z -scan experiments and beam propagation modeling were conducted to determine the nonlinear absorption and refractive index cross sections of n-type indium arsenide (InAs). A doubled carbon dioxide pulsed laser operating at 4.78μm was used to generate free carriers via two-photon absorption. Using published values for the two-photon absorption coefficient in InAs, a nonlinear beam propagation model and a data fitting routine were used to extract the nonlinear absorption and refractive index cross sections.
We examine optical limiting with Co4oluene for nanosecond optical pulses at 532 nm. When the input fluence is less than 50 i/cm2, optical limiting is due to a combination of reverse saturable absorption (excited state absorption) and selfdefocusing. Nonlinear scattering was not observed. For a peak input fluence greater than 50 J/cm2, an acoustic report and broad-band emission indicate that optical breakdown occurs. We fmd C60-tetrahydronaphthalene to be a better optical limiter, at 532 nm, than tetrahydronaphthalene solutions of C7,, C78, or CM. C-tetrahydronaphthalene is shown to be an optical limiter at 1.064 tim.
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