Toward Quantum Semiconductor Nanocavities

该项目的目标是制造高Q（~ 10，000），小体积（立方波长或更小）的3D半导体纳米腔。 单氧化物孔微腔产生了Q = 2，000，直径为2微米。 通过制造具有多个氧化铝孔的纳米腔将增加Q（Dennis Deppe，U. Texas - Austin），从而结合了蚀刻柱和氧化物孔的优点，或者通过使用非常小体积的光子晶体纳米腔（阿克塞尔谢勒，Caltech）。 将通过检测生长到纳米腔间隔物中心的量子点的光致发光的线宽来测量Q。 Deppe教授在InGaAs量子点的生长方面拥有丰富的经验，他将为这两种类型的纳米腔生长材料。 在此期间，重点将从750 nm的界面波动点转移到1300 nm的InGaAs更强限制的自组装量子点。 1.3毫米是一个有吸引力的波长，这不仅是因为它对于光通信的明显重要性，而且还因为真空拉比分裂与光子从腔中逃逸速率的比率是那里的两倍以上。 较长的波长增加了材料中波长腔的特征尺寸，使其更容易制造。 更强的约束保证更高的温度操作。 最后，PI获得了表征1.3 mm样品的仪器。最小体积，高Q值纳米腔是缩小发光二极管和VCSEL尺寸的自然纳米技术限制。 这样的结构也是当前感兴趣的量子信息处理的单光子源的需求或量子纠缠。 对于有用的单光子旋转栅门，Q/体积比可以比强耦合低，因此获得的Q和体积的值将确定对单光子源与强耦合的强调。 单个量子点和纳米腔模式之间的辐射耦合将被视为腔线宽的变窄，因为腔模式在杜瓦瓶中通过点的最低能量跃迁进行温度扫描，样品位置的温度依赖性非常小。强耦合将导致双峰透射或发光，并且单个光子的吸收将已经改变下一个探测光子的吸收光谱。

The goal of this project is to fabricate high-Q (~10,000), small-volume (cubic wavelength or smaller) 3D semiconductor nanocavities. Single-oxide-aperture microcavities have yielded Q = 2,000 with a diameter of 2 microns. The Q will be increased by fabricating a nanocavity with multiple aluminum-oxide apertures (Dennis Deppe, U. Texas - Austin), thus combining the advantages of etched pillars and oxide apertures, or by using a very small volume photonic-crystal nanocavity (Axel Scherer, Caltech). The Q will be measured by detecting the linewidth of photoluminescence of the quantum dots grown into the center of the nanocavity spacer. Professor Deppe, who has much experience with the growth of InGaAs quantum dots, will grow the material for both types of nanocavities. During this grant the emphasis will be shifted from interface-fluctuation dots at 750 nm to the more strongly confined self-assembled quantum dots of InGaAs at 1300 nm. 1.3 mm is an attractive wavelength not only because of its obvious importance for optical communications but also because the ratio of vacuum Rabi splitting to photon escape rate from the cavity is more than twice as large there. The longer wavelength increases the feature size of a wavelength-in-the-material cavity, making it easier to fabricate. The stronger confinement promises higher temperature operation. Finally instruments for characterizing 1.3-mm samples have been acquired by the PI.Minimum-volume, high-Q nanocavities are the natural nanotechnological limit for the shrinking size of light-emitting diodes and VCSEL's. Such structures are also of current interest to quantum information processing as sources of single photons on demand or for quantum entanglement. The Q/volume ratio can be lower for a useful single-photon turnstile than for strong coupling, so the values of Q and volume obtained will determine the emphasis upon single-photon source versus strong coupling. Radiative coupling between a single quantum dot and a nanocavity mode would be seen as a narrowing of the cavity linewidth as the cavity mode is temperature scanned through the dot's lowest energy transition in a dewar with very small temperature dependence of the sample position. Strong coupling would result in double-peaked transmission or luminescence, and absorption of a single photon would already change the absorption spectrum for the next probe photon.