Whispering-gallery mode resonators for highly unidirectional laser action
Whispering-gallery mode resonators for highly unidirectional laser action
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DOI：
10.1073/pnas.1015386107
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发表时间：
2010-12-28
影响因子：
11.1
通讯作者：
Capasso, Federico
中科院分区：
文献类型：
--
作者：
Wang, Qi Jie;Yan, Changling;Capasso, Federico
光学微腔可以被设计成利用全内反射，这导致谐振器支持具有高品质因子（Q因子）的回音壁模式（WGM）。然而，这些器件在实际应用中的关键问题之一，如设计微腔激光器，是由于它们的径向对称性，它们的发射是无方向性的，除了它们低效的功率输出耦合。在这里，我们报告的椭圆形谐振腔的设计与波长大小的缺口在边界处，支持面内高度单向激光发射从WGM。凹口充当小散射体，使得WGM的Q因子仍然非常高。使用中红外（λ类似于10 μ m）注入量子级联激光器作为模型系统，在室温下的面内光束发散度小至6度，峰值光功率类似于5 mW已被证明。光束发散对泵浦电流和凹口几何形状不敏感，证明了这种谐振器设计的鲁棒性。后者可扩展到可见光和近红外，从而为非常低阈值，高度单向微腔二极管激光器打开了大门。
Optical microcavities can be designed to take advantage of total internal reflection, which results in resonators supporting whispering-gallery modes (WGMs) with a high-quality factor (Q factor). One of the crucial problems of these devices for practical applications such as designing microcavity lasers, however, is that their emission is nondirectional due to their radial symmetry, in addition to their inefficient power output coupling. Here we report the design of elliptical resonators with a wavelength-size notch at the boundary, which support in-plane highly unidirectional laser emission from WGMs. The notch acts as a small scatterer such that the Q factor of the WGMs is still very high. Using midinfrared (lambda similar to 10 mu m) injection quantum cascade lasers as a model system, an in-plane beam divergence as small as 6 deg with a peak optical power of similar to 5 mW at room temperature has been demonstrated. The beam divergence is insensitive to the pumping current and to the notch geometry, demonstrating the robustness of this resonator design. The latter is scalable to the visible and the near infrared, thus opening the door to very low-threshold, highly unidirectional microcavity diode lasers.