Experimental study on subwavelength focusing optical field detection methods for micro-Fresnel zone plate

In this paper, the detection methods and detection systems for the subwavelength focusing optical field of the micro-Fresnel zone plate (FZP) are experimentally studied. First, a comparison is made between the micro/nanofabrication methods for micro-FZP, namely, focused ion beam (FIB) and electron beam lithography, and the results show that FIB is better suited for the amplitude-type micro-FZP fabrication. Subsequently, the experimental detection devices based on the wide-field microscopy amplification (WFMA) imaging method (indirect detection method) and scanning near-field optical microscopy (direct detection method) are, respectively, constructed for the detection of the subwavelength focusing optical field of micro-FZP. The experimental results are compared and analyzed with theoretical calculation results, indicating that the WFMA method is more suitable for the detection of micro-FZP subwavelength focusing optical field that is not sensitive to radial components. This study provides an experimental reference for the micro/nanofocusing optical field detection of micro/nano-optical components similar to micro-FZP and promotes the practical application of micro-FZP.