Two-photon absorption and non-resonant electronic nonlinearities of layered semiconductor TlGaS2

The ultrafast nonlinear optical properties of bulk TlGaS2 crystal, a semiconductor with a layered structure, are studied by combining intensity dependent transmission, time-resolved transient absorption, and optical Kerr effect coupled to optical heterodyne detection. TlGaS2 demonstrates obvious two-photon absorption and electronic nonlinearities at 800 nm. The two-photon absorption coefficient and the nonlinear refractive index are determined to be of the order of 10-10 cm/W and 10-14 cm2/W, respectively. Furthermore, both the real and imaginary parts of the complex third-order susceptibility tensor elements are extracted. The large ultrafast optical nonlinearities make TlGaS2 a promising material for application in photonic techniques.