Design of an all-optical tunable 2D photonic crystal in As2S3 film

Abstract

Amorphous arsenic trisulphide (As2S3) chalcogenide glass is widely used in photonics and optoelectronics due to its wide transparency in the infrared spectral range, its high linear refractive index (nAs2S3 = 2.42), which can be significantly modified by light with a suitable wavelength, and its important optical nonlinearity. In this work, we report the design of an all-optical tunable two-dimensional photonic crystal in a geometry which consists in a hexagonal lattice of holes patterned in As2S3 film with the aim to exhibit photonic band gap in the near infrared domain. We numerically investigated the possibility to all-optically tune the photonic band gap of an already patterned photonic crystal in As2S3 modifying only its refractive index by illumination with light of wavelength λ at the band gap energy (λ = 514.5 nm) or shorter, without affecting the lattice geometry. The influence of the variation of As2S3 refractive index (Δn) on the spectral position of the band gap and on its width has been determined for the light-induced modification of Δn up to the value of 0.09. For this value of Δn, a shift of almost 50 nm of the central wavelength of the photonic band gap has been obtained. These results are of great interest in the field of photonics offering a versatile solution to fabricate all-optical tunable photonic crystals in any optical material whose refractive index can be modified by light.