Integration Of Optical Waveguides Research Articles

Scalar Product in the Space of Waveguide Modes of an Open Planar Waveguide

To implement the method of adiabatic waveguide modes for modeling the propagation of polarized monochromatic electromagnetic radiation in irregular integrated optics structures it is necessary to expand the desired solution in basic adiabatic waveguide modes. This expansion requires the use of the scalar product in the space of waveguide vector fields of integrated optics waveguide. This work solves the first stage of this problem – the construction of the scalar product in the space of vector solutions of the eigenmode problem (classical and generalized) waveguide modes of an open planar waveguide. In constructing the mentioned sesquilinear form, we used the Lorentz reciprocity principle of waveguide modes and tensor form of the Ostrogradsky-Gauss theorem.

Metal-cladding directly defined active integrated optical waveguide device based on erbium-containing polymer

The Er-containing polymer is synthesized by free-radical polymerization. Based on the copolymer, metal-cladding directly defined waveguide technique is proposed. The technique is advantageous to realize the multi-functional integrated circuits.

Surface plasmon propagation on overcrossing metallic waveguides fabricated by a pick-and-place method

Abstract

Investigation of a UV-laser generated planar polymeric waveguide directly and after five years of preparation using an interferometric method

Polymeric integrated-optical waveguides were prepared in a planar chip using UV-laser lithographic method. Five waveguide samples were irradiated by an excimer laser of wavelength 248nm with different irradiation parameters (fluence and irradiation doses). Using Mach–Zehnder interferometer, the refractive index depth profiles of these samples are determined in two cases, directly and five years later of preparation. A crucial change of refractive indices profiles has been recorded after five years of preparation. In the first case we got double region waveguides fitted a Gaussian shape, while in the second one we observe a single region waveguide which has exponential shape. The photochemical reactions responsible for these changes in the two cases are demonstrated. This is quite important when such waveguides are used in the applications. Also it was interesting to investigate the aging impact on mode field distributions and the effective mode indices. The mode parameters are determined based on a theoretical model and the experimentally obtained data. The results show a notable change in the mode field distributions and the propagation coefficients as influence of aging.

Extension of the broadband single-mode integrated optical waveguide technique to the ultraviolet spectral region and its applications

We report here the fabrication, characterization, and application of a single-mode integrated optical waveguide (IOW) spectrometer capable of acquiring optical absorbance spectra of surface-immobilized molecules in the visible and ultraviolet spectral region down to 315 nm. The UV-extension of the single-mode IOW technique to shorter wavelengths was made possible by our development of a low-loss single-mode dielectric waveguide in the UV region based on an alumina film grown by atomic layer deposition (ALD) over a high quality fused silica substrate, and by our design/fabrication of a broadband waveguide coupler formed by an integrated diffraction grating combined with a highly anamorphic optical beam of large numerical aperture. As an application of the developed technology, we report here the surface adsorption process of bacteriochlorophyll a on different interfaces using its Soret absorption band centred at 370 nm. The effects of different chemical compositions at the solid-liquid interface on the adsorption and spectral properties of bacteriochlorophyll a were determined from the polarized UV-Vis IOW spectra acquired with the developed instrumentation. The spectral extension of the single-mode IOW technique into the ultraviolet region is an important advance as it enables extremely sensitive studies in key characteristics of surface molecular processes (e.g., protein unfolding and solvation of aromatic amino-acid groups under surface binding) whose spectral features are mainly located at wavelengths below the visible spectrum.

Monolithic integration of optical waveguide and fluidic channel structures in a thiol-ene/methacrylate photopolymer

We present a thiol-ene/methacrylate-based photopolymer capable of creating coplanar physical features (e.g. micro-fluidic channels) and optical index features (e.g. waveguides) using standard mask-based lithography techniques. This new photopolymer consists of two monomer species that polymerize at different rates. By selectively exposing different areas of a device for various amounts of time, we can select the state of the polymer (i.e. liquid, rubbery, or glassy) to create fluid channels or optical index structures such as waveguides. Using only three exposure steps and two masks, we demonstrate an integrated refractometer with a 90° channel-waveguide crossing to illustrate the fabrication process and the ability to create lithographically aligned waveguides across a gap.

Theoretical and numerical analysis of propagation and scattering of eigen- and non-eigenmodes of an irregular integrated-optical waveguide

We consider theoretical and numerical methods for studying propagation and scattering of laser radiation of eigenmodes and non-eigenmodes in an irregular integrated-optical waveguide. Scattering of non-eigenmodes in an irregular integratedoptical waveguide is investigated for the first time. We present thecalculated dispersion curves for TE and TM eigenmodes and TE non-eigenmodes. For the leaky TE0 modes we plot the dependence of the complex dispersion relation and show the vertical complex profile of the field. The dependence of the scattered laser radiation field on the effective refractive index is obtained for the given parameters of the waveguide. We compare for the first time thecalculated complex scattering diagram of laser radiation outside the waveguide layer in the plane, perpendicular to the plane of incidence, for the leaky and guided TE0 modes.

GRADIENT WAVEGUIDES WITH A GIVEN PROFILE OF REFRACTIVE INDEX ON THE BASIS OF CHALCOGENIDE GLASSY SEMICONDUCTORS FOR MID-INFRARED BAND

The calculation of basic parameters of single-mode planar integrated-optical waveguides based on selenide and telluride materials for the mid-infrared band (λ = 5-20 μm) as well as distribution of electric field component and coefficients of mode localization in planar integrated-optical structures with homogeneous, exponential and parabolic profile of refractive index of waveguide layer was carried out. It was shown that using the gradient CGS film as a waveguide layer with the given refractive index profile enables to adjust the waveguide parameters of a planar integral-optical waveguide in a wide range.

Optical Gratings Coated with Thin Si3N4 Layer for Efficient Immunosensing by Optical Waveguide Lightmode Spectroscopy.

New silicon nitride coated optical gratings were tested by means of Optical Waveguide Lightmode Spectroscopy (OWLS). A thin layer of 10 nm of transparent silicon nitride was deposited on commercial optical gratings by means of sputtering. The quality of the layer was tested by x-ray photoelectron spectroscopy and atomic force microscopy. As a proof of concept, the sensors were successfully tested with OWLS by monitoring the concentration dependence on the detection of an antibody-protein pair. The potential of the Si3N4 as functional layer in a real-time biosensor opens new ways for the integration of optical waveguides with microelectronics.

Determination of Refractive Index Profile and Mode Index from the Measured Mode Profile of Single-Mode LiNbO3-Diffused Waveguides

A refractive index profile and a mode index of single-mode LiNbO3 channel waveguides are simultaneously estimated from the measured near-field intensity distributions. A third-order low-pass Butterworth filter is used to filter the measured amplitude and its double derivative to remove high-frequency spatial noise and impulses. The mode index or effective index of the propagating mode is extracted by matching the index change profile equal to zero at the waveguide boundary. The proposed technique is applicable to any slowly varying, single-mode, integrated-optic waveguide for TE and TM modes and for any operating wavelength within the single-mode regime.

Piezoelectrics-Based Integrated Optical Waveguide for Mach-Zehnder Interferometer as the Modulator in Microwave Photonic Link

Microwave photonic link (MPL), which processes microwave signal with photonic technologies, has offered many advantages such as increased channel capacity, immunity to RF disturbance, reduction of size and weight, and low loss. External modulation of the MPL applies Mach-Zehnder interferometer (MZI) for the modulating. The traditional phase transitional behavior of the EO device lacks the performances required for quick response, low half-wave voltage V and high loaded power, while maintaining low noise, high SNR, and large dynamic range operation. This paper proposed a method in which the piezoelectric ceramic-based integrated optical waveguide with 3dB loss at the highest power was applied to the MZI. We built the physical model for the phase transitional behavior based on the piezoelectrics, analyzed the piezoelectric properties of ceramics. The impacts of the piezoelectric ceramic on the property of MPL were discussed numerically.

Molecularly imprinted polymer for label-free integrated optical waveguide bio(mimetic)sensors

A molecularly imprinted polymer (MIP) has been developed and characterized as a photonic material for integrated optics based antibiotic sensing. Key parameters – refractive index, optical attenuation and porosity – of the synthesized polymer have been determined by employing two light transmission methods: visible/near-infrared spectrophotometry and efficiency measurement of transmissive polymer diffraction gratings. In both cases, the porous polymer samples were infiltrated with colorless liquids with different refractive indexes, modulating the material optical behavior. The MIP optical response to target molecule (antibiotic enrofloxacin) has been also studied via optical diffraction. Based on the measured optical parameters and molecule recognition response, a Si 3N 4/SiO 2 strip waveguide sensor with a MIP sensing layer has been proposed and designed by numerical waveguide modeling.

Investigation of a UV-laser generated waveguide in a planar polymer chip using an improved interferometric method

Polymeric integrated-optical waveguides are prepared in a planar polymer chip by UV-laser lithographic methods. The waveguide samples are irradiated by an excimer laser at a wavelength Λ=248 nm with various irradiation parameters (different fluencies and irradiation doses). Mach–Zehnder interferometer is employed and the refractive index depth profiles of the waveguide samples are obtained. This profile covers two regions having exponential and Gaussian shapes. The model field distributions strongly depend on the refractive index of each region. The mode field distribution and the effective mode indices for each region have been calculated on the basis of a theoretical model and the experimentally measured data.

Structure of modes of smoothly irregular three-dimensional integrated optical four-layer waveguide

An asymptotic method is used for researching an integrated optical multilayer waveguide satisfying the condition of the smooth modification of the shape of the studied three-dimensional structure. Three-dimensional fields of smoothly deforming modes of the integrated optical waveguide are described analytically. An evident dependence of the contributions that the first order of smallness makes to the amplitudes of the electrical and magnetic fields of the quasi-waveguide modes is obtained. The canonical type of equations describing the propagation of quasi-TE and quasi-TM modes in the smoothly irregular part of a four-layer integrated optical waveguide is represented for an asymptotic method. With the help of the method of coupled waves and the perturbation theory method, the shifts of complex propagation constants for quasi-TE and quasi-TM modes are obtained in an explicit form. The elaborated theory is applicable for an analysis of similar structures of dielectric materials, magnetic materials, and metamaterials over a wide enough range of electromagnetic wavelengths.

Theoretical, experimental and numerical methods for investigating the characteristics of laser radiation scattered in the integrated-optical waveguide with three-dimensional irregularities

We consider theoretical, experimental and numerical methods which make it possible to analyse the key characteristics of laser radiation scattered in the integrated-optical waveguide with three-dimensional irregularities. The main aspects of the three-dimensional vector electrodynamic problem of waveguide scattering are studied. The waveguide light scattering method is presented and its main advantages over the methods of single scattering of laser radiation are discussed. The experimental setup and results of measurements are described. Theoretical and experimental results confirming the validity of the vector theory of three-dimensional waveguide scattering of laser radiation developed by the author are compared for the first time.

A Spectroscopic refractometer for a 375–1150 nm wavelength range

A spectroscopic refractometer is intended for measuring the index of refraction nλ of liquid and solid media at any wavelength λ in a 375–1150 nm wavelength range with an accuracy of ±5 × 10−5. It can be used, in particular, for determining nλ of monomers, compositions, and polymers, which are used for creating integrated-optical waveguides operating in a telecommunication spectrum region near 850 nm.

Solid immersion lens at the aplanatic condition for enhancing the spectral bandwidth of a waveguide grating coupler

We report a technique to substantially boost the spectral bandwidth of a conventional waveguide grating coupler by using a solid immersion cylindrical lens at the aplanatic condition to create a highly anamorphic beam and reach a much larger numerical aperture, thus enhancing the spectral bandwidth of a free-space propagating optical beam coupled into a single-mode planar integrated optical waveguide (IOW). Our experimental results show that the broadband IOW spectrometer thus created almost doubles (94% enhancement) the coupled spectral bandwidth of a conventional configuration. To exemplify the benefits made possible by the developed approach, we applied the technique to the broadband spectroscopic characterization of a protein submonolayer; our experimental data confirm the enhanced spectral bandwidth (around 380-nm) and illustrate the potentials of the developed technology. Besides the enhanced bandwidth, the broadband coupler of the single-mode IOW spectrometer described here is more robust and user-friendly than those previously reported in the literature and is expected to have an important impact on spectroscopic studies of surface-adsorbed molecular layers and surface phenomena.

Simulation of guided modes (eigenmodes) and synthesis of a thin-film generalised waveguide Luneburg lens in the zero-order vector approximation

Propagation of a guided mode (eigenmode) through an integrated optical generalised waveguide Luneburg lens is numerically simulated for the first time in terms of the previously obtained analytical solution of the vector electrodynamic problem in a smoothly irregular four-layer integrated optical 3D waveguide. The dispersion relation for a four-layer continuously irregular integrated optical 3D waveguide is calculated within the approximations of the asymptotic method of comparison waveguides and the method of adiabatic modes, in particular, taking into account the shift of the propagation constants of quasi-TE and quasi-TM modes. A generalised waveguide Luneburg lens with a full aperture is synthesised in the zero-order approximation. The results of numerical simulation demonstrate, on the one hand, a very good coincidence of the solution to the stated problem obtained in the approximation of the method of comparison waveguides with the previous results, and, on the other hand, advantages of our method: more rigorous solution of the problem, more complete consideration of its physical peculiarities, and higher accuracy of calculations. Another undoubted advantage of the analytical method proposed here is that it can be used to analyse similar structures fabricated of dielectrics, magnetics, and metamaterials, including nonlinear materials, in a wide range of electromagnetic wavelengths.

Integrated optic glass microcantilevers with Bragg grating interrogation

A new method for creating microcantilevers in glass allows integration of optical waveguides and Bragg gratings. Devices are fabricated by high precision sawing, followed by direct UV writing of waveguides with Bragg gratings and then chemical etching to release the freestanding glass structures. Optical measurement of the Bragg gratings together with piezo-actuation allows the mechanical resonances to be probed. By measuring the mechanical damping coefficient of the cantilever as a function of the gas pressure in a vacuum system the transition from the viscous to the molecular flow regime can be observed.

Theory of absorption integrated optical sensor of gaseous materials

The eigen and noneigen (leaky) modes of a three-layer planar integrated optical waveguide are described. The dispersion relation of a three-layer planar waveguide and other dependences are derived, and the cutoff conditions are analyzed. The diagram of propagation constants of the guided and radiation modes of an irregular asymmetric three-layer waveguide and the dependence of the electric field amplitudes of radiation modes of substrate on vertical coordinate in a tantalum integrated optical waveguide are presented. The operating principles of an absorption integrated optical waveguide sensor are investigated. The dependences of sensitivity of an integrated optical waveguide sensor on the sensory cell length, the coupling efficiency of the laser radiation into the waveguide, the absorption cross-section of the studied material, and the level of additive statistical noise are investigated. Some of the prospective areas of application of integrated-optical waveguide sensors are outlined.