Self-focusing, self-trapping and optical limiting of light beams in photorefractive Bi < inf > 12 < /inf > SiO < inf > 20 < /inf > :Fe crystal

Abstract

Nonlinear absorption, 1-D self-focusing and 1-D self-trapping of optical beams are studied in 150 ppm Fe-doped Bi12SiO20 (BSO:Fe) crystal using single beam Z-scan technique in nano second regime using coherent and incoherent laser pulses with out applying any external electric field across the crystal. When the crystal is placed in expanding beam one dimensional self-trapping is observed due to one dimensional self-focusing. The nonlinear absorption is also observed at high intensities due to trap assisted excited state absorption as well as two photon absorption. The ground state absorption and increased nonlinear absorption at 532 nm and 595 nm compared to pure BSO indicates the increased impurity traps in the crystal lattice due to iron incorporation. The studies reveal that incorporation of iron in BSO making it an excellent optical limiter.