Gain spectra measurement of strained and strain-compensated InGaAsP-AlGaAs laser structures for λ≈800 nm

InGaAsP single quantum wells (QWs) for wavelengths around 800 nm embedded in AlGaAs large optical-cavity waveguide structures are investigated by measuring modal gain spectra and broad-area (BA) laser parameters. The modal net-gain spectra are determined by the variable stripe-length method using current injection. Thick (18 nm) and nearly unstrained QWs show gain spectra without resolved subband structures. The modal gain in TE-polarization is twice as high as in TM-polarization. For thinner (13 nm) compressively strained (0.6%) QWs, the modal gain in TM-polarization and the transparency current density are lowered. For highly strained (1%) QWs, strain compensation by tensily strained GaAsP barriers improves the device performance. BA lasers with 5-nm-thick QWs with strain compensation show a 10% higher differential efficiency in comparison to structures without strain compensation