Showing papers on "Step-index profile published in 1998"

Low attenuation optical waveguide

Abstract: Disclosed is a single mode optical waveguide fiber having a core refractive index profile in which the profile parameters are selected to providean attenuation minimum. A set of profiles having the same general shape and dimensions is shown to have a group of profiles contained in a sub-set which exhibit a minimum of attenuation as compared to the remaining members of the set. The members of the sub-set have been found to have the lowest effective group index, n geff, and the lowest change in .beta.2 under waveguide fiber bending.

Fiber optical Bragg grating refractometer

Abstract: We have demonstrated an evanescent field refractive index fiber sensor comprising a 42-mm Bragg grating in an etched fiber together with a tunable Distributed Bragg Reflector (DBR) laser. Characterization of different aqueous sucrose solutions resulted in a resolution of roughly 10 mM sucrose. The sensor in the presented form has a theoretical sensitivity of higher than 10 -5 refractive index unit (riu) in a refractive index region close to the cladding index of the fiber. However, the technique allows for an even higher sensitivity than 10 -6 riu with a proper signal processing scheme.

Thermal Coefficients of the Optical Path Length and Refractive Index in YAG.

Abstract: The changes in optical path length and refractive index with temperature are measured at 633 nm in undoped YAG in the 85–285 K temperature range. At 100 K the change in optical path length with temperature is only ∼25% of its value at 300 K; the change of refractive index with temperature is also substantially reduced at low temperatures.

Demonstration of Long-Period-Grating Efficient Couplings with an External Medium of a Refractive Index Higher than that of Silica.

Abstract: We discuss the behavior of the transmission spectra of a long-period grating (LPG) with an external medium of refractive index higher than that of silica. We studied the evolution of the features of LPG’s surrounded by several liquid media for several kinds of fiber. The study demonstrated that the behavior depends strongly on the fiber type. Efficient couplings (efficiency greater than 50%) have been obtained with an external medium of a refractive index larger than that of silica. This result indicates that a LPG can operate with surrounding materials of a refractive index higher than that of silica, promising new applications for LPG’s as active optical filters.

Refracted Near-Field Measurements of Refractive Index and Geometry of Silica-on-Silicon Integrated Optical Waveguides.

Abstract: The standard refracted near-field technique for measuring the refractive-index profile of optical fibers cannot be directly used for silica-on-silicon integrated optical waveguides because of the opacity of silicon. A modified method is thus presented to characterize this kind of waveguide. The resolution it gives, both spatially and in the refracted index, is practically as good as that obtained with the standard technique for measuring optical fibers.

Thin film dichroic color separation filters for color splitters in liquid crystal display systems

Abstract: An optical filter is provided for use in color projection display imaging systems which utilize liquid crystal light valves for image modulation. The optical filter is a dichroic coating which separates light into different colors. The optical filter is located on a light transmissive surface of a color splitting device such as a Philips prism. The optical filter is formed from layers of at least two different dielectric materials including a high refractive index material, such as zirconium oxide and a low refractive index material such as aluminum oxide. The low refractive index material has an average refractive index of no less than about 1.6. The high refractive index material has an average refractive index which is sufficiently greater than the average refractive index of the low refractive index such that the average refractive index of the high refractive index material divided by the average refractive index of the low refractive index material yields a ratio that is greater than about 1.2 and less than about 1.55.

Anti-reflection film and process for preparation thereof

Abstract: This invention provides an anti-reflection film for use in various displays which prevents the reflection of light on the surface and enables necessary visual information to be clearly discerned. The anti-reflection film has a hard coat layer 4 , an intermediate refractive index layer 3 , a high refractive index layer 2 and a low refractive index layer 1 formed in this sequence on a transparent base film 5 , such that the refractive indices of the adjacent layers satisfy the relationship 2.20>refractive index of the high refractive index layer>refractive index of the intermediate refractive index layer>refractive index of the low refractive index layer >1.40.

Maximum effective area for non-zero dispersion-shifted fiber

Abstract: Summary form only given In this paper, we focus on design issues for non zero dispersion shifted (NZ-DSF) fibers with large effective areas We quantify performances of various index profile designs on a theoretical basis What is the maximum possible effective area to be expected given a specific bending loss and index profile shape

Dispersion compensating optical fiber, and communication system comprising the same

Abstract: Known dispersion-compensating (DC) optical fibers typically are sensitive to small changes in fiber parameter (eg, fiber diameter and/or core refractive index), and thus are difficult to manufacture The disclosed DC fibers are relatively insensitive to small departures from the nominal fiber parameters, and are therefore more manufacturable Exemplarily, the nominal refractive index profile of a DC fiber is selected such that the fiber supports LP01 and LP02 (and typically one or more further higher order modes), and the dispersion is substantially all in LP02 The total dispersion is more negative than -200 ps/nmkm over a relatively wide wavelength range The nominal refractive index profile typically comprises a refractive index "ring" that is spaced from the fiber core

Mode-field converters and long-period gratings fabricated by thermo-diffusion in nitrogen-doped silica-core fibers

Abstract: Summary form only given Novel nitrogen-doped silica-core pure-silica-cladding fibers provide exceptional possibilities to achieve abrupt variations of the refractive-index profile by thermo-diffusion of nitrogen A high diffusion coefficient of nitrogen in silica makes it possible to create deep changes in refractive index by means of short-time heat action on a fiber section with a length comparable to the fiber diameter Thus, N-doped silica fibers are most appropriate for various fiber-optic devices produced by thermo-diffusion

Infrared Refractive Index and Thermo-optic Coefficient Measurement at APL

Abstract: evelopment of infrared optical systems requires knowledge of the refractive index of the transmissive optical elements. Many Laboratory applications require the knowledge of the refractive index over a wide temperature range. The simplest expression of temperature dependence is the derivative of refractive index with respect to temperature, i.e., the thermo-optic coefficient. A convenient method for determining refractive index in the infrared is measuring interference between surfaces of a thick lamina. Such transmittance measurements, made at several temperatures, provide a comprehensive picture of the temperature-dependent refractive index.

Solid immersion lens with semiconductor material to achieve high refractive index

Abstract: An immersion system for a magneto-optical storage device has a spherical-segment-shaped lens The lens is formed of material that is transparent to the electromagnetic radiation of the wavelength λ at which the device is operated, and preferably of a semiconductor material The lens has a first refractive index n 1 which is greater than that of air A layer with a higher refractive index than the lens is disposed in the propagation path of the electromagnetic radiation The layer is composed of a material with a second refractive index n 2 that is greater than the first refractive index n 1 of the material of the lens

Fiber structure and textile using same

Abstract: A fiber structure includes alternate lamination including a predetermined number of a first portion having a refractive index na and a thickness da, and a second portion adjacent to the first portion and having a refractive index nb and a thickness db, wherein when the refractive index na is given by 1.3≦na, and a ratio nb/na is given by 1.01≦nb/na≦1.20, a reflection peak wavelength λ is equal to 2(nada+nbdb). Such fiber structure is used in a textile.

Refractive index behaviors of helium implanted optical planar waveguides in LiNbO3, KTiOPO4 and Li2B4O7

Abstract: LiNbO 3 , KTiOPO 4 (KTP) and Li 2 B 4 O 7 (LTB) are three materials presenting specific properties for electro-optic, second harmonic generation and acousto-optic integrated applications, respectively. An optical characterization was therefore realized in each of them using the `dark m-lines' spectroscopy. From the angular guided modes spectra are calculated the effective refractive indices which values serve to construct the index profiles by an inverse WKB method. Shifts between index profiles falls were observed. We discuss those particular behaviors and explain them considering three parameters: the model to draw index profile, the experimental measurements and the ionic implantation effects.

Antireflection film md image display device using the film

Abstract: PROBLEM TO BE SOLVED: To provide an antireflection film having a high antireflection function even if a transparent base having a high refractive index is used. SOLUTION: The transparent base 1 having the refractive index of >=1.55, a primer coating layer 2 having the refractive index of >=1.55, a hard-coating layer 3 having the refractive index of >=1.55 and a low-refractive index layer 6 having the refractive index below 1.55 are laminated in this order. Both of a difference between the refractive index of the transparent base 1 and the refractive index of the primer coating layer 2 and a difference between the refractive index of the transparent base 1 and the refractive index of the hard- coating layer 3 are regulated to <=0.1.

Single mode optical fiber having multi-step core structure and method of fabricating the same

Abstract: An optical fiber having a multi-step core structure, and a method of fabricating the same, are provided. The optical fiber includes a central core having a predetermined diameter a1 from an central axis and a refractive index n1, a first outer core having a diameter a2 and a refractive index n2 smaller than the refractive index n1 and surrounding the central core, a second outer core having a diameter a3 and a refractive index n3 smaller than the refractive indexn2 and surrounding the first outer core, and a cladding having a diameter a4 anda refractive index n0 smaller than the refractive index n3 and surrounding the second outer core. The diameter of the core is increased by making the refractive index distribution of the core multi-stepped, thus providing easy fabrication. The optical fiber has a low dispersion value in a 1550nm wavelength, thus making superspeed long distance transmission possible.

Inverted-graded index fiber structures for evanescent-wave chemical sensing

Abstract: The paper deals with a novel multimode fiber-optic structure, the inverted-graded index profile (IGI) fiber, and its feasibility for evanescent-wave chemical sensing. Results of the theoretical analysis of the sensitivity of the IGI fiber to changes of the refractive index and light absorption coefficient of its cladding are shown. Fabrication of IGI fibers doped in the core with GeO 2 or B 2 O 3 is described. The evanescent-wave sensitivity of the prepared IGI fibers to changes of the cladding refractive index and light absorption coefficient is given showing its increase in comparison with reference fibers with cores of pure silica and with the same polymer claddings as the IGI fibers.

Waveguide profile for large effective area

Abstract: Disclosed is a single mode optical waveguide fiber having a segmented core design. The core may have two or more segments. The highest refractive index portion (41) of the core is spaced apart from the centerline of the waveguide fiber. The relative index of the first or center segment (21) of the core is negative, where the reference refractive index is taken to be the minimum index clad. This family of core profiles provides effective areas in the range of 110 νm2 to 150 νm2 in the operating window around 1550 nm. Dashed lines (6) show alternative shapes for the index profiles (2 and 4). The negative relative index annular region illustrated by dashed line (5) shows the optional third core region having a negative relative index, using the minimum clad index as the reference index.

Diffraction grating type band-pass filter and method of making the same

Abstract: A band-pass filter formed in an optical waveguide, provided with a diffraction grating group having a period Λ of refractive index fluctuation changing in an axial direction with substantially a constant changing width Δn, comprises two periodic refractive index variable areas having periodes Λ different from each other; a zero area, disposed therebetween, having substantially a constant refractive index; and boundary areas, disposed between the zero area and the respective periodic refractive index variable areas, in which the changing width of refractive index monotonously changes between 0 and Δn.

Continuous-wave measurement of the fiber nonlinear refractive index.

Abstract: We propose a technique for measuring the nonlinear refractive index of fiber based on transmission-coefficient measurements in a fiber Sagnac interferometer. In contrast with traditional methods, the proposed method uses a single optical source operating in cw mode and direct intensity measurement, enabling one to avoid the errors caused by fiber dispersion and uncertainty of spectral peak difference measurements that occur with pulse-based methods. The nonlinear refractive index in 20-mol. % GeO2 fiber was measured to be 3.1±0.2×10-16 cm2 W-1 at 1064 nm.

Fourier transform near-infrared monitoring of reacting resins using an evanescent wave high-index fiber-optic sensor

Abstract: In this work, a high-index silica-based fiber-optic mini-bundle sensor was constructed and implemented with a Fourier transform near-infrared spectrometer in the spectral region from 10 000 to 4500 cm-1. The refractive index of the multimode step index fiber was 1.618. This arrangement allows the propagation of waveguiding modes when the sensor is immersed in most resin systems. The reactions of a polyisocyanurate resin system and an epoxy resin system were monitored and peak assignments were made and discussed with respect to their potential for use in real-time analysis to be applied to cure control. Last, cure monitoring with this sensor was successfully demonstrated in a glass-reinforced resin transfer molded epoxy part.

Graded-index characteristics in single-crystal fibers.

Abstract: Single-crystal fibers of Ti3+:Al2O3 have been grown by the laser-heated pedestal growth technique and shown to exhibit radial refractive-index gradients. A refractive-index increase of approximately 12% in the fiber core with respect to the fiber sidewalls has been measured. The index profile can be fitted with a parabolic model. Postgrowth treatment of Cr3+:Gd3Sc2Al3O12 fibers has been shown to produce a uniform cladding region with a graded-index core. The core index is some 12.5% larger than the cladding region, with an index profile shape that is approximately parabolic in nature.

Optical fibers having an inner core and an outer core

Abstract: A multimode optical fiber includes an inner core and an outer core on the inner core having different refractive index profiles. The refractive index profile of the outer core is graded, while the refractive index profile of the inner core may be graded. The refractive index profiles have the same value at the inner core--outer core boundary.

Antireflection film and manufacturing method therefor

Abstract: PROBLEM TO BE SOLVED: To transmit internal necessary visual information and to clearly read it by providing specified low refractive index layer, medium refractive index layer and high refractive index layer and specifying the thicknesses of the respective refractive index layers and the optical thickness of the film. SOLUTION: A medium refractive index layer 3, a high refractive index layer 2 and a low refractive index layer 1 are formed in this order on a transparent substrate film 5 through a bar code layer 4. Namely, the layers comprise the low refractive index layer 1 composed of a SiOx layers, the medium refractive index layer 3 provided by applying coating material composed of a binder and superfine particles having the refractive index larger than 1.5 and the high refractive index layer 2 having electric conductivity. This antireflection film has the relation: 2.20 > the refractive index of the high refractive index layer 2>1.40, thicknesses of the respective refractive index layers 1-3 of the low refractive index layer 1 of 80-110 nm, the high refractive index layer 2 of 30-110 nm and the medium refractive index layer 3 of 80-110 nm and the optical film thickness D smaller than the wavelength of visible light (D=n.d, n: the refractive index of the refractive index of the medium refractive index layer 3, d: the thickness of the medium refractive index layer 3). COPYRIGHT: (C)1998,JPO

Photonic crystal waveguide and its manufacture

Abstract: PROBLEM TO BE SOLVED: To stabilize characteristics of the photonic crystal waveguide and to reduce the manufacturing cost. SOLUTION: The photonic crystal waveguide is provided with a photonic crystal 14 structure which has a slab optical waveguide 3 on the top surface of a substrate 2 and also has refractive index variation areas 13 with a different refractive index from that of the core layer of the slab optical waveguide 3 arranged in a lattice array shape at part of the slab optical waveguide 3. In this case, the refractive index variation areas 13 are formed of the same material as the material constituting the core layer of the slab optical waveguide 3. The refractive index variation areas 13 are arranged in the lattice array shape on both the sides of an optical waveguide area 6 where light is propagated. The refractive index of the core layers of the refractive index variation areas 13 is larger than that of the core layer of an area off the refractive index variation areas 13 and the relative index difference is about 10 to 10 . A unit lattice is in regular triangle array.

Dispersion managed optical waveguide fiber

Abstract: Disclosed is a single mode optical waveguide fiber designated for compensating for positive dispersion in optical telecommunications systems. A key characteristic of the invention is that the novel dispersion compensating waveguide, viz., a waveguide having large negative dispersion, contains no dopants, such as fluorine, which lower the refractive index of silica. A refractive index profile design which includes a high refractive index center segment (5) surrounded by a plurality of alternating high (6, 10, 13) and low refractive index segments, provides a dispersion compensation fiber which has the optical properties required for the system to be compensated without sacrificing bend resistance, increasing splicing loss, or elevating polarization mode dispersion.

High performance single mode waveguide

Abstract: Disclosed is a single mode optical waveguide fiber having a segmented core design. In particular, the core comprises three segments (2, 6, 8), each having characteristic dimensions and refractive index profile. By proper choice of index profile in each segment, a waveguide fiber is made which has a mode field diameter of about 9.5, low, positive total dispersion over the operating window 1530 nm to 1565 nm as well as effective area greater than 60 νm2. The profile is further defined by the inner and outer profile volume and the ratio of outer to inner volume. Thus, inner volume is in the range 2.28 to 3.26 % νm2, the outer profile volume is in the range 3.70 to 13.75 % νm2, and the ratio of outer to inner volume is in the range 1.5 to 4.3.

Dual-core single-mode polymer fiber coupler

Abstract: We have observed light coupling between dual-core dye-doped polymer optical fibers. The experimentally observed coupling length is consistent with the standard coupled-mode theory for single-mode–single-mode coupling between step-index waveguides [ P. D. McIntyre A. W. Snyder , J. Opt. Soc. Am.63, 1518–1527 (1973)]. We also show that a graded refractive-index profile of such dual-core fibers can be made by controlled dye diffusion. The concentration, as measured by optical absorption, shows a graded profile that matches the refractive-index profile, confirming that dye concentration determines the refractive index.