Wavelength modulation in twin segment double quantum well (DQW) AlGaAs/GaAs diode lasers

Reports on a simple mechanism for tuning a twin segment AlGaAs/GaAs DQW laser diode structure over a wide (60 Å) range. Within the useful operating region, the two segment drive currents are used independently to control wavelength and output power. This device therefore has considerable promise for integration into a frequency division multiplexed (FDM) source. The device structure proposed makes use of the low loss and the absorption characteristics of GaAs quantum wells. A low inherent loss makes very long cavity lengths feasible without unreasonable values of threshold current, and in turn therefore permits very high round-trip gain. This then ensures that high absorption regions can be introduced within the cavity using the quantum-confined Stark effect, which distorts the spectral gain distribution, causing a change in lasing wavelength. In addition, a long optical cavity introduces the possibility of using the more closely spaced longitudinal modes as individual channels without a significant loss of bandwidth