Progress toward mid-IR chip-scale integrated-optic TDLAS gas sensors

We are building prototype chip-scale low-power integrated-optic gas-phase chemical sensors based on mid-infrared (3-5μm) Tunable Diode Laser Absorption Spectroscopy (TDLAS). TDLAS is able to sense many gas phase chemicals with high sensitivity and selectivity. Novel gas sensing elements using low-loss resonant photonic crystal cavities or waveguides will permit compact integration of a laser source, sampling elements, and detector in configurations suitable for inexpensive mass production. Recently developed Interband Cascade Lasers (ICLs) that operate at room temperature with low power consumption are expected to serve as monochromatic sources to probe the mid-IR molecular spectral transitions. Practical challenges to fabricating these sensors include: a) selecting and designing the high-Q microresonator sensing element appropriate for the selected analyte; b) coupling laser light into and out of the sensing element; and c) device thermal management, especially stabilizing laser temperature with the precision needed for sensitive spectroscopic detection. This paper describes solutions to these challenges.