The focusing performance of an aperiodic double layer metallic grating

• An aperiodic double layer metallic grating is designed.
• A subwavelength and long depth of focus focal spot is achieved.
• Focusing performance is insensitive to alignment errors between layers.

In this paper, a double-layer aperiodic metallic grating is designed and the focusing performance is numerically researched using the finite-difference time-domain method. A sub-wavelength focusing spot is achieved and the depth of focus is twice the length of the incident wavelength. With its ease of fabrication, the designed aperiodic double-layer metallic grating has great potential in applications such as data storage, laser direct writing and optical probe.

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