Characteristics of Correlated Photon Pairs Generated in Ultra-compact Silicon Slow-light Photonic Crystal Waveguides

TL;DR

This study characterizes correlated photon pairs generated in dispersion-engineered silicon slow-light photonic crystal waveguides, highlighting the effects of waveguide length and the key metrics for photon-pair sources.

Contribution

It provides detailed analysis of photon-pair generation bandwidth and key metrics in silicon slow-light photonic crystal waveguides with different lengths, advancing understanding of their performance.

Findings

Bandwidth for photon-pair generation depends on waveguide length.

Maximum CAR achieved was 33 at a low pair generation rate.

Noise sources limit the CAR performance.

Abstract

We report the characterization of correlated photon pairs generated in dispersion-engineered silicon slow-light photonic crystal waveguides pumped by picosecond pulses. We found that taking advantage of the 15 nm flat-band slow-light window (vg ~ c/30) the bandwidth for correlated photon-pair generation in 96 and 196 \mum long waveguides was at least 11.2 nm; while a 396 \mum long waveguide reduced the bandwidth to 8 nm (only half of the slow-light bandwidth due to the increased impact of phase matching in a longer waveguide). The key metrics for a photon-pair source: coincidence to accidental ratio (CAR) and pair brightness were measured to be a maximum 33 at a pair generation rate of 0.004 pair per pulse in a 196 \mum long waveguide. Within the measurement errors the maximum CAR achieved in 96, 196 and 396 \mum long waveguides is constant. The noise analysis shows that detector dark counts, leaked pump light, linear and nonlinear losses, multiple pair generation and detector jitter are the limiting factors to the CAR performance of the sources.