A widely tunable difference-frequency-generation laser for high-resolution spectroscopy in the 667–865 cm–1 range

Abstract

Mid-infrared (MIR) laser sources are used in a number of applications such as remote sensing, air pollution monitoring, combustion diagnostics, and molecular spectroscopy. Here, we present our work on the development of a MIR laser source based on the difference frequency generation (DFG) process between an external-cavity quantum-cascade-laser tunable over 1750-1835 cm -1 (pump source) and a CO2 gas laser tunable over 921-1083 cm -1 (signal source). The DFG process was realized in a nonlinear, orientation-patterned GaAs crystal, and resulted in an idler spectral range between 667-865 cm -1 with a linewidth of ~2.3 MHz and an output power of up to ~31 µW. Exploiting the fine tunability of our DFG laser source, we performed high-resolution absorption measurements of ethylene (C2H4) and acetylene (C2H2).

Mid-infrared laser-based detection of benzene

“…A long-pass filter (LPF), with a cut-on edge near 11.2 μm, was used to filter out both the pump and signal lasers. More details on our DFG laser can be found elsewhere 15 . The DFG laser setup was placed in a sealed box purged with nitrogen to reduce the effect of ambient water absorption, i.e., strong water absorption lines existing in the EC-QCL spectrum, on the measurements.…”

Laser-Based Sensor for Combustion Diagnostics in Mid-Infrared 11.56 ─ 15 μm

“…A pulsed CO2 gas laser, tunable between 9.23 and 10.86 μm, was used as a signal source to generate idler photons, i.e., DFG laser. Further details on our DFG laser source can be found in [1]. After the OP-GaAs, we used a long-pass filter (LF) to filter out the pump and signal lasers.…”