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。单氧化物孔径微腔的产量为Q = 2000，直径为2微米。Q将通过制造具有多个氧化铝孔的纳米腔来增加（Dennis Deppe， U. Texas - Austin），从而结合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来增加（Axel Scherer, Caltech）。Q将通过检测生长在纳米腔间隔器中心的量子点的光致发光线宽来测量。Deppe教授对InGaAs量子点的生长有着丰富的经验，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的界面涨落点转移到1300 nm的InGaAs的更强约束的自组装量子点。1.3 mm是一个有吸引力的波长，不仅因为它对光通信具有明显的重要性，而且因为真空拉比分裂与光子逃逸率的比率是空腔的两倍多。较长的波长增加了材料波长腔的特征尺寸，使其更容易制造。更强的约束保证了更高的温度运行。最后，PI获得了表征1.3 mm样品的仪器。最小体积、高q的纳米空腔是缩小发光二极管和VCSEL尺寸的天然纳米技术极限。这种结构也是当前量子信息处理的兴趣所在，可以作为单光子的源或用于量子纠缠。对于有用的单光子旋转门，Q/体积比可以比强耦合的更低，因此获得的Q值和体积将决定单光子源与强耦合的重点。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度的变窄，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很小。强耦合将导致双峰传输或发光，并且单个光子的吸收已经改变了下一个探针光子的吸收光谱。

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.