Whispering-Gallery Microlaser with Nanocomposite-Film Gain Medium

0115442 Rosenberger这个项目是研究单个熔融硅球微谐振器(直径100-1000微米)的回音廊模式(WGM)中的激光作用。微球WGM的高品质因数(Q)使激光具有非常低的阈值。使用逐层组装工艺，可以在微球上覆盖一层含有纳米HgTe包裹物的薄聚电解质膜。然后，复合薄膜用作增益介质，与WGM的消逝分量相互作用，泵浦激光通过锥形光纤的光学隧道耦合到WGM中。800 nm附近的泵浦可以产生1400-1700 nm范围的激光，激光发射通过相同的锥形光纤耦合到微谐振腔外。该项目的目标包括：验证激光的发生；优化激光输出；产生稳定的、可调谐的单模运转；同时发展理论对应的激光，以指导实验和解释其结果。为了实现这些目标，PI先前开发的微球调谐和锁频实验技术变得无价。在这个项目中，来自1550 nm附近的探测激光的光被耦合到微球中来测量光学增益。然后寻找输出阈值，并且输出的符合线宽变窄提供了激光的进一步证据。激光输出光谱的分析使用扫描单色仪、扫描共焦光学光谱分析仪和用作滤光器的第二调谐微球。通过压缩调谐激光微球，并使用第二个微球作为滤光器，可以产生可调的单模发射。理论分析包括对不同WGMS在不同泵浦条件下产生的激光阈值和相对增益进行了评估。对于正常运转的激光器和注入信号的微激光器，也探讨了可能的模式竞争和不稳定性。这里结合了两个令人兴奋的新研究领域：微球WGMS的共振光学增强和易于制造的纳米复合薄膜。潜在的影响是巨大的，因为一个微激光可以作为100个通道(或更多)波分复用的源。此外，随着导电和/或电致发光聚合物在薄膜中的未来使用，电泵浦可能会取代光泵浦。这样的微激光器对电信业来说可能是一笔巨大的财富。这项工作继续并扩展了初步的探索性研究，其早期结果是有希望的。申请的资金是为了在这一领域实现长期(3年)的协调努力，同时为三名博士生的教育和专业发展提供部分支持，并为每年两名本科生提供多学科实验和理论科学的实践介绍。

0115442RosenbergerThis project is an investigation of laser action in the whispering-gallery modes (WGMs) of individual fused-silica spherical microresonators (100-1000 um in diameter). The high quality factor (Q) of a microsphere WGM enables lasing with a very low threshold. Using a layer-by-layer assembly process, a microsphere can be coated with a thin polyelectrolyte film containing nanoparticle inclusions of HgTe. The composite film then serves as the gain medium, interacting with the evanescent component of a WGM into which pump laser light is coupled by optical tunneling via a tapered fiber. Pumping with a wavelength around 800 nm can produce lasing in the 1400-1700 nm range, with the laser emission coupled out of the microresonator by the same tapered fiber. The objectives of this project include the following: verify that lasing occurs; optimize the laser output; produce stable, tunable single-mode operation; and concurrentlydevelop the theoretical counterpart, for purposes of guiding the experiment and interpreting its results. To meet these objectives, the PIs previously developed experimental techniques for tuning and frequency-locking the microsphere become invaluable. In this project, light from a probe laser around 1550 nm is coupled into the microsphere to measure optical gain. Then an output threshold is sought, and the coincident linewidth narrowing of the output provides further evidence of lasing. Analysis of the laser output spectrum is performed using a scanning monochromator, a scanning confocal optical spectrum analyzer, and a second tuned microsphere acting as a filter. By compression-tuning the lasing microsphere and using a second microsphere as a filter, tunable single-mode emission can be produced. The theoretical analysis includes an evaluation of the laser threshold and relative gain that is produced in different WGMs under various pumping conditions. Possible mode competition and instability are also explored for normal laser operation and also for the microlaser with injected signal. Two exciting new areas of research are combined here: resonant optical enhancement in microsphere WGMs and easily-fabricated nanocomposite films. The potential impact is great, because a single microlaser can act as a source for 100-channel (or more) wave-division multiplexing. In addition, with the future use of conducting and/or electroluminescent polymers in the film, electrical pumping may replace optical pumping. Such a microlaser can be a tremendous asset to the telecommunications industry. This work continues and expands preliminary exploratory studies, the early results from which are promising. The requested funding is to enable a longer-term (3-year) concerted effort in this area, while providing partial support for the educational and professional development of three Ph.D. candidates, and a hands-on introduction to multidisciplinary experimental and theoretical science for two undergraduates each year.