Four-wave mixing in indium antimonide

We report a range of experiments in both the degenerate and nondegenerate regimes of four-wave mixing in indium antimonide using CW CO laser sources. For the degenerate case, we specify all the polarization source terms and the signals which they radiate. We identify the dominant term for the phase-conjugate signal experimentally, and confirm that this involves a large-period grating formed by the forward pump and probe. The third-order susceptibility was measured as
X^{(3)} \sim 1.1
esu. This was shown to be highly resonant with the InSb bandgap. By varying the pump-probe input angle, the period of the grating was changed, and thus a carrier diffusion length of
l_{D} = 60 \mu
m was determined. By probing the grating with a second laser, the dispersion of the grating was measured over a wide range of frequencies, and was found to be much less resonant with the band edge than
X^{(3)}
. Saturation of
X^{(3)}
was observed and possible sources are identified and discussed. The results of near-resonant nondegenerate mixing experiments are presented and the measured value of
X^{(3)} = 5 \times 10^{-7}
esu under these conditions is discussed in relation to the much larger degenerate, resonant
X^{(3)}
.