Experiments on the scalability of the coherent coupling of VCSEL arrays

A coherently coupled vertical cavity surface emitting laser (VCSEL) array, based on injection locking, was realized with master and slave lasers being integrated on the same monolithic chip. The radiation of the emitters is collimated by a micro lens array. The mechanical stability is achieved by a proprietary optical module.. consisting of the laser array, micro lens array, heat sink with Peltier element and a pin grid array for individual electric connections. For frequency and phase adjustment the individual operating currents have to be tuned with an accuracy of better than 0.1 %. This could be realized with a laser-trimmed array of micro resistors on a chip comparable in size to the laser chip. With 21 slave lasers nearly 90 % of the theoretically possible increase of the peak power density could be achieved. The coherent superposition is stable for hundreds of hours of operation. The small size of the micro resistors allows their integration on the laser chip thus reducing the number of connectors to only two - independent of the number of lasers.