We demonstrate the full frequency stabilization of a Quantum Cascade Laser Frequency Comb by using radio-frequency injection for locking the mode spacing and frequency locking to a crystalline microresonator for stabilizing the offset frequency. A final mode linewidth of 30 kHz over 2 ms is achieved.
In the race toward increasingly high-performance trace-molecule sensors, one of the most significant steps forward in the last decade for photoacoustic sensors was their combination with high-finesse optical cavities. Validated with different configurations, this technique demonstrated enhanced sensitivities below the part-per-trillion level (ppt) and record dynamic ranges. Here we present our advanced cantilever-based photoacoustic setup, based on a custom-made silicon cantilever embedded in a doubly-resonant configuration. The combination of a high-quality-factor acoustic resonator and a high-finesse optical cavity allows a final sensitivity enhancement by several orders of magnitude. The sensor was tested on strong N2O transitions around 4.5 μm wavelength with a continuous-wave quantum cascade laser.
We report a quartz-enhanced photoacoustic sensor (QEPAS) for nitric oxide (NO) detection using a mid-infrared fibercoupled quantum cascade laser (QCL) near 5.2 μm. The QCL radiation was coupled into an InF3 fiber (100 μm core diameter) for light delivery to the quartz tuning fork, a tiny piezoelectric element converting the acoustic wave induced mechanical vibration to the gas-absorption associated electrical signal. This mid-infrared fiber can achieve nearly single-mode light delivery for the target wavelength. The off-beam configuration was adopted for the fiber-coupled detection considering its simpler installation, optical alignment and comparative sensitivity to the traditional on-beam setup.
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