3D high precision laser printing of a flat nanofocalizer for subwavelength light spot array

Here, we demonstrate a flat nanofocalizer for converging light field into a uniform subwavelength light spot array based on the fractional Talbot effect by developing a direct laser writing technique with 3D fabrication precision. The fractional Talbot effect endows the device with the merits of high compression ratio and modular design capability for transforming a plane wave into arrayed light focal spots. By combining a synergistic laser printing technique, we introduce a buffer layer for improving the fabrication precision of structural height in favor of accurately manipulating the phase delay. For a given light wavelength at 750 nm, by precisely producing a nanofocalizer consisting of periodic unit elements with the dimensions of 300 ( w i d t h ) × 600 ( l e n g t h ) × 585 ( h e i g h t ) n m , we have achieved 5 × 6 light spot array with modular design, while the full width at half-maximum of a single focused light spot can be reduced to ∼ 0.82 λ . Our research may pave the way for realizing subwavelength optical devices capable of being readily integrated to existing optical systems.