Abstract
Taking advantage of robust facet passivation, we unveil a laser “fossil” buried within a broad area laser diode (LD) cavity when the LD was damaged by applying a high current. For the first time, novel physical phenomena have been observed at these dramatically elevated energy densities within the nanoscale LD waveguide. The observation of the laser “fossil” is interpreted with different mechanisms, including: the origination of bulk catastrophic optical damage (COD) due to locally high energy densities, heliotropic COD growth, solid-liquid-gas phase transformations, strong longitudinal phonon cooling effect on the molten COD wave front, and the formation of patterns due to laser lateral modes. For the first time the COD propagation is analyzed temporally by an acoustic phonon bouncing model and the COD velocity is extrapolated to be exponentially decreasing from more than 800 μm/μs to a few μm/μs within a 20 μs time period as the energy density dissipates.
Highlights
The material preparations and qualities, and the irradiation conditions[11,13,14]
For the COD originating near the AR facet, the interaction between the COD wave front and the longitudinal phonons reflected from the AR can be neglected because the phonons are scattered and minimally affects the COD wave front when it catches up the decelerated COD wave front
The lattice sites are clearly resolved for the electron-optical conversion layers (AlGaAs/InGaAs/AlGaAs) grown along y-axis by metal-organic chemical vapor deposition (MOCVD) and the zinc selenide (ZnSe) passivation laser grown along z-axis by MBE, indicating almost defect free 3D epitaxial growth
Summary
The material preparations and qualities, and the irradiation conditions[11,13,14]. It’s reported that the energy fluence threshold for permanent damage (Fth) varies from 0.1 to 1.5 J/cm[2,7,8,12,13,14]. The energy density of COD wave front increases at the beginning of the interaction due to the energy addition from the phonons and quickly drops with energy transfer to the partially transmitted and reflected phonons, which have extracted energy from the COD, leading to a pulse-like compression of the molten COD. It should be noted the semiconductor could further be heated up via stimulated Brillouin scattering (SBS), a strong photon-phonon interaction due to the high intense laser induced non-linearity when the intensity of the light field itself affects the propagating medium[18,19,20]. The enhancement may be further boosted due to the decreased threshold of optical intensity for broad-band pump lasers[22]
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