[OPTICAL REVIEW Vol. 10, No. 1 (2003) 13-18]

© 2003 The Optical Society of Japan

## Wave Localization of Doubly Periodic Guided-mode Resonant Grating Filters

Akio MIZUTANI, Hisao KIKUTA and Koichi IWATA

College of Engineering, Osaka Prefecture University, 1-1, Gakuen-cho, Sakai, Osaka 599-8531, Japan

(Received August 14, 2002; Accepted October 9, 2002)

It is known that a doubly periodic guided-mode resonant grating (GMRG) filter has a broad angular selectivity with a narrow spectral bandwidth. This means that the doubly periodic GMRG filter operates for small beam diameter and grating area. This report describes the wave localization in the doubly periodic GMRG filter. We investigated the spread area of light waves in the waveguide layer and the accumulation of field energy by numerical simulation using the finite differential time domain (FDTD) method. Simulation results showed that, in the case of a doubly periodic GMRG filter with a Q factor of 600, the field energy is spread over an area 5 μm in width, which corresponds to the expected value from the angular tolerance. And the magnitude of the field energy in the waveguide layer was Q factor times greater than the incident energy. On the other hand, a singly periodic GMRG filter with the same Q factor spread the field energy over an area 72 μm in width. This filter does not work for a small size structure or a small diameter light beam.

Key words: wavelength filter, photonic crystals, guided-mode resonant grating filter, doubly periodic grating, wave localization