(3) a large field of view superstructure lens
The size of the field of view of the optical lens determines the field of view of the optical instrument. The larger the field angle, the larger the field of view. Due to the limitation of off-axis aberrations, the field of view of traditional optical spherical lens is very limited (generally no more than ± 30 °). In 2018, the research team of Luo Xiangang, the State Key Laboratory of Microfabrication Optics Technology, Institute of Optoelectronics, Chinese Academy of Sciences, realized the use of local light field and gradient phase control of subwavelength structure to achieve a plane super lens with a field of view range of more than ± 60 °. The planar super lens is composed of two superstructured surfaces with the same structure and an ultra-thin (~ 0.127λ) intermediate dielectric layer. Under the irradiation of electromagnetic waves, the electromagnetic coupling between the sub-wavelength unit structures in the same plane of the super lens excites the horizontal catenary light field, and the electromagnetic coupling of the upper and lower two layers excites the vertical catenary light field. Thanks to the insensitive nature of catenary light field to the angle of incidence, this design converts the translational symmetry of the radiation source in the focal plane to the rotational symmetry of the far-field radiation, enabling beam scanning in the 120 ° × 120 ° angle range.
(4) Color imaging superstructure lens
The joint team of the academician Zhu Shining of Nanjing University and the team of Professor Cai Dingping from the Center for Applied Science of Taiwan Academia Sinica has made a significant breakthrough in the research direction of visible broadband achromatic cemented-double lens. For the first time, they used a wideband achromatic superstructure lens to achieve white light imaging and color picture imaging, and obtained a good achromatic imaging effect. They used different-sized dielectric pillar structures to obtain superstructured units with high efficiency and phase curves proportional to frequency. They introduced different sizes of dielectric slot structures to obtain larger phase compensation values. Using these integrated resonance units, a broadband achromatic metamorphic lens covering the visible light band (400nm-660nm, bandwidth is 1/2 of the center wavelength) can be formed.
Achromatic Cemented-Double Lens
(5) Adjustable and reconfigurable superstructure lens
The research group of Professor Feng Yijun from the Microwave Technology Laboratory of Nanjing University carried out research on active metamorphic surfaces, innovatively combined electromagnetic field theory and circuit theory, and established an effective microwave active metamorphic surface analysis method and design ideas to realize A metamorphic surface with a fully dynamically adjustable reflection phase of 0-360 degrees.
The design method and principle of reconfigurable lenses have good scalability, and can be further applied in the fields of terahertz, infrared and visible light. It can realize small and efficient optical lenses and dynamic imaging systems, and has broad application prospects.
Professor Feng's group introduced adjustable and reconfigurable high precision optical components, and realized the continuously variable transmission phase of the superstructure unit through reasonable optimization design. Under the action of an external voltage sequence, the focus of the super lens can be scanned quickly point by point along a specific trajectory, and it can also achieve multi-focus focusing at any position.
(6) Superstructure lens for tomography
The research team of Li Tao and Zhu Shining of Nanjing University developed the spectral zoom and tomography technology without mechanical movement by using the large chromatic aberration effect of the superstructure lens, and realized the stereoscopic tomography of biological cells. Great application potential in highly stable imaging systems.
They cleverly use the characteristics of large chromatic aberrations of superstructure lenses to perform wavelength-adjusted optical zoom. At the same time, they introduced aspheric design to improve the depth of field resolution and obtain high-resolution tomography. Utilizing the unique dispersion characteristics of metamorphic lenses, a high-resolution and high signal-to-noise ratio microtomography technology is demonstrated. This technology is no longer limited by the numerical aperture and lens size of the lens, and is highly integrated and stable. In terms of imaging systems, it shows great application potential.