Acquisition of an Optical Parametric Amplifier (OPA) Laser System

0076429梅林，罗伯特·丹奖授予密歇根大学光学参量放大器（OPA）。OPA将用于产生可调谐的超短光脉冲，利用共振激发探测和控制固体中的相干声子，并研究光生载流子与声子的相互作用。特别是量子点系统，要研究“声子瓶颈”。这一瓶颈对于单极子带间器件（如中红外探测器）非常重要，因为长激发态寿命可以降低噪声，但对于双极子带间器件（如近红外激光器）则不利，因为它限制了调制带宽。热载流子与脉冲产生的相干声子的相互作用是另一个新的探索领域。热载流子应产生受激声子发射，这可能对声子辅助隧道装置中的受控超快隧道和“声子激光器”的发展有用。OPA系统还将用于化学和生物系统的光子回波和荧光上转换测量，特别是光系统II的反应中心。荧光上转换将用于直接探测反应中心的激发态居群，并测试电荷分离过程的模型。光子回波实验将为颜料电子态与溶剂（蛋白质）浴之间的耦合提供重要信息。该仪器将用于培训研究生和本科生，他们将是主要用户。密歇根大学的几个小组将能够在他们的国家科学基金会资助的研究中使用该仪器。***这是一项授予密歇根大学的仪器购置奖。主要研究人员将购买一个光参量放大器（OPA）。当光照射在半导体材料上时，与材料中的原子紧密结合的电子被“释放”出来，在半导体中移动。当电子的初始能量很高时，它们被称为“热”电子。如果激发光是短（飞秒）激光脉冲的形式，那么脉冲就会产生热电子的爆发。这些电子不会保持高温，而是会通过产生晶体振动或“声子”迅速冷却到晶体温度。冷却过程可以用复杂的方法来控制。例如，如果半导体包含量子点，其中的电子状态是离散的，那么冷却速度可以大大降低。降低冷却速率（称为“声子瓶颈”）的研究将有助于开发新的红外探测器和激光器。对这一过程的研究可能会带来新的半导体器件概念。照射在绿色植物光合作用蛋白上的光也会导致电子运动，这一次是在蛋白质中，并通过膜产生氧气和碳水化合物。这台新仪器将用于这类研究以及其他由美国国家科学基金会资助的威斯康星大学的研究。研究生和本科生在精心设计的研究项目中使用这些仪器和技术将受益匪浅。

0076429Merlin, Roberto DAn award is made to the University of Michigan for the acquisition of an Optical parametric Amplifier (OPA). The OPA will be used to generate a tunable ultrashort optical pulses to probe, and control coherent phonons in solids using resonant excitation and to study the interaction of photogenerated carriers with phonons. In particular, quantum dot systems, to investigate "phonon bottleneck". The bottleneck is important for unipolar intersubband devices such as mid-infrared detectors, since a long excited state lifetime enables reduced noise, but detrimental to bipolar interband devices such as near-infrared lasers, as it limits the modulation bandwidth. The interaction of hot carriers with impulsively generated coherent phonons is an additional new area of exploration. The hot carriers should give rise to stimulated phonon emission which may be useful for controlled ultrafast tunneling in phonon-assisted-tunneling devices, and for the development of "phonon lasers." The OPA system will also be used for photon echo and fluorescence up-conversion measurements in chemical and biological systems, particularly reaction centers of photosystem II. Fluorescence up-conversion will be used to probe the excited state population in the reaction centers directly and test models for the charge separation process. Photon echo experiments will provide important information on the coupling between the pigment electronic states and the solvent (protein) bath. The instrument will be used in the training of graduate and undergraduate students who will be the primary users. Several groups at the University of Michigan will be able to use the instrument for their NSF funded research.***This is an instrument acquisition award to the University of Michigan. The principal investigators will purchase an Optical parametric Amplifier (OPA). When light shines on a semiconductor material, electrons which are tightly bound to the atoms in the material are "freed up" to move throughout the semiconductor. When the initial energy of the electrons is high, they are referred to as "hot" electrons. If the exciting light is in the form of a short (femtosecond) laser pulse, then the pulse generates a burst of hot electrons. These electrons will not stay hot, but will rapidly cool down to the crystal temperature by generating crystal vibrations, or "phonons." The cooling process can be controlled in sophisticated ways. For example, if the semiconductor contains quantum dots, in which the electronic states are discrete, then the cooling rate can be vastly reduced. The study of the reduced cooling rate (referred to as the "phonon bottleneck") will be useful for the development of new infrared detectors and lasers. The study of this process may lead to new semiconductor device concepts. Light shining on photosynthetic proteins in green plants also results in electron motion, this time in a protein and across a membrane with the potential used to produce oxygen and carbohydrates. This new instrument will be used in this type of research and other NSF funded research at the University of Wisconsin. Graduate and undergraduate students will benefit tremendously by using this instrument and techniques in well designed research projects.