Development of a compact solid-state laser sensor for detecting distributed, low-concentration widely environmental-pollution molecules

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In this research, a long-path absorption laser system has been developed as a remote sensor of low-concentration atmospheric molecules related to environmental pollution and global warming issues. The compact optical parametric oscillator (OPO) has been constructed for generating tunable infrared pulse beam of 20ns pulse width, 1〜10kHz pulse repetition frequency, 175MHz spectral width, 10〜150mW average power with single and stabilized frequency in the wavelength range of 1.50〜1.93μm and 2.36〜3.68μm. Using the long-path absorption laser radar, the atmospheric methane has been measured using a rough-surface topographic target at 150m range with the signal-to-noise ratio of 100, and the absorption accuracy of 10^<-2> in 1s integration time.Further improvement is possible in the system characteristics by increasing the laser efficiency and reducing the system noise to realize estimated ideal performance. Other molecules such as CO_2 and N_2O are possible to be detected with this system scheme.Application field of this sensor system covers 1) measurement of wide-area molecular density and spatial integrated height distribution using proper targets over the traffic loads, factories, airports and urban area, 2) new mobile systems based on a compact car and airplane are possible to measure transport characteristics of global air pollution and atmospheric environmental properties In a higher pulse energy model