Effects of compressive and tensile uniaxial stress on the operation of AlGaAs/GaAs quantum-well lasers

The consequences of strain on the threshold current, relaxation oscillation frequency, and wavelength of operation of lasers have been investigated using an external uniaxial stress impressed on Ga1−xAlxAs/GaAs ridge-guide quantum-well lasers employing graded index and separate confinement. Under the conditions of small strain (≤0.1%), the threshold current increases monotonically from compressive to tensile conditions by as much as 30%, the relaxation oscillation frequency decreases monotonically from compressive to tensile conditions by as much as 100% when operating close to threshold conditions, and the mode spectrum shifts in accord with the shifts expected in the subband energy levels. These observations indicate that changes in effective mass, and hence in transparency and differential gain, are the dominant causes of this variation. For smaller band-gap structures, such as Ga1−xInxAs1−yPy lasers, where carrier lifetime effects should be expected to dominate, we speculate that the threshold current density may show a decrease for both compressive and tensile strain.