High-sensitivity detectors based on cavity ring-down spectroscopy

Cavity ring-down spectroscopy (CRDS) can provide high sensitivity, high precision, and absolute calibration in a wide range of environments. We report on a compact cavity ring-down spectrometer that can measure atmospheric toxic industrial compounds such as hydrides and hydrazines. The ring-down spectrometer is fully contained in two 5 ¼" tall, 19" wide rack mount enclosures and utilizes a robust, near-infrared, fiber-coupled tunable diode laser. The instrument has a baseline sensitivity of 8 x 10 -11 cm -1 /Hz ½ . We will present the results of this study, which demonstrates the capability to detect toxic gases such as arsine, silane, and hydrazine (simulated using ammonia) in air at parts per billion (ppb) concentrations in less than 1 minute. We will also present results on CRDS instrument performance, including zero drift, precision, absolute accuracy, and linearity over a wide range of environmental operating conditions.