The catastrophic optical mirror damage (COMD) effect is analyzed for 808 nm emitting diode lasers in single-pulse
operation. During each single pulse, both nearfield of the laser emission and thermal image of the laser facet are
monitored with cameras being sensitive in the respective spectral regions. A temporal resolution in the μs-range is
achieved. The COMD is unambiguously related to the occurrence of a 'thermal flash' detected by thermal imaging. A
one-by-one correlation between emission nearfield, 'thermal flash', thermal runaway, and structural damage is observed.
As a consequence of the single-pulse-excitation technique, the propagation of 'dark bands' as observed in photo- or
cathodoluminescence maps in the plane of the active region from the front facet is halted after the first pulse. Because of
the rapidness of the thermal runaway, we propose the single-pulse technique for testing the facet stability and the
intentional preparation of early stages of COMD; even for diode lasers that regularly fail by other mechanisms.

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Catastrophic optical mirror damage in diode lasers monitored during single pulse operation

Experimental results of the combination of AlGaIn-AsSb-based multiple quantum well broad area lasers with a monolithically integrated Fourier-optical 4f spatial-frequency-filter set-up for transverse mode selection are presented. Laser chips with filters for the selection of the fundamental transverse mode and higher order modes (here exemplarily the mode number 6) are processed, their emission is characterized.

Monolithic integration of transverse mode selectors with antimonide broad area lasers

Antimonide broad area lasers (BAL) have been prepared that include a Fourier-optical 4f spatial frequency filter set-up as a transverse mode selector (TMS). The resonator is folded about the Fourier-transform mirror with its focal length f equal to the resonator branch length d (i. e. half resonator length). The resonator length 2d is 1.65 mm and the whole resonator is gain section as well as part of the TMS. The approach to integrate BAL and TMS monolithically is verified; the experiments are typically performed around 85 K temperature. The concept can be employed for any edge emitting BAL, but we used an AlGaInAsSb-based laser design with mid-infrared emission wavelength around 2 μm, where lasers with higher output powers within the fundamental transverse mode are still needed for many applications. Above a certain operating temperature (≈140 K) a double-hysteresis emerges in the output-power versus pump-current characteristics. This as well as the free spectral range strongly suggest that both resonator branches act together as one entity.

Chr. Doering

Papers

Internal Transverse Mode Selection in Folded-resonator Antimonide Broad Area Lasers