Optical field distribution in ZnO/MgZnO quantum dot nanostructure at 375-nm wavelength

Computer analysis of near and far-field intensities in zinc oxide based quantum dot nanostructure has been carried out for the optimization of smaller active region volume of quantum dot to achieve desired modal gain. Near and far-field intensity distribution along junction plane has been studied as a function of mole fractions of Mg and for varying quantum dot thickness. Solutions to the wave equations have been obtained for the transverse electric mode. Effective index method has been used to deduce the propagation constants in various regions of optical wave-guide. Excellent confinement of near field intensity for greater values of Mg composition has been attributed to the increased values of refractive index step between dot and barrier regions. For the thicker dots, greater fraction of the optical field has been confined to the dot region. Near field intensity spread has been deduced and articulated in terms of full width of half maximum (FWHM) as a function of Mg mole fraction and a dot thickness. It clearly shows nonlinear decrease with increase of both the Mg mole fraction and a dot thickness. The surface image clearly reveals a bright spot in the center corresponding to far-field emitted from the dot region at 375-nm wavelength. Far-field intensity reveals divergence of 16°.