Based on Nd:YAG laser, tunable diode laser, electro-optic amplitude modulator and the difference frequency generator, a servo scanning laser source is designed, and the principle of trace gas concentration measurement model is introduced as well, which can realize the gas concentration measurement in the band of mid-infrared and far-infrared. Based on the theory of electromagnetic field, mutual coupling equation about laser transmission in nonlinear crystal and the optical frequency conversion characteristics are analyzed theoretically. As a result, in the range of far-field, electric field intensity of coupled wave increases approximatively exponentially,then tends to be stable.

A novel near space target optical properties modeling method based on the reverse Monte Carlo optical tracking is proposed. Both the environment characteristics in near space and the light transmission characteristics in different detection platform mode are considered and analysis in detail. The invalid light can be eliminated adaptively in this model. According to the phase relationship of target-observing systems-the sun, the optical properties of the target can be obtained. Some numerical simulations are made to test the accuracy and capability of the proposed modeling method.