Enhancement of third-order nonlinear optical susceptibilities in compressively strained quantum wells under the population inversion condition

Third-order optical nonlinear susceptibilities /spl chi//sup (3)/ in compressively strained and nonstrained InGaAs-InGaAsP quantum wells (QW's) under the population inversion condition are discussed. The small effective mass of compressively strained QW's increases the contribution of the carrier density pulsation effect and the carrier heating effect of /spl chi//sup (3)/. The hole burning effect is also increased due to the decrease of the carrier-carrier scattering rate. The calculation including these effects shows an enhancement of factor 3 due to 0.8% compressive strain. The values of /spl chi//sup (3)/ are experimentally estimated from the data of nondegenerate four-wave mixing in /spl lambda//4-shifted distributed feedback lasers. /spl chi//sup (3)/ in 0.8% compressively strained QW's is three times larger than that in nonstrained QW's with the same linear gain.