Accurate optical power control of a vertical-cavity surface-emitting laser (VCSEL) array is achieved through the use of monolithically integrated photodetectors, which lie within the focal plane of the array and are interconnected into optoelectronic feedback loops. Piecewise linear device models, which also account for crosstalk and optoelectronic device variations, are developed to provide design guidelines. Direct digital control of the individual VCSEL output powers is then achieved through a custom CMOS driver chip based on programmable current-mode digital-to-analog converters. Experimental results verify the power control scheme and the developed models. The performance of this power control method in the presence of crosstalk and noise is also presented.
Mohammad Azadeh and Robert B. Darling, "Power Control of VCSEL Arrays Using Monolithically Integrated Focal Plane Detectors," J. Lightwave Technol. 20, 1478- (2002)