A phase-locked diode-laser system based on master-slave coupling of two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays by injection locking is presented. Frequencies and phases are adjusted by laser-trimmed microresistors. Additional beam-transformation optics consisting of two diffractive optical elements (DOEs) and a Fourier lens concentrates most of the far-field power in a nearly diffraction-limited beam. Both the VCSEL array and the microlens array are monolithically integrated and mounted in a compact module. With an array of 21 slave lasers a system coherence of 95% (for several hours) and of nearly 90% (for several months) has been demonstrated without any active phase control. The scalability of the output power has been verified by locking of an array of 77 slave lasers with a system coherence of 78%. The optical system efficiency is 20–23%; with beam-transformation optics this efficiency could be improved to 44%.
© 2003 Optical Society of America
(140.2010) Lasers and laser optics : Diode laser arrays
(140.3300) Lasers and laser optics : Laser beam shaping
(140.3520) Lasers and laser optics : Lasers, injection-locked
(140.3570) Lasers and laser optics : Lasers, single-mode
Guido Hergenhan, Bernd Lücke, and Uwe Brauch, "Coherent Coupling of Vertical-Cavity Surface-Emitting Laser Arrays and Efficient Beam Combining by Diffractive Optical Elements: Concept and Experimental Verification," Appl. Opt. 42, 1667-1680 (2003)