Focusing characteristics of a planar solid-immersion mirror

The focusing characteristics of a planar waveguide solid-immersion mirror with parabolic design have been investigated. The solid-immersion mirror is integrated into an optical waveguide, and light focusing is achieved with a parabolic mirror parallel to the waveguide plane and waveguide mode confinement normal to the waveguide plane. Optical-quality tantala silica planar waveguides can be obtained by evaporation. The parabolic sidewall reflects over 50% of the incident waveguide mode and generates a diffraction-limited focus. The measured spot size for the solid-immersion mirror described here is less than one third of the wavelength. Polarization analysis shows that the electric field near the focal region has components parallel and normal to the polarization state of the incident beam. The planar solid-immersion mirror is essentially free of chromatic aberration, and the alignment of the illumination beam is within a fraction of degrees.