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INVESTIGATION OF EXCITONIC STATES CREATED BY TWO-PHOTON PAIRS IN PARAMETRIC DOWN CONVERSION.

对参数下转换中双光子对产生的激子态的研究。

基本信息

批准号：
15540318
负责人：
FUJII Atsuhiro
金额：
$ 2.43万
依托单位：
Kumamoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

A nonlinear crystal pumped by laser light emits highly correlated photon pairs with parametric down conversion (PDC) processes. Excitonic state in a solid excited by these PDC photon pairs is thought to be different from those excited by normal two photons. We intended to study the phenomena in TlBr crystals doped with I^- ions.・We studied photo-luminescence due to the excitons in TlBr(I) under one photon excitation by a pulse Ti:S laser (455nm, 10ns) at different temperatures. Two broad emission bands were observed at 2.2 eV and 2.45 eV. Both emission bands decayed non-exponentially above 10 K while those decayed exponentially at 2 K. Analyzing their decay properties, these emission bands are ascribed to the two types of extrinsic self-trapping of the excitons.・We measured photo-luminescence of the excitons in TlBr(I) under normal two-photon excitation process. Two light sources were used : the fundamental of a Ti:S laser pumped by a pulsed Nd:YAG laser and that of a mode-locked Ti:S laser, whose pulse widths were 10ns and about 100fs, respectively. The results show little differences in the luminescence spectra under the one-photon excitation and the two-photon one.・We tried to observe the exciton luminescence under the excitation by entangled photon pairs of PDC light. The second harmonic of the ML Ti:S laser was fed to a nonlinear crystal BBO of Type II in the collinear configuration. The down converted photon pairs were found to be so small that we could not observe the exciton luminescence. Then the BBO crystal was excited by the second harmonic of the Ti:S laser whose pulse width was 10ns. The PDC light was seen to be stronger than that induced by the ML Ti:S laser. We will investigate the exciton luminescence in TlBr(I) under the excitation by entangled photon pairs of this PDC light. In addition we want to improve the output power of the ML Ti:S laser.

非线性晶体在激光泵浦下，通过参量下转换（PDC）过程发射出高度相关的光子对。由这些PDC光子对激发的固体中的激子态被认为不同于由正常的双光子激发的激子态。我们打算研究掺I^-离子的TlBr晶体中的现象。·用脉冲Ti：S激光（455 nm，10 ns）单光子激发TlBr（I），研究了不同温度下TlBr（I）中激子的光致发光。在2.2 eV和2.45 eV处观察到两个宽发射带。两个发射带在10 K以上非指数衰减，而在2 K时呈指数衰减。通过分析它们的衰减特性，这些发射带被归因于激子的两种非本征自陷。·我们测量了TlBr（I）中激子在正常双光子激发下的光致发光。实验采用脉冲Nd：YAG激光泵浦的Ti：S激光器的基频光和锁模Ti：S激光器的基频光，脉冲宽度分别为10 ns和100 fs左右。结果表明，在单光子激发和双光子激发下的发光光谱差别不大。我们试图观察PDC光的纠缠光子对激发下的激子发光。将ML Ti：S激光的二次谐波以共线结构馈入II型非线性晶体BBO。下转换光子对被发现是如此之小，我们不能观察到激子发光。然后用脉冲宽度为10 ns的Ti：S激光的二次谐波激发BBO晶体。PDC光被认为比ML Ti：S激光诱导的光更强。我们将研究这种PDC光的纠缠光子对激发下TlBr（I）中的激子发光。此外，我们还希望提高ML Ti：S激光器的输出功率。