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

本计画的目的是利用一维光子晶体的双共振特性，研制出在近红外与远红外波段都有亮度的太赫兹辐射源。我们进行了几次调查，以存档我们的目标如下。THz一维光子晶体结构的制备为了测量THz一维光子晶体，利用飞秒脉冲激光系统构建了THz时域光谱系统。我们制作了一维PC的有机聚合物或半导体基板通过简单的堆叠。我们成功地在有机聚合物或半导体衬底制成的一维PC的透射光谱中观察到太赫兹区域的光子带隙或光子局域模。一维光子晶体在近、远红外波段产生太赫兹波的增强我们用ZnTe晶体制作了腔型THz一维光子晶体，以放大THz光。然而，我们观察到太赫兹一维光子晶体的增强效果很差，这是因为入射脉冲在各层表面的强度降低。为了解决这一问题，我们采用两种有机高分子材料在聚丙烯薄膜上制备了多层红外增透膜。结果表明，在几个特定频率下，THz一维光子晶体的THz振幅是ZnTe晶体的1.5倍. GaNAs超晶格的光学性质GaNAs量子纳米结构作为未来太赫兹光电导天线受到了人们的关注。该结构是用我们研制的调制N自由基束序列RF-MBE生长的。在本项目中，我们研究了近红外区的结构性质和光学性质。

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.