We investigate the wavelength and threshold current variation with passive wave-guide length in inhomogeneously pumped single and double quantum well InGaAs/AlGaAs strained layer ridge wave-guide lasers. We observe a linear and extremely low increase in threshold current with unpumped length, both for single and double quantum well lasers. A large red shift in the lasing wavelength as the unpumped length is increased is also observed. We present a model, based on absorption saturation in the unpumped section, which describes both the wavelength shift and the threshold current variation. The increase in threshold current that we observe is much smaller than results reported in the literature for GaAs/AlGaAs lasers, where a large exponential dependence was attributed to gain saturation in the pumped section. Because the threshold current does not dramatically vary with unpumped length for our lasers, this is a potentially useful technique for shifting the output wavelength of the laser. Finally, we investigate the wavelength tuning behavior of lasers having two segments pumped with different currents. A wavelength tunability of ~13 nm for the DQW laser was observed.
Density dependence of the excitation gaps in an undoped Si/SiGe double-quantum-well heterostructure
