Design, implementation, and characterization of an optical power supply spot array generator for a four stage free-space optical backplane

In order to alleviate the throughput bottlenecks being encountered by high speed electronic computing and switching systems, research is turning its attention toward free-space photonics technology. Of particular interest currently is the use of Hybrid/SEED devices implemented as smart pixel arrays to encode the electronic data onto an array of constant power beams of light.This paper presents the design and implementation of a robust, scalable and modular optical power supply spot array generator for a modulator based free-space optical backplane demonstrator. Four arrays of 8 by 4 spots of (1/e$ sp2$ irradiance) 6.47$ mu$m radii pitched at 125$ mu$m in the vertical direction and 250$ mu$m in the horizontal were required to provide the light for the optical interconnect. Tight system tolerances demanded careful optical design, elegant optomechanics, and simple but effective alignment techniques. Issues such as spot array generation, polarization, power efficiency, and power uniformity are discussed and characterization results are presented