Based on the triangular lattice two-dimensional photonic crystal(PC), the lattice spacing along the transverse direction to propagation is altered, and a gradient PC(GPC) flat lens is designed. The band structures and...Based on the triangular lattice two-dimensional photonic crystal(PC), the lattice spacing along the transverse direction to propagation is altered, and a gradient PC(GPC) flat lens is designed. The band structures and equal frequency curves of the GPC are calculated;then, the imaging mechanism and feasibility are analyzed. The imaging characteristics of the GPC flat lens are investigated. It is observed that the GPC can achieve multiple types of super-resolution imaging for the point source. This GPC lens is allowed to be applied to imaging and other fields such as filtering and sensing.展开更多
In this Letter, a photonic crystal(PC) flat lens with a scatterer-size gradient is proposed, which simultaneously achieves imaging of the point source and sub-wavelength focusing of the plane wave in the first, second...In this Letter, a photonic crystal(PC) flat lens with a scatterer-size gradient is proposed, which simultaneously achieves imaging of the point source and sub-wavelength focusing of the plane wave in the first, second, and fifth bands. The imaging of the point source breaks through the diffraction limit in the second and fifth bands. The PC flat lens with the scatterer-size gradient is expected to be used in a new multifunctional optical imaging and focusing device, which improves the application potential of a PC flat lens.展开更多
Topological photonics have led to robust optical behavior of optical devices, which has alleviated the influence of manufacturing defects and perturbations on the device performance. Meanwhile, temporal coupled-mode t...Topological photonics have led to robust optical behavior of optical devices, which has alleviated the influence of manufacturing defects and perturbations on the device performance. Meanwhile, temporal coupled-mode theory(t-CMT) has been developed and applied widely. However, the t-CMT of cascaded coupled cavities(CCC) system and its corresponding high-order filter has yet to be established. Here, the t-CMT of CCC system is established based on the existing t-CMT. By combining the CCC with topological waveguides, a versatile design scheme of high-order nonreciprocal add-drop filter(HONAF) is proposed. The relationship between the coupling effect of cavities and transmission and the filtering performance of HONAF is analyzed quantitatively. Then, a method to improve the transmission efficiency and quality factor of the filter is given. The proposed HONAF is based on the combination of gyromagnetic photonic crystals and decagonal Penrose-type photonic quasicrystals. The transmission and filtering performance of the HONAF are numerically analyzed, which verifies the consistency between theoretical prediction and numerical simulation. The established t-CMT of CCC system can be widely used in coupled resonator optical waveguides and their related systems. The proposed HONAF with excellent performance can also be applied to wavelength division multiplexing/demultiplexing systems.展开更多
基金the National Natural Science Foundation of China(No.61405058)the Natural Science Foundation of Hunan Province(Nos.2017JJ2048 and 2020JJ4161)the Fundamental Research Funds for the Central Universities(No.531118040112).
文摘Based on the triangular lattice two-dimensional photonic crystal(PC), the lattice spacing along the transverse direction to propagation is altered, and a gradient PC(GPC) flat lens is designed. The band structures and equal frequency curves of the GPC are calculated;then, the imaging mechanism and feasibility are analyzed. The imaging characteristics of the GPC flat lens are investigated. It is observed that the GPC can achieve multiple types of super-resolution imaging for the point source. This GPC lens is allowed to be applied to imaging and other fields such as filtering and sensing.
基金supported by the National Natural Science Foundation of China (No. 61405058)the Natural Science Foundation of Hunan Province (No. 2017JJ2048)the Fundamental Research Funds for the Central Universities (No. 531118040112)
文摘In this Letter, a photonic crystal(PC) flat lens with a scatterer-size gradient is proposed, which simultaneously achieves imaging of the point source and sub-wavelength focusing of the plane wave in the first, second, and fifth bands. The imaging of the point source breaks through the diffraction limit in the second and fifth bands. The PC flat lens with the scatterer-size gradient is expected to be used in a new multifunctional optical imaging and focusing device, which improves the application potential of a PC flat lens.
基金supported by the National Natural Science Foundation of China(Grant Nos.61405058,and 62075059)the Natural Science Foundation of Hunan Province(Grant Nos.2017JJ2048,and 2020JJ4161)the Fundamental Research Funds for the Central Universities(Grant No.531118040112)。
文摘Topological photonics have led to robust optical behavior of optical devices, which has alleviated the influence of manufacturing defects and perturbations on the device performance. Meanwhile, temporal coupled-mode theory(t-CMT) has been developed and applied widely. However, the t-CMT of cascaded coupled cavities(CCC) system and its corresponding high-order filter has yet to be established. Here, the t-CMT of CCC system is established based on the existing t-CMT. By combining the CCC with topological waveguides, a versatile design scheme of high-order nonreciprocal add-drop filter(HONAF) is proposed. The relationship between the coupling effect of cavities and transmission and the filtering performance of HONAF is analyzed quantitatively. Then, a method to improve the transmission efficiency and quality factor of the filter is given. The proposed HONAF is based on the combination of gyromagnetic photonic crystals and decagonal Penrose-type photonic quasicrystals. The transmission and filtering performance of the HONAF are numerically analyzed, which verifies the consistency between theoretical prediction and numerical simulation. The established t-CMT of CCC system can be widely used in coupled resonator optical waveguides and their related systems. The proposed HONAF with excellent performance can also be applied to wavelength division multiplexing/demultiplexing systems.
