray, Lee M. Smith, Robert E. Benner, Carl W. Johnson, and Daniel D. Knowlton
Appl. Opt. 37(24) 5755-5759 (1998)

Shifted-excitation Raman difference spectroscopy for in vitro and in vivo biological samples analysis

Mário Augusto da Silva Martins, Dayana Gonçalves Ribeiro, Edson Aparecido Pereira dos Santos, Airton Abrahão Martin, Adriana Fontes, and Herculano da Silva Martinho
Biomed. Opt. Express 1(2) 617-626 (2010)