High-sensitivity detection of TNT.

We report high-sensitivity detection of 2,4,6-trinitrotoluene (TNT) by using laser photoacoustic spectroscopy where the laser radiation is obtained from a continuous-wave room temperature high-power quantum cascade laser in an external grating cavity geometry. The external grating cavity quantum cascade laser is continuously tunable over approximately 400 nm around 7.3 microm and produces a maximum continuous-wave power of approximately 200 mW.

Sub-parts-per-billion level detection of NO2 using room-temperature quantum cascade lasers.

We report the sub-parts-per-billion-level detection of NO2 using tunable laser-based photoacoustic spectroscopy where the laser radiation is obtained from a room-temperature continuous-wave high-power quantum cascade laser operating in an external grating cavity configuration. The continuously tunable external grating cavity quantum cascade laser produces maximum single-frequency output of approximately 300 mW tunable over approximately 350 nm centered at 6.25 microm.

Improved performance of quantum cascade lasers through a scalable, manufacturable epitaxial-side-down mounting process.

We report substantially improved performance of high-power quantum cascade lasers (QCLs) by using epitaxial-side-down mounting that provides superior heat dissipation properties. We used aluminum nitride as the heatsink material and gold-tin eutectic solder. We have obtained continuous wave power output of 450 mW at 20 degrees C from mid-IR QCLs.

Fiber-amplifier-enhanced photoacoustic spectroscopy with near-infrared tunable diode lasers.

A new approach to wavelength-modulation photoacoustic spectroscopy is reported, which incorporates diode lasers in the near infrared and optical fiber amplifiers to enhance sensitivity. We demonstrate the technique with ammonia detection, yielding a sensitivity limit less than 6 parts in 10(9), by interrogating a transition near 1532 nm with 500 mW of output power from the fiber amplifier, an optical pathlength of 18.4 cm, and an integration time constant of 10 s.