Fast rate dual-comb spectrometer in the water-transparent 7.5-11.5†µm region.

We introduce a dual-comb spectrometer based on erbium fiber oscillators at 250 MHz that operates in the 7.5-11.5 µm spectral range over optical bandwidths up to 9 THz with a multi-kHz acquisition rate. Over an observation bandwidth of 0.8 THz, the signal-to-noise ratio per spectral point reaches 168 Hz0.5 at an acquisition rate of 26 kHz, which allows the investigation of transient processes in the gas phase at high temporal resolution. The system also represents an attractive solution for multi-species atmospheric gas detection in open paths due to the water transparency of the spectral window, the use of thermo-electrically cooled detectors, and the out-of-loop phase correction of the interferograms.

Laser-based sensing in the long-wavelength mid-infrared: chemical kinetics and environmental monitoring applications.

We present chemical kinetics and environmental monitoring applications in the long-wavelength mid-infrared (LW-MIR) region using a new diagnostic that exploits a widely tunable light source emitting in the LW-MIR. The custom-designed laser source is based on a difference-frequency generation (DFG) process in a nonlinear orientation-patterned GaAs crystal. The pump laser, an external-cavity quantum cascade laser, is tuned in a continuous-wave (cw) mode, while the signal laser, a C O 2 gas laser, is operated in a pulsed mode with a kilohertz repetition rate. The idler wavelength can be tuned between 11.58 (863.56c m -1) and 15.00 µm (666.67c m -1) in a quasi-cw manner. We discuss the unique prospective applications offered by probing the LW-MIR region for chemical kinetics and environment-monitoring applications. We showcase the potential of the DFG laser source by some representative applications.