Optical intensity distribution of a plano-convex solid immersion mirror

Ignoring the effect of the small aperture, we deduce the optical field distribution of the so-called plano-convex solid immersion mirror with a small aperture on the apex (PC-SIM) by using the vector diffraction theory. The simulation results show that a PC-SIM, like a solid immersion lens (SIL), can achieve high resolution. Unlike the SIL, the PC-SIM can effectively reduce the spreading of the spot size with increasing distance from the interface. The size and intensity of the spot are related not only to the refractive index of the solid immersion medium but also to the structure parameter of the PC-SIM. The size of a spot smaller than a quarter wavelength can be obtained simply by optimizing the structure parameter of a PC-SIM but not by decreasing the size of the small aperture.