论文标题
模式映射Q> 500 000光子晶体纳米腔使用自由载体吸收
Mode mapping Q > 500 000 photonic crystal nanocavities using free carrier absorption
论文作者
论文摘要
我们展示了一种非线性光调节光谱法，以成像高Q光子晶体谐振器（PHCR）的模式曲线。这种远场成像方法适用于我们在Q = 619000 PHCR上证明的超高Q腔。我们使用405 nm泵梁扫描PHCR表面，该泵梁通过局部热调节调节折射率，同时探测共振的响应。我们使用PHCR的热光非线性通过高功率探测来增强分辨率。热光效应的空间分辨率通常受到光泵的宽热曲线的限制。在这里，我们超越了热极限，并表明我们可以接近泵灯的衍射极限。这是由于自由载体吸收，只有在光泵点和光学模式轮廓之间存在重叠时才加热PHCR。这是由一个热光学模型支持的，该模型重现了高分辨率模式映射。结果表明，对于较低的载体密度，可以达到观察到的增强分辨率。
We demonstrate a nonlinear photomodulation spectroscopy method to image the mode profile of a high-Q photonic crystal resonator (PhCR). This far-field imaging method is suitable for ultrahigh-Q cavities which we demonstrate on a Q = 619000 PhCR. We scan the PhCR surface with a 405 nm pump beam that modulates the refractive index by local thermal tuning, while probing the response of the resonance. We enhance resolution by probing at high power, using the thermo-optical nonlinearity of the PhCR. Spatial resolution of the thermo-optical effect is typically constrained by the broad thermal profile of the optical pump. Here we go beyond the thermal limit and show that we can approach the diffraction limit of the pump light. This is due to free carrier absorption that heats up the PhCR only when there is overlap between the optical pump spot and the optical mode profile. This is supported with a thermo-optical model that reproduces the high-resolution mode mapping. Results reveal that the observed enhanced resolution is reached for surprisingly low carrier density.
