本所声明  |  联系方式  |  中国科学院  |  数字认证(OA)   |  ARP  |  English  |  邮箱
新闻动态 > 学术活动 > 学术报告

9月14日学术报告

来源： 发布时间：2012-09-06【字体：大 中 小】

题目：Using nonlinear optics for IR detection in wide gap semiconductors

姓名：David J. Hagan

单位：University of Central Florida

时间：2012年9月14日（周五）上午10:00

地点：溢智厅

Abstract:

The magnitude of two-photon absorption (2PA) coefficients in large gap semiconductors are known to follow a universal law that states they scale as the inverse third power of the energy gap, i.e. E_g^(-3), This means that for a given energy gap, the 2PA coefficient is known and cannot be significantly enhanced by band gap engineering or other material modification. However we have now shown that in the highly nondegenerate case, where the input wavelengths are very different, the 2PA rate can be greatly enhanced over the degenerate case. We have recently verified this for several direct gap semiconductors in pump-probe transmission experiments with femtosecond and picosecond pulses, where we showed that, in many direct-gap semiconductors, nondegenerate 2PA coefficients are enhanced approximately 100-fold over the degenerate case. In GaAs, we observed 2PA coefficients around 1 cm/MW. Coefficients this large were previously only observed in narrow-gap semiconductors such as InSb.

Based on this effect, one may obtain sensitive gated detection using conventional semiconductor photodiodes. We have demonstrated this with standard GaN and GaAs photodiodes using extreme non-degenerate photon pairs with up to 14:1 energy ratio. We can also detect weak IR radiation by employing intense UV gating pulses. The minimum detected IR pulse energy in GaN is as low as 20 pJ energy while for a standard cooled MCT detector, the minimum detectable energy is 200 pJ. We have also now demonstrated cw detection using this method. It is worth noting that this process does not use IR crystals or phase-matching, as employed by (2) upconversion detection. In this talk, I will show how this detection scales to other semiconductors and how one might optimize device geometries for practical detection.

Biography:

David Hagan received his PhD degree in Physics at Heriot-Watt University, Edinburgh, Scotland in 1985. From 1985 -87 he was a research scientist at the Center for Applied Quantum Electronics and the University of North Texas. He moved to UCF in 1987 as a founding member of the CREOL faculty, where he is currently Professor of Optics and Physics and also serves as Associate Dean for Academic Programs. He is currently Editor in Chief of the OSA journal, Optical Materials Express and a Fellow of OSA. His current research interests include nonlinear optical materials, especially semiconductors and organics, and techniques for nonlinear optical characterization and spectroscopy.

欢迎大家参加！

所办公室

2012年9月6日

附件下载：

copyright 2000- 中国科学院上海光学精密机械研究所 沪ICP备05015387号-1
主办：中国科学院上海光学精密机械研究所 上海市嘉定区清河路390号(201800)

转载本站信息，请注明信息来源和链接。 沪公网安备 31011402010030号


上海光机所
微信公众号

尚光聚力
微信公众号