Research on divergence angle measurement technique of terahertz sources

The divergence angle is an important measurement index of the beam characteristics of terahertz sources and an important parameter in the design of terahertz optical system. The measurement principle of terahertz source divergence angle was studied, the measuring device was designed, which was composed of precise arc guide rail, chopper, narrow slit components, terahertz Golay detector, lock-in amplifier and computer system. And the calibration module of divergence angle measuring device was also designed, which included auto-collimator, optical angle gauges and CCD camera. And then, the divergence angle of terahertz Schottky frequency doubling source and the terahertz avalanche solid state source were measured. In addition, the uncertainty of measurement results was evaluated, and the uncertainty level reaches to U_\rmrel=3.2% (k=2). The accurate measurement of terahertz source divergence angle provides strong support for deep space detection, tactical communication, anti-stealth, battlefield concealed target recognition and so on.