STP799: Nonlinear Absorption and Self-Defocusing of Intense IR-Laser Radiation in Semiconductors Due to Generation of Free Carriers

    Danileiko, YK
    P. N. Lebedev Physical Institute of the USSR Academy of Sciences, Moscow,

    Lebedeva, TP
    P. N. Lebedev Physical Institute of the USSR Academy of Sciences, Moscow,

    Manenkov, AA
    P. N. Lebedev Physical Institute of the USSR Academy of Sciences, Moscow,

    Sidorin, AV
    P. N. Lebedev Physical Institute of the USSR Academy of Sciences, Moscow,

    Pages: 11    Published: Jan 1983


    Abstract

    Results of experimental studies of the interaction of high power CO2 (λ = 10.6 μm), CaF Er3+ (λ = 2.76 μm) and YAG Er3+ (λ = 2.96 μm) lasers with undoped Ge and Si are presented. The experiments included photoconductivity, microwave absorption and laser beam transmission measurements at various intensities up to the level of laser damage. For both the Ge and Si samples, nonequilibrium carrier generation has been observed with both CO2 and Er-laser excitation.

    It is shown that the carrier generation in Ge is due to two-photon ionization at the Er-laser wavelength, whereas none of the considered mechanisms (impact, multiphoton and thermal ionizations), explain the anomalous dependence of carrier density upon CO2-laser excitation intensity.

    Nonequilibrium carrier generation results in nonlinear absorption and self-defocusing, which in turn lead to the intensity saturation of high power laser beams. Analysis of these effects for prefocused beams is presented. It is shown, in particular, that the absence of bulk damage in Ge under CO2 and Er-laser radiation is attributed to these effects even at very high incident intensities. It is pointed out that these effects play an important role in the application of Ge as a material for use in high power IR lasers.

    Keywords:

    high power laser interaction with semiconductors, nonequilibrium carrier generation, photoconductivity, nonlinear absorption, self-defocusing, laser-produced damage, high-power laser materials, Ge, Si


    Paper ID: STP37285S

    Committee/Subcommittee: F01.02

    DOI: 10.1520/STP37285S


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