High-power, low-lateral divergence InP type-I lasers around 2 µm with tapered waveguide structures

High power and high brightness InP based lasers around 2 µm are attractive for many applications due to their intrinsic compatibility with photonic integrated circuits. However, high output power and low lateral divergence are difficult to be realized simultaneously with the traditional ridge waveguide structure. In this paper, we demonstrate significantly enhanced performance of 1.96 µm InP based InGaAs quantum well lasers by tapered waveguide structures. The double-channel waveguide laser with a straight waveguide section and a small-angle tapered optical amplifier section showed fundamental transverse mode lasing with an excellent beam quality. In agreement with our designed waveguide structures, the devices’ lateral divergence is remarkably reduced. For the device with a 3° tapered angle, the narrowest full width at half maximum (FWHM) of 8.2° of the far-field distribution is realized and the continuous-wave output power, measured at 25 °C, is increased up to 40 mW, which is much higher than the 12 mW of the laser with only a straight ridge waveguide.