Adaptive Control Enhanced Terahertz Radiation with LT-InGaAs Photoconductive Antennas

• Main Authors: Wu Hsiao-Ting, 吳曉婷
• Other Authors: Pan,Ci-Ling
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/81686256341560835957

碩士 === 國立清華大學 === 物理系 === 104 === In this thesis, we display an all-fiber laser (λ=1550nm) system with pulse shaping for enhaning THz generation by a LT-InGaAs photoconductive antennas (PCA). The laser system was designed to reduce the nonlinear effect in fiber component and match the bandwidth of the pulse shaper (C-band waveshaper 4000S) by picosecond chirped pulses. We also introduce a new method to reduce step number of freezing phase algorithm for adaptive control while maintaining the efficiency of pulse shaping. THz time-domain spectrometer uses adaptively controlled THz signal as the feedback signal. We found that the transform-limited pulse (TLP) is not the best incident pulse for THz generation by the PCA. The enhancement in the signal is 1.2 times of THz generation by TLP. In chirp control experiment, we studied the response of THz radiation with different pre-chirped pulses for excitation. We found significant enhancement near 20000, -30000 and -75000 fs2 chirp constant. Peak frequency shift, broadening and narrowing of bandwidth were also observed.