Quantum frequency conversion and strong coupling of photonic modes using four-wave mixing in integrated microresonators

TL;DR

This paper provides a detailed theoretical analysis of quantum frequency conversion in integrated microresonators, demonstrating high efficiency, spectral robustness, and strong mode coupling effects at low pump powers.

Contribution

It introduces a comprehensive quantum-mechanical model for frequency conversion, deriving formulas for efficiency and spectral properties, and explores strong coupling dynamics with Rabi-like oscillations.

Findings

Conversion efficiency exceeding 95% with less than 100 mW pump power

Spectral conversion probability density shows flat-topped peak at maximum efficiency

Identification of Rabi-like oscillations indicating strong mode coupling

Abstract

Single photon-level quantum frequency conversion has recently been demonstrated using silicon nitride microring resonators. The resonance enhancement offered by such systems enables high-efficiency translation of quantum states of light across wide frequency ranges at sub-watt pump powers. Using a quantum-mechanical Hamiltonian formalism, we present a detailed theoretical analysis of the conversion dynamics in these systems, and show that they are capable of converting single- and multi-photon quantum states. Analytic formulas for the conversion efficiency, spectral conversion probability density, and pump power requirements are derived which are in good agreement with previous theoretical and experimental results. We show that with only modest improvement to the state of the art, efficiencies exceeding 95% are achievable using less than 100 mW of pump power. At the critical driving strength that yields maximum conversion efficiency, the spectral conversion probability density is shown to exhibit a flat-topped peak, indicating a range of insensitivity to the spectrum of a single photon input. Two alternate theoretical approaches are presented to study the conversion dynamics: a dressed mode approach that yields a better intuitive picture of the conversion process, and a study of the temporal dynamics of the participating modes in the resonator, which uncovers a regime of Rabi-like coherent oscillations of single photons between two different frequency modes. This oscillatory regime arises from the strong coupling of distinct frequency modes mediated by coherent pumps.