PhD Thesis Defense
New physics and novel applications in various fields ranging from biology, and spectroscopy, to manipulation of quantum systems are driven by the availability of coherent light sources including frequency combs in the visible and mid-infrared spectral regimes. Nonlinear optical systems, that are parametrically driven by technologically mature near-infrared lasers, are leveraged in this regard to access challenging wavelengths where conventional lasers may be unavailable. It is of paramount importance to miniaturize these systems and replace the traditional bulky setups thereby paving the way for a plethora of applications. Optical parametric oscillators are among the most prominent examples of such nonlinear systems and beyond their indispensable usage as light sources (both classical and quantum) their unique non-equilibrium dynamics can endow a wealth of functionalities absent in their linear counterparts. These properties can be engineered and utilized for realizing highly sensitive sensors as well as special-purpose computing hardware that may outperform conventional digital computers. A network of these coupled parametric oscillators can be made to interact leading to emergent behaviors that are not expected from the individual constituents.
In this work, we experimentally and theoretically study the dynamics of individual and coupled optical parametric oscillators towards sensing and computing applications. We explore a previously avoided regime of operation for generating ultra-short pulses from these parametrically driven nonlinear resonators that lead to extreme pulse compression. We engineer the nonlinear dynamics of these systems to realize all-optical spectral phase transitions (both first-order and second-order) that behave as highly-sensitive sensors. We show how these critical phenomena can be utilized to enhance the solution accuracy of physics-based solvers in finding optimum solutions to combinatorial optimization problems in the context of coherent Ising machines. We also realize optical parametric oscillators in integrated lithium-niobate nanophotonic platform and demonstrate a mid-infrared frequency comb source that is widely tunable over an octave accompanied by visible frequency comb generation. We develop a comprehensive description to investigate the noise properties of optical parametric oscillators that provide new insights into the phase noise behavior of optical parametric oscillators in their various operating regimes. Finally, we propose a system of parametrically driven resonators as a synthetic medium with highly reconfigurable interactions that can host a plethora of emergent phenomena ranging from topological behaviors to non-Hermitian dynamics. These networks of nonlinear resonators display intriguing dynamical properties in contrast to their static counterparts in condensed-matter physics with implications in quantum sensing and robust device functionality.
Short Bio: Arkadev Roy is a graduate student in the Electrical Engineering department working with Prof. Alireza Marandi. He obtained his bachelor's degree from the Indian Institute of Technology, Kharagpur.