In this paper, we numerically demonstrate that the negative refraction of a photonic crystal immersion lens can bend a beam by unconventionally large convergence angles over π/2 in free space. This super-convergence feature leads to constructive interference of high-spatial-frequency waves in both lateral and axial directions and forms super-resolution focal areas beyond the evanescent fields. As such, a 57% reduction in the focal area compared with the diffraction-limited case of an objective with numerical aperture of 0.95 has been numerically achieved at a normalized frequency of 0.3 in a photonic crystal immersion lens, corresponding to a lateral resolution of 0.32λ as well as an axial resolution of 0.70λ.
↧