Abstract
Nonlinear absorption at 1.064 and 1.535 microm wavelengths by two photon and free carrier absorption processes in undoped and Fe doped InP has been investigated. Using picosecond and nanosecond duration lasers, a self-consistent set of the two photon and free carrier absorption coefficients are experimentally obtained through nonlinear transmission measurements for the first time. Reduced carrier recombination lifetime caused a decrease in nonlinear absorption of nanosecond duration laser pulses in Fe doped samples.
Highlights
Two photon absorption (2PA) in InP is a nonlinear optical phenomenon readily observed with lasers having irradiance in the MW/cm2 level or above if the photon energy of the laser is greater than half the bandgap energy of the semiconductor
The FCA process is quantified by the free carrier absorption cross section, σabs
We report the results of nonlinear absorption measurements conducted on 0.96 and 2.0 mm thick samples of undoped InP and a 0.92 mm thick Fe-doped InP sample using the irradiance scan method [5]
Summary
Two photon absorption (2PA) in InP is a nonlinear optical phenomenon readily observed with lasers having irradiance in the MW/cm level or above if the photon energy of the laser is greater than half the bandgap energy of the semiconductor. The FCA process is quantified by the free carrier absorption cross section, σabs. We report the results of nonlinear absorption measurements conducted on 0.96 and 2.0 mm thick samples of undoped (as grown) InP and a 0.92 mm thick Fe-doped (ntype) InP sample using the irradiance scan method [5]. Since FCA in InP predominantly arises from absorption due to holes [14], absorption coefficients of p-type InP samples (Zn:InP) with two different thicknesses and concentrations were measured as a function of wavelength. Hall measurements on these two samples provided their carrier concentrations, from which the hole absorption cross section at different wavelengths was determined. The hole σabs values were consistent with earlier measurements [4,6] but differed from the values obtained through NLA measurements presented here
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