The room-temperature (300 K), pulsed mode operation of a GaAs-based quantum-cascade laser is presented. This has been achieved by the use of a GaAs/Al0.45Ga0.55As heterostructure which offers the maximum Γ–Γ band offset (390 meV) for this material system without inducing the presence of indirect barrier states. Thus, better electron confinement is achieved, countering the loss of injection efficiency with temperature. These devices show ∼100 K increase in operating temperature with respect to equivalent designs using an GaAs/Al0.33Ga0.67As heterostructure. We also measure 600 mW peak power at 233 K a temperature readily accessible by Peltier coolers.
Measurements of the light emission under strong magnetic field from quantum cascade lasers emitting at 9 and 11 μm are reported. The laser intensity shows strong oscillations as a function of the magnetic field. This effect is due to changes in the lifetime of the upper state of the laser transition, which is controlled by electron-optical phonon scattering. This process is strongly modified by the extra confinement imposed by a magnetic field applied perpendicular to the plane of the layers, which breaks the electron dispersion into discrete Landau levels. The experimental results are in remarkable agreement with our calculations of the phonon-limited lifetime. We also show that this experiment provides direct indications of the ratio of the scattering rates associated with the two nonradiative transitions in the active region.
GaAs-based quantum-cascade lasers based on a bound-to-continuum transition have been realized and characterized. This band structure design combines the advantages of the well known three-well and superlattice active regions. We observed lasing of Fabry–Pérot lasers in pulsed mode up to a temperature of 100 °C. Multimode emission with a pulsed peak power of 340 mW is observed at room temperature and 42 mW at 80 °C. Further, from aging tests we expect a lifetime of over 60 years for these devices.
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