Nonlinear Frequency Conversion in III-V Semiconductor Photonic Crystals
STANFORD UNIV CA EDWARD L GINZTON LAB OF PHYSICS
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Nonlinear optical processes provide a physical mechanism for converting the frequency of light. This allows the generation of tunable light sources at wavelengths inaccessible with lasers, leading to a diverse set of applications in fields such as spectroscopy sensing, and metrology. To make these processes efficient has conventionally required relatively exotic materials that are incompatible with state of the art nanofabrication resulting in large-area devices that operate at high optical powers and cannot be integrated with on-chip optical and electronic circuits. This dissertation shows how optical nanocavities, by localizing light into sub-cubic optical wavelength volumes with long photon storage times, can greatly enhance the efficiency of nonlinear frequency conversion processes in III-V semiconductors, while simultaneously shrinking the device footprint, reducing the operating power, and providing a scalable on-chip platform. This approach also enables on-chip quantum frequency conversion interfaces, which are crucial for the construction of quantum networks. First, photonic crystal nanocavities in gallium phosphide are shown to generate second harmonic radiation with only nanowatts of coupled optical powers, and efficiency many orders of magnitude greater than in previous nanoscale devices. This approach is then extended to demonstrate sum-frequency generation in GaP photonic crystal cavities with multiple cavity modes, as well as broadband upconversion employing photonic crystal waveguides. The nanocavity-enhanced second harmonic generation is then integrated with a single quantum dot to create a single photon source triggered at 300 MHz by a telecommunication wavelength laser coupled with an external electro-optic modulator, a simpler and faster configuration than standard approaches.