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Narrow-Linewidth Megahertz-Repetition-Rate Optical Parametric Oscillator For High-Speed Flow And Combustion Diagnostics, Naibo Jiang, Walter R. Lempert, Gary L. Switzer, Terrence R. Meyer, James R. Gord
Narrow-Linewidth Megahertz-Repetition-Rate Optical Parametric Oscillator For High-Speed Flow And Combustion Diagnostics, Naibo Jiang, Walter R. Lempert, Gary L. Switzer, Terrence R. Meyer, James R. Gord
Terrence R Meyer
We demonstrate the ability to generate ultra-high-frequency sequences of broadly wavelength-tunable, high-intensity laser pulses using a custom-built optical parametric oscillator pumped by the thirdharmonic output of a "burst-mode" Nd:YAG laser. Burst sequences consisting of 6-10 pulses separated in time by 6-10 Îs are obtained, with average total conversion efficiency from the 355 nm pump to the near-IR signal and idler wavelengths of 33%. Typical individual pulse output energy for the signal and idler beams is in the range of 4-6 mJ, limited by the available pump energy. Line narrowing is demonstrated by means of injection seeding the idler wave using …
Probe-Pulse Optimization For Nonresonant Suppression In Hybrid Fs/Ps Coherent Anti-Stokes Raman Scattering At High Temperature, Joseph D. Miller, Mikhail N. Slipchenko, Terrence R. Meyer
Probe-Pulse Optimization For Nonresonant Suppression In Hybrid Fs/Ps Coherent Anti-Stokes Raman Scattering At High Temperature, Joseph D. Miller, Mikhail N. Slipchenko, Terrence R. Meyer
Terrence R Meyer
Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) offers accurate thermometry at kHz rates for combustion diagnostics. In high-temperature flames, selection of probe-pulse characteristics is key to simultaneously optimizing signal-to-nonresonant-background ratio, signal strength, and spectral resolution. We demonstrate a simple method for enhancing signal-to-nonresonant-background ratio by using a narrowband Lorentzian filter to generate a time-asymmetric probe pulse with full-width-half-maximum (FWHM) pulse width of only 240 fs. This allows detection within just 310 fs after the Raman excitation for eliminating nonresonant background while retaining 45% of the resonant signal at 2000 K. The narrow linewidth is comparable to that of a …