Continuous numerical aperture properties of a cylindrically polarized light illuminated sub-wavelength annular aperture.
We investigated the process of focusing a radially polarized (RP) light beam through a sub-wavelength annular aperture (SAA). We found that the result was a non-diffraction doughnut-shaped light beam which propagates in free space. After analyzing the electric field component of the focus generated by the SAA structure, we identified the relationship between the focal field generated by the SAA. We then compared it to a case with a traditional objective lens. From our findings, we propose that a SAA structure can be viewed as a continuous numerical aperture optical element.
Fang
Chun-Chieh
CC
Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan.
Cheng
Tsung-Dar
TD
Yeh
Jyi-Tyan
JT
Wu
Kuang-Chong
KC
Lee
Chih-Kung
CK
D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007909:Lenses; D008027:Light; D008029:Lighting / Q000295:instrumentation*; D008962:Models, Theoretical; D055096:Optical Devices; D012031:Refractometry / Q000295:instrumentation*; D012542:Scattering, Radiation; D020349:Surface Plasmon Resonance / Q000295:instrumentation*