A physical model of an annular-aperture solid immersion lens (SIL) is proposed, and its attractive features are presented numerically with the finite-difference time-domain method. Placing an appropriate annular aperture in front of the SIL shows that the focal depth can evidently be improved, combining the virtues of the annular-aperture technique and the SIL technique. With this proposed method the rigorous distance control condition in related devices can be relaxed, preventing scratches or collisions between the optical head and the recording medium. Potentially, this technique could have great prospects for applications in optical data recording, lithography, and other applications that depend on immersion media to meet the resolution criteria across the image field.
© 2004 Optical Society of America
(000.4430) General : Numerical approximation and analysis
(050.1940) Diffraction and gratings : Diffraction
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(210.4770) Optical data storage : Optical recording
(220.2560) Optical design and fabrication : Propagating methods
Cheng Liu and Seung-Han Park, "Numerical analysis of an annular-aperture solid immersion lens," Opt. Lett. 29, 1742-1744 (2004)