Solid-state microchip laser arrays

Microchip lasers with flat–flat cavities and small size have been previously demonstrated in a number of solid-state laser crystals with good efficiency, beam quality, and single frequency operation. An attractive way to scale the power of these lasers while maintaining the characteristics of the single microchip is by increasing the number of lasers operating in a single structure. In an incoherent array of lasers, the far-field modes overlap and the beam should have a divergence equal to the divergence of a single element. Additionally, such laser arrays have greatly reduced speckle. We used diode arrays to pump 1- and 2-mm thick flat–flat Nd: YAG microchip array wafers 25 mm in diameter. With a linear array of up to four elements operating cw, the pointing error of individual elements over the wafer is <5% of the divergence of each element, and the beam quality of individual elements is 1.5× diffraction-limited. Operation of a 2-D laser array with twenty-five elements was demonstrated using a pulsed diode laser array.