Nonlinear response of silicon photonic crystal micresonators excited via an integrated waveguide and fiber taper

TLDR

The study demonstrates a technique that efficiently couples light from a tapered single‑mode fiber into a high‑Q, ultra‑small silicon photonic crystal resonator. The authors use this efficient fiber‑to‑cavity coupling to investigate the cavity’s steady‑state nonlinear absorption and dispersion. The resonator achieves a quality factor of 4.7×10⁴, 44 % fiber‑to‑cavity coupling, exhibits optical bistability at 250 µW input (100 µW dropped, 3 fJ stored), and has an effective free‑carrier lifetime of ~0.5 ns.

Abstract

A technique is demonstrated which efficiently transfers light between a tapered standard single-mode optical fiber and a high-Q, ultra-small mode volume, silicon photonic crystal resonant cavity. Cavity mode quality factors of 4.7x10(4) are measured, and a total fiber-to-cavity coupling efficiency of 44% is demonstrated. Using this efficient cavity input and output channel, the steady-state nonlinear absorption and dispersion of the photonic crystal cavity is studied. Optical bistability is observed for fiber input powers as low as 250 microW, corresponding to a dropped power of 100 microW and 3 fJ of stored cavity energy. A high-density effective free-carrier lifetime for these silicon photonic crystal resonators of ~ 0.5 ns is also estimated from power dependent loss and dispersion measurements.