OP: Semiconductor Materials for Extremely Nondegenerate Photonics and 2-Photon Gain

非技术描述：典型的激光发射出能量相同的单光子流——小束光。在这个项目中，研究人员正在研究使激光同时发射两个能量截然不同的光子的方法。这为控制激光输出提供了巨大的灵活性，因为只要另一个光子的能量选择得当，其中一个发射的光子几乎可以达到任何期望的能量。这可能会导致半导体激光器在红外光谱中提供广泛可调的辐射。这种激光器的可用性将影响各种各样的应用，包括大气中污染物的传感、生物成像、显微镜、电信、艺术修复和激光雷达。研究小组正专注于研究使激光以这种方式发光的材料特性，以及如何减轻导致光被吸收的因素，因为光的吸收可能会阻碍激光的操作。特别是，使用纳米厚的半导体层用于激光发射正在被解决。这项研究主要是由研究生和本科生进行的，他们是中佛罗里达大学多元化学生团体的成员。技术描述：研究团队的目标是研究半导体，特别是量子阱的非简并吸收和发射特性，以验证团队最近的计算，即与体半导体相比，量子阱中横向磁（TM）偏振光的非简并双光子吸收或发射增强。同时，研究小组正在描述非简并双光子增益和激光的相关损耗机制，即自由载流子吸收、urban -tail吸收和非简并三光子吸收，特别是为了找到双光子增益克服损耗的机制。最令人感兴趣的是中红外光谱区域，其中多个半导体适合于测试双光子增益。具有TM极化的量子阱系统吸引了特别的兴趣，因为在这种极化下，双光子跃迁被计算为最增强，而自由载流子吸收可以消失。此外，与体半导体不同，双光子发射和三光子吸收的增强有望在不同的光子能量下发生。然而，这些过程中的每一个都需要仔细衡量，以便建立总体损失的实际情况。

Nontechnical Description: Typical lasers emit streams of single photons - small bundles of light - that are all at the same energy. In this project, the investigators are studying ways to make lasers simultaneously emit two photons at very different energies. This gives tremendous flexibility in controlling laser outputs, since one of the emitted photons can be at almost any desired energy, as long as the energy of the other is appropriately chosen. This may lead to semiconductor lasers that deliver radiation that is broadly tunable across the infrared spectrum. The availability of such lasers will impact a wide variety of applications, including sensing of pollutants in the atmosphere, biological imaging, microscopy, telecommunications, art restoration and laser radar. The research team is focusing on investigating the materials properties that enable lasers to emit light in this way, and on how to mitigate factors that cause light to be absorbed, as absorption of light could hinder laser operation. In particular, the use of nanometer-thick semiconductor layers for laser emission is being addressed. This research is largely carried out by graduate and undergraduate students who are members of the University of Central Florida's diverse student body. Technical Description: The research team aims to study the nondegenerate absorption and emission properties of semiconductors, particularly quantum wells, to verify the team's recent calculations that nondegenerate two-photon absorption or emission of Transverse Magnetic (TM)-polarized light is enhanced in quantum wells compared to bulk semiconductors. At the same time, the research team is characterizing the relevant loss mechanisms for nondegenerate two-photon gain and lasing, namely free-carrier absorption, Urbach-tail absorption and nondegenerate three-photon absorption, especially with a view to finding regimes where two-photon gain overcomes losses. Of greatest interest is the mid-IR spectral region where multiple semiconductors are appropriate for testing two-photon gain. Quantum-well systems with TM polarization attract particular interest because, at this polarization the two-photon transitions are calculated to be the most enhanced while free-carrier absorption can vanish. Additionally, unlike in bulk semiconductors, the enhancement of two-photon emission and three-photon absorption are expected to occur at different photon energies. However, each one of these processes needs to be carefully measured in order to build a practical picture of the overall losses.