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Sharper focal spot formed by higher-order radially polarized laser beams

2007; Optica Publishing Group; Volume: 24; Issue: 6 Linguagem: Inglês

10.1364/josaa.24.001793

1520-8532

Yuichi Kozawa, Shunichi Sato,

Near-Field Optical Microscopy

The intensity distributions near the focal point for radially polarized laser beams including higher-order transverse modes are calculated based on vector diffraction theory. For higher-order radially polarized mode beams as well as a fundamental mode (R-TEM01*) beam, the strong longitudinal component forms a sharper spot at the focal point under a high-NA focusing condition. In particular, double-ring-shaped radially polarized mode (R-TEM11*) beams can effectively reduce the focal spot size because of destructive interference between the inner and the outer rings with π phase shift. Compared with an R-TEM01* beam focusing in a limit of NA=1, the full width at half-maximum values of the focal spot for an R-TEM11* beam are decreased by 13.6% for the longitudinal component and 25.8% for the total intensity.