Optical field enhanced nonlinear absorption and optical limiting properties of 1-D dielectric photonic crystal with ZnO defect

We report on optical field enhanced nonlinear absorption and on the optical limiting properties of a 1-D photonic crystal with ZnO defect, fabricated by rf sputtering technique. The structural properties of the photonic crystal are studied using scanning electron microscopy (SEM) images. Light transmission spectroscopy measurement shows a broad photonic band gap with a defect mode. Open aperture Z-scan measurement with 532 nm pulsed laser illustrates a four times enhancement in the nonlinear absorption coefficient, due to local field enhanced two-photon absorption in the photonic crystal structure with respect to the single layer of ZnO reference. The enhancement of the nonlinear absorption in the photonic crystal, due to the strong confinement of the optical field around ZnO defect layer, leads to an optical power limiting behavior in the photonic crystal. The limiting threshold of the photonic crystal is found to be 0.74 J/cm2 @ 532 nm with 6 ns pulse width, 10 Hz repetition rate.