Microscopy cryostat system for exploring how intense THz pulses affect ultrafast photoluminescence dynamics in organic semiconductors and nanomaterials

探索光激发材料的光发射动力学提供了对材料基本性质的独特见解，并且可以对新型光子器件结构的发展产生重大影响。时间分辨光致发光（PL）是研究短激光脉冲照射下材料瞬态发光的常用技术。半导体、有机材料和纳米材料的光致发光通常是由称为激子的光激发引起的电子-空穴复合的结果。在许多情况下，材料的光发射的积累和衰减时间可以发生在皮秒的时间尺度上，这需要使用超快激光源和测量技术来实际观察这种快速过程。可能影响材料中PL动力学的因素包括样品形态、温度和高电场的存在，这些高电场往往会破坏激子并可能熄灭PL。我们建议使用强太赫兹（THz）脉冲的天线耦合，以实现高度局域化、皮秒持续时间、然后研究这些太赫兹电场瞬态随温度的变化对PL动力学的影响。我们已经在太赫兹脉冲，非线性太赫兹动力学，以及有机半导体和纳米材料的超快时间分辨太赫兹光谱方面拥有丰富的经验。（我们是加拿大第一个对材料进行时间分辨太赫兹光谱实验的实验室，也是世界上第一个使用该技术探测有机半导体中的带状输运的实验室。）本文要求的显微低温恒温系统将使我们能够在低温下对有机半导体和纳米材料进行微米空间分辨率和超快皮秒时间分辨率的PL测量，同时对样品施加强太赫兹脉冲。这种以前从未尝试过的方法，将为探测材料的光发射动力学和理解有机半导体和纳米材料中的激子解离机制提供一个强大的新工具。

Exploring the dynamics of light emission from photoexcited materials provides unique insight into the fundamental nature of materials and can have significant impact on the development of new photonic device structures. Time-resolved photoluminescence (PL) is a common technique for studying transient light emission from materials illuminated by short laser pulses. Photoluminescence from semiconductors, organic materials, and nanomaterials is typically the result of electron-hole recombination from photoexcitations called excitons. In many cases, the build-up and decay times of light emission from a material can occur over picosecond time scales, requiring the use of ultrafast laser sources and measurement techniques in order to actually observe such fast processes. Factors that may influence the PL dynamics in materials include sample morphology, temperature, and the presence of high electric fields that tend to break apart the excitons and possibly quench the PL. We propose to use antenna coupling of intense terahertz (THz) pulses in order to achieve highly localized, picosecond-duration, high-amplitude electric-field transients in photoexcited materials and then study the effects of these THz-electric-field transients on the PL dynamics as a function of temperature. We already have extensive experience with terahertz pulses, nonlinear terahertz dynamics, and ultrafast time-resolved THz spectroscopy of organic semiconductors and nanomaterials. (We were the first lab in Canada to perform time-resolved THz spectroscopy experiments on materials, and the first lab in the world to use the technique for probing bandlike transport in organic semiconductors.) The microscopy cryostat system requested here will allow us to perform micrometer-spatially-resolved and ultrafast picosecond-time-resolved PL measurements on organic semiconductors and nanomaterials at low temperatures while simultaneously applying intense THz pulses to the samples. This approach, which has never been tried before, would provide a powerful new tool for probing the dynamics of light emission from materials and understanding exciton dissociation mechanisms in organic semiconductors and nanomaterials.