The wafer level hermetic package method was studied experimentally in low temperature for optoelectronic devices with benzo-cyclo-butene(BCB) material. The results show that the bonding temperature is below 250℃, the...The wafer level hermetic package method was studied experimentally in low temperature for optoelectronic devices with benzo-cyclo-butene(BCB) material. The results show that the bonding temperature is below 250℃, the helium hermetic capability of both silicon-BCB-silicon and silicon-BCB-glass package are better than 6×10~ -4 Pa·cm^3/s. The shear strength is enough for package. The hermeticity is still good after the 15 cycles’ thermal shock test. The relationship between the leakage rate and the distance from the hole to the device border were also discussed with a seepage model.展开更多
In this paper, five factors, namely the HF （hydrofluoric acid） concentration, field strength, illumination intensity as well as the oxidizing-power and conductivity of electrolytes were found to strongly affect the ...In this paper, five factors, namely the HF （hydrofluoric acid） concentration, field strength, illumination intensity as well as the oxidizing-power and conductivity of electrolytes were found to strongly affect the fast pore etching. The oxidizing power of aqueous HF electrolyte of different concentrations was especially measured and analysed. A positive correlation between optimal bias and HF concentration was generally observed and the relationship was semiquantitatively interpreted. Pore density notably increased with enhanced HF-concentration or bias even on patterned substrates where 2D （two-dimensional） nuclei were densely pre-textured. The etch rate can reach 400μm/h and the aspect ratio of pores can be readily driven up to 250.展开更多
Via anodizing patterned and unpatterned samples with a high HF concentration （[HF]）, the degree of deviation from pore-formation theory was found to be markedly different. Based on the analysis of scanning electron ...Via anodizing patterned and unpatterned samples with a high HF concentration （[HF]）, the degree of deviation from pore-formation theory was found to be markedly different. Based on the analysis of scanning electron microscope （SEM） micrographs and current-voltage （I - V） curves, the variation of physical and chemical parameters of patterned and unpatterned substrates was found to be crucial to the understanding of the observations. Our results indicate that the initial surface morphology of samples can have a considerable influence upon pore formation. The electric-field effect as well as current-burst-model was employed to interpret the underlying mechanism.展开更多
Formation and deposition of amyloid-beta(Aβ) are considered one of the main drivers of Alzheimer's disease(AD). For more than 30 years, Aβ has challenged researchers through its complex physicochemical propertie...Formation and deposition of amyloid-beta(Aβ) are considered one of the main drivers of Alzheimer's disease(AD). For more than 30 years, Aβ has challenged researchers through its complex physicochemical properties and multiple peptide processing steps that involve several proteases(Andreasson et al., 2007).展开更多
This paper describes the design,characterization and fabrication of a planar In0.53Ga0.47As based planar Gunn diode on an In P semi-insulating substrate.The planar Gunn diode was designed in Coplanar Waveguide(CPW)for...This paper describes the design,characterization and fabrication of a planar In0.53Ga0.47As based planar Gunn diode on an In P semi-insulating substrate.The planar Gunn diode was designed in Coplanar Waveguide(CPW)format with an active channel length and width of 4μm and 120μm respectively,and modeled using the Advanced Design System(ADS-2009)simulation package.The initial experimental measurements have given a fundamental oscillation frequency of 63.5 GHz with a RF output power of-6.6 d Bm,which is the highest recorded power for an In P based planar Gunn diode.展开更多
A low-voltage-driven digital-droplet-transporting chip with an open structure is designed,fabricated and characterized.The digital microfluidic chip is fabricated by the silicon planar process.Using only a single elec...A low-voltage-driven digital-droplet-transporting chip with an open structure is designed,fabricated and characterized.The digital microfluidic chip is fabricated by the silicon planar process.Using only a single electrode panel,the droplet on the chip can be manipulated by electrostatic force under a dc driving voltage.The actuation principle is proposed and verified by the experiment.The experimental results show that the minimum driving voltage decreases as the thickness of the dielectric layer decreases.The driving voltage for a 3µL deionized(DI)water droplet is reduced to 15 V in air and 13.5 V in oil by employing a thin dielectric layer of 600 nm with a high dielectric constant and a coating hydrophobic layer on the top.The DI water droplets are also demonstrated to be transported in two dimensions smoothly in a programmable manner,and the maximum transport speed reaches 96 mm/s.The droplets of normal saline,a solution of 0.9 wt%NaCl,are also successfully manipulated on the chip.展开更多
This paper describes how the power efficiency of fully integrated Dickson charge pumps in high- voltage IC technologies can be improved considerably by implementing charge recycling techniques, by replacing the normal...This paper describes how the power efficiency of fully integrated Dickson charge pumps in high- voltage IC technologies can be improved considerably by implementing charge recycling techniques, by replacing the normal PN junction diodes by pulse-driven active diodes, and by choosing an appropriate advanced smart power IC technology. A detailed analysis reveals that the combination of these 3 methods more than doubles the power efficiency compared to traditional Dickson charge pump designs.展开更多
Electro-optical/infrared (EO/IR) sensors and photovoltaic power sources are being developed for a variety of defense and commercial applications. One of the critical technologies that will enhance both EO/IR sensor an...Electro-optical/infrared (EO/IR) sensors and photovoltaic power sources are being developed for a variety of defense and commercial applications. One of the critical technologies that will enhance both EO/IR sensor and photovoltaic module performance is the development of high quality nanostructure-based antireflection coatings. In this paper, we review our work on advanced antireflection structures that have been designed by using a genetic algorithm and fabricated by using oblique angle deposition. The antireflection coatings are designed for the wavelength range of 250 nm to 2500 nm and an incidence angle between 00 and 400. These nanostructured antireflection coatings are shown to enhance the optical transmission through transparent windows over a wide band of interest and minimize broadband reflection losses to less than one percent, a substantial improvement over conventional thin-film antireflection coating technologies.展开更多
Exceptional point(EP)is referred to degeneracies in a non-Hermitian system where two or more eigenvalues and their corresponding eigenvectors coalesce.Recently there have been significantly increased interests in harn...Exceptional point(EP)is referred to degeneracies in a non-Hermitian system where two or more eigenvalues and their corresponding eigenvectors coalesce.Recently there have been significantly increased interests in harnessing EPs to enhance responsivities and achieve ultrasensitive detections in optics,electronics and acoustics,although there are few similar studies focused on using surface acoustic wave(SAW)sensing technologies,probably due to its great technical challenges.Herein,we proposed a scheme for accessing EPs in an on-chip architecture consisted of coupledSAW-resonators system,forming a passive parity-time(PT)symmetric system.We demonstrated that by tuning additional losses in one of resonators and regulating the system in the proximity of the EP,the sensor exhibited significantly enhanced responses.As an example,we present an EP-based SAW gas sensor,which showed a muchimproved sensitivity compared to that of a conventional delay-line SAW sensor.The fundamental mechanisms behind this excellent sensing performance have been elucidated.展开更多
Silver nanowires （AgNWs） have emerged as a promising nanomaterial for next generation stretchable electronics. However, until now, the fabrication of AgNW- based components has been hampered by complex and time-cons...Silver nanowires （AgNWs） have emerged as a promising nanomaterial for next generation stretchable electronics. However, until now, the fabrication of AgNW- based components has been hampered by complex and time-consuming steps. Here, we introduce a facile, fast, and one-step methodology for the fabrication of highly conductive and stretchable AgNW/polyurethane （PU） composite electrodes based on a high-intensity pulsed light （HIPL） technique. HIPL simultaneously improved wire-wire junction conductivity and wire-substrate adhesion at room temperature and in air within 50 μs, omitting the complex transfer-curing-implanting process. Owing to the localized deformation of PU at interfaces with AgNWs, embedding of the nanowires was rapidly carried out without substantial substrate damage. The resulting electrode retained a low sheet resistance （high electrical conductivity） of 〈10 Ω/sq even under 100% strain, or after 1,000 continuous stretching-relaxation cycles, with a peak strain of 60%. The fabricated electrode has found immediate application as a sensor for motion detection. Furthermore, based on our electrode, a light emitting diode （LED） driven by integrated stretchable AgNW conductors has been fabricated. In conclusion, our present fabrication approach is fast, simple, scalable, and cost- efficient, making it a good candidate for a future roll-to-roll process.展开更多
The development of responsive metamaterials has enabled the realization of compact tunable photonic devices capable of manipulating the amplitude,polarization,wave vector and frequency of light.Integration of semicond...The development of responsive metamaterials has enabled the realization of compact tunable photonic devices capable of manipulating the amplitude,polarization,wave vector and frequency of light.Integration of semiconductors into the active regions of metallic resonators is a proven approach for creating nonlinear metamaterials through optoelectronic control of the semiconductor carrier density.Metal-free subwavelength resonant semiconductor structures offer an alternative approach to create dynamic metamaterials.We present InAs plasmonic disk arrays as a viable resonant metamaterial at terahertz frequencies.Importantly,InAs plasmonic disks exhibit a strong nonlinear response arising from electric field-induced intervalley scattering,resulting in a reduced carrier mobility thereby damping the plasmonic response.We demonstrate nonlinear perfect absorbers configured as either optical limiters or saturable absorbers,including flexible nonlinear absorbers achieved by transferring the disks to polyimide films.Nonlinear plasmonic metamaterials show potential for use in ultrafast terahertz(THz)optics and for passive protection of sensitive electromagnetic devices.展开更多
We present novel Schottky barrier field effect transistors consisting of a parallel array of bottom-up grown silicon nanowires that are able to deliver high current outputs. Axial silicidation of the nanowires is used...We present novel Schottky barrier field effect transistors consisting of a parallel array of bottom-up grown silicon nanowires that are able to deliver high current outputs. Axial silicidation of the nanowires is used to create defined Schottky junctions leading to on/off current ratios of up to 106. The device concept leverages the unique transport properties of nanoscale junctions to boost device performance for macroscopic applications. Using parallel arrays, on-currents of over 500 gA at a source-drain voltage of 0.5 V can be achieved. The transconductance is thus increased significantly while maintaining the transfer characteristics of single nanowire devices. By incorporating several hundred nanowires into the parallel arra36 the yield of functioning transistors is dramatically increased and device- to-device variability is reduced compared to single devices. This new nanowire- based platform provides sufficient current output to be employed as a transducer for biosensors or a driving stage for organic light-emitting diodes （LEDs）, while the bottom-up nature of the fabrication procedure means it can provide building blocks for novel printable electronic devices.展开更多
Linear light-processing functions(e.g.,routing,splitting,filtering)are key functions requiring configuration to implement on a programmable photonic integrated circuit(PPIC).In recirculating waveguide meshes(which inc...Linear light-processing functions(e.g.,routing,splitting,filtering)are key functions requiring configuration to implement on a programmable photonic integrated circuit(PPIC).In recirculating waveguide meshes(which include loop-backs),this is usually done manually.Some previous results describe explorations to perform this task automatically,but their efficiency or applicability is still limited.In this paper,we propose an efficient method that can automatically realize configurations for many light-processing functions on a square-mesh PPIC.At its heart is an automatic differentiation subroutine built upon analytical expressions of scattering matrices that enables gradient descent optimization for functional circuit synthesis.Similar to the state-of-the-art synthesis techniques,our method can realize configurations for a wide range of light-processing functions,and multiple functions on the same PPIC simultaneously.However,we do not need to separate the functions spatially into different subdomains of the mesh,and the resulting optimum can have multiple functions using the same part of the mesh.Furthermore,compared to nongradient-or numerical differentiation-based methods,our proposed approach achieves 3×time reduction in computational cost.展开更多
Via systematic investigation of the anodization of both patterned and unpatterned specimens, phenomena of pronounced discrepancy with respect to pore size, pore density and pore etch-rate were evidenced. Based on the ...Via systematic investigation of the anodization of both patterned and unpatterned specimens, phenomena of pronounced discrepancy with respect to pore size, pore density and pore etch-rate were evidenced. Based on the detailed analysis of scanning electron microscope (SEM) micrographs and current-voltage curves, the competition between physical and chemical elements was found to be crucial to understanding the observations. The results indicate that the size, density and growth-speed of pores may act as an evident function of the initial morphology of the sample surface, despite a nearly fixed width of the space charge region. Electric-field effect as well as current-burst-model (CBM) was employed to interpret the underlying mechanism.展开更多
Ceramic microthrusters with an embedded Pt resistive heater,two temperature sensors,and a Pt or Ag catalytic bed were made of high-temperature co-fired alumina ceramics.To increase the surface area by a factor of 1.21...Ceramic microthrusters with an embedded Pt resistive heater,two temperature sensors,and a Pt or Ag catalytic bed were made of high-temperature co-fired alumina ceramics.To increase the surface area by a factor of 1.21,and so the catalytic effect,the Pt catalytic bed was made porous by mixing the Pt paste with 15—20vol.%graphite sacrificial paste before screen printing it.Ag was in-situ electroplated on the porous Pt surface after sintering.Decomposition of 50wt.%hydrogen peroxide as a monopropellant was studied both qualitatively and quantitatively by changing the catalyst(between Ag and Pt),flow rate(15—55 μl/min),and operating temperature(115—300℃).A reference device without catalyst exhibited an unstable behavior as a result of no,or vety little,decomposition,whereas the Ag catalyst was more stable,and the Pt one even more stable.Also,Pt was found to be slightly more effective.Quantitatively,there were small differences between Pt and Ag in the power needed to maintain the temperature.The inventive methods to make the Pt bed porous as well as in-situ electroplating Ag were success-fully demonstrated.展开更多
This paper presents a tunable multi-threshold micro-electromechanical inertial switch with adjustable threshold capability.The demonstrated device combines the advantages of accelerometers in providing quantitative ac...This paper presents a tunable multi-threshold micro-electromechanical inertial switch with adjustable threshold capability.The demonstrated device combines the advantages of accelerometers in providing quantitative acceleration measurements and g-threshold switches in saving power when in the inactive state upon experiencing acceleration below the thresholds.The designed proof-of-concept device with two thresholds consists of a cantilever microbeam and two stationary electrodes placed at different positions in the sensing direction.The adjustable threshold capability and the effect of the shock duration on the threshold acceleration are analytically investigated using a nonlinear beam model.Results are shown for the relationships among the applied bias voltage,the duration of shock impact,and the tunable threshold.The fabricated prototypes are tested using a shock-table system.The analytical results agree with the experimental results.The designed device concept is very promising for the classification of the shock and impact loads in transportation and healthcare applications.展开更多
A MEMS compressed period-tunable grating device with a wide tuning range has been designed, fabricated and characterized. To increase the tuning range, avoid instability with tuning and improve the performance, we pro...A MEMS compressed period-tunable grating device with a wide tuning range has been designed, fabricated and characterized. To increase the tuning range, avoid instability with tuning and improve the performance, we propose in this paper a period-tunable grating which is compressed by large-displacement comb actuators with tilted folded beams. The experimental results show that the designed grating device has a compression range of up to 144μm within 37 V driving voltage. The period of the grating can be adjusted continuously from 16 to 14 μm with a tuning range of 12.5%. The maximum tuning range of the first-order diffraction angle is 0.34° at 632.8 nm and the reflectivity of the grating is more than 92.6% in the mid-infrared region. The grating device can be fabricated by simple processes and finds applications in mid-infrared spectrometers.展开更多
We present integrated-optic building blocks and functional photonic devices based on amorphous siliconon-insulator technology. Efficient deep-etched fiber-to-chip grating couplers, low-loss single-mode photonic wire w...We present integrated-optic building blocks and functional photonic devices based on amorphous siliconon-insulator technology. Efficient deep-etched fiber-to-chip grating couplers, low-loss single-mode photonic wire waveguides, and compact power splitters are presented. Based on the sub-μm photonic wires, 2 × 2 Mach–Zehnder interferometers and add/drop microring resonators(MRRs) with low device footprints and high finesse up to 200 were realized and studied. Compact polarization rotators and splitters with ≥10 d B polarization extinction ratio were fabricated for the polarization management on-chip. The tuning and trimming capabilities of the material platform are demonstrated with efficient microheaters and a permanent device trimming method, which enabled the realization of energy-efficient photonic circuits. Wavelength multiplexers in the form of cascaded filter banks and 4 × 4 routers based on MRR switches are presented. Fabrication imperfections were analyzed and permanently corrected by an accurate laser-trimming method, thus enabling eight-channel multiplexers with record low metrics of sub-m W static power consumption and ≤1°C temperature overhead. The high quality of the functional devices, the high tuning efficiency, and the excellent trimming capabilities demonstrate the potential to realize low-cost, densely integrated, and ultralow-power 3D-stacked photonic circuits on top of CMOS microelectronics.展开更多
We demonstrate a pH sensor based on ultrasensitive nanosize Schottky junctions formed within bottom-up grown dopant-flee arrays of assembled silicon nanowires. A new measurement concept relying on a continuous gate sw...We demonstrate a pH sensor based on ultrasensitive nanosize Schottky junctions formed within bottom-up grown dopant-flee arrays of assembled silicon nanowires. A new measurement concept relying on a continuous gate sweep is presented, which allows the straightforward determination of the point of maximum sensitivity of the device and allows sensing experiments to be performed in the optimum regime. Integration of devices into a portable fluidic system and an electrode isolation strategy affords a stable environment and enables long time robust FET sensing measurements in a liquid environment to be carried out. Investigations of the physical and chemical sensitivity of our devices at different pH values and a comparison with theoretical limits are also discussed. We believe that such a combination of nanofabrication and engineering advances makes this Schottky barrier-powered silicon nanowire lab-on-a-chip platform suitable for efficient biodetection and even for more complex biochemical analysis.展开更多
基金Key Programof Knowledge Innovation Engineering for Chinese Academy of Sciences
文摘The wafer level hermetic package method was studied experimentally in low temperature for optoelectronic devices with benzo-cyclo-butene(BCB) material. The results show that the bonding temperature is below 250℃, the helium hermetic capability of both silicon-BCB-silicon and silicon-BCB-glass package are better than 6×10~ -4 Pa·cm^3/s. The shear strength is enough for package. The hermeticity is still good after the 15 cycles’ thermal shock test. The relationship between the leakage rate and the distance from the hole to the device border were also discussed with a seepage model.
基金supported by Chinese National ‘863’ Project (Grant No 2006AA04Z312)‘973’ Project (Grant No 2006CB300403)the National Natural Science Foundation of China (Grant No 60772030)
文摘In this paper, five factors, namely the HF （hydrofluoric acid） concentration, field strength, illumination intensity as well as the oxidizing-power and conductivity of electrolytes were found to strongly affect the fast pore etching. The oxidizing power of aqueous HF electrolyte of different concentrations was especially measured and analysed. A positive correlation between optimal bias and HF concentration was generally observed and the relationship was semiquantitatively interpreted. Pore density notably increased with enhanced HF-concentration or bias even on patterned substrates where 2D （two-dimensional） nuclei were densely pre-textured. The etch rate can reach 400μm/h and the aspect ratio of pores can be readily driven up to 250.
基金Project supported by the National High Technology Development Program of China (Grant No 2006AA04Z312)the National Basic Research of China (Grant No 2006CB300403)
文摘Via anodizing patterned and unpatterned samples with a high HF concentration （[HF]）, the degree of deviation from pore-formation theory was found to be markedly different. Based on the analysis of scanning electron microscope （SEM） micrographs and current-voltage （I - V） curves, the variation of physical and chemical parameters of patterned and unpatterned substrates was found to be crucial to the understanding of the observations. Our results indicate that the initial surface morphology of samples can have a considerable influence upon pore formation. The electric-field effect as well as current-burst-model was employed to interpret the underlying mechanism.
基金Ministerium für Wissenschaft und Gesundheit (MWG),Rheinland Pfalz,Neurodeg X Forschungskolleg (to BB)。
文摘Formation and deposition of amyloid-beta(Aβ) are considered one of the main drivers of Alzheimer's disease(AD). For more than 30 years, Aβ has challenged researchers through its complex physicochemical properties and multiple peptide processing steps that involve several proteases(Andreasson et al., 2007).
基金supported by ESPRC through EP/H011862/1,and EP/H012966/1
文摘This paper describes the design,characterization and fabrication of a planar In0.53Ga0.47As based planar Gunn diode on an In P semi-insulating substrate.The planar Gunn diode was designed in Coplanar Waveguide(CPW)format with an active channel length and width of 4μm and 120μm respectively,and modeled using the Advanced Design System(ADS-2009)simulation package.The initial experimental measurements have given a fundamental oscillation frequency of 63.5 GHz with a RF output power of-6.6 d Bm,which is the highest recorded power for an In P based planar Gunn diode.
基金by the National Basic Research Program of China under Grant No 2011CB309501the Fund for Creative Research of NSFC under Grant No 61021064+1 种基金the Key Project of NSFC under Grant No 60936001the National Natural Science Foundation of China under Grant No 60876037.
文摘A low-voltage-driven digital-droplet-transporting chip with an open structure is designed,fabricated and characterized.The digital microfluidic chip is fabricated by the silicon planar process.Using only a single electrode panel,the droplet on the chip can be manipulated by electrostatic force under a dc driving voltage.The actuation principle is proposed and verified by the experiment.The experimental results show that the minimum driving voltage decreases as the thickness of the dielectric layer decreases.The driving voltage for a 3µL deionized(DI)water droplet is reduced to 15 V in air and 13.5 V in oil by employing a thin dielectric layer of 600 nm with a high dielectric constant and a coating hydrophobic layer on the top.The DI water droplets are also demonstrated to be transported in two dimensions smoothly in a programmable manner,and the maximum transport speed reaches 96 mm/s.The droplets of normal saline,a solution of 0.9 wt%NaCl,are also successfully manipulated on the chip.
文摘This paper describes how the power efficiency of fully integrated Dickson charge pumps in high- voltage IC technologies can be improved considerably by implementing charge recycling techniques, by replacing the normal PN junction diodes by pulse-driven active diodes, and by choosing an appropriate advanced smart power IC technology. A detailed analysis reveals that the combination of these 3 methods more than doubles the power efficiency compared to traditional Dickson charge pump designs.
文摘Electro-optical/infrared (EO/IR) sensors and photovoltaic power sources are being developed for a variety of defense and commercial applications. One of the critical technologies that will enhance both EO/IR sensor and photovoltaic module performance is the development of high quality nanostructure-based antireflection coatings. In this paper, we review our work on advanced antireflection structures that have been designed by using a genetic algorithm and fabricated by using oblique angle deposition. The antireflection coatings are designed for the wavelength range of 250 nm to 2500 nm and an incidence angle between 00 and 400. These nanostructured antireflection coatings are shown to enhance the optical transmission through transparent windows over a wide band of interest and minimize broadband reflection losses to less than one percent, a substantial improvement over conventional thin-film antireflection coating technologies.
基金supported by National Key R&D Program of China under Grant 2022YFE0103300 and 2020YFA0211400.
文摘Exceptional point(EP)is referred to degeneracies in a non-Hermitian system where two or more eigenvalues and their corresponding eigenvectors coalesce.Recently there have been significantly increased interests in harnessing EPs to enhance responsivities and achieve ultrasensitive detections in optics,electronics and acoustics,although there are few similar studies focused on using surface acoustic wave(SAW)sensing technologies,probably due to its great technical challenges.Herein,we proposed a scheme for accessing EPs in an on-chip architecture consisted of coupledSAW-resonators system,forming a passive parity-time(PT)symmetric system.We demonstrated that by tuning additional losses in one of resonators and regulating the system in the proximity of the EP,the sensor exhibited significantly enhanced responses.As an example,we present an EP-based SAW gas sensor,which showed a muchimproved sensitivity compared to that of a conventional delay-line SAW sensor.The fundamental mechanisms behind this excellent sensing performance have been elucidated.
文摘Silver nanowires （AgNWs） have emerged as a promising nanomaterial for next generation stretchable electronics. However, until now, the fabrication of AgNW- based components has been hampered by complex and time-consuming steps. Here, we introduce a facile, fast, and one-step methodology for the fabrication of highly conductive and stretchable AgNW/polyurethane （PU） composite electrodes based on a high-intensity pulsed light （HIPL） technique. HIPL simultaneously improved wire-wire junction conductivity and wire-substrate adhesion at room temperature and in air within 50 μs, omitting the complex transfer-curing-implanting process. Owing to the localized deformation of PU at interfaces with AgNWs, embedding of the nanowires was rapidly carried out without substantial substrate damage. The resulting electrode retained a low sheet resistance （high electrical conductivity） of 〈10 Ω/sq even under 100% strain, or after 1,000 continuous stretching-relaxation cycles, with a peak strain of 60%. The fabricated electrode has found immediate application as a sensor for motion detection. Furthermore, based on our electrode, a light emitting diode （LED） driven by integrated stretchable AgNW conductors has been fabricated. In conclusion, our present fabrication approach is fast, simple, scalable, and cost- efficient, making it a good candidate for a future roll-to-roll process.
基金supported in part by the National Science Foundation under contract ECCS 1309835the Air Force Office of Scientific Research under contract FA9550-09-1-0708+1 种基金support from DOEBasic Energy Sciences under Grant No.DE-FG02-09ER46643,under which the THz measurements were performedsupported by a Multidisciplinary University Research Initiative from the Air Force Office of Scientific Research(AFOSR MURI Award No.FA9550-12-1-0488)。
文摘The development of responsive metamaterials has enabled the realization of compact tunable photonic devices capable of manipulating the amplitude,polarization,wave vector and frequency of light.Integration of semiconductors into the active regions of metallic resonators is a proven approach for creating nonlinear metamaterials through optoelectronic control of the semiconductor carrier density.Metal-free subwavelength resonant semiconductor structures offer an alternative approach to create dynamic metamaterials.We present InAs plasmonic disk arrays as a viable resonant metamaterial at terahertz frequencies.Importantly,InAs plasmonic disks exhibit a strong nonlinear response arising from electric field-induced intervalley scattering,resulting in a reduced carrier mobility thereby damping the plasmonic response.We demonstrate nonlinear perfect absorbers configured as either optical limiters or saturable absorbers,including flexible nonlinear absorbers achieved by transferring the disks to polyimide films.Nonlinear plasmonic metamaterials show potential for use in ultrafast terahertz(THz)optics and for passive protection of sensitive electromagnetic devices.
文摘We present novel Schottky barrier field effect transistors consisting of a parallel array of bottom-up grown silicon nanowires that are able to deliver high current outputs. Axial silicidation of the nanowires is used to create defined Schottky junctions leading to on/off current ratios of up to 106. The device concept leverages the unique transport properties of nanoscale junctions to boost device performance for macroscopic applications. Using parallel arrays, on-currents of over 500 gA at a source-drain voltage of 0.5 V can be achieved. The transconductance is thus increased significantly while maintaining the transfer characteristics of single nanowire devices. By incorporating several hundred nanowires into the parallel arra36 the yield of functioning transistors is dramatically increased and device- to-device variability is reduced compared to single devices. This new nanowire- based platform provides sufficient current output to be employed as a transducer for biosensors or a driving stage for organic light-emitting diodes （LEDs）, while the bottom-up nature of the fabrication procedure means it can provide building blocks for novel printable electronic devices.
文摘Linear light-processing functions(e.g.,routing,splitting,filtering)are key functions requiring configuration to implement on a programmable photonic integrated circuit(PPIC).In recirculating waveguide meshes(which include loop-backs),this is usually done manually.Some previous results describe explorations to perform this task automatically,but their efficiency or applicability is still limited.In this paper,we propose an efficient method that can automatically realize configurations for many light-processing functions on a square-mesh PPIC.At its heart is an automatic differentiation subroutine built upon analytical expressions of scattering matrices that enables gradient descent optimization for functional circuit synthesis.Similar to the state-of-the-art synthesis techniques,our method can realize configurations for a wide range of light-processing functions,and multiple functions on the same PPIC simultaneously.However,we do not need to separate the functions spatially into different subdomains of the mesh,and the resulting optimum can have multiple functions using the same part of the mesh.Furthermore,compared to nongradient-or numerical differentiation-based methods,our proposed approach achieves 3×time reduction in computational cost.
基金Supported by the Hi-Tech Research and Development Program of China (Grant No. 2006AA04Z312)National Basic Research Program of China (Grant No. 2006CB300403)
文摘Via systematic investigation of the anodization of both patterned and unpatterned specimens, phenomena of pronounced discrepancy with respect to pore size, pore density and pore etch-rate were evidenced. Based on the detailed analysis of scanning electron microscope (SEM) micrographs and current-voltage curves, the competition between physical and chemical elements was found to be crucial to understanding the observations. The results indicate that the size, density and growth-speed of pores may act as an evident function of the initial morphology of the sample surface, despite a nearly fixed width of the space charge region. Electric-field effect as well as current-burst-model (CBM) was employed to interpret the underlying mechanism.
基金The Swedish National Space Board and the Centre for Natural Disasters Science(CNDS)are acknowledged forproject fundingThe Knut and A lice Wallenberg Foundation is acknowledged for funding the laboratory facilitiesPeter Sturesson at the Department of Engineering Sciences,Uppsala University is gratefully thanked for help with the SEM.Dhananjay V.Barbade,who participated in the previous study,is appreciated for inspiration to this work.
文摘Ceramic microthrusters with an embedded Pt resistive heater,two temperature sensors,and a Pt or Ag catalytic bed were made of high-temperature co-fired alumina ceramics.To increase the surface area by a factor of 1.21,and so the catalytic effect,the Pt catalytic bed was made porous by mixing the Pt paste with 15—20vol.%graphite sacrificial paste before screen printing it.Ag was in-situ electroplated on the porous Pt surface after sintering.Decomposition of 50wt.%hydrogen peroxide as a monopropellant was studied both qualitatively and quantitatively by changing the catalyst(between Ag and Pt),flow rate(15—55 μl/min),and operating temperature(115—300℃).A reference device without catalyst exhibited an unstable behavior as a result of no,or vety little,decomposition,whereas the Ag catalyst was more stable,and the Pt one even more stable.Also,Pt was found to be slightly more effective.Quantitatively,there were small differences between Pt and Ag in the power needed to maintain the temperature.The inventive methods to make the Pt bed porous as well as in-situ electroplating Ag were success-fully demonstrated.
基金supported by King Abdullah University of Science and Technology(KAUST).
文摘This paper presents a tunable multi-threshold micro-electromechanical inertial switch with adjustable threshold capability.The demonstrated device combines the advantages of accelerometers in providing quantitative acceleration measurements and g-threshold switches in saving power when in the inactive state upon experiencing acceleration below the thresholds.The designed proof-of-concept device with two thresholds consists of a cantilever microbeam and two stationary electrodes placed at different positions in the sensing direction.The adjustable threshold capability and the effect of the shock duration on the threshold acceleration are analytically investigated using a nonlinear beam model.Results are shown for the relationships among the applied bias voltage,the duration of shock impact,and the tunable threshold.The fabricated prototypes are tested using a shock-table system.The analytical results agree with the experimental results.The designed device concept is very promising for the classification of the shock and impact loads in transportation and healthcare applications.
基金Project supported by the State Key Development Program for Basic Research of China(No.2006CB30040)
文摘A MEMS compressed period-tunable grating device with a wide tuning range has been designed, fabricated and characterized. To increase the tuning range, avoid instability with tuning and improve the performance, we propose in this paper a period-tunable grating which is compressed by large-displacement comb actuators with tilted folded beams. The experimental results show that the designed grating device has a compression range of up to 144μm within 37 V driving voltage. The period of the grating can be adjusted continuously from 16 to 14 μm with a tuning range of 12.5%. The maximum tuning range of the first-order diffraction angle is 0.34° at 632.8 nm and the reflectivity of the grating is more than 92.6% in the mid-infrared region. The grating device can be fabricated by simple processes and finds applications in mid-infrared spectrometers.
基金supported by DFG and TUHH in the funding programme Open Access Publishing
文摘We present integrated-optic building blocks and functional photonic devices based on amorphous siliconon-insulator technology. Efficient deep-etched fiber-to-chip grating couplers, low-loss single-mode photonic wire waveguides, and compact power splitters are presented. Based on the sub-μm photonic wires, 2 × 2 Mach–Zehnder interferometers and add/drop microring resonators(MRRs) with low device footprints and high finesse up to 200 were realized and studied. Compact polarization rotators and splitters with ≥10 d B polarization extinction ratio were fabricated for the polarization management on-chip. The tuning and trimming capabilities of the material platform are demonstrated with efficient microheaters and a permanent device trimming method, which enabled the realization of energy-efficient photonic circuits. Wavelength multiplexers in the form of cascaded filter banks and 4 × 4 routers based on MRR switches are presented. Fabrication imperfections were analyzed and permanently corrected by an accurate laser-trimming method, thus enabling eight-channel multiplexers with record low metrics of sub-m W static power consumption and ≤1°C temperature overhead. The high quality of the functional devices, the high tuning efficiency, and the excellent trimming capabilities demonstrate the potential to realize low-cost, densely integrated, and ultralow-power 3D-stacked photonic circuits on top of CMOS microelectronics.
文摘We demonstrate a pH sensor based on ultrasensitive nanosize Schottky junctions formed within bottom-up grown dopant-flee arrays of assembled silicon nanowires. A new measurement concept relying on a continuous gate sweep is presented, which allows the straightforward determination of the point of maximum sensitivity of the device and allows sensing experiments to be performed in the optimum regime. Integration of devices into a portable fluidic system and an electrode isolation strategy affords a stable environment and enables long time robust FET sensing measurements in a liquid environment to be carried out. Investigations of the physical and chemical sensitivity of our devices at different pH values and a comparison with theoretical limits are also discussed. We believe that such a combination of nanofabrication and engineering advances makes this Schottky barrier-powered silicon nanowire lab-on-a-chip platform suitable for efficient biodetection and even for more complex biochemical analysis.
