Ppb-level NH photoacoustic sensor combining a hammer-shaped tuning fork and a 9.55 µm quantum cascade laser.

We present a quartz enhanced photoacoustic spectroscopy (QEPAS) gas sensor designed for precise monitoring of ammonia (NH) at ppb-level concentrations. The sensor is based on a novel custom quartz tuning fork (QTF) with a mid-infrared quantum cascade laser emitting at 9.55 µm.

Quartz-enhanced photoacoustic NH sensor exploiting a large-prong-spacing quartz tuning fork and an optical fiber amplifier for biomedical applications.

A sensor system for exhaled ammonia (NH) monitoring exploiting quartz-enhanced photoacoustic spectroscopy (QEPAS) was demonstrated. An erbium-doped fiber amplifier (EDFA) with an operating frequency band targeting an NH absorption line falling at 1531.68 nm and capable to emit up to 3 W of optical power was employed.

Compact quartz-enhanced photoacoustic sensor for ppb-level ambient NO detection by use of a high-power laser diode and a grooved tuning fork.

A compact quartz-enhanced photoacoustic sensor for ppb-level ambient NO detection is demonstrated, in which a high-power blue laser diode module with a small divergence angle was employed to take advantages of the directly proportional relationship between sensitivity and power, hence improving the detection sensitivity. In order to extend the stability time, a custom grooved quartz tuning fork with 800-μm prong spacing is employed to avoid complex signal balance and/or optical spatial filter components. The sensor performance is optimized and assessed in terms of optical coupling, power, gas flow rate, pressure, signal linearity and stability.