Development of bright THz emitter using doubly resonant one-dimensional photonic crystal in near and far infrared region

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The aim of this project is development of bright THz emitter using doubly resonant one-dimensional photonic crystal in near and far infrared region. We performed several investigations in order to archive our aim as below.1. Fabrication of THz one dimensional photonic crystal (1D-PC) structuresTHz time domain spectroscopy system using femtosecond pulse laser system was constructed in order to measure THz 1D-PC. We fabricated 1D-PC made of organic polymers or semiconductor substrates by simple stacking. We successfully observed photonic band gap or photon localized mode in THz region in transmission spectra of 1D-PC made of organic polymers or semiconductor substrates.2. Enhancement of THz generation in 1D-PC in near and far infrared regionWe fabricated the cavity type THz 1 D-PC with a ZnTe crystal in order to amplify the THz light. Unfortunately we observed the poor enhancement effect using THz 1D-PC because of the reduction of incident pulses intensity at the each surfaces of layers. In order to avoid this problem, we put anti-reflection multi-layer coatings for infrared excitation light using two kinds of the organic polymers on the polypropylene films. As a result, we observed 1.5 times larger THz amplitude in the THz 1D-PC with anti-reflection coatings compared with the ZnTe crystal at several specific frequencies.3. Optical properties of GaNAs super latticeWe paid attention to GaNAs quantum nano-structures as future photoconductive antenna for THz generation. The structures were grown by modulated N radical beam sequence of RF-MBE which we were developed. In this project, we investigated structural properties and optical properties in near infrared region.