Narrow farfield, low threshold tapered lasers

In this paper we propose a new technique based on tapering of the waveguide layer along the cavity by Shadow Masked Growth (SMG), which yields low threshold lasers with a narrow farfield. Due to the diffusion limited MOVPE growth process the growth velocity V_gr on the substrate depends on the width of the channel W and the thickness H of the spacerlayer. The velocity will decrease with decreasing width W and increasing thickness H and vice versa. This makes it possible to change the thickness of the layer at predefined places on the substrate by varying the width of the channel. The prepatterned substrates are defined by lithography and wet etching