Nonlinear optical studies of photonic crystal waveguides

This paper reports on nonlinear optical investigations of 2D photonic crystals etched into GaAs/AlGaAs waveguides by means of second-harmonic generation (SHG) from the surface of the samples. 130-fs laser pulses from a tunable Ti:sapphire source at 800 nm and from an optical parametric oscillator in the range 1.4 to 1.6 micron have been chosen to excite SH signals in reflection and diffraction directions. The measured angles of diffracted second-harmonic beams agree with those predicted from nonlinear diffraction conditions. The intensities of the reflected and diffracted SH signals are measured by varying the angle of incidence, input polarization and wavelength. Their observed behavior reflects the GaAs crystalline symmetry and the photonic crystal structure, respectively. Moreover, the measured high diffraction-to-reflection intensity ratio suggests the possibility of tailoring the nonlinear response using diffraction modes.