US Patent 7830938 Laser diode

The present invention provides a laser diode having both a small vertical far-field beam divergence and a large vertical optical confinement factor, as well as a method of fabricating the laser diode. The laser diode comprises a layer stack of semiconductor material, which includes a mode-splitting layer having a low refractive index inserted between waveguide layers. In addition to increasing the vertical near-field beam width of the laser diode, the mode-splitting layer also produces a shoulder in an optical mode generated in an active layer of the layer stack, increasing vertical overlap of the optical mode with the active layer.