Modulation cancellation method for measurements of small temperature differences in a gas.

An innovative spectroscopic technique based on balancing and cancellation of modulated signals induced by two excitation sources is reported. For its practical implementation, we used quartz-enhanced photoacoustic spectroscopy as an absorption-sensing technique and applied the new approach to measure small temperature differences between two gas samples. The achieved sensitivity was 30 mK in 17 s.

Resonant optothermoacoustic detection: technique for measuring weak optical absorption by gases and micro-objects.

We report a laser spectroscopy technique for detecting optical absorption in gases and micro-objects via linked thermal effects and by using a sharp mechanical resonance in a quartz crystal. The performance of this technique is studied using near-IR diode lasers and two gases, pure CO(2) and C(2)H(2) diluted in nitrogen. A 7.

Ultrasensitive detection of nitric oxide at 5.33 microm by using external cavity quantum cascade laser-based Faraday rotation spectroscopy.

A transportable prototype Faraday rotation spectroscopic system based on a tunable external cavity quantum cascade laser has been developed for ultrasensitive detection of nitric oxide (NO). A broadly tunable laser source allows targeting the optimum Q(3/2)(3/2) molecular transition at 1875.81 cm(-1) of the NO fundamental band.