High-Power LOC Lasers: Synthesis and Mode Control

Heterojunction laser diodes of GaAs and (A1Ga)As have become increasingly sophisticated structures fabricated by liquid-phase epitaxy (LPE). Because of progress made both in the technology and in our theoretical understanding of laser diodes, it is now possible to design devices for specific applications. There is general interest in devices both for high peak power (pulsed) operation at room temperature and in diodes capable of reliable continuous room-temperature operation. Both types of devices require low thermal and electrical resistance but other requirements differ. The high-power pulsed lasers need not have very low threshold current densities, but they must be capable of withstanding catastrophic degradation resulting from excessive optical flux density at the emitting facet. The cw lasers, on the other hand, operate at low power levels (tens of milliwatts) and require low threshold current densities to minimize thermal dissipation problems. The beam divergence should be as low as possible in all devices to reduce the size of the external optical collimating system. In this final report, we discuss techniques used to achieve the control of material parameters of state-of-the-art high-power laser diodes with particular emphasis on the question of radiation pattern control.