This thesis presents an experimental study of the coherent nonlinear optical processes in aluminum nitride microring resonators. Backed by mature semiconductor nanofabrication processes, photonic integrated circuits hold promise as miniaturized and scalable platforms for classical and quantum information processing. Among different on-chip components, microresonator attracts a lot of research efforts because of its unique properties of high Q, small mode volume, and easily engineered optical modes. These properties are ideal for the study of nonlinear optical processes, which are fundamental to applications including microcomb generation, parametric frequency conversion, harmonics, and spontaneous parametric down-conversion. However, the efficiency of nonlinear processes, especially second-order nonlinear process, was limited by the imperfections in the choice of material, device design, and fabrication. In this thesis, we present an systematic theoretical and experimental study on improving the efficiency of cavity nonlinear optical processes. We largely improve the figure-of-merit of the second-order nonlinear process and enable applications such as high-efficiency second-harmonic generation, frequency conversion, visible frequency comb, all-optical control of nonlinear optical process, and integrated down-conversion photon-pair sources.
First, we develop the general theoretical framework for the cavity nonlinear process, working out all the requirement for improving the efficiency. These requirements include high-quality factor resonator, phase matching condition, and critical coupling. According to the theoretical guidance, we fabricate devices with a second-harmonic generation efficiency of 2500%W-1, which is currently the state-of-the-art value among all the integrated photonic platform. On the other hand, we greatly improve the conversion efficiency between visible and telecom frequency bands, and, for the first time, realize the strong coupling between optical modes of different colors.
By combining both second- and third- order nonlinearity, we next demonstrate an unprecedented high-efficiency device for the visible-band frequency comb generation. Optical frequency combs are key to state-of-the-art applications including frequency metrology, optical clocks, astronomical measurements and sensing. While third-order nonlinear process (Kell effect) alone allows for wide-band frequency comb generation in the infrared band, realizing rnicrocornbs in the short wavelength range is limited by the large material dispersion and increasing optical loss. Benefiting from our demonstrated high efficiency second-order nonlinear process, we find a way to combine the two nonlinear processes in a single rnicroririg cavity. We realize a surprisingly high on-chip conversion efficiency of 22% from an infrared pump laser to the visible comb, which marks the first step towards high-efficiency visible microcomb generation and its utilization.
Armed with the capability of manipulating several nonlinear processes in the same uncroring cavity, we then explore the all-optical control of linear and nonlinear energy transfer. We demonstrate a coherent interplay between second- and third- order nonlinear processes. We then utilize this effect to control the stimulated four-wave mixing process and realize a suppression ratio of 34.5.
We then switch gear to the single photon regime where the mirroring is used to generate correlated photon-pairs through spontaneous parametric down-conversion process. We demonstrate such an on-chip parametric down-conversion source of photon pairs based on second-order nonlinearity in an aluminum-nitride mirroring resonator. We show the potential of our source for quaiitum information processing by measuring the high visibility anti-bunching of heralded single photons with nearly ideal state purity.
Apart from photon pair source, the other components for fully integrated quantum photonic chip include high efficiency on-chip pump light filters and on-chip single photon detectors. We design and fabricate an on-chip long-pass filter which can provide 70 dB attenuation for visible light near 775 nm with less than 3 dB insertion loss for light in the telecom C-band near 1550 nm, which is ideal for the application as an on-chip pump light filter. In the end of this thesis, we also present our efforts in fabricating and packaging the fully integrated quantum photonic chips.
|Advisor:||Tang, Hong X.|
|School Location:||United States -- Connecticut|
|Source:||DAI-B 80/07(E), Dissertation Abstracts International|
|Subjects:||Applied physics, Engineering, Optics|
|Keywords:||Frequency Comb, Intergrated Photonic Circuits, Optical Nonlinearity, Parametic Down-Conversion, Second Harmonic Generation, Strong Coupling|
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