Equipment Enhancement for Femtosecond Pump-Probe Apparatus

该合同将用于额外的仪器，以扩大微型传热实验室现有飞秒泵探针实验装置的效用。目前的实验利用了来自被动锁模Ti:Sapphire激光器的超短（~ 190fs）脉冲。该激光器以76兆赫兹的重复频率产生约16 nJ/脉冲的脉冲。在过去的七年中，该装置已成功地用于瞬态热反射实验，以测量金属薄膜中的热输运。它还被用于瞬态热传导实验，以研究用于光伏电池的氢化非晶硅（a-Si:H）和类似合金薄膜样品中的快速载流子动力学。最近，它已被用于获得亚皮秒分辨率的瞬态反射率的磷化铟（InP）基薄膜在热载子弛豫。这些实验对这些薄膜材料的热物理性质以及光学和电子性质提供了更好的理解。将再生放大器系统添加到当前设置中，将产生具有相似时间和光谱特性的超短脉冲，但脉冲能量增加了两个数量级以上，并且从单次射击到~300 kHz的重复频率可调。该系统具有提供高脉冲能量（使熔化和高度非平衡系统的研究成为可能）和显著降低重复率（使低导热材料的研究成为可能）的能力，将改进和加强现有的实验，同时使新的研究领域得以追求。微电子和光电子工业的进步在很大程度上取决于薄膜技术的发展。随着薄膜生长和沉积技术的不断改进，这一领域发展迅速。虽然薄膜技术以惊人的速度发展，但我们对微观和纳米结构中能量载体动力学的基本理解并没有跟上。通过这些研究提高对激发态载流子动力学的理解，将证明对光电、微电子和光伏行业等都是有益的。

This award is for additional instrumentation to expand the utility of the existing femtosecond pump-probe experimental setup in the Microscale Heat Transfer Laboratory. The current experiment utilizes the ultra-short (~190 fs) pulses from a passively mode locked Ti:Sapphire laser. This laser produces pulses with ~16 nJ/pulse at a repetition rate of 76 MHz. This facility has successfully been used over the past seven years in transient thermoreflectance experiments to make measurements of thermal transport in thin metallic films. It has also been used in transient thermotransmission experiments to study the fast carrier dynamics in thin film samples of hydrogenated amorphous silicon (a-Si:H) and similar alloys used in photovoltaic cells. More recently it has been used to attain sub-picosecond resolution of the transient reflectance of indium phosphide (InP) based films during hot carrier relaxation. These experiments have provided a better understanding of the thermophysical as well as optical and electronic properties of these thin film materials.The addition of the regenerative amplifier system to the current setup will produce ultrashort pulses of similar temporal and spectral characteristics, but with an increased pulse energy of more than two orders of magnitude and with a tunable repetition rate from single shot to ~300 kHz. This system, with the ability to provide high pulse energy (enabling studies of melting and of highly non-equilibrium systems) and a significantly reduced repetition rate (enabling studies on low thermal conductivity materials), will improve and enhance existing experiments while enabling new areas of research to be pursued. Advancements in the micro- and opto-electronics industries depend greatly on the development of thin film technology. This field has progressed rapidly with continued improvements in film growth and deposition techniques. While thin film technology has grown at a prodigious rate, our fundamental understanding of the dynamics of energy carriers in micro- and nanostructures has not kept pace. An improved understanding of excited carrier dynamics through these studies should prove beneficial for the optoelectronic, microelectronic, and photovoltaic industries, to name just a few.