975 nm high power diode lasers with high efficiency and narrow vertical far field enabled by low index quantum barriers

For optimal coupled power into fiber, high power diode lasers should operate efficiently with smallest possible vertical far field emission angle. Although waveguide and cladding layers can be designed to achieve small angles, the refractive index profile of the active region itself restricts the minimum achievable value. We show that the use of low index quantum barrier layers leads to substantially reduced far field angles, while sustaining high power conversion efficiency. 90 μm stripe lasers that use such designs have narrow vertical far field angles of 30° (95% power content), power conversion efficiency of 58% and operate reliably at 10 W output.