Observation of extremely large quadratic susceptibility at 9.6<i>–</i>10.8<i>μ</i>m in electric-field-biased AlGaAs quantum wells

Abstract

We have observed an extremely large second-order susceptibility for second-harmonic generation of 9.6--10.8 \ensuremath{\mu}m radiation due to intersubband transitions in electric-field-biased GaAs quantum wells. For 92-A\r{} GaAs wells with 309-A\r{} ${\mathrm{Al}}_{0.48}$${\mathrm{Ga}}_{0.52}$As barriers under a bias of 36 kV/cm, the peak value of the susceptibility was 28 nm/V, 73 times larger than bulk GaAs. The magnitude and sign of the susceptibility depend on the bias field, and are in accord with theoretical predictions.