Eigenmode confinement in the dielectrically apertured Fabry-Perot microcavity

The three-dimensional (3-D) optical confinement of the dielectrically apertured Fabry-Perot microcavity is analyzed by considering electromagnetic coupling between the confined region and parasitic waveguide modes that exist outside the aperture, If the cavity length is close to one-half the emission wavelength and for large enough aperture sizes, all parasitic waveguide modes can be evanescent except one which couples only weakly to the emitting region. If the aperture diameter is too small, loss of optical confinement is predicted, and the optical mode size at which this occurs can be estimated from the cavity length and the relative shifts in the vertical resonances inside and outside the apertured region.