Beam shaping of a broad-area laser diode using 3D integrated optics

Typical high power broad-area semiconductor lasers exhibit a highly astigmatic beam profile. However, many applications require a homogenous and circular symmetric beam. Thus coupling into circular multimode optical fibers is often employed. The strip-like astigmatic output of the diode laser underfills the circular multimode fiber, thus a decrease in beam quality occurs after fiber coupling due to mode mixing inside the optical fiber. This Letter presents a 3D integrated optics approach to shape the output of a broad-area laser diode. Ultrafast laser inscription is utilized to create a pair of photonic lanterns connected back to back inside a glass chip that captures and shapes the output of a commercial 976 nm wavelength broad-area laser diode with 95 μm emitter width. Compared to coupling to a 105 μm diameter, 0.15 numerical aperture step-index multimode fiber, the photonic chip-based approach results in a 13× higher beam quality and 7× greater brightness.