Near-field evolution in strongly pumped broad area diode lasers

Abstract

Many applications such as pumping of solid state lasers or ignition of explosives require high optical output powers during a short period. Pulsed operated diode lasers meet these requirements. They can be driven at elevated power levels, well above the ones specified for continuous wave (cw) operation. The optical near-field intensity of a diode laser in this operation regime is a key parameter since it determines the beam properties of the device. High power AlGaAs/GaAs quantum well broad area diode lasers are subjected to single pulse step tests carried out up to and beyond their ultimate limits of operation. Laser near-fields are monitored on a picosecond time scale using a streak-camera setup during pulse currents of up to ~50 times the threshold current. A transition from gain guiding to thermally-induced index guiding of the near-field is shown. Further power increase is prevented by catastrophic optical damage (COD). This sudden failure mechanism is studied in conjunction with filamentary properties of the near-field. The defect growth dynamics resolved on the picosecond time scale is used to gather inside into the physics behind COD.

Unveiling laser diode “fossil” and the dynamic analysis for heliotropic growth of catastrophic optical damage in high power laser diodes

“…In addition, an intense laser beam is further strongly self-focused by the thermal lensing effect in LD’s and the focused interaction zone is tightly confined within a region less than 1 μm 3 , leading to a locally higher energy density which can rapidly liquefy and even sublimate the solid. The phase-transformed solid can break the confinement of the surrounding lattice 16 .…”