Researchers at Massachusetts Institute of Technology's Lincoln Laboratory in Lexington have designed a high-brightness laser diode that uses a slab-coupled waveguide with multiquantum-well gain regions to produce high power with nearly circular modes. The structure of the laser allows a low power density at the facet and a mode size large enough for coupling to a single-mode optical fiber without the aid of lenses.As a "proof of concept" device, the scientists constructed a ridge-waveguide InGaAsP-InP laser that operated at 1.3 µm. Reporting in the June issue of IEEE Photonics Technology Letters, they said that the 7.7-mm-long laser produced 0.6 W -- 80 percent of which could be butt-coupled into a single-mode fiber.