Nonlinear Photonic Crystal Nanocavities and Waveguides

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Science and Engineering Goals: The research will be based on the previous-grant breakthrough of strong coupling between a single quantum dot and a photonic crystal slab nanocavity. Strong-coupling nanocavities are the natural nanotechnological limit for the shrinking size of LED's and VCSEL's. Device improvement (larger splitting-to-linewidth ratio) will be sought by increasing Q (by reducing the quantum dot density which introduces background absorption) and decreasing the dipole dephasing rate g (by pumping the dot resonantly into its ground or excited state). Also quantum dots will be grown at shorter wavelengths (1000nm) where quantum detectors and Ti:Sa lasers make quantum research easier. For these new truly quantum nanodevices to find applications in quantum information processing, they need to be more accessible to control pulses. The nanocavities will be coupled to photonic crystal waveguides so light can be coupled in and out efficiently via end-fire coupling or grating couplers. Waveguide coupling will accelerate the study of nanocavity nonlinear optical switching and bistability in transmission geometry and eventually will interconnect nanocavities to form rudimentary integrated optical circuits. Collaborations with Professors Scherer (Caltech) and Moloney (Arizona) who have photonic crystal computational capabilities will help to determine the tradeoff between vertical access and waveguide access and to interpret our experimental measurements. The long term goal is to utilize the strong coupling dot-photon entanglement to construct a quantum phase gate and to transfer a quantum state enabling the sharing of entanglement among spatially distant quantum dots.Broader Impact: The two graduate students (one African American) participating in this research project will gain experience with manipulating and nanopositioning semiconductor samples, resolution-limited optics, cw and fs laser spectroscopy, weak signal detection, quantum physics, etc. They will share their research results at international meetings and publish them in refereed and broad-audience journals. The nanophotonics industry benefits from the education of undergraduate and graduate students in the basic physics and experimental skills of nanodevices. This project will further solidify the productive collaboration with Axel Scherer's renowned photonic crystal fabrication group at Caltech. This research will lead to advances in the fundamental understanding of quantum optical devices and to technological progress in semiconductor nanodevices. Making the cavity smaller and smaller, increasing the Q, and optimizing the coupling are as important for quantum-dot photonic-crystal lasers as for devices designed around strong coupling.