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

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 4.7 x 10(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 muW, corresponding to a dropped power of 100 muW and 3 fJ of stored cavity energy. A high-density effective free-carrier lifetime for these silicon photonic crystal resonators of similar to 0.5 ns is also estimated from power dependent loss and dispersion measurements. (C) 2005 Optical Society of America.