Research on two-photon absorption enhancement of CdS in one-dimensional photonic band gap structures

Abstract

One-dimensional photonic crystals (1D PC) with single CdS defect layer in TiO2/SiO2 dielectric thin films stack with different periods and structural parameters were fabricated by vacuum deposition. Two-photon absorption (TPA) of the CdS defect layer in the photonic crystals was investigated by pump-probe measurement. Experimental results show a significant enhancement of TPA coefficient in the CdS defect layer in one-dimensional photonic crystal. Different magnitude of enhanced two-photon absorption coefficient of CdS defect layer in one-dimensional photonic crystal with different photonic band gap has been observed. The enhanced two-photon absorption effect results from the electric field enhancement due to the light localization in the CdS defect layer. The electric field enhancement in defect laser was determined by the structural parameters of one-dimensional photonic crystal such as period, the position and width of bandgap and defect mode. The highest electric field intensity at defect layer is obtained with the alternated quarter-wavelength dielectric thin films of high and low refractive indexes and a defect mode matched with incident light wavelength.