Abstract

High-power applications for diode lasers have recently been of increasing interest. In particular, one- and two-dimensional laser arrays are being investigated for this purpose. Among the most promising approaches for achieving coherent operation of the lasers in these arrays is the use of an external cavity. Successful implementations of such a system have been reported recently [1,2,3]. Since diode lasers typically have a beam divergence of a few tens of degrees, collimating the laser outputs leads to greatly improved far-field patterns, which, in turn, translates into more power in the main lobe of the combined output. Achieving this collimation in the case of a diode laser array, with its small device-to-device distance, requires an array of similarly spaced microlenses with very short focal length, small diameter and small F number. In this paper, we describe the fabrication and performance of a Fresnel microlens array etched directly in InP wafers: these microlenses have been used successfully to collimate the output of GaInAsP/InP buried-heterostructure (BH) diode lasers [4].

© 1987 Optical Society of America