- Ahmet Ali Yanik is an Assist. Professor in the Jack Baskin School of Engineering at University of California, Santa C... moreAhmet Ali Yanik is an Assist. Professor in the Jack Baskin School of Engineering at University of California, Santa Cruz. His current research focuses on isolation and single cell analysis of Circulating Tumor Cells from human blood using optofluidic-nanoplasmonic platforms. His research interests include nanoplasmonic and metamaterial devices for ultrasensitive infrared spectroscopy of biomolecules/chemicals as well as high-throughput, cost effective, BioNEMS technologies for life sciences, point-of-care diagnostics and global health. His expertise is in high-end nanolithography and bio-patterning as well as theory and engineering of nanophotonic devices. He received his Ph.D. degree in applied theoretical physics from Purdue University, under the supervision of Prof. Supriyo Datta. During his PhD, he studied spin dependent electron transport in low dimensional molecular/nano-electronic devices and introduced one of the most advanced quantum transport models (spin-NEGF) that exists today. Before joining to UCSC, he was a senior research associate at BioMEMS Resource Center (Mehmet Toner Group) at Harvard University Medical Schooledit
The field of plasmonics is capable of enabling interesting applications in different wavelength ranges, spanning from the ultraviolet up to the infrared. The choice of plasmonic material and how the material is nanostructured has... more
The field of plasmonics is capable of enabling interesting applications in different wavelength ranges, spanning from the ultraviolet up to the infrared. The choice of plasmonic material and how the material is nanostructured has significant implications for ultimate performance of any plasmonic device. Artificially designed nanoporous metals (NPMs) have interesting material properties including large specific surface area, distinctive optical properties, high electrical conductivity, and reduced stiffness, implying their potentials for many applications. This paper reviews the wide range of available nanoporous metals (such as Au, Ag, Cu, Al, Mg, and Pt), mainly focusing on their properties as plasmonic materials. While extensive reports on the use and characterization of NPMs exist, a detailed discussion on their connection with surface plasmons and enhanced spectroscopies as well as photocatalysis is missing. Here, we report on different metals investigated, from the most used na...
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In this paper, we introduce a novel sensor scheme which merges nano-photonics and nano-fluidics on a single platform through the use of free-standing photonic crystals (PhCs). PhCs offer great freedom to manipulate the spatial extent and... more
In this paper, we introduce a novel sensor scheme which merges nano-photonics and nano-fluidics on a single platform through the use of free-standing photonic crystals (PhCs). PhCs offer great freedom to manipulate the spatial extent and the spectral characteristics of the electromagnetic fields. Also, nanoholes in PhCs provide a natural platform to transport solutions. By harnessing these nano-scale openings, we theoretically and experimentally demonstrate that both fluidics and light can be manipulated at sub-wavelength scales. In this scheme, the free standing PhCs are sealed in a chamber such that only the nano-scale hole arrays enable the flow between the top and the bottom channels. The nanohole arrays are used as sensing structures as well as nanofluidic channels. Compared to the conventional fluidic channels, we can actively steer the convective flow through the nanohole openings for effective delivery of the analytes to the sensor surface. This scheme also helps to overcome the surface tension of highly viscous solution and guarantees that the sensor can be totally immersed in solution. We apply this method to detect refractive index changes in aqueous solutions. Bulk measurements indicate that active delivery of the convective flow results in better performance. The sensitivity of the sensor reaches 510 nm/RIU for resonance located around 850 nm with a line-width of {10 nm in solution. Experimental results are matched very well with numerical simulations. We also show that cross-polarization measurements can be employed to further improve the detection limit by increasing the signal-to-noise ratio.
Research Interests: Photonic Crystals, Nanophotonics, Photonics, Aqueous Solutions, Sensors, and 13 moreNumerical Simulation, Photonic Crystal, Nanostructures, Electromagnetic Fields, Nanostructure, Refractive Index, Polarization, Electromagnetic Field, Optical physics, Surface Tension, Aqueous Solution, Signal to Noise Ratio, and Electrical And Electronic Engineering
In this study we introduce the spectroscopic modifications of Pippard relations and apply them to the disorder-induced Raman modes of NH4Cl in the first-order (P=0) and second-order (2.8 kbar) phase regions in this crystalline system. We... more
In this study we introduce the spectroscopic modifications of Pippard relations and apply them to the disorder-induced Raman modes of NH4Cl in the first-order (P=0) and second-order (2.8 kbar) phase regions in this crystalline system. We obtain linear variations of the specific heat CP with our observed frequency shifts [(1/ν)(∂ν/∂T)P] of those Raman modes studied for the first-order and second-order phase transitions in NH4Cl. This will be discussed in detail.
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We introduce a novel sensor scheme that combines nano-photonics and nano-fluidics on a single platform using free-standing photonic crystals. The sensor with 510 nm/RIU sensitivity can lead to enhanced analyte delivery to the sensor... more
We introduce a novel sensor scheme that combines nano-photonics and nano-fluidics on a single platform using free-standing photonic crystals. The sensor with 510 nm/RIU sensitivity can lead to enhanced analyte delivery to the sensor surface.
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Confinement of light through plasmonic structures is utilized in biosensing applications [1], spectroscopy [2] and optical trapping [3]. Nanoplasmonic structures have been used for ultrasensitive biosensors with high multiplexing... more
Confinement of light through plasmonic structures is utilized in biosensing applications [1], spectroscopy [2] and optical trapping [3]. Nanoplasmonic structures have been used for ultrasensitive biosensors with high multiplexing characteristics [4], spectroscopy systems with high enhancement factors [5] and high nm-size precision optical tweezers [6]. However, most of these structures operate for single operations. Biosensors with refractive index sensitivity are lack of near field enhancement and spectroscopic structures with enhanced near field capabilities do not possess sharp ...
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In this work, we are demonstrating resonant light transmission through hybrid multi-layered plasmonic crystals, which are formed by a coupled nanohole and a nanoparticle array. This structures are shown to provide the conventional... more
In this work, we are demonstrating resonant light transmission through hybrid multi-layered plasmonic crystals, which are formed by a coupled nanohole and a nanoparticle array. This structures are shown to provide the conventional extraordinary optical transmission (EOT) peaks and also a newly found cavity-based mode is introduced with an emphasis to its high sensing capabilities. Plasmon hybridization in coaxial nanocavities is also addressed, where the nanohole array and the nanoparticle array are in the same layer.
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A quantum transport model incorporating spin scattering processes is presented using the nonequilibrium Green’s function formalism within the self-consistent Born approximation. This model offers a unified approach by capturing the... more
A quantum transport model incorporating spin scattering processes is presented using the nonequilibrium Green’s function formalism within the self-consistent Born approximation. This model offers a unified approach by capturing the spin-flip scattering and the quantum effects simultaneously. A numerical implementation of the model is illustrated for magnetic tunnel junction devices with embedded magnetic impurity layers. This model seems to explain three experimentally observed features regarding the dependence of the junction magnetoresistances (JMRs) on the barrier thickness, barrier height, and number of magnetic impurities. It is shown that small variations in magnetic impurity spin states and concentrations could cause large deviations in JMRs.
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Abstract Coherent transport in single wall carbon nanotubes in the presence of spin-orbit coupling is investigated theoretically. Reflectionless contacts are used for probing the electronic transport through infinite SWCNTs for different... more
Abstract Coherent transport in single wall carbon nanotubes in the presence of spin-orbit coupling is investigated theoretically. Reflectionless contacts are used for probing the electronic transport through infinite SWCNTs for different spin polarizations. It is shown that the spin-orbit interactions give rise to flipping of the electron spin states for sufficiently long CNTs. Spin flip processes are clearly distinguished in the lowest conduction mode, while mode mixing in different conduction modes obscures the spin flipping length for higher ...
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We demonstrate enhanced diffractive coupling resulting in sharpened extinction resonances in periodic arrays of metal nanoparticles embedded effectively below the substrate surface. Strongly enhanced near fields with large spatial overlap... more
We demonstrate enhanced diffractive coupling resulting in sharpened extinction resonances in periodic arrays of metal nanoparticles embedded effectively below the substrate surface. Strongly enhanced near fields with large spatial overlap with the substrate material are shown to be associated with these extinction features. In particle arrays fabricated on substrates there is a phase velocity mismatch between light propagating above and
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ABSTRACT We introduce a novel sensor scheme combining nano-photonics and nano-fluidics on a single platform through the use of free-standing photonic crystals. By harnessing nano-scale openings, we theoretically and experimentally... more
ABSTRACT We introduce a novel sensor scheme combining nano-photonics and nano-fluidics on a single platform through the use of free-standing photonic crystals. By harnessing nano-scale openings, we theoretically and experimentally demonstrate that both fluidics and light can be manipulated at sub-wavelength scales. Compared to the conventional fluidic channels, we actively steer the convective flow through the nanohole openings for effective delivery of the analytes to the sensor surface. We apply our method to detect refractive index changes in aqueous solutions. Bulk measurements indicate that active delivery of the convective flow results in better sensitivities. The sensitivity of the sensor reaches 510 nm/RIU for resonance located around 850 nm with a line-width of approximately 10 nm in solution. Experimental results are matched very well with numerical simulations. We also show that cross-polarization measurements can be employed to further improve the detection limit by increasing the signal-to-noise ratio.
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Abstract Short interaction lengths limit the application of infrared absorption spectroscopy to the study monolayer thickness films. We employ periodic infrared antenna arrays to obtain 10 4− 10 5 enhancement of protein absorption signals... more
Abstract Short interaction lengths limit the application of infrared absorption spectroscopy to the study monolayer thickness films. We employ periodic infrared antenna arrays to obtain 10 4− 10 5 enhancement of protein absorption signals corresponding to zepto-mole sensitivity.
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Infrared absorption spectroscopy offers direct access to the vibrational signatures of molecular structure. Although absorption cross sections are nearly 10 orders of magnitude larger than the Raman cross sections, they are small in... more
Infrared absorption spectroscopy offers direct access to the vibrational signatures of molecular structure. Although absorption cross sections are nearly 10 orders of magnitude larger than the Raman cross sections, they are small in comparison with those of fluorescent labels. Sensitivity improvements are therefore required in order for the method to be applicable to single molecule/monolayer studies. In this work, we
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The excitation of localized surface plasmon resonances (LSPRs) in noble metal nanoparticles leads to strongly confined fields in the vicinity of the particle for incident radiation of a specific resonant frequency [1]. These unique... more
The excitation of localized surface plasmon resonances (LSPRs) in noble metal nanoparticles leads to strongly confined fields in the vicinity of the particle for incident radiation of a specific resonant frequency [1]. These unique properties of noble metal nanoparticles have been recognized as a means with which to achieve antenna like functionalities at optical frequencies [2]. Applications in biological sciences and device engineering include surface enhanced spectroscopies [3], increased fluorescence emission [4], and absorption enhancement in photovoltaic cells ...
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In this letter, we demonstrate creation of hybridized elementary plasmonic excitations in specially designed cavities in metallic films through surface propagating plasmons (SPP). This phenomena is explained by developing a quasi-static... more
In this letter, we demonstrate creation of hybridized elementary plasmonic excitations in specially designed cavities in metallic films through surface propagating plasmons (SPP). This phenomena is explained by developing a quasi-static model in a much similar way to widely known hybridization effects in nanoshells [1]. Accordingly, complex behavior of extraordinary light transmission (EOT) effect through these nanocavities is remarkably well explained and connected to the antenna behavior of nanoparticles [2]. Creation of hybridized plasmonic excitations in the ...
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We demonstrate a strategy for surface-enhanced Raman spectroscopy (SERS) of supported lipid membranes with arrays of plasmonic nanoantennas. Colloidal lithography refined with plasma etching is used to synthesize arrays of triangular... more
We demonstrate a strategy for surface-enhanced Raman spectroscopy (SERS) of supported lipid membranes with arrays of plasmonic nanoantennas. Colloidal lithography refined with plasma etching is used to synthesize arrays of triangular shaped gold nanoparticles. Reducing the separation distance between the triangle tips leads to plasmonic coupling and to a strong enhancement of the electromagnetic field in the nanotriangle gap. As a result, the Raman scattering intensity of molecules that are located at this plasmonic "hot-spot" can be increased by several orders of magnitude. The nanoantenna array is then embedded with a supported phospholipid membrane which is fluid at room temperature and spans the antenna gap. This configuration offers the advantage that molecules that are mobile within the bilayer membrane can enter the "hot-spot" region via diffusion and can therefore be measured by SERS without static entrapment or adsorption of the molecules to the antenna ...
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Research Interests: Plasmonics, Silicon, Nanoparticles, Nanotechnology, Optical Sensor, and 12 moreSurface Plasmons, Light, Surface plasmon resonance, Metals, Optical physics, Electromagnetic phenomena, Length scale, Antenna Array, Optics and Photonics, Equipment Design, Electrical And Electronic Engineering, and Near Field
Biodetection systems have been developed for wide range of fields from defense applications to biology and pharmacology. In that sense, On-Chip Plasmonic-Sensors have received significant attention for biosensing applications since they... more
Biodetection systems have been developed for wide range of fields from defense applications to biology and pharmacology. In that sense, On-Chip Plasmonic-Sensors have received significant attention for biosensing applications since they can enable highly sensitive biodetection, operate in real time and can be highly-multiplexed for high throughput screening of biological solutions [1-2]. However, these nanobiosensors are limited by the delivery of the analytes to the sensor surface. To address this problem, in our recent article, we used nanofluidics integrated to ...
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We demonstrate a novel fabrication approach for high-throughput fabrication of engineered infrared plasmonic nanorod antenna arrays with Nanostencil Lithography (NSL). NSL technique, relying on deposition of materials through a shadow... more
We demonstrate a novel fabrication approach for high-throughput fabrication of engineered infrared plasmonic nanorod antenna arrays with Nanostencil Lithography (NSL). NSL technique, relying on deposition of materials through a shadow mask, offers the flexibility and the resolution to fabricate radiatively engineer nanoantenna arrays for excitation of collective plasmonic resonances. Overlapping these collective plasmonic resonances with molecular specific absorption bands can enable ultrasensitive vibrational spectroscopy. First, nanorod antenna arrays fabricated using NSL are investigated using SEM and optical spectroscopy, and compared against the nanorods with the same dimensions fabricated using EBL. No irregularities on the periodicity or the physical dimensions are detected for NSL fabricated nanorods. We also confirmed that the antenna arrays fabricated by NSL shows high optical quality similar to EBL fabricated ones. Furthermore, we show nanostencils can be reused multiple times to fabricate selfsame structures with identical optical responses repeatedly and reliably. This capability is particularly useful when high-throughput replication of the optimized nanoparticle arrays is desired. In addition to its high-throughput capability, NSL permits fabrication of plasmonic devices on surfaces that are difficult to work with electron/ion beam techniques. Nanostencil lithography is a resist free process thus allows the transfer of the nanopatterns to any planar substrate whether it is conductive, insulating or magnetic. As proof of the versatility of the NSL technique, we show fabrication of plasmonic structures in variety of geometries. We also demonstrate that nanostencil lithography can be used to achieve functional plasmonic devices in a single fabrication step, on variety of substrates. We introduced NSL for fabrication of nanoplasmonic structures including antenna arrays on rigid surfaces such as silicon, CaF2 and glass. In conclusion, Nanostencil Lithography enables plasmonic substrates supporting spectrally narrow far-field resonances with enhanced near-field intensities which are very useful for vibrational spectroscopy. We believe this nanofabrication scheme, enabling the reusability of stencil and offering flexibility on the substrate choice and nano-pattern design could significantly enhance wide-use of plasmonics in sensing technologies.
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We demonstrate a novel fabrication approach for high-throughput fabrication of engineered plasmonic antenna arrays and metamaterials with Nanostencil Lithography (NSL). NSL technique, relying on deposition of materials through a shadow... more
We demonstrate a novel fabrication approach for high-throughput fabrication of engineered plasmonic antenna arrays and metamaterials with Nanostencil Lithography (NSL). NSL technique, relying on deposition of materials through a shadow mask, offers the flexibility and the resolution to fabricate radiatively engineer nanoantenna arrays for excitation of collective plasmonic resonances. We confirmed that the antenna arrays fabricated by NSL shows high
Research Interests: Antennas, Nonlinear Optics, Spectroscopy, Plasmonics, Nanofabrication, and 16 moreMetamaterials, Nanoparticles, Vibrational Spectroscopy, Transparency, Magnetism, Fabrication, Lithography, Electrons, High Resolution, Very high throughput, Antenna Array, Non Linear Optics, Ion Beam, Plasmons, Ion Beams, and Near Field
We demonstrate a novel fabrication approach for high-throughput fabrication of engineered infrared plasmonic nanorod antenna arrays with nanostencil lithography (NSL). NSL technique, relying on deposition of materials through a shadow... more
We demonstrate a novel fabrication approach for high-throughput fabrication of engineered infrared plasmonic nanorod antenna arrays with nanostencil lithography (NSL). NSL technique, relying on deposition of materials through a shadow mask, offers the flexibility and the resolution to radiatively engineer nanoantenna arrays for excitation of collective plasmonic resonances. As stencil, we use suspended silicon nitride membrane patterned with nanoapertures and
Research Interests: Engineering, Antennas, Electron Microscopy, Spectroscopy, Electron Beam Lithography, and 15 moreNanoparticles, Vibrational Spectroscopy, Magnetism, Silicon Nitride, Fabrication, Absorption, Lithography, Electrons, Infrared, Very high throughput, Antenna Array, Ion Beam, Ion Beams, Electron Beams, and Near Field
In this work, we are demonstrating resonant light transmission through hybrid multi-layered plasmonic crystals, which are formed by a coupled nanohole and a nanoparticle array. This structures are shown to provide the conventional... more
In this work, we are demonstrating resonant light transmission through hybrid multi-layered plasmonic crystals, which are formed by a coupled nanohole and a nanoparticle array. This structures are shown to provide the conventional extraordinary optical transmission (EOT) peaks and also a newly found cavity-based mode is introduced with an emphasis to its high sensing capabilities. Plasmon hybridization in coaxial nanocavities
Performances of surface biosensors are often controlled by the analyte delivery rate to the sensing surface instead of sensors intrinsic detection capabilities. In a microfluidic channel, analyte transports diffusively to the biosensor... more
Performances of surface biosensors are often controlled by the analyte delivery rate to the sensing surface instead of sensors intrinsic detection capabilities. In a microfluidic channel, analyte transports diffusively to the biosensor surface severely limiting its performance. At low concentrations, this limitation, commonly known as mass transport problem, causes impractically long detection times extending from days to months. In this
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Abstract: We demonstrate a versatile fabrication approach for high-resolution, large area patterning of optical antennas and metamaterials with reusable nanostencils. This technique offers simple and high-throughput fabrication scheme for... more
Abstract: We demonstrate a versatile fabrication approach for high-resolution, large area patterning of optical antennas and metamaterials with reusable nanostencils. This technique offers simple and high-throughput fabrication scheme for any geometric design on variety of substrates. OCIS codes: (220.4241) Nanofabrication; (250.5403) Plasmonics; (160.3918) Metamaterials. ... A new generation of plasmonic antennas and metamaterials operating at the visible and infrared frequencies is opening up a myriad of exciting possibilities. Enabling sub-wavelength ...
Nanoplasmonics and metamaterials are at the core of a myriad of new exciting opportunities poised to revolutionize biomedical sciences, drug discovery and point-of-care diagnostics. Although significant progress has been achieved in... more
Nanoplasmonics and metamaterials are at the core of a myriad of new exciting opportunities poised to revolutionize biomedical sciences, drug discovery and point-of-care diagnostics. Although significant progress has been achieved in plasmonics, many fundamental questions and practical challenges are still remaining to address. For example, for biosensors based on refractive index change, the detection limit depends on both the sensitivity of plasmons to the local dielectric environment and their resonance line-width. Narrower line-widths allow smaller shifts to ...
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Abstract Plasmonics, by localizing light below sub-diffraction limit and enhancing local field intensities, is enabling exciting possibilities in bio-detection field. In this talk, I will present novel plasmonic systems for ultrasensitive... more
Abstract Plasmonics, by localizing light below sub-diffraction limit and enhancing local field intensities, is enabling exciting possibilities in bio-detection field. In this talk, I will present novel plasmonic systems for ultrasensitive vibrational nanospectroscopy and biomolecular identification.
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Abstract We demonstrate a novel hybrid platform merging label free nanoplasmonic sensing with actively controlled nanofluidic surface delivery to overcome mass transport limitations. We show 14-fold improvement in mass transport rate... more
Abstract We demonstrate a novel hybrid platform merging label free nanoplasmonic sensing with actively controlled nanofluidic surface delivery to overcome mass transport limitations. We show 14-fold improvement in mass transport rate constants appearing in the exponentials.
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Abstract We demonstrate a novel approach for high-throughput and high-resolution fabrication of engineered infrared plasmonic antenna arrays with reusable nanostencils. Optical responses of these plasmonic antennas are comparable to that... more
Abstract We demonstrate a novel approach for high-throughput and high-resolution fabrication of engineered infrared plasmonic antenna arrays with reusable nanostencils. Optical responses of these plasmonic antennas are comparable to that of arrays fabricated by electron-beam lithography.
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Abstract Extraordinary light transmission through Fabry-Perot cavities in 3-D plasmonic crystals created by two physically separated plasmonic layers is demonstrated. These cavity resonances show large field enhancements and are highly... more
Abstract Extraordinary light transmission through Fabry-Perot cavities in 3-D plasmonic crystals created by two physically separated plasmonic layers is demonstrated. These cavity resonances show large field enhancements and are highly sensitive to refractive index changes.
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Abstract Photonic and plasmonic interactions in multi-layered plasmonic crystals, formed by coupling nanohole-nanoparticle arrays, are investigated. The hybrid structure exhibits extraordinary optical transmission as in single layer... more
Abstract Photonic and plasmonic interactions in multi-layered plasmonic crystals, formed by coupling nanohole-nanoparticle arrays, are investigated. The hybrid structure exhibits extraordinary optical transmission as in single layer nanohole arrays and supports Fabry-Perot mode with improved sensitivity.
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Abstract We propose and demonstrate a scheme enabling construction of a scalable metamaterial supporting multi-spectral electromagnetically induced transparency-like effects through hybridization of coupled meta-atoms. Tailoring of... more
Abstract We propose and demonstrate a scheme enabling construction of a scalable metamaterial supporting multi-spectral electromagnetically induced transparency-like effects through hybridization of coupled meta-atoms. Tailoring of intra-and inter-layer near-field interactions give rise to the discussed phenomenon.
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The subject of light transmission through optically thin metal films perforated with arrays of subwavelength nanoholes has recently attracted significant attention. In this work, we present experimental and calculated results on optical... more
The subject of light transmission through optically thin metal films perforated with arrays of subwavelength nanoholes has recently attracted significant attention. In this work, we present experimental and calculated results on optical transmission/reflection of the U-shaped nanoapertures for enhanced optical transmission and resolution. We propose different structure designs in order to prove the effect of geometry on resonance and enhanced
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In this paper, we present numerical and experimental results on optical properties of a multi-resonant UT-shaped plasmonic nanoaperture antenna for enhanced optical transmission and near-field resolution. We propose different structure... more
In this paper, we present numerical and experimental results on optical properties of a multi-resonant UT-shaped plasmonic nanoaperture antenna for enhanced optical transmission and near-field resolution. We propose different structure designs in order to prove the effect of geometry on resonance spectrum and near-field enhancement. Theoretical calculations of transmission spectra and field distributions of UT-shaped nano-apertures are performed by using
Research Interests: Antennas, Electron Beam Lithography, Structural Design, Nanostructures, Fabrication, and 13 moreOptical Properties, Spectrum, Tunable Filter, Infrared, Optical Modulator, Three Dimensional, Transmittance, Reactive ion etching, Optical Modulators, Apertures, Numerical Calculation, Near Field, and Spectral Response
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Confinement of light through plasmonic structures is utilized in biosensing applications [1], spectroscopy [2] and optical trapping [3]. Nanoplasmonic structures have been used for ultrasensitive biosensors with high multiplexing... more
Confinement of light through plasmonic structures is utilized in biosensing applications [1], spectroscopy [2] and optical trapping [3]. Nanoplasmonic structures have been used for ultrasensitive biosensors with high multiplexing characteristics [4], spectroscopy systems with high enhancement factors [5] and high nm-size precision optical tweezers [6]. However, most of these structures operate for single operations. Biosensors with refractive index sensitivity are lack of near field enhancement and spectroscopic structures with enhanced near field capabilities do not possess sharp ...
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The microfluidic isolation of target cells using adhesion-based surface capture has been widely explored for biology and medicine. However, high-throughput processing can be challenging due to interfacial limitations such as transport,... more
The microfluidic isolation of target cells using adhesion-based surface capture has been widely explored for biology and medicine. However, high-throughput processing can be challenging due to interfacial limitations such as transport, reaction, and non-specific fouling. Here, it is shown that antibody-functionalized capture surfaces with discontinuous permeability enable efficient target cell capture at high flow rates by decreasing fouling. Experimental characterization and theoretical modeling reveal that "wall effects" affect cell-surface interactions and promote excess surface accumulation. These issues are partially circumvented by reducing the transport and deposition of cells near the channel walls. Optimized microfluidic devices can be operated at higher cell concentrations with significant improvements in throughput.
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Research Interests: Microfluidics, Computer Aided Design, Crystallization, Nanotechnology, Numerical Simulation, and 13 moreTransducers, Photonic Crystal, Resonance, Nanostructures, Optical devices, Refractive Index, Optical physics, Aqueous Solution, Signal to Noise Ratio, Equipment Design, Equipment Failure Analysis, Electrical And Electronic Engineering, and Refractometry
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One of the primary advantages of nanoscale sensors is that they often can provide conceptually new ways of performing sensing that are not feasible with their large-scale analogs. For example, the small size of nanoscale sensor elements,... more
One of the primary advantages of nanoscale sensors is that they often can provide conceptually new ways of performing sensing that are not feasible with their large-scale analogs. For example, the small size of nanoscale sensor elements, such as plasmonic metal nanoparticles, allows them to be combined with nanofluidic systems. Among the potential applications of such a combination is the efficient delivery of analyte to the sensor surface. With this in mind, in this work we look to address the challenge of creating and positioning nanoplasmonic sensor elements within nanofluidic pores. A scheme is presented that allows for the production of arrays of pores in a thin (220 nm) silicon nitride membrane with one plasmonic nanoparticle sensor element in each pore. The high throughput fabrication protocol is parallel and enables multiple sensor chips to be produced simultaneously, yet with accurate tuning of the dimension and shape of the nanoparticles. The presented system is shown to possess polarization-sensitive plasmonic resonances that can be tuned significantly in the visible wavelength range by just varying one process parameter. The thickness of the membrane could be optimized to minimize the influence of the optical membrane interference on the plasmonic readout. The sensitivity of the plasmon resonances to changes in refractive index, which forms the basis for using the system for biosensing, was found to be competitive with other nanoplasmonic sensors.