In this paper, split-ring-based metamaterial sheets are designed for the purpose of achieving far-field subwavelength focusing, with the aid of a time-reversal technique. The metamaterial sheets are inserted into a su...In this paper, split-ring-based metamaterial sheets are designed for the purpose of achieving far-field subwavelength focusing, with the aid of a time-reversal technique. The metamaterial sheets are inserted into a subwavelength array consist- ing of four element antennas, with the element spacing being as small as 1/15 of a wavelength. Experiments are performed to investigate the effect of the metamaterial sheets on the focusing resolution. The results demonstrate that in the presence of the metamaterial sheets, the subwavelength array exhibits the ability to achieve super-resolution focusing, while there is no super-resolution focusing without the metamaterial sheets. Further investigation shows that the metamaterial sheets are contributive to achieving super-resolution by weakening the cross-correlations of the channel impulse responses between the array elements.展开更多
As an example of our new approach to complex near-field （NF） scattering of electromagnetic waves, the timereversal （TR） transmission process on an NF current-element array is mapped to the statistical process on a...As an example of our new approach to complex near-field （NF） scattering of electromagnetic waves, the timereversal （TR） transmission process on an NF current-element array is mapped to the statistical process on a kinetic Ising transmission chain. Equilibrium statistical mechanics and non-equilibrium Monte Carlo （MC） dynamics help us to find signal jamming, aging, annihilating, creating, and TR symmetry breaking on the chain with inevitable background noises; and these results are general in NF systems where complex electromagnetic scattering arises.展开更多
Optical imaging deep inside scattering medium has always been one of the challenges in the field of bioimaging,which significantly drawbacks the employment of con-focal microscopy system.Although a variety of feedback...Optical imaging deep inside scattering medium has always been one of the challenges in the field of bioimaging,which significantly drawbacks the employment of con-focal microscopy system.Although a variety of feedback techniques,such as acoustic or nonlinear fluorescence-based schemes have realized the refocusing of the coherent light,the problems of non-invasively refocusing and locating of linearly-excited fluorescent beads inside the scattering medium have not been thoroughly explored.In this paper,we linearly excited the fluorescent beads inside a scattering medium by using our homemade optical con-focal system,collected the fluorescence scattering light as the optimized target,and established a theoretical model of target contrast enhancement,which is consistent with the experimental data.By improving both the cost function and variation rate within the genetic algorithm,we could refocus the fluorescence scattering field while improving the contrast enhancement factor to 12.8 dB.Then,the positions of the fluorescent beads are reconstructed by subpixel accuracy centroid localization algorithm,and the corresponding error is no more than 4.2μm with several fluorescent beads within the field of view.Finally,the main factors such as the number of fluorescent beads,the thickness of the scattering medium,the modulating parameter,the experimental noise and the system long-term stability are analyzed and discussed in detail.This study proves the feasibility of reconstructing fluorescent labeled cells inside biological tissues,which provides certain reference value for deep imaging of biological tissues.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61071031,61331007,and 61107018)the Research Fund for the Doctoral Program of Higher Education of China(Grant Nos.20100185110021 and 20120185130001)+1 种基金the Fundamental Research Funds for the Central Universities,China(Grant No.E02205205)the Project ITR1113,China
文摘In this paper, split-ring-based metamaterial sheets are designed for the purpose of achieving far-field subwavelength focusing, with the aid of a time-reversal technique. The metamaterial sheets are inserted into a subwavelength array consist- ing of four element antennas, with the element spacing being as small as 1/15 of a wavelength. Experiments are performed to investigate the effect of the metamaterial sheets on the focusing resolution. The results demonstrate that in the presence of the metamaterial sheets, the subwavelength array exhibits the ability to achieve super-resolution focusing, while there is no super-resolution focusing without the metamaterial sheets. Further investigation shows that the metamaterial sheets are contributive to achieving super-resolution by weakening the cross-correlations of the channel impulse responses between the array elements.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No.20100185110021)the National Natural Science Foundation of China (Grant No.61071031)
文摘As an example of our new approach to complex near-field （NF） scattering of electromagnetic waves, the timereversal （TR） transmission process on an NF current-element array is mapped to the statistical process on a kinetic Ising transmission chain. Equilibrium statistical mechanics and non-equilibrium Monte Carlo （MC） dynamics help us to find signal jamming, aging, annihilating, creating, and TR symmetry breaking on the chain with inevitable background noises; and these results are general in NF systems where complex electromagnetic scattering arises.
基金Project supported by the National Key Research and Development Program of China(Grant No.2019YFC0119800)the Youth Talent Support Program of Universities of Hebei Province,China(Grant No.BJ2021038)+2 种基金the National Natural Science Foundation of China(Grant No.12004265)the Natural Science Foundation of Hebei Province,China(Grant No.A2020210001)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi,China(Grant No.2019L0541)。
文摘Optical imaging deep inside scattering medium has always been one of the challenges in the field of bioimaging,which significantly drawbacks the employment of con-focal microscopy system.Although a variety of feedback techniques,such as acoustic or nonlinear fluorescence-based schemes have realized the refocusing of the coherent light,the problems of non-invasively refocusing and locating of linearly-excited fluorescent beads inside the scattering medium have not been thoroughly explored.In this paper,we linearly excited the fluorescent beads inside a scattering medium by using our homemade optical con-focal system,collected the fluorescence scattering light as the optimized target,and established a theoretical model of target contrast enhancement,which is consistent with the experimental data.By improving both the cost function and variation rate within the genetic algorithm,we could refocus the fluorescence scattering field while improving the contrast enhancement factor to 12.8 dB.Then,the positions of the fluorescent beads are reconstructed by subpixel accuracy centroid localization algorithm,and the corresponding error is no more than 4.2μm with several fluorescent beads within the field of view.Finally,the main factors such as the number of fluorescent beads,the thickness of the scattering medium,the modulating parameter,the experimental noise and the system long-term stability are analyzed and discussed in detail.This study proves the feasibility of reconstructing fluorescent labeled cells inside biological tissues,which provides certain reference value for deep imaging of biological tissues.
