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Spectral beam combining of linear arrays of quantum cascade (QC) lasers emitting at 4.6 µm is demonstrated as a viable approach towards power-upscaling. By using an external cavity setup equipped with a diffraction grating and a partially transmitting output mirror providing wavelength selective feedback to each emitter, up to 8 individual QC lasers are combined with an optical coupling efficiency of 60% for an array of 6 emitters. The resulting beam quality (M2

This paper presents the operation and fabrication of GaInAs/Al(Ga)AsSb quantum cascade lasers. This article also focuses on the development of processing technology to enhance the heat removal from the active region of the lasers by depositing a thick gold layer on both sides of the laser ridge. Due to the improved heat removal devices emitting at around 4.9 /spl mu/m, the quantum cascade laser can be operated at high duty cycle (/spl ges/ 50%) up to a heat-sink temperature of 130 K.

Summary form only given. We report on a new design of GaInAs-AlInAs quantum cascade lasers (QCLs) improving the concept of Bragg reflectors by incorporating "blocking barriers" into the active regions. These barriers significantly enhance the confinement of electrons in the initial state of the laser transition by selectively blocking direct tunneling through the exit barrier (reducing the tunneling probability by a factor of 2). The high tunneling probability of electrons in the final state into the injector's miniband is maintained by reducing the total width of the exit barrier appropriately.