Dispersion of the lowest-order optical nonlinearity in InSb

Second-harmonic generation has been studied in InSb. The fundamental source was a CO2 laser, and the second-harmonic photon energies were near the band edge. The non-linear susceptibility d14 is the largest known and shows significant frequency dependence. In a 2.6% range of photon energies, |d14| changes by 31% while the linear susceptibility at the second harmonic, χlin(2ω), changes by only 2.8%. In addition d14=|d14|ei is complex with ≅-50°. © 1971 The American Physical Society.