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Proceedings Paper

A robust optical parametric oscillator and receiver telescope for differential absorption lidar of greenhouse gases
Author(s): Iain Robinson; James W. Jack; Cameron F. Rae; John B. Moncrieff
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Paper 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.

Paper Details

Date Published: 20 October 2015
PDF: 7 pages
Proc. SPIE 9645, Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing XI, 96450U (20 October 2015); doi: 10.1117/12.2197251
Show Author Affiliations
Iain Robinson, The Univ. of Edinburgh (United Kingdom)
James W. Jack, The Univ. of Edinburgh (United Kingdom)
Cameron F. Rae, Univ. of St. Andrews (United Kingdom)
John B. Moncrieff, The Univ. of Edinburgh (United Kingdom)

Published in SPIE Proceedings Vol. 9645:
Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing XI
Upendra N. Singh; Doina Nicoleta Nicolae, Editor(s)

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