Gain spectra for GaAs double−heterostructure junction lasers have been obtained with high resolution. This is accomplished by using an automated data aquisition system to analyze the Fabry−Perot resonance modulation in the spontaneous emission spectra. For active regions doped with Ge at a level of 4×1017 cm−3, the gain in the TE polarization at a fixed wavelength increases linearly with current, below lasing threshold. However, the peak gain (at a variable wavelength) increases slightly faster than linearly with current. The photon energy at which gain is a maximum increases logarithmically with current. Gain in the TM polarization depicts the same general behavior as that for the TE case, except that it is slightly less than the TE gain. It is concluded that for this particular doping the spectral gain characteristics are intermediate between those for undoped and heavily doped active regions. Above the threshold for lasing in the TE mode the TE gain spectra are well saturated, with new fine details revealed in the saturated spectra. On the other hand, gain in the nonlasing TM polarization is not well saturated above threshold, with marked differences in gain between high and low photon energies relative to the TE lasing energy.

The rapid degradation at 300°K in the cw regenerative output of stripe-geometry GaAs double-heterostructure junction lasers is shown to be a result of the formation of a local optical absorber in the laser cavity. Gain measurements performed on diodes before and after degradation show that the optical loss within the cavity increases during degradation. By observing the (predominantly) spontaneous emission from the active region directly through the n-GaAs substrate, it is confirmed that the increased loss is localized in a region where little or no spontaneous emission takes place at lasing energies. In such diodes, the internal radiative efficiency of the undegraded portion of the optical cavity shows a relatively small decrease compared to the external differential quantum efficiency. When the local absorber extends over a sufficient length of the cavity the electronic gain in the undegraded section is insufficient to overcome the loss and the device ceases to act as a regenerative optical oscillator. Net gain measurements on DH laser devices in which the active region is lightly (≈ 1017) n-doped indicate that the optical gain increases linearly with current prior to degradation. At lasing threshold the medium exhibits net gain over a wavelength range of 100 Å. After degradation the gain dependence on current can become superlinear due to the saturation of the optical absorber. Estimates on the attenuation constant in the local absorber at low currents give a value of ≈ 60 cm−1 at 8800 Å. For pulsed currents close to lasing threshold the attenuation constant increases to nearly 160 cm−1 at 8760 Å.

Impurity-free selective layer disordering, utilizing Si3N4 masking stripes and SiO2 defect (vacancy) sources, is used to realize room-temperature continuous AlxGa1−xAs-GaAs quantum well heterostructure lasers.

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Saturation of the junction voltage has been observed to occur at the onset of lasing in cw stripe-geometry (AlGa)As double-heterostructure junction lasers. Simultaneous measurements of the nonlasing but amplified spontaneous emission confirm that saturation of the optical gain and spontaneous emission accompany the voltage saturation as expected. With well-behaved lasers the observed saturation is maintained over currents to at least 50% above threshold. In other devices, a loss of saturation is commonly observed to occur simultaneously with a nonlinearity in the current dependence of the lasing emission.