Research on two-photon absorption enhancement in one-dimensional photonic crystals with double defect modes

Abstract

One-dimensional photonic crystals with two CdS defect layers which had two defect modes of 762 nm and 800 nm was fabricated by vacuum deposition process. Two-photon absorption coefficient was investigated by pump-probe measurement. The two-photon absorption coefficient was enhanced at two defect modes. 307 cm/GW two-photon absorption coefficient at defect mode of 800 nm was greater than 116 cm/GW at defect mode of 762 nm and they were 48 and 18 times as large as that of a single CdS thin film. The enhancement of two-photon absorption coefficients was due to the enhanced electric field intensity ascribed to light localization in the two CdS defect layers. The transfer matrix method was used to calculate the internal electric field intensity in the one-dimensional photonic crystal sample. It was found that the electric field intensity in defect layers at defect mode of 800 nm was larger than that of 762 nm.