Real-time detection of 13CH4 in ambient air by use of mid-infrared cavity leak-out spectroscopy

Sensing hydrocarbons with interband cascade lasers and substrate-integrated hollow waveguides

Tunable diode laser absorption spectroscopy (TDLAS) is an excellent analytical technique for gas sensing applications.

Laser spectroscopy for atmospheric and environmental sensing

Lasers and laser spectroscopic techniques have been extensively used in several applications since their advent, and the subject has been reviewed extensively in the last several decades. This review is focused on three areas of laser spectroscopic applications in atmospheric and environmental sensing; namely laser-induced fluorescence (LIF), cavity ring-down spectroscopy (CRDS), and photoluminescence (PL) techniques used in the detection of solids, liquids, aerosols, trace gases, and volatile organic compounds (VOCs).

Time resolved simultaneous detection of 14NO and 15NO via mid-infrared cavity leak-out spectroscopy

We present a ring-down absorption spectrometer based on a continuous-wave CO laser in the mid-infrared spectral region near lambda = 5 microm. Using a linear ring-down cavity (length: 0.5 m) with high reflective mirrors (R = 99.988 %), we observed a noise-equivalent absorption coefficient of 3 x 10(-10) cm(-1)Hz(-1/2). This corresponds to a noise-equivalent concentration of 800 parts per trillion (ppt) for (14)NO and 40 ppt for (15)NO in 1 s averaging time. We achieve a time resolution of 1 s which allows time resolved simultaneous detection of the two N isotopes. The delta(15)N value was obtained with a precision of +/-1.2 per thousand in a sample with a NO fraction of 11 ppm. The simultaneous detection enables the use of (15)NO as a tracer molecule for endogenous biomedical processes.

Mid-infrared cavity leak-out spectroscopy for ultrasensitive detection of carbonyl sulfide

We present a ringdown absorption spectrometer based on a continuous-wave CO laser in the mid-infrared spectral region near lambda = 5 microm. Using a linear ringdown cavity (length, 0.5 m) with R > = 99.99% mirrors, we observed a noise-equivalent absorption coefficient of 7 x 10(-11) cm(-1) Hz(-1/2). This is 2 orders of magnitude improved compared with previous values. With this setup we studied the spectroscopic detection of carbonyl sulfide (here abbreviated OCS) traces in ambient air and in exhaled breath. We achieved a detection limit of 7 parts in 10(12) (parts per trillion) OCS in ambient air, which is unprecedented and shows great promise for environmental and biomedical applications.

Parts per trillion sensitivity for ethane in air with an optical parametric oscillator cavity leak-out spectrometer

Spectroscopic detection of ethane in the 3-microm wavelength region was performed by means of a cw optical parametric oscillator and cavity leak-out. We achieved a minimum detectable absorption coefficient of 1.6 x 10(-10) cm 1/square root of Hz, corresponding to an ethane detection limit of 6 parts per trillion/square root of Hz. For 3-min integration time the detection limit was 0.5 parts per trillion. The levels are to our knowledge the best demonstrated so far. These frequency-tuning capabilities facilitated multigas analysis with simultaneous monitoring of ethane, methane, and water vapor in human breath.