Metal-clad Optical Waveguide Research Articles

Wideband slow light assisted by ultrahigh-order modes

A new mechanism for slow light is introduced by employing a symmetrical metal-cladding optical waveguide with millimeter scale. The basis is the anomalous dispersion of the ultrahigh-order modes near zero wavenumber, where the effective index approaches zero. Without use of any coherent or material resonance, this scheme is not subject to limitations of the delay-bandwidth product and can generate arbitrarily small group velocities over an unusually large frequency bandwidth.

Double-channel narrowband filter based on Goos-Hänchen shift

We propose a double-channel narrowband filter based on anomalous large Goos-Hänchen shift reflected from a symmetrical metal-cladding optical waveguide. We demonstrate that two filtering peaks are 859.604nm and 859.688nm respectively. The 3 dB bandwidth is found to be 0.036 nm with an extinction ratio of 15.3dB at a light wavelength of 859.60nm. The filtering peaks can be tuned by choosing an appropriate incident angle and a aperture position.

亚毫米尺度对称金属包覆波导中传输损耗的抑制

亚毫米尺度对称金属包覆波导中传输损耗的抑制

Transverse electric and transverse magnetic mode selective filters in metal clad high index buffer layer optical waveguides: design and analysis

Theoretical attenuation characteristics of a metal clad four-layer thin film optical waveguide with a high index buffer are presented. Metal clad optical waveguides with a high index buffer layer possess a unique property which arises from the effect of periodic coupling between the lossless modes of a dielectric waveguide and the lossy modes supported by the high index buffer clad with metal. It is observed that both transverse electric (TE) and transverse magnetic (TM) pass polarizers can be produced using this structure. High extinction ratio polarizers for a high index dielectric buffer layer and a metallic overlayer for ion exchanged planar optical waveguides for λ = 0.6328 µm have been designed; this corresponds to the most commonly used He–Ne laser. Results are presented for As2S3 as a buffer layer and Al, Au and Ag as metal claddings. We have shown that a waveguide polarizer extinction coefficient as high as 800 dB can be obtained for both polarizations. An oscillatory behavior similar to that of semiconductor clad waveguides is observed for both TE and TM mode losses. The effect of the buffer thickness and index on the guided modes is also presented.

THEORETICAL MODELING OF A METAL-CLAD PLANAR WAVEGUIDE BASED BIOSENSORS FOR THE DETECTION OF PSEUDOMONAS-LIKE BACTERIA

In this paper, a metal-clad planar optical waveguide biosensor with five layer structure is studied theoretically for the detection of Pseudomonas and Pseudomonas-like bacteria. Using a very simple boundary matching technique, we derive the mode equation and other necessary formulae for the proposed biosensor and analyse its performance under different conditions related to its constituents. The numerical results presented in this paper leads to a significant optimization of the important design parameters to sense micro-scale biological objects. Also, we compare our computed results with the results given for a biosensor with four layer structure. In addition, we discuss the importance and need of the inclusion of the thickness of an affinity layer as fifth layer in the four layer structure of the metal clad planar waveguide.

Frequency-Dependent Locally One-Dimensional FDTD Implementation With a Combined Dispersion Model for the Analysis of Surface Plasmon Waveguides

The implicit finite-difference time-domain (FDTD) method based on the locally one-dimensional scheme is extended to the frequency-dependent version for the analysis of the Drude-Lorentz model. The piecewise linear recursive convolution method is introduced, in which a large time step can be utilized. Analyses of a metal-cladding optical waveguide supporting a surface plasmon polariton reveal that the present method provides wavelength responses comparable to those of the explicit FDTD, while reducing the computational time to less than 50%.

Oscillating wave displacement sensor using the enhanced Goos–Hänchen effect in a symmetrical metal-cladding optical waveguide

An oscillating wave displacement sensor based on the enhanced Goos-Hänchen (G-H) effect in a symmetrical metal-cladding optical waveguide is proposed. Since the detected signal is irrelevant to the power fluctuation of the incident light and the magnitude of the G-H shift is enhanced to hundreds of micrometers, a 40 pm resolution is demonstrated in our experiment without employing any complicated optical equipment and servo techniques.

基于亚毫米尺度金属包覆波导的脉冲展宽

基于亚毫米尺度金属包覆波导的脉冲展宽

Modal attenuation in metal-clad graded-index slab optical waveguides

The paper presents the influence of refractive profile shape on the distribution of modal attenuation in planar metal-clad optical waveguide structures. A calculation method has been presented in which we applied the Snyder–Love expression on modal attenuation coefficients and matrix method 4 × 4 for the analysis of planar waveguides. The obtained results are almost identical with the exact results for refractive profiles: the parabolic, exponential, Gaussian and linear ones. It has been demonstrated that the applied calculation method can be used in waveguides of any profiles of the refractive index.

Wavelength Sensing With Subpicometer Resolution Using Ultrahigh Order Modes

The ultrahigh order modes of a symmetrical metal-cladding optical waveguide, which exhibit strong wavelength dispersion characteristics, are used to track small wavelength changes of the light output of laser diodes. In the case of free-space coupling, the wavelength shift is transformed into an intensity variation of the light reflected on a surface of the waveguide. The sensitivity considering the divergence of the incident light and the thickness of the upper cladding is analyzed. A wavelength resolution of 0.5 pm at a center wavelength of 859.8 nm is demonstrated experimentally

Characterization of surface-plasmon modes in metal-clad optical waveguides

Finite-element analysis, based on the vector H-field formulation and incorporating the perturbation technique, is used to calculate the complex propagation characteristics of metal-coated dielectric waveguides. The propagation and attenuation characteristics of the surface-plasmon modes at the metal/dielectric interfaces are presented. The effects on the optical properties of metal-clad optical fibers with infinite and finite cladding thickness and the formation of the supermodes due to the coupling between the surface-plasmon modes in the presence of different surrounding materials are also investigated.

Oscillating wave sensors based on ultrahigh-order modes in symmetric metal-clad optical waveguides

An oscillating wave sensor that uses ultrahigh-order modes in symmetric metal-clad waveguide with submillimeter scale is investigated to measure minute changes in refractive index (RI) of aqueous solution. In the proposed sensor, the sample acts as the guiding layer where oscillating wave propagates. Owing to the concentrated power in the sensing region and the use of the very sensitive ultrahigh-order modes, it is demonstrated both theoretically and experimentally that its sensitivity is enhanced by one order of magnitude than that of evanescent wave sensor. The sensor also provides a wide detection range of RI from 1 to 2.0 or higher.

Determination of dc Kerr coefficients of polymer filmswith prism-optical waveguide configuration

A prism-optical waveguide coupling system, which consists of a prism and a symmetrical metal-cladding polymer optical waveguide, is used to analyze the field-induced intensity variation due to the quadratic electro-optic (QEO) effect. As a result, not only the dc Kerr coefficient, but also the whole components of the QEO tensor of the polymer film are determined experimentally.

Frequency response of metal clad planar optical waveguides

The propagation characteristics of metal clad planar optical waveguide as a function of wavelength are investigated theoretically for Al, Ag, and Au. The results obtained show that attenuation of the propagation modes in these guides is highly dependent on wavelength, which can be used to design an efficient integrated optical waveguide polarizer with high extinction ratios, or to select the wavelength for the surface plasmon based metal clad optical waveguide sensors. It is observed that Al is the only metal that still supports the surface plasmons in the UV region.

Picometer displacement sensing using the ultrahigh-order modes in a submillimeter scale optical waveguide

An improved scheme for displacement measurement using the ultrahigh-order guided modes in a symmetrical metal-cladding optical waveguide is proposed. Based on this idea together with the lock-in amplification technique, a sensor with a stable displacement resolution of 3.3 pm is experimentally demonstrated without any complicated servo system.

Study of ultrahigh-order modes in a symmetrical metal-cladding optical waveguide

We report theory and experiment on ultrahigh-order modes in a symmetrical metal-cladding thick optical waveguide. The waveguide consists of a LiNbO3 slab or a glass slab with a thickness greater than 0.1mm, two gold films deposited on the upper and bottom sides of the slab serving as the cladding of the waveguide. By using the free-space coupling technique, ultrahigh-order modes (m>2000) are excited, and its high sensitivity to both refractive index and thickness of the guide, as well as the polarization independence are demonstrated.

Free-space coupling of a light beam into a symmetrical metal-cladding optical waveguide

We report on a coupling method, which transfers energy of a light beam from free space into a symmetrical metal-cladding optical waveguide from the top surface without employing the prism, grating, tapered film, and other coupling components. In the experiment, a glass flat with a thickness about 100 μm, sandwiched between two gold films is used as a guiding layer. A top gold film of 46 nm thick serves as a coupling layer as well as the cladding and a base gold film of 200 nm serves as the substrate of the waveguide. Up to 50% of the incident light energy fed into the waveguide has been demonstrated.

Finite-element analysis of lossy TE–TM modes in metal-clad optical waveguides

Finite-element analysis employing the scalar and vector H-field formulations and with the aid of the perturbation technique is used to calculate the TE-TM complex propagation characteristics of integrated optical devices in gallium arsenide, lithium niobate, and silica fiber, incorporating a lossy metal cladding. The propagation and attenuation properties of several types of metal-clad planar optical waveguide, which exhibit surface-plasmon properties for the TM polarization, are reviewed, and the modal loss caused by the metal cladding in a titanium-diffused lithium niobate electro-optic directional coupler modulator, an indium gallium arsenide phosphide-based TE-TM optical polarizer, and a submicron metal-clad silica fiber suitable for near-field optical scanning microscopy is calculated.

Effect of SiOx buffer layer on propagation loss in LiNbO3 channel waveguides

SiO x buffer layer is widely employed in metal-clad Z-cut LiNbO3 optical waveguides to prevent excessive propagation loss and disturbances induced by the direct loading of the metal on the guiding layer. The dependence of propagation loss in proton-exchange LiNbO3 channel waveguides induced by a SiOx buffer layer on the annealing time is studied using a nondestructive measurement method. These studies reveal that the propagation loss is degraded for annealing times of less than 3 h, while it can be improved by about 0.08 dB/cm for annealing times longer than 6 h. By extending the annealing time to 8 h, we demonstrate a propagation loss reduction of 0.09 dB/cm. The physical mechanisms, including surface roughness, refractive index changes, oxidation of the SiOx buffer layer, optical confinement, and surface scattering of the LiNbO3 channel waveguide are also investigated.

Metal-clad optical waveguides with cardioid-shaped cross sections and their modal characteristics

Metal-clad optical waveguides with cardioid-shaped cross sections and their modal characteristics