Characteristic research of photoconductive antenna for broadband THz generation

Abstract

Photoconductive effect based on femtosecond laser pulses to generate terahertz (THz) pulses has been analyzed, and broadband THz radiation has been detected effectively by using the free space electro-optic sampling (FE-EOS). Furthermore, THz pulses generated by the home-made photoconductive antenna and transmitted through the air have been detected by the THz time domain spectroscopy (THz-TDS) system, and the influences under different conditions employed on photoconductive antenna for THz generation have been measured and discussed. 1 , communications, noninvasive material and structure detection. In this case, the efficient sources for THz radiation are the first step to be solved. As for THz generation, pure electrical method, pure optical method and mixed method can be all used. For example, nonlinear transmission lines, optical rectification, and photoconductive effect can be used for the broadband THz generation; and for the narrowband THz generation, multiplication circuits, photo-mixing, optical parametric conversion can be used 2, 3 . Because the frequency of the terahertz radiation is too high for the detectors to be detected directly, the Digital Sampling Measurement (DSM) is used to solve this problem. There are two methods based on DSM for THz detection, photo-conductive sampling (PCS) and free space electro-optic sampling (FS-EOS) 4 . Actually, PCS method is based on the reverse process of the photoconductive effect method used in THz generation, and FS-EOS is the reverse process of the optical rectification. In this work, THz pulse has been effectively generated by the home-made photoconductive antenna and detected by the FS-EOS.