The smile effect of the laser bar increases the difficulty of laser beam coupling and limits its application. In this paper, the smile effect in the high-power laser on the microchannel cooler (MCC) and the method of reducing the smile effect by balancing the thermal-induced stress are studied. The model of diode laser packaging with MCC is established based on the finite-element method (FEM). The effect of the thickness of the N-foil on the smile effect and stress is analyzed. The bar is bent into a convex shape after the bar is bonded to the heat sink, according to the simulation. With the increase of the thickness of the N-foil, the bar deformation gradually decreases, and then the middle part of the bar reversely increases. The thermal-induced stress on the bar is balanced by optimizing the thickness of the N-foil. The minimum deformation was less than 0.2 μm.
The lateral leakage current is influenced by the height of ridge waveguide. We design two structures to restrict the lateral leakage current of ridge diode lasers, called ‘step-ridge’ structure and ‘groove-ridge’ structure. In order to obtain a better output electrical characteristic, we optimize the geometry of the two structures. For ‘step-ridge’ structure, we simulate various step-widths (including up-step widths and down-step widths). For ‘groove-ridge’ structure, we simulate different widths of groove and distances between injection section and groove. The lateral leakage currents of both two structures were calculated under the same injection current. In conclusion, both two structures can effectively reduce the leakage carrier by at most 80%, the ‘step-ridge’ diode lasers can improve around 6.5% wall-plug efficiency, but the ‘groove-ridge’ diode lasers would reduce the wall-plug efficiency at the same time.
We design a 976nm fiber coupling module with 20 single-emitter diode lasers by ray tracing. Each emitter has an output power of 10 W. This is achieved by beam collimation of the fast and slow axis, fast-axis beam stacking using overlapping mirrors, and polarization beam combining. Through polarization multiplexing, the output power can be nearly doubled with no loss of beam quality. The core diameter of output fiber is 105μm with a numerical aperture (NA) of 0.22. Finally, the simulated result indicates that the module can have an output power over 190W. At the same time, the brightness of 14.43 MW∙cm-2∙str-1 and the coupling efficiency of 95% can be achieved.
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