Study of pulsed terahertz wave emission and detection from III-V and II-VI materials.

摘要

Pulsed terahertz (THz) wave technology that utilize ultrafast laser for THz wave generation and detection has been developing for decades. In this dissertation we will study several types of semiconductors for the purpose of powerful THz wave generation and broadband THz wave detection.; Bulk semiconductor materials have been demonstrated to generate pulsed THz waves primarily by one of two processes: optical rectification (second order nonlinear effect) or ultrafast transport of charged carriers. There are also several methods using semiconductors as the pulsed THz wave detectors. In this dissertation we focus on studying the THz wave detection by EO sampling.; The THz wave from a n-type GaAs can be enhanced by growing Beryllium (Be)-doped low-temperature-grown (LTG) GaAs layers on the surface of bulk GaAs. The modified structure can radiate THz transients with power four times greater than reference emitters without LTG GaAs layers.; Both our calculation and experiments of THz wave radiation from InAs wafers irradiated with femtosecond pulses indicate that a wafer with a low carrier concentration is better as a THz wave source than another with a high carrier concentration.; ZnTe crystals have been the most widely used emitters and sensors of THz pulses at far-IR range. Our research of the generation and detection of THz waves from (110)-oriented ZnxCd1-xTe crystals indicate the optimum composition is x = 0.05 with a Ti:sapphire laser.; GaSe crystals were studied for the broadband detection of THz waves. The THz electric field amplitude measured with a GaSe crystal exceeds that detected by a ZnTe crystal with comparable detection bandwidth. The ultra-broadband THz spectrum generated and detected with a 10 mum crystal has reached 100 THz.; The above studies of THz wave emitters and detectors provide advanced solutions toward high power generation, sensitive detection and broad THz wave spectrum. These results will significantly benefit the modern applications of pulsed THz wave technology.