Three-core ARROW-type diode laser: novel high-power, single-mode device, and effective master oscillator for flared antiguided MOPA´s

A novel type of strong-index-guided laser structure for achieving coherent, high-power (~1 W) reliable operation is proposed, analyzed, and demonstrated for the first time. The three-core antiresonant-reflective-optical waveguide (ARROW) laser combines the relatively large fabrication tolerances of single-core ARROW-type devices with the excellent intermodal-discrimination properties of small-element-number (<10) resonant antiguided arrays (i.e., resonant optical-waveguide (ROW) devices.) Thus, the three-core ARROW device should prove a more practical device to fabricate than large element (>10) ROW arrays, which are known to have tight fabrication tolerances. For single-spatial-mode selectivity the device relies both on ARROW-type (lateral) reflectors and interelement loss. The effect of interelement loss on the resonant in-phase mode and the unwanted nonresonant modes is calculated, and the results are used to design optimal structures. For structures of index step, Δn, of 0.1; element/interelement width ratio of 5; 500 cm^-1 interelement-loss coefficient; and 7.5-μm-wide individual elements, intermodal discrimination ⩾5 cm^-1 is obtained over a relatively large range in Δn: ~0.01. Above-threshold analysis shows that, due to strong index guiding, the structures are virtually immune to gain spatial hole burning. The central-lobe energy content is 65-70%, and the emitting aperture is 25 μm, which should provide 1 W CW reliable single-mode power from devices with oxide-free facets. Preliminary experimental results are obtained from Al-free 0.98-μm emitting structures: diffraction-limited beam operation up to 30× threshold and 0.55 W peak pulsed output power. Finally it is shown that three-core ARROW devices used as integrated master oscillators (MO´s) for flared antiguided master-oscillator power amplifiers (MOPA´s), provide uniform MOPA near-field intensity profiles, thus opening the way to achieving 3-5 W CW diffraction-limited power from stable, flared MOPA´s