Time-Resolved SRS Laser Spectroscopy

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200W Pump Laser

Dr. Jun Kojima of the Ohio Aerospace Institute with Dr. David Fischer and Dr. Quang-Viet Nguyen of the NASA Glenn Research Center recently tested a new architecture for SRS laser spectroscopy to realize time-resolved combustion diagnostics.

The new experimental apparatus features a 200 W second-harmonic Nd:YAG pulse laser to measure Raman scattering. This new technology provides much faster gating than previously reported techniques, a wider dynamic range and higher sensitivity in combustion. The high-speed diagnostics are enabled by the utilization of an emICCD camera and the latest 10-kHz laser (Patara-HP200). This technique allows scientists and engineers to capture molecular signatures in combustion in a shorter period (e.g., 3000 shots can be accumulated in 0.3 s to record signal with higher SNR).

Cutting Edge Optronics manufactured the laser that was used as the excitation source. The laser was operated at a 10-kHz repetition rate to interrogate a flame, and the scattering light was collected by fiber-coupled lens optics and transmitted to a volume-transmissive lens spectrograph equipped with the emICCD camera. This diagnostic system reached the highest signal level ever achieved in the NASA facility.

Dr. Kojima’s assessment of the 10-kHz Laser:

CEO’s laser (PATARA 200W pulsed YAG) met our high expectation. The overall engineering quality, balanced optical specification (including highest energy per pulse at 10 kHz), and system controllability excelled over the competitors. My team has built a high-speed (10 kHz) Raman diagnostic system with the laser for multiple applications including high-pressure combustion and rocket plume measurements. I am seeing a new frontier of combustion instability diagnostics with CEO’s lasers.

For more details about the time-resolved SRS set up, click here.

Kojima, J and Shah, M. “Time-Resolved SRS Spectroscopy Facilitates Combustion Research.” Photonics Spectra. Dec. 2013. Apr. 2014.

Approved for Public Release 14-0864
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