Microresonator optical parametric oscillators based on the third-order optical nonlinearity represent a versatile approach to on-chip, coherent light generation at any user-targeted wavelength across an exceptionally broad spectral range.
In contrast to direct bandgap semiconductor lasers, optical parametric oscillators can access a much wider range of potential wavelengths, provided that phase- and frequency-matching of the underlying nonlinear optical process is respected. However, to produce useful amounts of output power at high conversion efficiencies, it is not enough for these conditions to be satisfied for the process of interest, but other competing nonlinear optical processes must also be suppressed. This is of particular importance to our research, as we have been able to demonstrate wide wavelength access across a large portion of the visible spectrum in microresonator optical parametric oscillators, but have not yet demonstrated highly efficient operation.
Most works that have studied optical parametric oscillation process in a highly idealized context in which the resonator only supports three modes, so that potential competing processes are by definition not allowed. In recent work, led by Jordan Stone, we theoretically and numerically study optical parametric oscillation in more realistic microresonators (like the ones we experimentally study in the lab), identifying the physical mechanisms behind key competing nonlinear processes and some routes to suppress them, so that high conversion efficiencies can be achieved. We anticipate that this work will provide a useful blueprint as we and other groups seek to advance microresonator optical parametric oscillators to the point that they can be used in spectroscopy and coherent control of quantum systems.
Stone, J. R., G. Moille, X. Lu, and K. Srinivasan, "Conversion Efficiency in Kerr-Microresonator Optical Parametric Oscillators: From Three Modes to Many Modes", Physical Review Applied, vol. 17, pp. 024038, 2022.