Tunable coupled-mode dispersion compensation and its application to on-chip resonant four-wave mixing

TL;DR

This paper introduces a tunable mode coupling technique for dispersion compensation in silicon microresonators, significantly enhancing four-wave mixing efficiency and enabling large free spectral ranges for integrated photonic applications.

Contribution

It presents a novel active dispersion engineering method using localized mode coupling controlled by thermal tuning, improving FWM performance in silicon microresonators.

Findings

8 dB enhancement in FWM efficiency

Peak wavelength conversion efficiency of -37.9 dB

Largest FSR for FWM in silicon to date

Abstract

We propose and demonstrate localized mode coupling as a viable dispersion engineering technique for phase-matched resonant four-wave mixing (FWM). We demonstrate a dual-cavity resonant structure that employs coupling-induced frequency splitting at one of three resonances to compensate for cavity dispersion, enabling phase-matching. Coupling strength is controlled by thermal tuning of one cavity enabling active control of the resonant frequency-matching. In a fabricated silicon microresonator, we show an 8 dB enhancement of seeded FWM efficiency over the non-compensated state. The measured four-wave mixing has a peak wavelength conversion efficiency of -37.9 dB across a free spectral range (FSR) of 3.334 THz ($\sim$27 nm). Enabled by strong counteraction of dispersion, this FSR is, to our knowledge, the largest in silicon to demonstrate FWM to date. This form of mode-coupling-based, active dispersion compensation can be beneficial for many FWM-based devices including wavelength converters, parametric amplifiers, and widely detuned correlated photon-pair sources. Apart from compensating intrinsic dispersion, the proposed mechanism can alternatively be utilized in an otherwise dispersionless resonator to counteract the detuning effect of self- and cross-phase modulation on the pump resonance during FWM, thereby addressing a fundamental issue in the performance of light sources such as broadband optical frequency combs.