Controlling of two photon absorption properties by altering composition ratio of GaSxSe1−x crystals

Linear and nonlinear optical properties of mixed GaSxSe1−x crystals grown by Bridgeman were investigated. Two photon absorption properties of the studied crystals were investigated by using open aperture Z-scan technique with 4 ns pulse duration at 1064 nm wavelength. Linear absorption measurement results showed that the band gap energies of the mixed crystals increase with increasing the S ratio in crystals and oppositely, two photon absorption coefficients decrease with increasing the S ratio in mixed crystals exposed to nanosecond pulse duration. The increasing of two photon absorption coefficients can be attributed to lower energy band gap values. At the same input intensities, the highest two photon absorption coefficient is found as 3.56 × 10−6 cm/W for GaSe and the lowest one is obtained as 2.42 × 10−6 cm/W for GaS crystals. In this study, the experimental results indicate that two photon absorption properties and optical band gap energies are related with each other and can be controlled by altering the S/Se ratio of the mixed GaSxSe1−x crystals.