1.3-μm large spot size laser for efficient fiber coupling

Abstract

Taper and truncation loss calculations, experimental internal reflections, and far-field characteristics and coupling efficiencies into single-mode fiber are reported for a 1.3-?m large spot laser design with laterally tapered active region and a weakly guiding passive waveguide underneath. In the front passive section, the taper is truncated. Modeled taper loss and truncation loss at the end of the taper are compared. It is shown that for taper lengths exceeding 125 ?m, truncation loss dominates taper loss unless the truncated active width is smaller than ~ 0.2 mm. Reflectometer experiments show that for a truncated active width of 0.2 ?m, reflections at the truncation point are negligible, in agreement with modeling results. Experimental far fields are shown to become narrower and smoother as the taper length or the passive section length is increased. Coupling efficiencies into a single-mode fiber are reported. Up to 56% butt-coupling is achieved, with 1 dB lateral fiber positional tolerance of up to 2.4 ?m horizontally and 2.3 ?m vertically.