Symmetrical Metal-cladding Optical Waveguide Research Articles

Second-harmonic generation in a metal-clad nonlinear optical waveguide.

Efficient optical nonlinear effects in waveguides play an important role in integrated photonic functionalities. The dispersion characteristics need to be well designed to satisfy the phase-matching condition of the interacting waves in waveguides. Here we demonstrate a novel phase-matching process of second-harmonic generation (SHG) in a symmetrical metal-cladding optical waveguide (SMCOW) with a nonlinear guiding layer. Ultrahigh order modes in SMCOWs possess small propagation constants, and can be actively tuned to satisfy the phase-matching condition via free-space coupling. We establish a model of SHG in the SMCOW and experimentally verify it as well. This mechanism could also be applied to or referenced in other nonlinear frequency conversion processes.

Efficient microfluidic photocatalysis in a symmetrical metal-cladding waveguide.

In this paper, a symmetrical metal-cladding optical waveguide based microfluidic chip with a self-organized and free-standing TiO2 nanotube membrane was utilized to perform efficient photocatalysis. The chip has a microchannel bonded with TiO2 nanotube coated glass. The employment of microfluidic chip for hydrolysis reaction can enable the transfer of mass and photons. Moreover, the incorporation of the double metal-cladding waveguide enhances the light-matter interaction and effectively improves the efficiency of photocatalysis.

Analysis and experimental investigation of the temperature property of sensors based on symmetrical metal-cladding optical waveguide

Symmetrical metal-cladding waveguide (SMCW) is a kind of new waveguide construction, and it consists of a planar glass slab sandwiched in two metal films with different thicknesses. The metal in this structure is usually a noble metal, such as Au, Ag and Cu etc. One of the characteristics of the glass is the sub-millimeter thickness, which is useful for exciting the ultrahigh order mode. Since the SMCW structure was proposed, it has received much attention from the researchers for its excellent characteristics of free-space coupling technique and ultrahigh order mode excitation. This free-space coupling technology has a higher sensitivity compared with the end-face coupling, prism coupling and grating coupling techniques. The ultrahigh order mode is very sensitive to the incident light wavelength, the thickness of guiding layer and the refractive index, but not sensitive to polarization. Based on the thermal-optical effect and thermal expansion effect of metal film and guiding layer materials, we research the temperature property of the SMCW structure. Researching methods include simulation analysis and experimental demonstration. First, we calculate the relation of the thickness and dielectric property of metal films, and the thickness and refractive index of the guiding layer with the temperature. Results show that these four factors are nearly proportional to the temperature difference. Then, we simulate the relationship of the reflectivity of the SMCW structure with those four factors by means of single-factor investigation under spectral and angular interrogation mode of operation, and find that the temperature-dependence of thickness of the guiding layer makes the chief contribution to the waveguide function of SMCW. Meanwhile, we analyze the sensitivity of the sensors based on SMCW structure, and the result shows that the sensitivity of this kind of sensor can be up to 21.89 pm/K (spectral mode) and 1.449×10-3 rad/K (angular mode). Finally, we demonstrate the simulation results by experiment. In our experiment, a series of reflectivity is measured at temperatures varying from 320 to 380 K, and the value is expressed in the form of voltage output of PSD (position sensitive diode). The sensor shows a good linearity and a high average resolution of 0.517×10-3 rad/K; furthermore, we fit the experimental data and get the linear function between angle shifts and temperature difference of Δθ = 0.02965×ΔT. So, once the temperature has any minute variation, it will easily give a change in the resonance incident angle and show the effect of sensor. Owing to the advantages of high sensitivity, low cast and easy fabrication, the temperature sensor based on SMCW will be a promising sensor in many fields.

Influence of Temperature on Reflectivity of Symmetrical Metal-Cladding Optical Waveguide

The influence of temperature on the reflectivity of symmetrical metal-cladding optical waveguide (SMCOW) is studied theoretically by means of single-factor investigation under spectral and angular interrogation mode of operation. The theoretical model for temperature dependence of reflectivity includes the temperature dependence of refractive index and thickness of guiding layer, the temperature dependence of the metal film thickness and metal-dielectric function. It is found that the effect of temperature on the reflectivity of SMCOW is mainly attributed to the temperature dependence of refractive index and thickness of guiding layer; on the contrary, the temperature properties of metal film hardly contribute to the influence of temperature on the reflectivity. Based on the analysis, the sensitivities of SMCOW with guiding layer made up of different optical glasses are computed under both spectral and angular interrogation. This letter is supposed to provide direction in designing SMCOW sensors against the temperature variation.

Spontaneous-Emission Coupling from an Excited Atom into a Symmetrical Metal-Cladding Optical Waveguide

We consider the coupling behavior which transfers the energy of the spontaneous emission from an atom embedded in free space into a symmetrical metal-cladding optical waveguide. The ratio for spontaneous emission into the waveguide modes is derived by using a compact form of Green's function for a multilayer. Up to 90% of the spontaneous emission energy fed into the waveguide is demonstrated when the atom is positioned above the waveguide in a limited space range.

All-optical modulator based on a ferrofluid core metal cladding waveguide chip

We propose a novel optical intensity modulator based on the combination of a symmetrical metal cladding optical waveguide (SMCW) and ferrofluid, where the ferrofluid is sealed in the waveguide to act as a guiding layer. The light matter interaction in the ferrofluid film leads to the formation of a regular nanoparticle pattern, which changes the phase match condition of the ultrahigh order modes in return. When two lasers are incident on the same spot of the waveguide chip, experiments illustrate all-optical modulation of one laser beam by adjusting the intensity of the other laser. A possible theoretical explanation may be due to the optical trapping and Soret effect since the phenomenon is considerable only when the control laser is effectively coupled into the waveguide.

Conical reflection of light during free-space coupling into a symmetrical metal-cladding waveguide

Novel conical reflection of light by a thick three-layered metal-clad optical waveguide is observed. A symmetrical metal-cladding optical waveguide is used, which exhibits extraordinary conical reflection during free-space coupling of light to the waveguide. The phenomenon is attributed to the leakage of excited ultrahigh-order guided modes and their inter- and intramode coupling interaction.

Magnetic modulation of magnetic-fluid based on the symmetrical metal-cladding optical waveguide

A new type of symmetrical metal-cladding optical waveguide structures is proposed.The guiding layer that supports the oscillating field is submillimeter scale and severs as the sample room.The water-based Fe3O4 magnetic fluid with a volume fraction of 0.15% is injected into the sample room.The ultrahigh order modes are excited by a 860 nm laser beam on the structure with small incident angle(5).Owing to the strong concentration of the magnetic field,the sensitivity of the ultrahigh-order modes is very high.The rise and fall time of magnetic fluid is 2 ms when 10 mT magnetic field is applied.

Wideband slow-light modes for time delay of ultrashort pulses in symmetrical metal-cladding optical waveguide

A widebandwidth optical delay line is a useful device for various fascinating applications, such as optical buffering and processing of ultrafast signal. Here, we experimentally demonstrated effective slow light of sub-picosecond signal over 10 THz frequency range by employing the wide slow light modes in thick symmetrical metal-cladding optical waveguide (SMCOW). Ultrahigh-order guided modes travelling as slow light in waveguide together with strong confinement provided by metal-cladding makes this scheme nearly material dispersion independent and compatible with wide bandwidth operation.

A Temperature Sensor Based on a Symmetrical Metal-Cladding Optical Waveguide

A compact temperature sensor based on a symmetrical metal-cladding optical waveguide using free-space coupling is proposed and demonstrated theoretically and experimentally. The symmetrical Au-cladding optical waveguide is based on a thin LiNbO3 slab sandwiched between two metal films, which serve as the coupling layer and reflecting panel, respectively. The sensitivity of this sensor of 9.08 × 10−2 deg/°C, 6.6 × 10−2 deg/°C and 4.8 × 10−2 deg/°C corresponding to 3238-order, 3237-order and 3236-order modes, respectively, are obtained. Higher resolution is predicted with a larger linear expansion coefficient material and a higher resolution θ/2θ goniometer.

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

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

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

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.

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.