Multichannel Waveguide Research Articles

Quantitative Multiplex Detection of Pathogen Biomarkers on Multichannel Waveguides

No single biomarker can accurately predict disease. An ideal biodetection technology should be capable of the quantitative, reproducible, and sensitive detection of a limited suite of such molecules. To this end, we have developed a multiplex biomarker assay for protective antigen and lethal factor of the Bacillus anthracis lethal toxin using semiconductor quantum dots as the fluorescence reporters on our waveguide-based biosensor platform. The platform is extendable to a wide array of biomarkers, facilitating rapid, quantitative, sensitive, and multiplex detection, better than achievable by conventional immunoassay. Our assay allows for the sensitive (limit of detection 1 pM each), specific (minimal nonspecific binding), and rapid (15 min) detection of these biomarkers in complex biological samples (e.g., serum). To address the issue of reproducibility in measurement and to increase our sample throughput, we have incorporated multichannel waveguides capable of simultaneous multiplex detection of biomarkers in three samples in quadruplicate. In this paper, we present the design, fabrication, and development of multichannel waveguides for the simultaneous detection of lethal factor and protective antigen in serum. Evaluation of the multichannel waveguide shows an excellent concordance with single-channel data and effective, simultaneous, and reproducible measurement of lethal toxins in three samples.

Through‐thickness embossing process for fabrication of three‐dimensional thermoplastic parts

AbstractThe standard embossing process is limited to the fabrication of surface structures on relatively large polymer substrates. To overcome this limitation, a hybrid punching and embossing process was investigated for through‐thickness embossing of three‐dimensional parts. The embossing tool included a punching head and to‐be‐ replicated features in the socket behind the punching head. The built‐in punching head facilitated a through‐thickness action and provided a closed‐die environment for embossing pressure buildup. The method was used to emboss multichannel millimeter waveguides which requires uniform edges and accurate dimensions. With a tool temperature of 140°C, an embossing time of 3 min and a total cycle time of 7 min, discrete 4‐channel waveguides were successfully embossed from a room‐temperature ABS substrate. A computer model was established to study the flow behavior during through‐thickness embossing. It was found that nonisothermal embossing conditions help confine the polymer in the cavity and reduce the outflow into the surrounding region, thus achieving complete fill of the cavity. POLYM. ENG. SCI., 47:2075–2084, 2007. © 2007 Society of Plastics Engineers

Spin Hall effect and zitterbewegung in an electron waveguide

We study spin-resolved probability distributions for electrons in a multichannel waveguide in the presence of a spin-orbit interaction. For a spin-polarized electron injection, a zitterbewegung pattern is predicted in the probability distribution of electrons in the waveguide. For a spin-unpolarized injection, the spin-resolved electron probability in the waveguide shows spin accumulations. In addition to the spin Hall phenomenon---namely, accumulations of opposite spins at the lateral edges of the waveguide---we predict the existence of a regular stripe pattern of spin accumulations in the internal region of the waveguide. We show that the predicted zitterbewegung and spin Hall effect stem from the same mechanism and are formed from coherent states of electrons in the waveguide.

Bistable Solitons in Single- and Multichannel Waveguides with the Cubic-Quintic Nonlinearity

We consider spatial solitons in a channel waveguide or in a periodic array of rectangular potential wells (the Kronig-Penney (KP) model) in the presence of the uniform cubic-quintic (CQ) nonlinearity. Using the variational approximation and numerical methods, we find two branches of fundamental (single-humped) soliton solutions. The soliton characteristics, in the form of the integral power Q (or width w) vs. the propagation constant k, reveal a strong bistability with two different solutions found for a given k. Violating the known Vakhitov-Kolokolov criterion, the solution branches with dQ/dk > 0 and dQ/dk < 0 are simultaneously stable. Various families of higher-order solitons are also found in the KP version of the model: symmetric and antisymmetric double-humped solitons, three-peak solitons with and without the phase shift π between the peaks, etc. In a relatively shallow KP lattice, all the solitons belong to the semi-infinite gap beneath the linear band structure of the KP potential, while finite gaps between the bands remain empty (solitons in the finite gaps can be found if the lattice is much deeper). But in contrast to the situation known for the model combining a periodic potential and the self-focusing Kerr nonlinearity, the fundamental solitons fill only a finite zone near the top of the semi-infinite gap, which is a manifestation of the saturable character of the CQ nonlinearity.

Bistable Solitons in Single- and Multichannel Waveguides with the Cubic-Quintic Nonlinearity

We consider spatial solitons in a channel waveguide or in a periodic array of rectangular potential wells (the Kronig-Penney (KP) model) in the presence of the uniform cubic-quintic (CQ) nonlinearity. Using the variational approximation and numerical methods, we find two branches of fundamental (single-humped) soliton solutions. The soliton characteristics, in the form of the integral power Q (or width w) vs. the propagation constant k, reveal a strong bistability with two different solutions found for a given k. Violating the known Vakhitov-Kolokolov criterion, the solution branches with dQ/dk > 0 and dQ/dk < 0 are simultaneously stable. Various families of higher-order solitons are also found in the KP version of the model: symmetric and antisymmetric double-humped solitons, three-peak solitons with and without the phase shift π between the peaks, etc. In a relatively shallow KP lattice, all the solitons belong to the semi-infinite gap beneath the linear band structure of the KP potential, while finite gaps between the bands remain empty (solitons in the finite gaps can be found if the lattice is much deeper). But in contrast to the situation known for the model combining a periodic potential and the self-focusing Kerr nonlinearity, the fundamental solitons fill only a finite zone near the top of the semi-infinite gap, which is a manifestation of the saturable character of the CQ nonlinearity.

Optical Path Redirected Multichannel Waveguide Connectors for Surface Mount Technologies

Novel optical path redirected multichannel waveguide connectors that are fully compatible with surface mount technologies are demonstrated. These connectors have three-dimensional waveguide devices with multichannel optical inputs-outputs and optical path redirection for higher integration. A wafer-level stack and lamination process was used to fabricate these waveguide devices. To ensure low-cost fabrication and suitability for mass production, the fabricated waveguide connectors were mounted on printed circuit boards using a flip-chip bonder. These connectors can be efficiently coupled to commercially available multichannel mechanically transferable connectors. In this letter, we describe the fabrication of these waveguide connectors and the test results for them.

Fluid detection with photonic crystal-based multichannel waveguides

A simple fluid detection scheme, based on light propagation through linear defect waveguides in photonic crystals, is demonstrated with isopropanol and xylene. The two-channel photonic crystal waveguide sensor is made from a GaAs-based heterostructure. The preferential channeling of light is controlled by the change in the refractive index of the corresponding waveguide branch due to the presence of the inserted fluid in the guide regions only.

Light propagation in periodic microcavities

We demonstrated light propagation in a type of optical waveguide, which consisted of periodically arrayed dielectric particles. Although the form is similar to a photonic crystal waveguide, our method used resonance frequencies instead of band-gap frequencies. Advantages provided by this waveguide are that dynamic optical interconnection can be realized and that a multichannel waveguide is easily formed. To fabricate the system of periodic microcavities, we used polystyrene-latex particles that have a uniform size of 15.6 μm. Some discrete frequencies of fluorescence were selected to agree with the phase matching condition and they were propagated through the microspheres. The assembled microspheres can be taken as a multichannel waveguide.

Scattering of vibrational waves in perturbed two-dimensional multichannel asymmetric waveguides as on an isolated step

We investigate the scattering of vibrational waves at the step interface between two structurally different waveguides, namely, one and two coupled atomic layers occupying the half spaces on either side of the step. The model presented is also instructive for the study of the scattering of surface phonons by random isolated steps in vicinal surfaces. The complexity of the scattering of vibrational waves, in contrast with coherent electron transport, which in part may be attributed to the vector character of the vibrational fields, is further enhanced in the present study owing to the intrinsic asymmetry of the system normal to the step as well as to its two-dimensional extended character. A detailed discussion of the reflection and transmission spectra is presented for the scattering processes in the two possible geometries normal to the step.

Characteristics of the radiation from a multichannel waveguide CO2 amplifier with a multichannel phase-locked master oscillator

Measurements were made of the parameters of the radiation from a two-channel single-pass CO2 amplifier of the waveguide type with a two-channel phase-locked master oscillator. The mutual coherence of the amplified laser beams was conserved at the amplifier output and the distribution of the radiation intensity in the far-field zone resembled the distribution at the output of the master oscillator. A numerical investigation was made of the characteristics of the amplifier radiation taking into account a random scatter of the parameters of the individual channels in two-channel and multichannel amplifiers.

Scattering of vibrational waves in perturbed quasi-one-dimensional multichannel waveguides

Scattering of vibrational waves in perturbed quasi-one-dimensional multichannel waveguides

A new iterative method for the analysis of longitudinally invariant waveguide couplers

In this paper, a new iterative method to solve for the modal indices and field profiles of the supermodes of multichannel waveguide structures is proposed. This method combines the shift inverse power method with the simultaneous iteration method, and can be applied to any longitudinally invariant waveguide couplers problem very efficiently. Using this method, the characteristics of the leading supermodes can be obtained simultaneously. The validity and accuracy of this method are assessed by comparing to other existing methods for symmetric two-channel waveguide couplers. Results are in good agreement. Asymmetric two-channel and symmetric three-channel waveguide couplers are then considered to show the usefulness and versatility of the proposed method.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Sensitivity analysis of a thin-film optical waveguide biochemical sensor using evanescent field absorption

A multichannel thin-film optical waveguide sensor for determining aqueous biochemical concentration with a high dynamic range of measurement is proposed. The sensitivity dependence of the proposed sensor on interaction length and waveguide thickness is investigated for dye solutions and three different hemoglobin concentration levels of carboxyhemoglobins. The sensitivity is inversely proportional to the waveguide thickness while proportional to the interaction length. As a consequence the variability of the interaction length makes the proposed sensor a flexible tool for concentration measurements. Moreover, an efficient method for determining the absorption coefficient is discussed.

Dynamic response analysis of truss-type structural networks: A wave propagation approach

A typical space structure is composed of piece-wise periodic arrays of connected truss units. These arrays can intersect each other, and form multiple closed loops. In this paper, a detailed step-by-step numerical procedure is provided for computing the response of such a structure to external excitations. The basic idea is to treat an array of connected truss units as a multi-channel waveguide, capable of transmitting several types of wave motions. Each waveguide, or each junction where several waveguides intersect, can be characterized by a wave scattering matrix, which is composed of the transmission and reflection submatrices. A reflection submatrix reverses the direction of incoming waves, whereas a transmission submatrix permits the incoming waves to enter, or to be directed to other waveguides. By use of wave scattering matrices in the formulation, the numerical computation always follows the directions of propagation of various waves. Thus, numerical stability is assured, since the amplitude of wave motion decays as it propagates along a path due to structural damping. The numerical procedure described herein represents an extension of the author's previous works by (1) describing, for the first time, the dynamics of individual truss arrays in terms of scattering matrices, (2) adopting a new bookkeeping system to accommodate more complicated configurations of structural networks, and (3) developing an efficient procedure to eliminate step-by-step superfluous unknowns, thus simplifying the calculation. Combination of the three advances makes it possible to treat, for the first time, such complicated configurations as multiple closed loops. Since the actual truss-type construction is retained when obtaining the wave scattering matrices, the procedure is considered more accurate than those based on substitution for truss construction of Timoshenko beam elements. Application of the procedure is illustrated by an example.

Transient temperature-induced modulation of the radiation in multichannel fiber waveguides

Transient temperature-induced phase perturbations and modulation of radiation in multichannel fiber waveguides were observed experimentally. A temperature drop of ΔT0 ~ 10 − 2 °C in a two-mode fiber waveguide of 130 m length created a transient temperature field giving rise to a phase shift up to 10π. Complete relaxation of the temperature gradient took 10 − 5 s. The results indicated that interference of probe waves in multichannel waveguides can be used in high-precision studies of transient temperature-induced processes.

Investigation of an electrooptic multichannel-waveguide modulator as a controlled transparency

An investigation was made of a multichannel LiNbO3 waveguide modulator of light in space and time, suitable for processing of analog and digital signals. This modulator had 26 channels and the half-wave control voltage was 4.5 V. A theoretical analysis and an experimental study were made of the functional performance of this modulator depending on the channel interconnections and on the nature of the signals applied to the modulator. The feasibility of processing analog and digital signals was studied.

Fabrication of waveguide ‐ fiber array couplers using laser‐machined V‐groove techniques in perspex substrates

AbstractWe report an inexpensive and versatile technique for coupling multichannel waveguides to a fiber array using V‐grooves in perspex substrates that are accurately machined by a computer‐controlled CO2 laser system. An excess loss of less than 1 dB could be achieved for coupling between 1 × 2, 1 × 3, and 1 × 4 branching circuits and an array of N‐port fibers.

16-channel optical FDM distribution/transmission experiment utilising multichannel frequency stabiliser and waveguide frequency selection switch

A 16-channel, 622 Mbit/s optical FDM distribution/transmission system experiment is demonstrated for a fibre length of 13 km. The feasibility of a multicarrier frequency stabiliser and waveguide frequency selection switch for 5 GHz frequency intervals is verified.

Surface Acoustic Wave Convolver Using Multi-Channel Waveguide

We have studied on a new type surface acoustic wave convolver consisting of multi channel waveguide, namely, in which the drawbacks inherent to an acoustoelectric convolver, and also to an elastic convolver are eliminated. We have adopted focussed interdigital transducers as the input to the new convolver, and improved its frequency characteristics and the time bandwidth product.

Multichannel waveguide junctions for guided-wave optics

We propose and analyze a new class of multichannel optical waveguide junctions. These junctions consist of a multimode channel waveguide that branches into several single-mode channels. We show that such waveguide junctions, when properly designed, can route each of the spatial modes of the multimode waveguide into a different single-mode channel. These waveguide junctions should be useful in selective mode excitation, routing, switching, modulation, and wavelength multiplexing/demultiplexing of guided waves, as well as for mode control in semiconductor lasers.