fabrication-and-operation-of-a-nano-optical-conveyor-belt

Fabrication and Operation of a Nano-Optical Conveyor Belt

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological ...

Stanford University

Optical resolution beyond the diffraction limit can be achieved by use of a metallic nanoaperture in a near-field optical system. Conventional nanoapertures have very low power throughput. Using a numerical finite-difference time domain method, we discovered a unique C-shaped aperture that provides approximately 3 orders of magnitude more power throughput than a conventional square aperture with a similar near-field spot size of approximately 0.1 lambda. Microwave experiments at 6 GHz quantitatively confirmed the simulated transmission enhancement. The high transmission of the C-aperture--or one of the related shapes--is linked to both a propagation mode in the aperture and local surface plasmons.

Ultrahigh light transmission through a C-shaped nanoaperture.

We describe the design and implementation of a high-data-rate high-capacity digital holographic storage disk system. Various system design trade-offs that affect density and data-rate performance are described and analyzed. In the demonstration system that we describe, high-density holographic recording is achieved by use of high-resolution short-focal-length optics and correlation shift multiplexing in photopolymer disk media. Holographic channel decoding at a 1-Gbit/s data rate is performed by custom-built electronic hardware. A benchmark sustained optical data-transfer rate of 10 Gbits/s has been successfully demonstrated.

High-transfer-rate high-capacity holographic disk data-storage system.

Micrometer-sized reflection holograms can be written into a rapidly rotating homogeneous photopolymer disk at the focus of a high-numerical-aperture beam and its retroreflection to implement high-capacity multilayer digital data storage. This retroreflection is generated by an optical system with positive unity magnification to ensure passive alignment of the counterpropagating beam. Analysis reveals that the storage capacity and transfer rate of this bit-based holographic storage system compare favorably with traditional page-based systems but at a fraction of the system complexity and cost. The analysis is experimentally validated at 532 nm by writing and reading 12 layers of microholograms in a 125-microm photopolymer disk continuously rotating at 3600 rpm. The experimental results predict a capacity limit of 140 Gbytes in a millimeter-thick disk or over 1 Tbyte with the wavelength and numerical aperture of Blu-Ray.

Microholographic multilayer optical disk data storage.

We describe laser ablation of Si under water by 5 ns, 355 nm and 100 fs, 800 nm pulses. Compared to that in air, an approximately twofold improvement in the ablation rate is found in water for femtosecond and nanosecond pulses. For higher laser irradiances, the plasma that forms at the water-air interface hampers further improvement of the ablation rate. We investigated the enhanced ablation process in water and found that the cavity-confinement geometry that increases the laser energy coupling to the target and allows more energy to be transferred to the cavity sidewalls plays an important role in the escalated material removal process. In addition, we show that the water layer that effectively reduces the oxidation and redeposition of the ablated debris is also responsible for improvements in the ablation process.

Laser ablation of silicon in water with nanosecond and femtosecond pulses.

Tilt tolerance of media is compared for bit-based and page-based holographic storage systems having an equal diffraction efficiency per bit detector, dynamic range of the medium, and surface recording density. We have formalized the diffraction efficiency degradation caused by aberrations of a reconstructing reference beam induced by tilt of the medium, using a coupled wave theory in the Fourier domain. The bit-based holographic storage system has a larger media tilt tolerance compared with a page-based system with relatively large page size.

Media tilt tolerance of bit-based and page-based holographic storage systems.

We present a C-shaped nanoaperture-enhanced Ge photodetector that shows 2-5 times the photocurrent enhancement over that from a square aperture of the same area at 1310 nm wavelength. We demonstrate the polarization dependence of the C-aperture photodetector over a wide wavelength range. Our experimental observation agrees well with finite-difference time-domain simulation results.

C-shaped nanoaperture-enhanced germanium photodetector.

We present a design of a linear optical waveguide that utilizes a C-shaped metallic nano-aperture that efficiently transports light while maintaining a spot size of lambda/10. The performance of a C-aperture waveguide is superior to both a regular ridge waveguide and other surface plasmon based metal nano-optical waveguides. The energy transport mechanisms are explained by the coupling of an aperture surface resonance and the thickness resonances inside the guide channel. Finite-difference time-domain simulations of gold C-aperture waveguides are performed for a 1.5 microm wavelength incident plane wave. The 1/e decay length in power transmission is predicted to be approximately 2.5 microm. The total power throughput is 1.66 for the 2.55 microm long guide, with an intensity 6 times that of the incident wave at a distance 120 nm from the exit plane, having a spot size of 150 nm.

Low-loss subwavelength metal C-aperture waveguide.

Einzelmolek&uuml;l-Fluoreszenz Resonanz Energietransfer (FRET) ist eine allgemein anerkannte Methode zur Bestimmung der r&auml;umlichen Trennung zwischen Molek&uuml;len. In Kombination mit gepulsten &quot;interleaved&quot; Erregung (PIE) ist zus&auml;tzliche Informationen &uuml;ber die St&ouml;chiometrie der molekularen Interaktionen erhalten. PIE-FRET, erfordert jedoch wie mit standard-konfokale Optik, implementiert die Verd&uuml;nnung der Probe werden auf biologisch niedrigen Konzentrationen. Hier zeigen wir, dass PIE-FRET-Messwerte Nanometer gro&szlig;e &Ouml;ffnungen sinnvolle biochemische Daten bei 1000 x h&ouml;here Konzentrationen erzielen.

Gepulste-&uuml;berlappend Erregung FRET Messungen an einzelnen duplex DNA-Molek&uuml;le innerhalb der C-f&ouml;rmigen Nanoapertures.

Trasferimento di energia risonante di fluorescenza di singola molecola (FRET) &egrave; un metodo ampiamente accettato per determinare la separazione spaziale fra le molecole. In combinazione con eccitazione interleaved pulsato (PIE), sono ottenuti ulteriori informazioni circa la stechiometria di interazioni molecolari. PIE-FRET, tuttavia, come &egrave; implementato con ottica confocale standard, richiede la diluizione del campione a concentrazioni biologicamente basse. Qui, ci mostra che PIE-FRET misurazioni all&#39;interno di aperture di dimensioni nanometriche resa dati significativi biochimici a 1000 x concentrazioni pi&ugrave; elevate.

Misurazioni di FRET pulsato-interleaved eccitazione su singole molecole di DNA duplex all&#39;interno a forma di C nanoapertures.

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Single-molecule fluorescence resonant energy transfer (FRET) is a widely accepted method for determining the spatial separation between molecules. In combination with pulsed interleaved excitation (PIE), additional information about the stoichiometry of molecular interactions is obtained. PIE-FRET, however, as implemented with standard confocal optics, requires the dilution of the sample to biologically low concentrations. Here, we show that PIE-FRET measurements inside nanometer-sized apertures yield meaningful biochemical data at 1000 x higher concentrations.

Pulsed-interleaved excitation FRET measurements on single duplex DNA molecules inside C-shaped nanoapertures.

Transfert d&#39;&eacute;nergie de r&eacute;sonance Single-molecule fluorescence (FRET) est une m&eacute;thode commun&eacute;ment accept&eacute;e pour d&eacute;terminer la s&eacute;paration spatiale entre les mol&eacute;cules. En combinaison avec excitation entrelac&eacute;e puls&eacute;e (PIE), des informations suppl&eacute;mentaires sur la stoechiom&eacute;trie des interactions mol&eacute;culaires sont obtenues. PIE-FRET, cependant, tel qu&#39;impl&eacute;ment&eacute; avec une optique standard confocale, exige la dilution de l&#39;&eacute;chantillon biologique de faibles concentrations. Ici, nous montrons que les mesures de PIE-FRET &agrave; l&#39;int&eacute;rieur des ouvertures de taille nanom&eacute;trique fournissent des donn&eacute;es biochimiques significatives &agrave; 1000 x des concentrations plus &eacute;lev&eacute;es.

Mesures frette puls&eacute; entrelacement d&#39;excitation des mol&eacute;cules d&#39;ADN duplex unique &agrave; l&#39;int&eacute;rieur en forme de C nanoapertures.

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&#xB2E8;&#xC77C; &#xBD84;&#xC790; &#xD615;&#xAD11; &#xACF5;&#xBA85; &#xC5D0;&#xB108;&#xC9C0; &#xC804;&#xB2EC; (FRET) &#xBD84;&#xC790; &#xAC04;&#xC758; &#xACF5;&#xAC04; &#xBD84;&#xB9AC;&#xB97C; &#xACB0;&#xC815; &#xD558;&#xB294; &#xB370; &#xAD11;&#xBC94;&#xC704; &#xD558; &#xAC8C; &#xD5C8;&#xC6A9;&#xB41C; &#xBC29;&#xBC95;&#xC785;&#xB2C8;&#xB2E4;. &#xD384;&#xC2A4; &#xC778;&#xD130;&#xB9AC;&#xBE59;&#xB41C; &#xC5EC;&#xAE30; (&#xC6D0;&#xD615;)&#xC640; &#xD568;&#xAED8;, &#xBD84;&#xC790; &#xC0C1;&#xD638; &#xC791;&#xC6A9;&#xC758;&#xB294; stoichiometry&#xC5D0; &#xB300; &#xD55C; &#xCD94;&#xAC00; &#xC815;&#xBCF4;&#xB97C; &#xAC00;&#xC838;&#xC635;&#xB2C8;&#xB2E4;. &#xADF8;&#xB7EC;&#xB098; &#xC6D0;&#xD615; &#xBB34;&#xC11C; &#xC6CC; &#xD45C;&#xC900; confocal &#xAD11;&#xD559; &#xAD6C;&#xD604; &#xD558;&#xB824;&#xBA74; &#xC0D8;&#xD50C; &#xC0DD;&#xBB3C;&#xD559;&#xC801;&#xC73C;&#xB85C; &#xB0AE;&#xC740; &#xB18D;&#xB3C4; &#xD76C;&#xC11D;. &#xC5EC;&#xAE30;, &#xC6B0;&#xB9AC;&#xB294; &#xB098;&#xB178;&#xBBF8;&#xD130; &#xD06C;&#xAE30;&#xC758; apertures &#xB0B4;&#xBD80; &#xC6D0;&#xD615; &#xBB34;&#xC11C; &#xC6CC; &#xCE21;&#xC815; &#xB192;&#xC740; &#xB18D;&#xB3C4; x 1000&#xC5D0;&#xC11C; &#xC758;&#xBBF8; &#xC788;&#xB294; &#xC0DD; &#xD654; &#xD655; &#xC801;&#xC778; &#xB370;&#xC774;&#xD130;&#xB97C; &#xC5BB;&#xC744; &#xBCF4;&#xC5EC;&#xC90D;&#xB2C8;&#xB2E4;.

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Transferencia de energ&iacute;a resonante de una sola mol&eacute;cula de fluorescencia (FRET) es un m&eacute;todo ampliamente aceptado para determinar la separaci&oacute;n espacial entre las mol&eacute;culas. En combinaci&oacute;n con excitaci&oacute;n intercalada pulsada (PIE), se obtiene informaci&oacute;n adicional sobre la estequiometr&iacute;a de las interacciones moleculares. PIE-FRET, sin embargo, como est&aacute;n implementados con &oacute;ptica confocal est&aacute;ndar, requiere la diluci&oacute;n de la muestra biol&oacute;gica bajas concentraciones. A continuaci&oacute;n, os mostramos que medidas de PIE-FRET dentro de aberturas de tama&ntilde;o nanom&eacute;trico producci&oacute;n datos bioqu&iacute;micos significativos en 1000 x concentraciones m&aacute;s altas.

Mediciones de traste de excitaci&oacute;n pulsada-intercalado en mol&eacute;culas individuales de ADN d&uacute;plex interior en forma de C nanoapertures.

We present a design for a subwavelength C-shaped optical waveguide with a 90 degrees junction that efficiently transports light while maintaining tight confinement with an exit spot size of lambda/7. Finite-difference time-domain simulations of perfect electric conductors and Au C-aperture waveguides are performed for optical frequencies. A design resonant near 780 nm is presented, with a spot size of 107 nm x 107 nm and an energy density enhancement factor of 10 for a bent waveguide of total length 1.4 microm.

Design of a subwavelength bent C-aperture waveguide.

We report a high-intensity nano-aperture vertical-cavity surface-emitting laser (VCSEL) utilizing a bowtie-shaped aperture. A maximum power of 188 microW is achieved from a 180 nm bowtie aperture at a wavelength of 970 nm. The near-field full width at half-maximum intensity spot size 20 nm away from the bowtie aperture is 64 nm x 66 nm from simulation, and the peak near-field intensity is estimated to be as high as 47 mW/microm(2). This intensity is high enough to realize near-field optical recording, and the small spot size corresponds to storage densities up to 150 Gbits/in(2). The bowtie-aperture VCSEL also enables other applications, such as compact high-intensity probes for ultrahigh-resolution near-field imaging and single molecule fluorescence and spectroscopy.

High-intensity bowtie-shaped nano-aperture vertical-cavity surface-emitting laser for near-field optics.

We report an improved fabrication method for C-shaped near-field apertures resonant in the near-IR regime. The apertures are created in a metal layer on a silicon nitride membrane using a focused ion beam and a through membrane milling technique that avoids two problems with fabricating very small apertures: gallium contamination and edge rounding. Finite-difference time-domain simulations predict a 63x more intense near field with a 2.2x smaller spot versus conventionally milled apertures. We verify the position of the simulated resonance peaks with experimental far-field transmission measurements where we also find an increase of 8.8x in intensity. Our method has applications to many other plasmonic devices including bow-tie and fractal apertures, periodic arrays, and gratings.

Improved focused ion beam fabrication of near-field apertures using a silicon nitride membrane.

We report high-intensity nano-aperture Vertical-Cavity Surface- Emitting Lasers (VCSELs) with sub-100nm near-field spots using ridge apertures. Power transmission efficiency through different ridge apertures, including bowtie, C, H and I-shaped apertures on VCSELs were studied. Significantly higher transmission efficiencies were obtained from the ridge apertures than those from conventional square apertures. Mechanisms for high transmission through the ridge apertures are explained through simulation and waveguide theory. A new quadruple-ridge aperture is proposed and designed via simulation. With the high-intensity and small spot size, VCSELs using these ridge nano-apertures are very promising means to realize applications such as ultrahigh-density near-field optical data storage and ultrahigh-resolution near-field imaging etc.

High transmission through ridge nano-apertures on Vertical-Cavity Surface-Emitting Lasers.

We report a fast and accurate algorithm for numerical computation of two-dimensional non-separable linear canonical transforms (2D-NS-LCTs). Also known as quadratic-phase integrals, this class of integral transforms represents a broad class of optical systems including Fresnel propagation in free space, propagation in graded-index media, passage through thin lenses, and arbitrary concatenations of any number of these, including anamorphic/astigmatic/non-orthogonal cases. The general two-dimensional non-separable case poses several challenges which do not exist in the one-dimensional case and the separable two-dimensional case. The algorithm takes approximately N log N time, where N is the two-dimensional space-bandwidth product of the signal. Our method properly tracks and controls the space-bandwidth products in two dimensions, in order to achieve information theoretically sufficient, but not wastefully redundant, sampling required for the reconstruction of the underlying continuous functions at any stage of the algorithm. Additionally, we provide an alternative definition of general 2D-NS-LCTs that shows its kernel explicitly in terms of its ten parameters, and relate these parameters bidirectionally to conventional ABCD matrix parameters.

Fast and accurate computation of two-dimensional non-separable quadratic-phase integrals.

A fast and accurate algorithm is developed for the numerical computation of the family of complex linear canonical transforms (CLCTs), which represent the input-output relationship of complex quadratic-phase systems. Allowing the linear canonical transform parameters to be complex numbers makes it possible to represent paraxial optical systems that involve complex parameters. These include lossy systems such as Gaussian apertures, Gaussian ducts, or complex graded-index media, as well as lossless thin lenses and sections of free space and any arbitrary combinations of them. Complex-ordered fractional Fourier transforms (CFRTs) are a special case of CLCTs, and therefore a fast and accurate algorithm to compute CFRTs is included as a special case of the presented algorithm. The algorithm is based on decomposition of an arbitrary CLCT matrix into real and complex chirp multiplications and Fourier transforms. The samples of the output are obtained from the samples of the input in approximately N log N time, where N is the number of input samples. A space-bandwidth product tracking formalism is developed to ensure that the number of samples is information-theoretically sufficient to reconstruct the continuous transform, but not unnecessarily redundant.

Fast and accurate algorithm for the computation of complex linear canonical transforms.

We report a new optical near-field transducer comprised of a metallic nano-antenna extending from the ridge of a C-shaped metallic nano-aperture. Finite-difference time domain simulations predict that the C-aperture nano-tip (CAN-Tip) provides high intensity (650x), high optical resolution (~λ/60), and background-free near-field illumination at a wavelength of 980 nm. The CAN-Tip has an aperture resonance and tip antenna resonance which may be tuned independently, so the structure can be made resonant at ultraviolet wavelengths without being unduly small. This near-field optical resolution of 16.1 nm has been experimentally confirmed by employing the CAN-Tip as an NSOM probe.

Ultra-high resolution resonant C-shaped aperture nano-tip.

Optical tweezers have been widely used to manipulate biological and colloidal material, but the diffraction limit of far-field optics makes focused beams unsuitable for manipulating nanoscale objects with dimensions much smaller than the wavelength of light. While plasmonic structures have recently been successful in trapping nanoscale objects with high positioning accuracy, using such structures for manipulation over longer range has remained a significant challenge. In this work, we introduce a conveyor belt design based on a novel plasmonic structure, the resonant C-shaped engraving (CSE). We show how long-range manipulation is made possible by means of handoff between neighboring CSEs, and we present a simple technique for controlling handoff by rotating the polarization of laser illumination. We experimentally demonstrate handoff between a pair of CSEs for polystyrene spheres 200, 390, and 500 nm in diameter. We then extend this technique and demonstrate controlled particle transport down a 4.5 μm long "nano-optical conveyor belt."

Nano-optical conveyor belt, part II: Demonstration of handoff between near-field optical traps.

We propose a method for peristaltic transport of nanoparticles using the optical force field over a nanostructured surface. Nanostructures may be designed to produce strong near-field hot spots when illuminated. The hot spots function as optical traps, separately addressable by their resonant wavelengths and polarizations. By activating closely packed traps sequentially, nanoparticles may be handed off between adjacent traps in a peristaltic fashion. A linear repeating structure of three separately addressable traps forms a "nano-optical conveyor belt"; a unit cell with four separately addressable traps permits controlled peristaltic transport in the plane. Using specifically designed activation sequences allows particle sorting.

Lambertus Hesselink

Applied Physics

Stanford University

Fabrication and Operation of a Nano-Optical Conveyor Belt

Lambertus Hesselink

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Applied Physics

Stanford University

Fabrication and Operation of a Nano-Optical Conveyor Belt

Applied Physics