Label-free far-field subdiffraction imaging based on hyperbolic metamaterial

Super-resolution optical microscopy is an important technology due to the non-contact and non-destructive advantages. Currently, most of the super-resolution imaging methods rely on fluorescent dyes, which limited their applications. The label-free far-field microscopy imaging method based on the frequency shift effect has been proposed and developed in recent years. However, its spatial resolution is limited by the refractive index of waveguide materials. Based on the characteristic of optical spatial spectrum band-pass filtering in hyperbolic metamaterials (HMM), a large-area uniform bulk plasmon polariton (BPP) field with high spatial frequency can be achieved by combining with nano-scale gratings. Due to the large wave vector of the BPP illumination, the high-frequency information of the object can be transferred to the passband in traditional imaging systems and participate in super-resolution imaging. Illuminated by a BPP field with 2.66 k₀ at a wavelength of 532 nm, a double-slit structure with a 100 nm-wide center-to-center distance has been resolved with a 0.85 numerical aperture standard objective based on this method. The lateral resolution is improved to λ/5.32. By further improving the transverse wave vector of BPP, it can be improved to λ/7.82. This design is label-free and conveniently integrated with traditional microscopes, which provides a visual super-resolution imaging method for applications in biomedicine, on-chip industry, material science, and other fields.