Diode-pumped Monolithic Ring Research Articles

Room-temperature mid-infrared laser sensor for trace gas detection

Design and operation of a compact, portable, room-temperature mid-infrared gas sensor is reported. The sensor is based on continuous-wave difference-frequency generation (DFG) in bulk periodically poled lithium niobate at 4.6 mum, pumped by a solitary GaAlAs diode laser at 865 nm and a diode-pumped monolithic ring Nd:YAG laser at 1064.5 nm. The instrument was used for detection of CO in air at atmospheric pressure with 1 ppb precision (parts in 10(9), by mole fraction) and 0.6% accuracy for a signal averaging time of 10 s. It employed a compact multipass absorption cell with a 18-m path length and a thermoelectrically cooled HgCdTe detector. Precision was limited by residual interference fringes arising from scattering in the multipass cell. This is the first demonstration of a portable high-precision gas sensor based on diode-pumped DFG at room temperature. The use of an external-cavity diode laser can provide a tuning range of 700 cm(-1) and allow the detection of several trace gases, including N(2) O, CO(2), SO(2), H(2) CO, and CH(4).

Continuous-wave tunable 87-μm spectroscopic source pumped by fiber-coupled communications lasers

Tunable narrow-band cw difference-frequency generation at 8.7 microm was demonstrated in silver gallium selenide (AgGaSe(2)) at room temperature. The crystal was pumped by an injection-seeded Er/Yb-codoped fiber amplifier at 1.554 microm and a fiber-coupled diode-pumped monolithic ring Nd:YAG laser at 1.319 microm. The difference-frequency output was used for high-resolution spectroscopy of sulfur dioxide (SO(2)).