Photonic integrated circuits enable tight integration of optical components used as building blocks for much larger optical systems, similarly to electronic integrated circuits. In particular, silicon-based photonics can leverage the yield and scaling technology improvements that also benefit the electronics industry. Moreover, photonic integrated circuits can reduce the power consumption in communication and computation applications, and open the door to new applications in sensing and ranging.

The design of linear and nonlinear passive photonic components is key to the performance improvement of integrated photonics. In the first part of this dissertation, we present a platform for creating on-chip frequency combs using materials with a large third-order nonlinear index. Specifically, using chalcogenide glass waveguides, we produce a frequency comb spanning greater than an octave bandwidth using input optical pulses on the picojoule level. In the second part, we discuss fabrication processes and optical designs to improve the fiber-to-chip coupling loss, which is a limiting factor in large-scale optical switch applications. We present the design of an adiabatic evanescent coupler that is polarization diverse and has a bandwidth greater than 100 nm in the O band. Our design achieves better than 2 dB insertion loss and is compatible with different photonic fabrication processes.




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