This paper presents the theoretical investigation of hierarchical sub-wavelength photonic structures with various periods and numbers of layers, which were fabricated using a high-order waveguide-mode interference fie...This paper presents the theoretical investigation of hierarchical sub-wavelength photonic structures with various periods and numbers of layers, which were fabricated using a high-order waveguide-mode interference field. A 442-nm laser was used to excite high-order waveguide modes in an asymmetric metal-cladding dielectric waveguide structure. The dispersion curve of the waveguide modes was theoretically analyzed, and the distribution of the interference field of high-order waveguide modes was numerically simulated using the finite-element method. The various dependences of the characteristics of hierarchical sub-wavelength photonic structures on the thickness and refractive index of the photoresist and the waveguide mode were investigated in detail. These hierarchical sub-wavelength photonic structures have various periods and numbers of layers and can be fabricated by a simple and low-cost method.展开更多
Photonic crystal fibers （PCFs） with a stepped raised-core profile and one layer equally spaced holes in the cladding are analyzed. Using effective index method and considering a raised step refractive index differen...Photonic crystal fibers （PCFs） with a stepped raised-core profile and one layer equally spaced holes in the cladding are analyzed. Using effective index method and considering a raised step refractive index difference between the index of the core and the effective index of the cladding, we improve the characteristic parameters such as numerical aperture and V-parameter, and reduce its bending loss to about one tenth of a conventional PCF. Implementing such a structure in PCFs may be one step forward to achieve low loss PCFs for communication applications.展开更多
Synapse-specific connectivity and dynamics determine microcircuit function but are challenging to explore with classic paired recordings due to their low throughput.We therefore implemented optomapping,a~100-fold fast...Synapse-specific connectivity and dynamics determine microcircuit function but are challenging to explore with classic paired recordings due to their low throughput.We therefore implemented optomapping,a~100-fold faster two-photon optogenetic method.In mouse primary visual cortex(V1),we optomapped 30,454 candidate inputs to reveal 1,790 excitatory inputs to pyramidal,basket,and Martinotti cells.Across these cell types,log-normal distribution of synaptic efficacies emerged as a principle.For pyramidal cells,optomapping reproduced the canonical circuit but unexpectedly uncovered that the excitation of basket cells concentrated to layer 5 and that of Martinotti cells dominated in layer 2/3.The excitation of basket cells was stronger and reached farther than the excitation of pyramidal cells,which may promote stability.Short-term plasticity surprisingly depended on cortical layer in addition to target cell.Finally,optomapping revealed an overrepresentation of shared inputs for interconnected layer-6 pyramidal cells.Thus,by resolving the throughput problem,optomapping uncovered hitherto unappreciated principles of V1 structure.展开更多
By inserting an air cavity into a one-dimensional photonic crystal of LiF/GaSb, a tunable filter covering the whole visible range is proposed. Following consideration of the dispersion of the materials, through modula...By inserting an air cavity into a one-dimensional photonic crystal of LiF/GaSb, a tunable filter covering the whole visible range is proposed. Following consideration of the dispersion of the materials, through modulating the thickness of the air cavity, we demonstrate that a single resonant peak can shift from 416.1 to 667.3 nm in the band gap at normal incidence by means of the transfer matrix method. The research also shows that the transmittance of the channel can be maximized when the number of periodic Li F/Ga Sb layers on one side of the air defect layer is equal to that of the other side. When adding a period to both sides respectively, the full width at half maximum of the defect mode is reduced by one order of magnitude. This structure will provide a promising approach to fabricate practical tunable filters in the visible region with ultra-wide tuning range.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61505074)the National Key Basic Research Program of China(Grant No.2013CBA01703)the Hong Liu Young Teachers Training Program Funded Projects of Lanzhou University of Technology(Grant No.Q201509)
文摘This paper presents the theoretical investigation of hierarchical sub-wavelength photonic structures with various periods and numbers of layers, which were fabricated using a high-order waveguide-mode interference field. A 442-nm laser was used to excite high-order waveguide modes in an asymmetric metal-cladding dielectric waveguide structure. The dispersion curve of the waveguide modes was theoretically analyzed, and the distribution of the interference field of high-order waveguide modes was numerically simulated using the finite-element method. The various dependences of the characteristics of hierarchical sub-wavelength photonic structures on the thickness and refractive index of the photoresist and the waveguide mode were investigated in detail. These hierarchical sub-wavelength photonic structures have various periods and numbers of layers and can be fabricated by a simple and low-cost method.
文摘Photonic crystal fibers （PCFs） with a stepped raised-core profile and one layer equally spaced holes in the cladding are analyzed. Using effective index method and considering a raised step refractive index difference between the index of the core and the effective index of the cladding, we improve the characteristic parameters such as numerical aperture and V-parameter, and reduce its bending loss to about one tenth of a conventional PCF. Implementing such a structure in PCFs may be one step forward to achieve low loss PCFs for communication applications.
基金supported by CIHR 295104,HBHL,FRQS 259572,and RBIQ 35450 fellowships.C.G.won NSERC USRA,FRQNT BPC,RI-MUHC,FRQS,and CIHR CGS-M studentships.K.E.B.was funded by IBRO.T.A.L.won the NSERC USRA.P.J.S.is funded by the MGH FoundationCFI LOF 28331+2 种基金CIHR PGs 156223,191969,and 191997FRSQ CB 254033NSERC DG/DAS 2024-06712,2017-04730,and 2017-507818。
文摘Synapse-specific connectivity and dynamics determine microcircuit function but are challenging to explore with classic paired recordings due to their low throughput.We therefore implemented optomapping,a~100-fold faster two-photon optogenetic method.In mouse primary visual cortex(V1),we optomapped 30,454 candidate inputs to reveal 1,790 excitatory inputs to pyramidal,basket,and Martinotti cells.Across these cell types,log-normal distribution of synaptic efficacies emerged as a principle.For pyramidal cells,optomapping reproduced the canonical circuit but unexpectedly uncovered that the excitation of basket cells concentrated to layer 5 and that of Martinotti cells dominated in layer 2/3.The excitation of basket cells was stronger and reached farther than the excitation of pyramidal cells,which may promote stability.Short-term plasticity surprisingly depended on cortical layer in addition to target cell.Finally,optomapping revealed an overrepresentation of shared inputs for interconnected layer-6 pyramidal cells.Thus,by resolving the throughput problem,optomapping uncovered hitherto unappreciated principles of V1 structure.
基金Project supported by the National Natural Science Foundation of China(Nos.61575138,61307069,51205273)the Top Young Academic Leaders and the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi
文摘By inserting an air cavity into a one-dimensional photonic crystal of LiF/GaSb, a tunable filter covering the whole visible range is proposed. Following consideration of the dispersion of the materials, through modulating the thickness of the air cavity, we demonstrate that a single resonant peak can shift from 416.1 to 667.3 nm in the band gap at normal incidence by means of the transfer matrix method. The research also shows that the transmittance of the channel can be maximized when the number of periodic Li F/Ga Sb layers on one side of the air defect layer is equal to that of the other side. When adding a period to both sides respectively, the full width at half maximum of the defect mode is reduced by one order of magnitude. This structure will provide a promising approach to fabricate practical tunable filters in the visible region with ultra-wide tuning range.
