UC Merced

The longitudinal component of radially polarized electric field in the focal region has attracted particular attention in the laser optics due to its several special characteristics, namely, the directional characteristic on propagation axis, strong intensity and small focal size when tightly focused with high-numerical-aperture optical system, which find applications

such as particle acceleration, molecule microscopy, material processing, and particle trapping. It has been proposed and experimentally demonstrated that paraboloidal reflector creates smaller focal size compared with lens.

Comparatively little attention has been paid to its microwave version since, in microwave regime, the directional property in focal region has not been the main interest. Only very recently, after the introduction of planar slot antenna which can generate microwaves with focusing for near field scanning, the longitudinal component of radially polarized microwave

with the slot antenna has been experimentally investigated. However, the focusing of radially polarized microwave with paraboloidal reflector is much more versatile in applications as in the optical regime.

The experimental observation of this longitudinal component is newly performed in this work with a configuration of two-paraboloidal-mirror system. This longitudinal field of microwave and the two-mirror system can also be exploited in some applications such as microwave scanning, microwave acceleration in free space, and creating Bessel-like beam

which can be used in high resolution tomography, micro-manipulation in optical regime and long range communication in microwave regime. Two applications, microwave particle acceleration and quasi Bessel beam, are investigated in this work. A new method of ultratight focusing acceleration is proposed and a more precise analysis of quasi Bessel beam with variable cone angles is demonstrated.