Coherence Interpretation of the Hong-Ou-Mandel Effect

Sun Hyun YOUN*

Bettina Gertjerenken, P. G. Kevrekidis

Oyvind Alv Liberg

Peter L. Kaulfuss, Paul M. Alsing, A. Matthew Smith +2 more

We present an exact analytic expression for the Hong-Ou-Mandel manifold (HOMM) for any number of identical microring resonators (MRRs) in a linear chain. The HOMM is the higher-dimensional manifold of solutions for which the HOM effect is obtained; for the types of MRR systems investigated in this work, it is a one-dimensional curve. We investigate the extreme stability of this HOMM, showing that the HOM effect in linear arrays of MRRs is highly robust. We further use this expression to derive three figures of merit for the HOMM of linear chains of MRRs: the minimum MRR coupling value ${\ensuremath{\tau}}_{c}$, the curvature of the one-dimensional HOMM ${\overline{\ensuremath{\xi}}}_{N}$, and the 5% tolerance in the probability for complete destructive interference to occur on the HOMM $\ensuremath{\delta}{\ensuremath{\tau}}_{N}$. We promote these metrics to characterize the pros and cons of various linear chains of MRRs and inform design and fabrication.

Jianbin Liu, Yu Zhou, Wentao Wang +4 more

The spatial second-order interference of two independent pseudothermal light beams in a Hong-Ou-Mandel interferometer is studied experimentally and theoretically. The similar cosine modulation in the second-order coherence function as the one with entangled-photon pairs in a Hong-Ou-Mandel interferometer is observed. Two-photon interference based on Feynman's path integral theory is employed to interpret the results. The experimental results and theoretical simulations agree with each other very well.

Peter L. Kaulfuss, Paul M. Alsing, Richard J. Birrittella +3 more

Micro-Ring Resonators (MRRs) allow us to access the Hong-Ou-Mandel (HOM) effect at a variety of tunable parameter combinations along exact analytic solutions. This higher-dimensional space of parameters for which the HOM effect occurs constitutes what is known as a Hong-Ou-Mandel manifold (HOMM). Using a parallel series of non-identical MRRs and changing relative round-trip phase shifts between MRRs allows for the manipulation of the wavelength locations of the HOM effect. Through clever design and fabrication, we can mold the HOMM to place multiple HOM effects, or lack thereof, precisely at desired locations in wavelength. In this paper we discuss how to adjust non-identical MRR parameters to change the resulting HOMM. We also promote example designs that exhibit advantageous HOMM structures, and highlight some of the diverse possibilities that can be accessed with different circuit design. Our main examples are: 1) a wavelength division multiplexer example that matches the HOM effect locations with the already established channels to integrate with a classical communication network and 2) a HOM-based entanglement switch that allows for the rapid switching between 2-photon NOON state outputs and completely separable single photon outputs.