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The transverse mode control in oxide confined vertical-cavity surface-emitting lasers is discussed by modeling the dielectricaperture as a uniform waveguide and an extra reflectivity at the oxide layer. The phase of the extra reflectivity and the refractive index step can be adjusted to change the mode threshold gain. We calculate the lateral refractive index step from the mode wavelength difference between aperture and perimeter modes, and compare it with that obtained from the weighted average index. The mode reflectivity in terms of the lateral optical confinement factor at the oxide layer is considered in calculating the threshold gain for transverse modes. The numerical results show that higher transverse modes can be suppressed by adjusting the position of a thin AlAs-oxide layer inside a three-quarter-wave layer in the distributed Bragg reflector.
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