Mode confinement and near field intensity analysis in a GaN-based blue–green laser diode

Abstract

Field intensity analysis of a GaN-based channel substrate planer blue–green laser diode has been carried out at a 507 nm wavelength for better optical confinement to explore its applicability in optical storage. Our analysis reveals that a thin active layer does not support higher order modes. However, an active layer thickness of 0.23 µm supports the fundamental transverse mode and mode 1. The change in the geometry of the channel region provides guiding effects along the X-direction in a structure. It was found that an increase in the channel depth causes an increase of the effective refractive index in a nonlinear manner and the confinement factor increases in a nonlinear manner with the active layer thickness. It is inferred from our analysis that an increase in aluminium mole fraction in the clad leads to an excellent confinement of near field intensity, which has been attributed to an increase of refractive index step. The full width at half maximum (FWHM) of near field intensity was found to be 0.35 and 0.31 µm corresponding to aluminium mole fractions of 5% and 15%, respectively. The near field intensity distribution in the channel waveguide (3D) along the X- and Y-directions clearly shows confinement at the centre of the active region.