Manufacturing-tolerant compact red-emitting laser diode designs for next generation applications

Quantum well laser diodes with low far-field divergence remain a requirement for many applications such as optical interconnects and data networks, pump sources and next generation holographic red-green-blue displays requiring compact, high power, visible light sources with high spatial and spectral coherence. Many designs exist, but the structure must be easy to grow reproducibly, which has commercial advantages. The authors´ low far-field divergence design widens the vertical mode in such a way as to decrease the far-field divergence without significantly reducing the confinement factor, thus keeping threshold current lower. In this study, the authors calculate the sensitivity of their design, which has high refractive index mode expansion layers inserted in the cladding, to unintentional variations in layer thickness and composition during growth. They obtain consistency in measured far-fields for three wafers grown over an interval of a year, with a full-width-half-maximum vertical far-field divergence of 17° for a narrow design (Design A) and just under 13° for a very narrow design (Design B). They have demonstrated a useful, reproducible design, adding to the range of versatile semiconductor lasers available for every application.