Multiple resonant excitations of surface plasmons in a graphene stratified slab are realized by Otto configuration at terahertz frequencies. The proposed graphene stratified slab consists of alternating dielectric lay...Multiple resonant excitations of surface plasmons in a graphene stratified slab are realized by Otto configuration at terahertz frequencies. The proposed graphene stratified slab consists of alternating dielectric layers and graphene sheets, and is sandwiched between a prism and another semi-infinite medium. Optical response and field distribution are determined by the transfer matrix method with the surface current density boundary condition.Multiple resonant excitations appear on the angular reflection spectrum, and are analyzed theoretically via the phase-matching condition. Furthermore, the effects of the system parameters are investigated. Among them, the Fermi levels can tune the corresponding resonances independently. The proposed concept can be engineered for promising applications, including angular selective or multiplex filters, multiple channel sensors, and directional delivery of energy.展开更多
Thermal emission is often presented as a typical incoherent process. Incorporating periodic structures on the tungsten surface offers the possibility to obtain coherent thermal emission sources. Here we illustrate gra...Thermal emission is often presented as a typical incoherent process. Incorporating periodic structures on the tungsten surface offers the possibility to obtain coherent thermal emission sources. Here we illustrate grating as an example to examine the influence of the geometric parameters on the thermal emission properties. It is found that for very shallow gratings, only surface plasmon polariton（SPP） modes can be excited and the emission efficiency is closely related with the filling factor. When the ratio of the depth to period of the grating is in the range from 1/20 to 1/2, the field between the adjacent corners can be coupled to each other across the air gap for the filling factor larger than 0.5 and produce a similar resonance as in an air rod. Further increase of the grating depth can cause the groove of the grating forming metal–insulator–metal（MIM） structures and induce surface plasmon standing wave modes. Our investigations will not only be helpful for manipulating thermal emission properties according to applications, but also help us understand the coupling mechanism between the incident electromagnetism waves and gratings with different parameters in various research fields.展开更多
A highly sensitive and selective two-photon sensing scheme for detection of cartap was developed by using Au@Ag bimetallic core-shell nanoparticles.Cartap was found to induce the aggregation of Au@Ag nanoparticles and...A highly sensitive and selective two-photon sensing scheme for detection of cartap was developed by using Au@Ag bimetallic core-shell nanoparticles.Cartap was found to induce the aggregation of Au@Ag nanoparticles and up to 700-fold enhancement in two-photon photoluminescence.Huge enhancement in two-photon photoluminescence allows achieving a detection limit of as low as 0.0062 mg/kg,which is better than the conventional colorimetric methods.This two-photon sensing scheme has a broad dynamic range and displays excellent selectivity in detection of cartap against over other ten kinds of commonly used insecticides.展开更多
基金National Natural Science Foundation of China(NSFC)(11604276,61601393,11501481)Key Scientific Project of Fujian Province in China(2015H0039)
文摘Multiple resonant excitations of surface plasmons in a graphene stratified slab are realized by Otto configuration at terahertz frequencies. The proposed graphene stratified slab consists of alternating dielectric layers and graphene sheets, and is sandwiched between a prism and another semi-infinite medium. Optical response and field distribution are determined by the transfer matrix method with the surface current density boundary condition.Multiple resonant excitations appear on the angular reflection spectrum, and are analyzed theoretically via the phase-matching condition. Furthermore, the effects of the system parameters are investigated. Among them, the Fermi levels can tune the corresponding resonances independently. The proposed concept can be engineered for promising applications, including angular selective or multiplex filters, multiple channel sensors, and directional delivery of energy.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61378082 and 61675070)the Project of High-level Professionals in the Universities of Guangdong Province,China
文摘Thermal emission is often presented as a typical incoherent process. Incorporating periodic structures on the tungsten surface offers the possibility to obtain coherent thermal emission sources. Here we illustrate grating as an example to examine the influence of the geometric parameters on the thermal emission properties. It is found that for very shallow gratings, only surface plasmon polariton（SPP） modes can be excited and the emission efficiency is closely related with the filling factor. When the ratio of the depth to period of the grating is in the range from 1/20 to 1/2, the field between the adjacent corners can be coupled to each other across the air gap for the filling factor larger than 0.5 and produce a similar resonance as in an air rod. Further increase of the grating depth can cause the groove of the grating forming metal–insulator–metal（MIM） structures and induce surface plasmon standing wave modes. Our investigations will not only be helpful for manipulating thermal emission properties according to applications, but also help us understand the coupling mechanism between the incident electromagnetism waves and gratings with different parameters in various research fields.
基金the Ministry of Education, Singapore (R-143-000-607-112)the National Research Foundation, Prime Minister’s Office, Singapore under its Competitive Research Program (NRF-CRP10-2012-04)Medium Sized Centre Programme
文摘A highly sensitive and selective two-photon sensing scheme for detection of cartap was developed by using Au@Ag bimetallic core-shell nanoparticles.Cartap was found to induce the aggregation of Au@Ag nanoparticles and up to 700-fold enhancement in two-photon photoluminescence.Huge enhancement in two-photon photoluminescence allows achieving a detection limit of as low as 0.0062 mg/kg,which is better than the conventional colorimetric methods.This two-photon sensing scheme has a broad dynamic range and displays excellent selectivity in detection of cartap against over other ten kinds of commonly used insecticides.
