Coherent addition of laser arrays using binary optics

Coherent beam superposition has been demonstrated using binary-phase grating couplers. The method of Amplitude-to-Phase conversion has been used to completely fill the laser array aperture with a uniform beam, concentrating the far-field energy into the centrallobe. Diffractive coupling using the Talbot Effect has been demonstrated and miniature Talbot cavities with direct lateral mode control have been made. The lateral modes of the miniature Talbot cavity are controlled by the cavity length and position of the reflective coating at the output coupling mirror. A figure shows the design of this Talbot cavity along with a measurement of its far-field output pattern. The output is nearly diffraction-limited. The most promising techniques involve miniaturized cavity designs which can be monolithically integrated. The Coupled Micro-Cavity with hybrid reflective / diffractive binary optical elements is a compact cavity which is designed on a single substrate. A figure shows how the nearest neighbor reflective coupling works in this cavity. The experimental far-field output from this device is also shown.