Generation of spatial solitons in narrow-gap semiconductors

Summary form only. Stable spatial solitons with two transverse dimensions can exist in materials characterized by a saturable nonlinearity that exactly compensates for the diffraction. Narrow-gap semiconductors, in particular III-V alloys with a small effective mass of conduction electrons, exhibits a large degree of nonparabolicity. In fact, in some narrow-gap semiconductors like InSb, the dispersion relation mimics that of a relativistic electron with a small effective mass, and with an effective "speed of light" several order smaller than the speed of light in a vacuum. In response to a laser pulse, due to the velocity-dependent mass the conduction electrons can simulate the dynamics of a relativistic plasma, at a pulse intensity which is a tiny fraction of the intensity required to create similar conditions in a normal gaseous plasma.