Gain spectra measurement of strained InGaAsP / GaAsP / AlGaAs single and double quantum well laser structures for wavelengths near 800 nm

InGaAsP/GaAsP/AlGaAs single (SQW) and double quantum wells (DQW)

of different thickness are compared by modal gain spectra, measured with the variable stripe length method using current injection. Modal gain spectra of thick SQWs show transitions from several electron levels in TE polarization and low modal gain in TM-polarization. DQW spectra show no switching to transitions to higher electron levels up to excitation densities over 1 kA/cm². The modal gain of the DQWs in TM polarization is much higher due to the tensily strained GaAsP barrier between the quantum wells. SQWs are favored over DQWs in lasers, which need low threshold gain. DQWs are preferred for lasers with threshold gain above 15 cm^-1 and if a high differential gain is required.