Transmissivity comparison of two kinds of SIL for near-field optical storage

A solid immersion lens(SIL) using in high-density optical recording works by changing evanescent waves(in the condition of high N.A.) into propagating waves through tunneling effect, and the rays are focused on recording medium. So the transmissivity and the tunnel width is a sharp conflict. The analysis and brief calculation in this paper show that, the transmissivity angular spectrum of hemisphere SIL(HSIL) and super hemisphere SIL(SSIL) is obviously different. When the tunnel width is narrow(about 1/10 lambda), the former(HSIL) has a high transmissivity than the latter(SSIL) only when the N.A. is near the highest. But if the width becomes larger, the transmissivity of SSIL is always better than that of HSIL. And when the width is about 1/2 lambda, the high-N.A. transmissivity of both is nearly zero.