Two-Photon Sepctroscopy on Excitons in Cu_2O with Developing a High Precision Spectroscopy Systen

Cu_2O是一种能明显观察到万尼尔激子序列的模型材料。高分辨光谱研究发现，在高质量的Cu_2O晶体中，具有大主量子数的激子态（Rydberg激子态）是稳定的。另一方面，由于激子的玻色-爱因斯坦凝聚（BEC）， Cu_2O中的ls-激子引起了人们的注意。本工作的目的是研究Ryberg激子态和ls激子态，并开发一种新的高精度光谱系统。本工作的主要成果如下：1。研制了一种由连续波调q YAG激光器激发的高重复频率（^-lkHz）可调红外激光器。采用高分辨率单色仪和CCD相机，研制了高分辨率、高灵敏度的光谱系统。测量了3[s-d]和4[s-d]激子双态的反磁位移来识别激子。从外显子的BEC的角度，测量并讨论了与l -正激子双光子激发相关的光学过程。通过对双光子激子激发的发射光谱分析，研究了邻激子的弛豫过程。开发了一种测量液氦温度下Cu_2O光导率和光电效应的系统。测量了Cu_2O的光电效应。证明了单光子和双光子光伏光谱学，并验证了其实用性。

Cu_2O is one of model materials in which Wannier exciton series are clearly observed. It has been found from high resolution spectroscopic studies sofar that exciton states of large principle quantum numbers(Rydberg exciton state)are stable in high quality Cu_2O crystals. One the other hand, ls-excitons in Cu_2O gather much notice due to the Bose-Einstein condensation(BEC)of excitons. The purpose of this work is to examine the Ryberg exciton states and the ls exciton state with developing a new spectroscopy system of high precision. Achievements of this work are as follows ;1.A high repetition(^-lkHz)frequency tunable IR laser excited by a CW Q-swiched YAG laser has been developed. A spectroscopy system of high resolution and high sensitivity has been also developed using a high resolution monochromator and a CCD camera.2.Diamagnetic shifts of 3[s-d]and 4[s-d]exciton doublet states have been measured to identifys and dexciton.3.Optical processes associated with the two-photon excitation of ls-ortho-excitons have been measured and discussed in view of the BEC of extions.4.Relaxation processes of ls-ortho-excitons have been examined from analyzes of emission spectra associated with the two-photon excitation of ls-ortho-excitons.5.A system to measure photo conductivity and photo-voltaic effects of Cu_2O at liquid helium temperature has been developed.6.Photo-voltaic effects of Cu_2O has been measured. One-and two-photon photo-voltaic spectroscopy has been demonstrated and its usefulness has been verified.