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

Third-order optical nonlinear susceptibilities χ⁽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 χ⁽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 χ⁽³⁾ are experimentally estimated from the data of nondegenerate four-wave mixing in λ/4-shifted distributed feedback lasers. χ⁽³⁾ in 0.8% compressively strained QW´s is three times larger than that in nonstrained QW´s with the same linear gain