Fig. 1. Focusing characteristics of single/multi-microsphere systems and the application of spatial and temporal optical filed manipulation in super-resolution micro-nanomanufacturing

Fig. 2. Factors influencing the focusing characteristics of single microsphere. (a) Light intensity distribution formed by microsphere focusing incident plane light, where the small inset in the bottom right corner of each figure indicates the main distribution area of light field intensity^[24]. (b) Optical field distribution of photonic nanojets generated by differently polarized incident light^[41]: (b1) circle polarized incident light; (b2) radial polarized incident light; (b3) azimuthal polarized incident light. (c) Light field distribution of different shapes of Bessel beams incident on microsphere^[42]: (c1) incident Bessel beam with central lobes larger than the diameter of the microsphere; (c2) incident Bessel beam with central lobes smaller than the diameter of the microsphere. (d) Light field distribution curves and different structures fabricated by different regions of intensity distribution^[24]. (e) Adjusting the incident light intensity changes the structure’s shape^[24]: (e1) before changes in incident light field intensity; (e2) after changes in incident light field intensity. (f) SEM images of conical hollow “nano-volcano” three-dimensional structure^[44]: (f1) structure prepared with a microsphere diameter of 750 nm; (f2) structure prepared with a microsphere diameter of 1.9 μm. (g) Simulation of the light field intensity distribution along the z-axis under different refractive indices^[45]. (h) Schematic diagram of internal light field intensity distribution within a single microsphere when subjected to substrate light reflection^[45]. (i) Schematic diagram of central overlay engineered microsphere with super-resolution focusing ability^[55]

Fig. 3. Factors influencing the focusing characteristics of multiple microspheres. (a) Schematic diagram of structure preparation using a single-layer microsphere array on a glass slide^[34]; (b) schematic illustration of energy flow from internal to boundary microspheres within a microsphere array^[61], where figures 1 and 2 represent internal and boundary microspheres, respectively; (c) light field distribution beneath microspheres under different conditions^[62], where figures (c1) and (c2) show light field distribution beneath a single microsphere and the central microsphere of microsphere array, respectively; (d) hexagonal field distribution formed on the surface of a gold-coated sphere^[43]; (e) fabrication of hexagonal aperture structures using a single-layer microsphere^[43]; (f) hexagram patterns fabricated by adjusting the spacing between adjacent microspheres, transparent layer thickness, and polarization of incident light^[43]

Fig. 4. Advances in spatial modulation of optical fields. (a) Schematic diagram of a compound lens consisting of a plano-convex lens and a dielectric microsphere lens^[63]; (b) schematic diagram of AFM cantilever scanning probe technique^[64]; (c) schematic diagram of AFM cantilever microsphere‒substrate distance control system^[65]; (d) schematic diagram of microsphere‒substrate distance control system using pipette^[66]; (e) schematic diagram of optical trapping of microspheres near the sample surface using optical tweezers^[67]; (f)‒(g) structures fabricated using microsphere arrays with different incident angles^[69], where figure (f) corresponds to off-axis irradiation angle of 30° and figure (g) corresponds to off-axis irradiation angle of 60°; (h) fabrication of C-shaped structures using continuous off-axis irradiation^[39]; (i) laser micro-nanomanufacturing with angular nanosphere lens and resulting periodic patterns^[70]; (j) schematic diagram of dual-beam illumination on microspheres^[71]

Fig. 5. Optimization strategy for fabrication of microsphere micro-nanostructures based on temporal optical field control techniques. (a) Relationship between pulse delay and average size of nano-apertures^[76]; (b) relationship between ablation threshold and pulse delay simulated by plasma model, where the dashed line represents the ablation threshold under single-pulse conditions, and the asterisks indicate the ablation thresholds under different pulse delays^[76]; (c) minimum nano-aperture under dual-pulse conditions with a laser fluence of 0.93 mJ/cm² and a pulse delay of 2500 fs^[76]; (d) morphological changes in structures prepared under single-pulse and dual-pulse with different pulse delay time at the same laser fluence (1.98 J/cm²)^[77]