Photoconductive emitters for terahertz generation hold promise for highly efficient down-conversion of optical photons because it is not constrained by the Manley-Rowe relation.Existing terahertz photoconductive devic...Photoconductive emitters for terahertz generation hold promise for highly efficient down-conversion of optical photons because it is not constrained by the Manley-Rowe relation.Existing terahertz photoconductive devices,however,faces limits in efficiency due to the semiconductor properties of commonly used GaAs materials.Here,we demonstrate that large bandgap semiconductor GaN,characterized by its high breakdown electric field,facilitates the highly efficient generation of terahertz waves in a coplanar stripline waveguide.Towards this goal,we investigated the excitonic contribution to the electro-optic response of GaN under static electric field both through experiments and first-principles calculations,revealing a robust excitonic Stark shift.Using this electro-optic effect,we developed a novel ultraviolet pump-probe spectroscopy for in-situ characterization of the terahertz electric field strength generated by the GaN photoconductive emitter.Our findings show that terahertz power scales quadratically with optical excitation power and applied electric field over a broad parameter range.We achieved an optical-to-terahertz conversion efficiency approaching 100%within the 0.03–1 THz bandwidth at the highest bias field(116 kV/cm)in our experiment.Further optimization of GaN-based terahertz generation devices could achieve even greater optical-toterahertz conversion efficiencies.展开更多
Stretchable triboelectric nanogenerators(TENGs)have garnered significant attention as wearable power sources by enabling the realization of self-powered systems through integration with other wearable platforms.Howeve...Stretchable triboelectric nanogenerators(TENGs)have garnered significant attention as wearable power sources by enabling the realization of self-powered systems through integration with other wearable platforms.However,achieving intrinsically stretchable TENGs with stable performance under deformation remains a major challenge,particularly in forming robust dielectric/electrode interfaces and fabricating fully stretchable materials.Here,we propose the intrinsically stretchable ionogel-based TENGs(S-iTENG)with a monolithic structure by directly coating silver nanowires(AgNWs)onto free-standing ionogel.The ionogel serves as the substrate,charge-generating,and trapping layer,simplifying device configuration.Its hydrophilic characteristics improve the wettability of AgNWs and their interfacial adhesion.The optimized S-iTENG exhibits a power density of~109.8 mW·m^(-2),excellent stretchability(~195%),and stable operation even under 80%strain.The practical feasibility of the S-iTENG is demonstrated in self-powered sensory platforms.Overall,these results highlight the significance of monolithic,substrate-free S-iTENG as wearable energy harvesters and key components for future wearable electronics.展开更多
With the development of conformable photonic platforms,particularly those that could be interfaced with the human body or integrated into wearable technology,there is an ever-increasing need for mechanically flexible ...With the development of conformable photonic platforms,particularly those that could be interfaced with the human body or integrated into wearable technology,there is an ever-increasing need for mechanically flexible optical photonic elements in soft materials.Here,we realize mechanically flexible liquid crystal(LC)waveguides using a combination of ultrafast direct laser writing and ultraviolet(UV)photo-polymerization.Results are presented that demonstrate that these laser-written waveguides can be either electrically switchable(by omitting the bulk UV polymerization step)or mechanically flexible.Characteristics of the waveguide are investigated for different fabrication conditions and geometrical configurations,including the dimensions of the waveguide and laser writing power.Our findings reveal that smaller waveguide geometries result in reduced intensity attenuation.Specifically,for a 10-μm-wide laser-written channel in a 14-μm-thick LC layer,a loss factor of-1.8 dB/mm atλ=650 nm was observed.Following the UV polymerization step and subsequent delamination of the glass substrates,we demonstrate a free-standing flexible LC waveguide,which retains waveguide functionality even when bent,making it potentially suitable for on-skin sensors and other photonic devices that could interface with the human body.For the flexible LC waveguides fabricated in this study,the loss in a straight waveguide with a cross-sectional area of 20μm×20μm was recorded to be-0.2 dB/mm.These results highlight the promising potential of electrically responsive and mechanically moldable optical waveguides using laser writing and UV-assisted polymer network formation.展开更多
基金supported by the National Science Foundation under the award number 2414287 and the theoretical work on pump-probe spectroscopy and calculations of the GaN excitonic electro-optic effect were supporte by the National Science Foundation under grant DMR-2325410The Center for Computational Study of Excited-State Phenomena in Energy Materials(C2SEPEM)at Lawrence Berkeley National Laboratory,supported by the US Department of Energy,Office of Science,Basic Energy Sciences,Materials Sciences and Engineering Division under contract no.DE-AC02-05CH11231,as part of the Computational Materials Sciences Program provided advanced codes for excited state computations+3 种基金The first-principles calculations were performed using computation resources at the National Energy Research Scientific Computing Center(NERSC)The U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,Materials Sciences and Engineering Division under Contract No.DE-AC02-05-CH11231(van der Waals heterostructure program KCFW16)supported the device fabricationThe waveguide simulations were performed at the Molecular Graphics and Computation Facility(MGCF)at UC Berkeley and the MGCF is in part supported by NIH S10OD034382S.D.C.acknowledges support from the Kavli ENSI Heising-Simons Junior Fellowship.
文摘Photoconductive emitters for terahertz generation hold promise for highly efficient down-conversion of optical photons because it is not constrained by the Manley-Rowe relation.Existing terahertz photoconductive devices,however,faces limits in efficiency due to the semiconductor properties of commonly used GaAs materials.Here,we demonstrate that large bandgap semiconductor GaN,characterized by its high breakdown electric field,facilitates the highly efficient generation of terahertz waves in a coplanar stripline waveguide.Towards this goal,we investigated the excitonic contribution to the electro-optic response of GaN under static electric field both through experiments and first-principles calculations,revealing a robust excitonic Stark shift.Using this electro-optic effect,we developed a novel ultraviolet pump-probe spectroscopy for in-situ characterization of the terahertz electric field strength generated by the GaN photoconductive emitter.Our findings show that terahertz power scales quadratically with optical excitation power and applied electric field over a broad parameter range.We achieved an optical-to-terahertz conversion efficiency approaching 100%within the 0.03–1 THz bandwidth at the highest bias field(116 kV/cm)in our experiment.Further optimization of GaN-based terahertz generation devices could achieve even greater optical-toterahertz conversion efficiencies.
基金supported by the Nano&Material Technology Development Program through the National Research Foundation of Korea(NRF),funded by the Ministry of Science and ICT(No.RS-2025-02221332)supported by the Nano&Material Technology Development Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(RS-2023-00283244).
文摘Stretchable triboelectric nanogenerators(TENGs)have garnered significant attention as wearable power sources by enabling the realization of self-powered systems through integration with other wearable platforms.However,achieving intrinsically stretchable TENGs with stable performance under deformation remains a major challenge,particularly in forming robust dielectric/electrode interfaces and fabricating fully stretchable materials.Here,we propose the intrinsically stretchable ionogel-based TENGs(S-iTENG)with a monolithic structure by directly coating silver nanowires(AgNWs)onto free-standing ionogel.The ionogel serves as the substrate,charge-generating,and trapping layer,simplifying device configuration.Its hydrophilic characteristics improve the wettability of AgNWs and their interfacial adhesion.The optimized S-iTENG exhibits a power density of~109.8 mW·m^(-2),excellent stretchability(~195%),and stable operation even under 80%strain.The practical feasibility of the S-iTENG is demonstrated in self-powered sensory platforms.Overall,these results highlight the significance of monolithic,substrate-free S-iTENG as wearable energy harvesters and key components for future wearable electronics.
基金funded in whole,or in part,by the UKRI(EP/R004803/01,P.S.S.,EP/R511742/1,S.M.M.,S.J.E.,and M.J.B.)。
文摘With the development of conformable photonic platforms,particularly those that could be interfaced with the human body or integrated into wearable technology,there is an ever-increasing need for mechanically flexible optical photonic elements in soft materials.Here,we realize mechanically flexible liquid crystal(LC)waveguides using a combination of ultrafast direct laser writing and ultraviolet(UV)photo-polymerization.Results are presented that demonstrate that these laser-written waveguides can be either electrically switchable(by omitting the bulk UV polymerization step)or mechanically flexible.Characteristics of the waveguide are investigated for different fabrication conditions and geometrical configurations,including the dimensions of the waveguide and laser writing power.Our findings reveal that smaller waveguide geometries result in reduced intensity attenuation.Specifically,for a 10-μm-wide laser-written channel in a 14-μm-thick LC layer,a loss factor of-1.8 dB/mm atλ=650 nm was observed.Following the UV polymerization step and subsequent delamination of the glass substrates,we demonstrate a free-standing flexible LC waveguide,which retains waveguide functionality even when bent,making it potentially suitable for on-skin sensors and other photonic devices that could interface with the human body.For the flexible LC waveguides fabricated in this study,the loss in a straight waveguide with a cross-sectional area of 20μm×20μm was recorded to be-0.2 dB/mm.These results highlight the promising potential of electrically responsive and mechanically moldable optical waveguides using laser writing and UV-assisted polymer network formation.
