A robust optical parametric oscillator and receiver telescope for differential absorption lidar of greenhouse gases

Abstract

We report the development of a differential absorption lidar instrument (DIAL) designed and built specifically for the measurement of anthropogenic greenhouse gases in the atmosphere. The DIAL is integrated into a commercial astronomical telescope to provide high-quality receiver optics and enable automated scanning for three-dimensional lidar acquisition. The instrument is portable and can be set up within a few hours in the field.The laser source is a pulsed optical parametric oscillator (OPO) which outputs light at a wavelength tunable near 1.6 µm. This wavelength region, which is also used in telecommunications devices, provides access to absorption lines in both carbon dioxide at 1573 nm and methane at 1646 nm. To achieve the critical temperature stability required for a laserbased field instrument the four-mirror OPO cavity is machined from a single aluminium block. A piezoactuator adjusts the cavity length to achieve resonance and this is maintained over temperature changes through the use of a feedback loop. The laser output is continuously monitored with pyroelectric detectors and a custom-built wavemeter.The OPO is injection seeded by a temperature-stabilized distributed feedback laser diode (DFB-LD) with a wavelength locked to the absorption line centre (on-line) using a gas cell containing pure carbon dioxide. A second DFB-LD is tuned to a nearby wavelength (off-line) to provide the reference required for differential absorption measurements. A similar system has been designed and built to provide the injection seeding wavelengths for methane. The system integrates the DFB-LDs, drivers, locking electronics, gas cell and balanced photodetectors.The results of test measurements of carbon dioxide are presented and the development of the system is discussed, including the adaptation required for the measurement of methane.

Atmospheric boundary layer height from ground-based remote sensing: a review of capabilities and limitations

“…A DIAL transmits laser beams at two wavelengths exploiting the differential attenuation (Lammert and Bösenberg, 2006) to derive vertical profiles of water vapour (Behrendt et al, 2007) or trace gases such as CO 2 (Gibert et al, 2008), CH 4 (Robinson et al, 2015), ozone (Banta et al, 1998;Ravetta and Ancellet, 1998), or NO 2 (Piters et al, 2012). Thanks to recent developments, compact DIAL systems are becoming increasingly available.…”

Remote Sensing of Atmospheric Methane with IR OPO Lidar System

“…A diode-pumped KTP OPO Nd:YLF laser has been designed and used in the 2-km path integral measurements of carbon dioxide concentration [9]. As a result of further research, a system suitable for field measurements has been created, which allows automated detection of CO 2 and CH 4 in three dimensions [10].…”

Near/Mid IR Differential Absorption OPO Lidar System for Gas Analysis of the Atmosphere

“…Using it, the authors successfully measured path-integral carbon dioxide concentration (path length is ~2 km). As a result of further research [24], a system capable of in-field automatic detection of CO2 and CH4 in three dimensions has been designed [24].…”