Fast carrier dynamics in new GaAs deep-center laser for 1.3μm-1.5μm fiber optics

Abstract

The ongoing quest for semiconductor lasers with low threshold has led to the development of new materials (quantum wells, wires, and dots) and new optical resonators (microdisks and photonic bandgap crystals). In a novel approach to thresholdless lasers, we have developed a new growth technique for self-assembled deep-centers in the technologically important semiconductor gallium-arsenide (GaAs). We recently demonstrated the first GaAs deep-center laser. These lasers, which intentionally utilize GaAs deep-center transitions, exhibit a threshold current density of less than 70mA/cm2 in continuous-wave mode at room temperature at the important 1.54 μm fiber-optic wavelength in a single-pass geometry. We studied fast carrier dynamics in the new GaAs deep-center laser. The low threshold current was a consequence of fast subpicosecond capture of free holes onto deep-centers. This fast capture of free holes onto deep-centers allowed fast depopulation of electrons out of the lower energy level of the optical transition. We demonstrated laser action at many wavelengths between 1.2 μm and 1.6 μm, including fiber-optic wavelengths. A significance is that it has been a long-sought goal to tune the stimulated-emission from the same semiconductor over a wide wavelength range. A semiconductor source of tunable coherent radiation would have many applications, e.g., fiber-optics, spectroscopy, lab-on-a-chip, chemical species identification.