Classical Applications and Quantum Aspects of Microresonator-based Optical Frequency Combs

Chip-based microresonators have realized the miniaturization of the optical frequency combs in the past two decades. They provide a platform connecting the optical frequencies and the electronic frequencies, which revolutionized areas such as metrology, instrumentation and spectroscopy. The high repetition rate that can go up to 1 THz is one of the most interesting features of the microcombs. The corresponding large comb spacing and high-speed carrier are advantageous to wavelength multiplexing, high-speed RF generation, coherent sampling, and self-referencing. However, the detection of comb repetition rate, the precursor to all comb-based applications, becomes challenging at these repetition rates due to the limited bandwidth of photodiodes and electronics. In the first part of this dissertation, I introduce a new way to detect and stabilize the high microcomb repetition rate that doesn't require high-speed photodiodes or electronic devices. To leverage this feature of high repetition rate and large comb spacing, a microcomb-based arbitrary RF waveform generator (AWG) is demonstrated. This all-optics-based AWG has potential to be fully integrated on a photonic chip and achieve ultra-high analog bandwidths.
On the other hand, a microresonator works as both a cavity and a nonlinear medium. The nonlinear optics process inside the microresonator could contribute to many quantum applications. Over the last few years, a large variety of quantum optics experiments have been performed in the photonic integrated circuits. They opened new paths towards applications such as quantum computing, quantum metrology and quantum sensing. In the second part of this dissertation, some quantum aspects of the microcombs are introduced and a squeezed quantum microcomb on a chip is demonstrated for the first time, which could serve as a deterministic approach to scale up the quantum system.