From Event: SPIE Optical Engineering + Applications, 2016
Low-wavenumber Raman spectroscopy has long been demonstrated as a method of optical characterization in a variety of applications, such as thermal detection and semiconductor analysis. However, accessing low-wavenumber Raman shifts remains a challenge, usually requiring an expensive and complex multi-stage spectrographic system to measure several cm-1 Raman shifts. In this work, we demonstrate a method to measure low-wavenumber Raman shifts down to 1 cm-1 using atomic filters. By using a narrow-band Faraday anomalous dispersion optical filter to remove spontaneous emission noise from the laser cavity and a heated atomic cell as a notch filter to remove the excitation laser, the system is able to measure low Raman shifts (down to 1 cm-1). To demonstrate the capabilities, we measure the broadband Raman spectrum from a silica optical fiber with approximately 0.3 cm-1 resolution, detecting both Stokes and Anti-Stokes Raman shift as low as 0.7 cm-1.
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