Broadband spatial self-phase modulation of black phosphorous

Spatial self-phase modulation (SSPM) experiments on two-dimensional (2D) black phosphorus (BP) nanoflake suspensions are performed with focused femtosecond pulsed lasers at 350-1160 nm. In the broadband region, the slope of the SSPM ring number versus laser intensity varies from 0.99 to 0.34, which is larger than 0.25 in MoS2. We deduce the portion of the fluid globe (xi) to be 0.0067, which is a constant independent of laser intensity, when the laser intensity is above 10 W/cm(2). The nonlinear refractive index of BP is measured to be similar to 10(-5) cm(2)W(-1), and the third-order nonlinear susceptibility is chi((3)) similar to 10(-8) esu at multiple wavelengths. (C) 2016 Optical Society of America