Investigation Of Far-field Super-resolution Imaging Method Based On Super-oscillatory Phenomenon

The advances in imaging technology have driven the development of the science and technology and have a wide and profound influence across all fields, such as physics, chemistry, biology, material, medicine, etc. Diffraction, as an essential property of the light, gives a fundamental constraint on the resolution of arbitrary imaging systems. Overcoming the diffraction limit and improving the resolution of an imaging system have been the hot and tough issues in the world. Recently, super-resolution imaging technologies, such as the scanning near-field optical microscopy, negative refreactive index lens and stimulated emission depletion microscopy, have made some progress in microscopy imaging and micro-nano lithography, but they could not be used in the telescopy mode as the objects are located in the far-field and could not be manipulated artificially. The super-oscillatory phenomenon based on the delicate interference of band-limited wavevectors could generate information beyond the cutoff spatial frequency of the light field in the far-field. And the phenomenon could be used in the telecopy system to realize super-resolution imaging, but the super-oscillatory field suffers from the narrowband working wavelength and low energy efficeincy. To solve those problems, we carry out the super-resolution imaging principles and methods based on the super-oscillatory field in this thesis. The thesis mainly includes the following works and results.1. A real-time, free of posterior data processing and incoherent super-resolution telescope system is proposed and designed. The local light transfer model and super-resolution imaging mechanism in the telescope system are presented based on the super-oscillatory phenomenon. Experimentally, a minimal resolvable ability to 0.55 of Rayleigh criterion is abtained and the super-resolution imaging behaviors of off-axis targets and complex objects are investigated in the telescope system. The superimposing images of large targets could be used to extend the super-oscillatory viewing field.2. Conventional super-oscillatory lenses, benefiting from the constructive light interference, suffer from the narrowband working wavelength due to the fragility of the super-oscillatory field. To overcome the limitation of narrow working wavelength bandwidth, a broadband super-oscillatory lens is proposed with sub-wavelength nano-apertures, which could generate the unique nearly dispersionless phase profile when illuminated by variant wavelengths. The behaviors of the chromatic focus shift and focuses with variant incident wavelengths are investigated. In experiment, the focusing spots with 0.674 times the spot size of the Abbe diffraction limit are demonstrated in the visible and near-infrared light wavelength range.3. Two axial aberration-free methods are proposed to overcome the focus shift of the broadband super-oscillatory lens. The first one is utilized the frequency response behaviors of sub-wavelength nano-apertures with sectional elements to realize axial achromatic sub-diffraction focusing. The second design, combining the broadband phase modulation of sub-wavelength nano-apertures with a conventional achromatic lens, could achieve axial aberration-free sub-diffraction focuses with a broadband illumination. Broadband sub-diffraction focuses and super-resolution images are demonstrated when illuminated by variant incoherent light sources with central wavelengths at 450 nm, 550 nm and 650 nm and a bandwidth of 40 nm. Also, a white-light super-resolution image is demonstrated with a broadband white-light illumination.