Planar Waveguide Structure Research Articles

The Influence of the Rotational Speed of the Polymer SU8 on the Thickness of the Waveguide Layer

The paper presents results of investigations concerning the measurement of the refractive index and thickness of planar waveguide structures, obtained by the photopolymerization of polymer SU8. Sodium-calcium glass was used as the substrate. As the knowledge of the quoted parameters is from the viewpoint of the structure of various types of optical sensors of crucial importance, the way of their determination has been presented. The paper deals also with the method of constructing planar polymer waveguides, taking into account problems connected with their adhesion to glass substrates.

Mid-IR laser oscillation in Cr^2+:ZnSe planar waveguide

We demonstrate 2.6 µm mid-infrared lasing at room temperature in a planar waveguide structure. Planar waveguides were fabricated using pulsed laser deposition (PLD) by depositing chromium doped zinc selenide thin films on sapphire substrate (Cr2+:ZnSe/sapphire). Highly doped Cr2+:ZnSe/Sapphire thin film sample was also used to demonstrate passive Q-switching of Er:YAG laser operating at 1.645 µm.

Bright optical spatial solitons in a photorefractive waveguide

The propagation characteristics of optical spatial solitons in a photorefractive waveguide have been investigated under the Wentzel–Kramers–Brillouin–Jeffreys (WKBJ) approximation. The presence of a waveguide structure enhances the focusing effect and reduces the threshold power for soliton formation. A planar waveguide structure embedded in photorefractive material traps a solitary wave of lower power, which would not have formed a spatial soliton in photorefractive material without waveguiding. The larger the waveguide coefficient, the lower the power of the beam that can be self-trapped. The existence of bistable states has also been predicted.

Terahertz photonic band gap for the transverse-magnetic modes formed by using a planar waveguide structure with a photonic crystal electrode

We have investigated the terahertz (THz) emission from a semiconductor superlattice placed in a waveguide structure with a photonic crystal surface electrode of a honeycomb lattice pattern. For uniformly applying bias voltages, we inserted a semitransparent Ti film between the superlattice layer and the photonic crystal electrode. It is found that optimization of the sheet resistivity of the Ti layer is crucial to suppress the coupling between the waveguide mode and the surface leaky mode and obtain a clear photonic band gap. When the Ti layer was 40 nm, a large extinction ratio of ∼120 in the THz emission intensity was obtained at the midgap frequency around 1.7 THz.

Spin wave resonance excitation in ferromagnetic films using planar waveguide structures

We explore a new geometry allowing effective excitation of the lowest antisymmetric standing spin wave mode in ferromagnetic metallic films with symmetrical boundary conditions. The approach is based on the use of a coplanar waveguide with the ferromagnetic film, Permalloy (Py), playing the role of the signal line. In addition, we study a signal line which is a sandwich of Py inside two nonmagnetic metallic films. We find that the thickness and conductivity of the metal films can significantly alter the amount of absorption, at ferromagnetic resonance, between the symmetric and antisymmetric spin wave modes. The experimental results are supported by numerical calculations indicating the origin of the strength of the absorption.

Direct write of optical diffractive elements and planar waveguides with a digital micromirror device based UV photoplotter

A photoplotter, based on a digital micromirror device as real-time reconfigurable mask, is designed to direct-write microstructures in different photosensitive materials. Binary and multilevel elements, such as computer generated holograms with 2, 4 and 8 phase levels and planar optical waveguide structures with tapers and/or long period gratings, are fabricated in a single processing step. Direct parallel write into different photosensitive materials with attractive optical properties is proposed and first results are shown in a commercially available organic–inorganic hybrid material.

Study of planar waveguide structure of He+ ion-implanted Sn2P2S6 crystal with multiple-angle-of-incidence ellipsometry technique

Study of planar waveguide structure of He+ ion-implanted Sn2P2S6 crystal with multiple-angle-of-incidence ellipsometry technique

Phase matched second harmonic generation in planar two-dimensional photonic crystals

We report a detailed numerical study of phase matched second harmonic generation for narrow beams (of few wavelengths width) in quadratic nonlinear photonic crystals under realistic situations, i.e. considering the dispersion of real materials (in particular Al0.3Ga0.7As), considering experimentally convenient architecture (in particular the planar waveguiding structure) and considering different symmetries of the lattice (the square and rhombic symmetries). We find that in the case of the Al0.3Ga0.7As in planar structures, for the rhombic configuration of the photonic crystal the sign and modulus of the diffraction can be manipulated for the second harmonic wave whereas out-of-plane losses vanish for both fundamental and second harmonic waves, thus making the predicted structure interesting for experiments and applications.

Measurements of the Attenuation by Means οf the Scattered Light of Planar Waveguide Structure, Basing on the Polymer SU8 on a Substrate οf Sodium-Calcium Glass

The paper presents the results of investigations concerning the measurement of the attenuation of planar waveguide structures obtained by means of the photopolymerization of the polymer SU8. The applied substrate was sodium‐calcium glass. Attenuation is one of the fundamental parameters of optical waveguide, the knowledge of which is of crucial importance in the construction of various kinds of optical sensors. A method of its measurement has been presented, consisting in the recording of the intensity of scattered light making use of CCD camera. The paper deals also with the generation of planar polymer waveguide, taking into account problems connected with the adhesion to glass substrates.

Free-electron masers based on planar Bragg waveguides

A new scheme of the free-electron maser (FEM) with a ribbon electron beam is proposed in which the radiation is channeled in an open planar Bragg waveguide structure of two parallel plates with corrugated inner surfaces. The direction of corrugation is parallel to the radiation group velocity vector. The electron beam propagates in the waveguide at a large angle to its axis. The electron translation velocity is parallel to the direction of propagation of one of the partial waves that form the waveguide mode, which makes the maximum Doppler up-shift of the radiation frequency possible. A nonlinear analysis shows that the proposed FEM scheme provides a high gain (up to 30 dB). Using the Bragg waveguide, it is possible to ensure effective mode filtration, thus controlling the spatial structure of the output radiation.

Modal Characterization of a Planar Waveguide in Bismuth Borate Crystal

We report on the fabrication and modal property studies of planar waveguide structure in x-cut bismuth borate biaxial crystal formed by He ion implantation with triple energies. The prism coupling method is used to measure the effective refractive indices of this waveguide. We reconstruct the refractive index distribution of this waveguide by the reflectivity calculation method. Our results indicate that a broadened optical barrier is produced by the multiple He ion implantations. The so-called tunneling effect of the non-stationary mode in this type of barrier waveguide is presented by the well-known finite difference beam propagation method.

Er:YAl 3(BO 3) 4 glassy thin films from polymeric precursor and sol-gel methods: Waveguides for integrated optics

This paper presents the characterization of single-mode waveguides for 980 and 1550 nm wavelengths. High quality planar waveguide structure was fabricated from Y 1 − x Er x Al 3(BO 3) 4 multilayer thin films with x = 0.02, 0.05, 0.1, 0.3, and 0.5, prepared through the polymeric precursor and sol-gel methods using spin-coating. The propagation losses of the planar waveguides varying from 0.63 to 0.88 dB/cm were measured at 632.8 and 1550 nm. The photoluminescence spectra and radiative lifetimes of the Er 3+ 4I 13/2 energy level were measured in waveguiding geometry. For most samples the photoluminescence decay was single exponential with lifetimes in between 640 μs and 200 μs, depending on the erbium concentration and synthesis method. These results indicate that Er doped YAl 3(BO 3) 4 compounds are promising for low loss waveguides.

Gradient index circuit by waveguided metamaterials

Metamaterials are artificially structured materials that provide considerable flexibility for control of electromagnetic waves. The metamaterial concept can also be applied to the design of planar waveguiding structures. Here, we illustrate this design approach with the development of two-dimensional (2D) planar gradient index (GRIN) circuits. To form the structure, we make use of a 2D complementary split ring resonator, which exhibits an electric response to guided transverse-electric waves. To confirm the properties of the planar GRIN structure predicted from numerical simulations, we present experimental results for a beam-steering and a focusing GRIN circuit. These examples illustrate the versatility of the metamaterial approach in the design of complex waveguiding structures.

Analytical approximation solutions for 3-D optical waveguides: Review

The rectangular dielectric waveguide is the most commonly used structure in integrated optics, especially in semi-conductor diode lasers. Demands for new applications such as high-speed data backplanes in integrated electronics, waveguide filters, optical multiplexers and optical switches are driving technology toward better materials and processing techniques for planar waveguide structures. The infinite slab and circular waveguides that we know are not practical for use on a substrate because the slab waveguide has no lateral confinement and the circular fiber is not compatible with the planar processing technology being used to make planar structures. The rectangular waveguide is the natural structure. In this review, we have discussed several analytical methods for analyzing the mode structure of rectangular structures, beginning with a wave analysis based on the pioneering work of Marcatili. We study three basic techniques with examples to compare their performance levels. These are the analytical approach developed by Marcatili, the perturbation techniques, which improve on the analytical solutions and the effective index method with examples.

Highly transparent partially fluorinated methacrylate polymers for optical waveguides

A series of recently synthesized partially fluorinated methacrylate homopolymers and copolymers with varying fluorination degree were evaluated as coupling layers in polymeric optical waveguides. These materials show very low absorption (and high transparency) over a wide wavelength range (in the visible and near infrared region) and their refractive index can be tuned in the range of 1.43–1.49 (at 400 nm), mainly by varying the fluorination degree. Simulations of the fundamental transverse electric (TE 0) mode in three layer planar waveguide structures with a poly(methyl methacrylate) (PMMA) cladding layer showed that its intensity and profile can be appropriately controlled by varying the width and thickness of the coupling layer as well as tuning the refractive index difference between the coupling and the cladding layer.

Discrete diffraction of light in optically induced bulk and planar photonic superlattices in photorefractive lithium niobate

Experimental multielement planar and channel waveguide structures induced by coherent radiation in bulk samples of photorefractive lithium niobate and planar waveguides on their basis including those formed in a projection scheme with scaling of image dimensions are described. The possibility of linear and nonlinear light localization in optically-induced bulk and planar one-dimensional photorefractive photonic superlattices is demonstrated.

Design of novel three port optical gates scheme for the integration of large optical cavity electroabsorption modulators and evanescently-coupled photodiodes

This paper presents a novel scheme to monolithically integrate an evanescently-coupled uni-travelling carrier photodiode with a planar short multimode waveguide structure and a large optical cavity electroabsorption modulator based on a multimode waveguide structure. By simulation, both electroabsorption modulator and photodiode show excellent optical performances. The device can be fabricated with conventional photolithography, reactive ion etching, and chemical wet etching.

The study of multilayer planar optical waveguide structure with nonlinear cladding

A novel method for analyzing the multilayer and multibranch optical waveguides with nonlinear cladding is presented. This method can also be used to analyze the multiple-quantum-well (MQW) waveguide structure. Numerical simulation results show that our analyses are reasonable.

Stress reduction in planar waveguide using polymer top layer

Planar optical waveguides consisting of layers from different materials created at elevated temperatures usually exhibit substantial stresses. By controlling the layer thickness of polymeric top layer on planar waveguide structures, it is possible to use very thin layers for stress compensation, significantly reducing required deposition times. It is possible to reduce birefringence within planar device by controlling top polymer layer thickness with thermal expansion coefficient greater than silica or PMMA.

BURIED PLANAR WAVEGUIDE IN KTiOPO4 FORMED BY Cs+ ION EXCHANGE AND Si+ ION IMPLANTATION

Buried planar waveguide was produced by Cs +– K + ion exchange and Si + ion implantation in z-cut KTiOPO 4 (KTP) single domain crystals. The dark mode spectra of the waveguide were obtained by the prism-coupling method. The refractive index profiles of the Cs +– K + ion exchanged sample were reconstructed using the inverse Wenzel–Kramers–Brillouin (iWKB) method and the analysis of the refractive index profile has shown an exponential distribution in the exchange layer. The Si + ions implanted into the Cs +– K + exchange sample with the energy of 550 keV at a dose of 1.0×1015 ions/cm2 at room temperature to form a buried planar waveguide structure. The program code TRIM'98 (transport of ions in matter) is used to simulate the implantation process. The near field patterns of propagation light in buried waveguide was studied by the end-coupling method.