Differential interference contrast (DIC) microscopy allows high-contrast, low-phototoxicity, and label-free imaging of transparent biological objects, and has been applied in the field of cellular morphology, cell segmentation, particle tracking, optical measurement and others. Commercial DIC microscopy based on Nomarski or Wollaston prism resorts to the interference of two polarized waves with a lateral differential offset (shear) and axial phase shift (bias). However, the shear generated by these prisms is limited to the rectilinear direction, unfortunately resulting in anisotropic contrast imaging. Here we propose an ultracompact metasurface-assisted isotropic DIC (i-DIC) microscopy based on a grand original pattern of radial shear interferometry, that converts the rectilinear shear into rotationally symmetric along radial direction, enabling single-shot isotropic imaging capabilities. The i-DIC presents a complementary fusion of typical meta-optics, traditional microscopes and integrated optical system, and showcases the promising and synergetic advancements in edge detection, particle motion tracking, and label-free cellular imaging.

A high-performance electromagnetic interference (EMI) shielding structure based on pure graphene (without doping) consists of several graphene sheets separated by transparent polyethylene terephthalate (PET) films. We report the theoretical and experimental design, and characterization of the multi-layer graphene/PET structures. With a total graphene thickness of only 4 nm, the graphene/PET sample demonstrated an average shielding effectiveness of 19.14 dB at 18–26.5 GHz, with a maximum microwave absorbance of 95.82% at 25.7 GHz, while maintaining a normalized visible transmittance of 80.5%. For the multi-layer graphene/PET samples, the contribution of absorption to the total shielding exceeds 96%, indicating that absorption is the dominant shielding mechanism, instead of reflection. The microwave absorbance of the multi-layer graphene/PET structure increases rapidly from the mono- to the four-layer structures, and then more gradually as the number of layers continues to increase when the thickness of PET is 1 mm. In addition, the microwave absorbance can be improved two-fold by increasing the separation between graphene layers. We believe that this multi-layer graphene/PET structure, which exhibits high-performance microwave absorption and shielding, has great potential for applications in transparent EMI shielding devices, especially if EMI absorption is required.

We report a nested multi-ring array metallic mesh (NMA-MM) that shows a highly uniform diffraction pattern theoretically and experimentally. Then a high-performance transparent electromagnetic interference (EMI) shielding structure is constituted by the double-layer interlaced NMA-MMs separated by transparent quartz-glass substrate. Experimental results show that double-layer interlaced NMA-MM structure exhibits a shielding effectiveness (SE) of over 27 dB in the Ku-band, with a maximal SE of 37 dB at 12 GHz, normalized optical transmittance of 90%, and minimal image quality degradation due to the interlaced arrangement. It thus shows great potential for practical applications in transparent EMI shielding devices.

A high-performance transparent electromagnetic interference (EMI) shielding material based on a graphene/metallic mesh/transparent dielectric (GMTD) hybrid structure is designed and characterized. It consists of stacked graphene and metallic mesh layers, with neighboring layers separated by a quartz-glass substrsate. The GMTD hybrid structure combines the microwave-reflecting characteristics of the metallic mesh and the microwave-absorbing characteristics of graphene to achieve simultaneously high visible transmittance, strong microwave shielding effectiveness (SE), and low microwave reflection. Experiments show that a double-graphene and double-metallic mesh GMTD hybrid structure with a mesh periodicity of 160 µ m provides microwave SE exceeding 47.79 dB in the K _u -band, and an SE exceeding 32.12 dB in the K _a -band, with a maximum value of 37.78 dB at 26.5 GHz. SE by absorption exceeds 30.78 dB in the K _a -band, with a maximum value of 34.55 dB at 26.5 GHz, while maintaining a normalized visible transmittance of ~85% at 700 nm. This remarkable performance favors the application of the proposed structure as a transparent microwave shield and absorber, and offers a new strategy for transparent EMI shielding.