Abstract

Work on monolithic phase-locked arrays of diode lasers has been carried out for the last decade. Gain-guided arrays have demonstrated some impressive results, but the devices are inherently unstable. Positive-index-guided devices, while stable with changes in the drive condition, have been plagued either by self-focusing due to gain spatial hole burning (i.e., evanescently coupled devices) or by weak overall interelement coupling (i.e., Y-junction coupled devices). Arrays of negative-index guides (antiguides) are both immune to gain spatial hole burning as well as strongly coupled. Resonant leaky wave coupling¹ allows, for the first time, that each element equally couples to all others (i.e., parallel coupling). Such devices are called resonant optical waveguide (ROW) arrays.² ROW arrays have two main characteristics: (1) they must include means of suppressing oscillation of antiresonant array modes (e.g., out-of-phase modes); and (2) they have strong discrimination against adjacent mode oscillation (Δα = 10-20 cm−¹). Out-of-phase modes have been suppressed by diffraction coupling,³ the incorporation of a monolithic spatial filter based on the Talbot effect,^4,5 and/or enhanced interelement loss.⁵ Best results to date are diffraction-limited beam operation to 10× threshold and 450 mW from ten-element devices.⁵ Fringe visibility measurements confirm full coherence across the array. Nonresonant twenty-element devices have demonstrated inphaselike operation to 325 mW in beams with 80% of the energy in the main lobe, and lobe widths twice the diffraction limit.

© 1989 Optical Society of America