Thermally Induced Current Bifurcation and Drastically Collapse of Output Optical Power in VCSEL Arrays

Based on a compact electro-opto-thermal model, thermally induced current bifurcation and drastically collapse of output optical power in vertical cavity surface emitting laser (VCSEL) arrays are studied. Taking a VCSEL array with two cells for example, the phenomenon of the current bifurcation and the behavior around the bifurcation point is studied and substantiated by experiments and simulations. With the aid of the electro-opto-thermal equivalent circuit of VCSEL arrays, the impact of series resistance and cell spacing on current bifurcation is investigated with respect to the temperature dependencies of bias current and output optical power. Additional ballasting resistance is helpful to eliminate current bifurcation at an expense of increasing the total quadratic power dissipation. Increasing cell spacing is helpful to alleviate thermal coupling effect and delay the current bifurcation. VCSEL arrays with proper design of additional ballasting resistance and increasing cell spacing can alleviate thermally induced current bifurcation and hence improve the total output optical power.