Abstract
We have developed a direct detection 1.6 μm differential absorption lidar (DIAL) technique to perform range-resolved measurements of vertical CO2 concentration profiles in the atmosphere. Our 1.6 μm DIAL system consists of the optical parametric generator (OPG) and amplifier (OPA) transmitter that excited by the LD pumped Nd:YAG laser with high repetition rate (500 Hz). The OPG system consists of a quasi-phase-matched (QPM) crystal and does not need a cavity. The output power of the OPA system is 6 mJ, the full width at half maximum (FWHM) of the spectrum is about 280 MHz and spectrum purity is 91.0 +- 0.2 ~ 0.5%. CO2 concentration error from fluctuation of the spectrum purity is 0.3% at 6 km altitude and 0.4 % at 10 km altitude.
Highlights
In recent years, there have been significant advances in a QPM nonlinear optical frequency conversion [1, 2]
Optical parametric oscillator (OPO), amplifier (OPA), and generator (OPG) devices are widely recognized as versatile coherent tunable spectroscopic sources
We developed an optical parametric oscillator (OPO) laser system for 1.6 μm CO2 differential absorption lidar (DIAL) [5]
Summary
There have been significant advances in a QPM nonlinear optical frequency conversion [1, 2]. Optical parametric oscillator (OPO), amplifier (OPA), and generator (OPG) devices are widely recognized as versatile coherent tunable spectroscopic sources. We developed an optical parametric oscillator (OPO) laser system for 1.6 μm CO2 DIAL [5]. We have developed a new high-power 1.6 μm laser transmitter based on a parametric master oscillator-power amplifier (MOPA) system pumped by a LD-pumped Q-switched Nd:YAG laser which has the injection seed laser locked to the iodine absorption line. The master oscillator is the OPG system and the amplifier is the OPA system [6]. Since the OPO system has a cavity mirror, running the system without mode hopping requires complex control of cavity length. The OPG system has no cavity mirror, so there is no need to control cavity length. We describe characteristics of the OPG system for the 1.6 μm CO2-DIAL
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