Numerical simulation of optical confinement in simple double heterostructure of ZnO / Mg x Zn 1-x O and hybrid double heterostructure of Al x Ga 1-x N/ZnO have been carried out at 375 nanometer wavelength using MATLAB. Field distribution along the junction plane has been studied as a function of mole fractions of Mg and Al for different thickness of active layers. The spread of field has been estimated as a function of mole fractions and articulated as Full Width at Half Maximum (FWHM). It was found to be decreasing nonlinearly with increase of Mg mole fraction in simple heterostructure and increasing in a nonlinear manner with increase of Al mole fraction in hybrid heterostructure. FWHM deduced from our analysis was 0.265 micron for 9% and 0.16 micron for 30% Mg mole fraction. For hybrid heterostructure, FWHM values estimated were 0.13 micron and 0.1475 micron for corresponding Al mole fraction values of 9% and 30%, respectively. The narrower confinement of field intensity around the center of the active layer for the higher values of Mg mole fraction has been attributed to an increase of refractive index step between active and barrier layers. The confinement factor as a function of mole fractions and active layer thickness has been explored, and it was found to be increasing with active layer thickness. Our analysis explores the optical confinement of mode 0 in simple and hybrid heterostructures of ZnO .
