Showing papers on "Step-index profile published in 2002"

Optical multilayer structure and its production method, optical switching device, and image display

Abstract: An optical multilayer structure such that there is a degree of freedom of selection of constituent materials, quick response is possible even in the visible region, and the reliability of the wiring is high. In the optical mulitlayer structure (1), a first layer (11) formed in contact with a substrate (10) and absorbing light, a gap portion (12) having a variable size causing a light interference phenomenon, and a second layer (13) which is transparent are provided in this order on the substrate (10). The following formula (1) is satisfied where N1 (=n1-i·k1 where n1 is the refractive index, k1 is the extinction coefficient, i is the imaginary unit) is the complex refractive index of the first layer (11), n2 is the refractive index of the second layer (13), and the refractive index of the entrance medium is 1.0. (1)

Unusual photon tunneling in the presence of a layer with a negative refractive index

Abstract: Recent experiments give evidence of a negative refractive index at microwave frequencies in a microstructured material. This discovery may allow some unique features associated with negative- refraction materials to be observed and applied. This letter describes the calculated results for photon tunneling via evanescent fields in the presence of a layer of negative-refraction material, also known as a left-handed material (LHM) in contrast to the conventional right-handed materials (RHMs). We show that photons may tunnel through a much greater distance when a LHM that has the same magnitudes of refractive index, relative permeability, and thickness as those of the RHM (which could also be air or vacuum) is included between two semi-infinite media.

Magnetically-modulated refractive index of magnetic fluid films

Abstract: We developed a setup to probe the refractive index of the magnetic fluid films under external magnetic fields. This setup possesses a high resolution of 0.0001 in the measured refractive index. It was found that the refractive index of the magnetic fluid depends linearly on the concentration of the dilute magnetic fluid under zero field. For a given magnetic fluid film, the refractive index increases with the increasing field strength over a critical value, and then becomes saturated as the field reaches around 200 Oe. It is noteworthy that the magnetically modulated refractive index of the magnetic fluid films could have great potential in electro-optical applications.

Dual core photonic crystal fibers(pcf) with special dispersion properties

Abstract: An optical fibre for transmitting light, said optical fibre having an axial direction and a cross section perpendicular to said axial direction, said optical fibre comprising: (1) a first core region comprising a first core material having a refractive index Nco,1; (2) a microstructured first cladding region surrounding the first core region, said first cladding region comprising a first cladding material and a plurality of spaced apart first cladding features or elements that are elongated in the fibre axial direction and disposed in the first cladding material, said first cladding material having a refractive index Ncl,l and each said first cladding feature or element having a refractive index being lower than Ncl,1, whereby a resultant geometrical index N?ge,cl, 1? of the first cladding region is lowered compared to Ncl,1; (3) a second core region surrounding said first cladding region, said second core region comprising a second core material having a refractive index Nco,2, and (4) a second cladding region surrounding the second core region, said second cladding region comprising a second cladding material having a refractive index Ncl,2, wherein the first core material, the first cladding material and the first cladding features, the second core material, and the second cladding material are selected and arranged so that Nco,1 > Nge,cl,1, Nco,2 > Nge,cl,l, and Nco,2 > Ncl,2.

Interferometer and method for measuring the refractive index and optical path length effects of air

Abstract: Apparatus and methods particularly suitable for use in electro-optical metrology and other applications to measure and monitor the refractive index of a gas in a measurement path and/or the change in optical path length of the measurement path due to the gas while the refractive index of the gas may be fluctuating due to turbulence or the like and/or the physical length of the measuring path may be changing. More specifically, the invention employs electronic frequency processing to provide measurements of dispersion of the refractive index, the dispersion being substantially proportional to the density of the gas, and/or measurements of dispersion of the optical path length, the dispersion of the optical path length being related to the dispersion of the refractive index and the physical length of the measurement path. The refractive index of the gas and/or the optical path length effects of the gas are subsequently computed from the measured dispersion of the refractive index and/or the measured dispersion of the optical path length, respectively. The information generated by the inventive apparatus is particularly suitable for use in interferometric distance measuring instruments (DMI) to compensate for errors related to refractive index of gas in a measurement path brought about by environmental effects and turbulence induced by rapid stage slew rates. In preferred embodiments, differential plane mirror interferometer architectures are utilized, the operating wavelengths are approximately harmonically related and may be monitored and/or controlled to meet precision requirements, heterodyne and superheterodyne processing are beneficially used, and phase redundancy is resolved.

Apparatus for measuring thickness profile and refractive index distribution of multiple layers of thin films by means of two-dimensional reflectometry and method of measuring the same

Abstract: The present invention relates to a non-contact, non-destructive measuring apparatus that measures thickness profile and refractive index distribution of a single or multiple layers of thin films by means of the principle of reflectometry. According to the present invention, by employing more than one narrow band-pass optical filters and a two-dimensional array of CCD sensors, and by finding an optimal solution for the nonlinear functional relationship between the thickness of said thin film or thin films and the corresponding refractive indexes by using an iterative numerical computation method, said apparatus simultaneously measures local area-wise thickness profile and refractive index distribution among others of said a single layer or multiple layers of thin films on a substrate.

Photoinduced refractive index change in As2Se3 by 633nm illumination.

Abstract: Photodarkening of amorphous As2Se3 thin films was generated by a 633-nm HeNe laser. The refractive index and absorption coefficient of the chalcogenide glass was determined, both before and after exposure, by analyzing the material's transmission spectrum. In order to accurately determine the optical constants, the thin film's non-uniform thickness was accounted for. The increase in the refractive index and the coefficient of absorption was investigated and was found to demonstrate saturation with increased exposure time. Index changes as high as 0.05, or 2%, were obtained in As2Se3, a promising glass for all-optical switching.

Dopant dependence of effective nonlinear refractive index in GeO 2 - and F-doped core single-mode fibers

Abstract: We describe the dopant dependence of the effective nonlinear refractive index n/sub 2eff/ in GeO/sub 2/- or F-doped core fibers theoretically and experimentally. We show that the dopant dependence of the nonlinear refractive index n/sub 2/ of F-doped bulk glass is the inverse of that of GeO/sub 2/-doped bulk glass. We also show that the effective nonlinear refractive index n/sub 2eff/ in F-doped core fibers, estimated by using the dopant content dependence of n/sub 2/, is in good agreement with our experimental results. Moreover, we confirm that n/sub 2eff/ in an optical fiber strongly depends on the refractive index profile of its core.

Anti-reflection film and process for the preparation of the same

Abstract: An anti-reflection film comprises a transparent support and a low refractive index coating layer. The low refractive index coating layer has a refractive index lower than a refractive index of the support. The low refractive index coating layer has an essentially uniform thickness, while the layer has a surface roughness in terms of an arithmetic mean (Ra) in the range of 0.05 to 2 μm.

Simultaneous refractive index and temperature measurement using cascaded long-period grating in double-cladding fibre

Abstract: A compact scheme for simultaneous temperature and surrounding refractive index (SRI) measurement using two long-period gratings (LPGs) of different periods inscribed side-by-side in a single piece of a double-cladding fibre is presented. One of the LPGs is sensitive to both SRI and temperature, whilst the second is sensitive to temperature only.

Accurate refractive index profiling in a graded-index plastic optical fiber exceeding gigabit transmission rates

Abstract: An optimum index profile offering the highest bit rate communication was formed in a poly methyl methacrylate (PMMA)-based graded-index plastic optical fiber (GI-POF) by modifying the polymerization process. The interfacial-gel polymerization process we have proposed to fabricate the PMMA-based GI-POF is capable of forming a nearly optimum refractive index profile. However, the theoretically calculated bandwidth from the measured index profile was reduced compared with a GI-POF with an optimum profile. In this paper, we report how to obtain a PMMA-based GI-POF having exactly the optimum index profile. The bandwidth of this ideal GI-POF was experimentally measured and a very high value of 2.88 GHz, even for a 150-m fiber length, was confirmed. The calculated bandwidth agreed well with the experimentally measured one. These results indicate that very low modal dispersion can be expected in a GI-POF fabricated by the modified interfacial-gel polymerization process.

Modal characteristic equation and dispersion curves for an elliptical step-index fiber with a conducting helical winding on the core-cladding boundary - an analytical study

Abstract: A special type of elliptical step-index fiber with a conducting helical winding on the core-cladding boundary is proposed and investigated theoretically. Using elliptic cylindrical coordinates, boundary conditions are derived and longitudinal field components for the even and odd modes are obtained. The characteristic equation for the waveguide to be studied is determined by solving the fourth-order determinantal equation, which also contains complex quantities. In order to study the fundamental mode, the modal index /spl nu/ is put as /spl nu/=1. The equations obtained involve modified Mathieu functions of the first order and their derivatives. Applying approximations, cutoff conditions are obtained. Numerical computations are made. Dispersion curves are obtained for different pitch angles of the helical winding.

Radiation sensitive refractive index changing composition and refractive index changing method

Abstract: A composition having a refractive index sensitively changeable by a radiation which comprises (A) a decomposable compound, (B) a non-decomposable compound having a refractive index lower than that of the decomposable compound (A), (C) a radiation-sensitive decomposing agent, and (D) a stabilizer. The irradiation of the composition with a radiation ray via a mask decomposes the above (C) and (A) components in a irradiated portion, resulting in the occurrence of the difference in refractive index between an irradiated portion and a non-irradiated portion, which leads to the formation of a pattern having regions of different refractive indexes.

Scalable antiguided ribbon laser

Abstract: A new scalable fiber laser approach to phase locking of multiple gain cores in an antiguided structure is described and modeled. In essence, the waveguide comprises a periodic sequence of gain-loaded and no-gain segments that has a uniform refractive index (referred to as the ribbon) encapsulated within a reduced-index cladding region. Our calculations reveal that the constant-index profile within the ribbon structure provides optimal mode discrimination; the refractive index must be constant within ±0.001 to ensure single-mode operation for a five-core design. One-dimensional and two-dimensional calculations are pursued to support the design criteria. Slight periodic variation in the refractive index of the ribbon laser leads to the emergence of a photonic bandgap, in analogy to so-called holey fibers. Our constant-index design, together with the periodic gain profile, may be described as a photonic metal.

Photonic bandgap fibre, and use thereof

Abstract: An object of the present invention is to provide new designs of microstructured optical fibres that may be fabricated without use of voids, such as fibres being realized using silica and silica doping techniques. The invention relates to a microstructured optical fibre that guides light in a core region (52), where the fibre has a cladding region that comprises a background material (51) and a number of cladding features or elements (50) that are elongated in the longitudinal direction of the fibre and have a higher refractive index than the cladding background material. The core region has a lower effective refractive index than the cladding, and the fibre may guide light in the core by photonic bandgap effects. The present invention provides designs of photonic bandgap fibres that may operate without the use of voids in the cladding, thereby simplifying fabrication of photonic bandgap fibres compared to prior art. The invention further provides photonic bandgap fibers with tuneable waveguiding properties, such as tuneable polarization. The invention further relates to a number of specific fibre designs that provide improvements with respect to dispersion characteristics, mode field diameters, propagation losses, polarization mode dispersion and other issues of relevance to optical communication systems.

Fiber lasers having a complex-valued Vc-parameter for gain-guiding

Abstract: The instant invention concerns optical fibers that have complex-valued V c -parameters due to gain g established by active dopants that are doped into the fiber core in accordance with a doping profile. In particular, the doping levels are very high, such that the gain g makes a sufficiently large contribution to an imaginary part of the complex-valued V c -parameter to define at least one gain-guided mode, e.g., the fundamental mode or several low-order modes of radiation in the optical fiber. The fiber does not require any index-guiding effects to a single mode or just a few of the lowest-order modes in large cross-section cores having diameters in the range from 50 μm to 500 μm in diameter and yield kilowatt level output power. The fiber may, in addition to gain-guiding, take advantage of a refractive index profile to provide for index-guiding or index-antiguiding effects in addition to gain-guiding.

Novel optical fiber refractometric transducer employing hemispherical detection element

Abstract: We present the results of a theoretical numerical analysis of a novel fiber optic refractometric transducer. It consists of a hemispherical glass detection element and a pair of the multimode optical fibers attached symmetrically to the element's flat equatorial plane. The internal reflection of light from the element's spherical surface is sensitive to the refractive index of the surrounding medium. We exploit several internal reflections in series and the focusing of the beam by the element's spherical surface to achieve enhanced sensitivity to the refractive index of the surrounding medium and reduced intrinsic optical loss in the transducer. We present the data on the effect of transducer's parameters on its transmission function. We show that the transducer can operate in a relatively wide range of the refractive index of the surrounding medium (we show this for the interval n = 1.0 to n = 1.45). We also present experimental data confirming our theoretical results.

Reflection reducing film and electronic image display device

Abstract: PROBLEM TO BE SOLVED: To provide a reflection reducing film and an electronic image display device in which degradation in the appearance due to the interference of light can be suppressed and the reflectance can be decreased. SOLUTION: The reflection reducing film has a multilayered structure formed on one or both surfaces of a transparent resin film, with the multilayered structure composed of, from the outermost layer, a reflection reducing layer comprising at least a low refractive index layer and a high refractive index layer, a hard coat layer and a first interference layer. The maximum of the peak-to- peak difference of the reflectance in the region from 500 to 650 nm is ≤1.0%. It is preferable that the refractive index of the transparent resin film ranges from 1.55 to 1.70, that the refractive index and optical film thickness of the first interference layer range from 1.50 to 1.65 and 125 to 160 nm, respectively, and that the refractive index and the film thickness of the hard coat layer range from 1.45 to 1.55 and from 2 to 25 μm, respectively. The refractive index of each layer preferably satisfies the relation of (refractive index of the transparent resin film)>(refractive index of the first interference layer)>(refractive index of the hard coat layer). COPYRIGHT: (C)2003,JPO

Athermal arrayed waveguide grating

Abstract: The invention is an optical device having a plurality of optical waveguides and comprising at least one waveguide, which is defined by a core region having first and second sections that are series connected and are capable of transmitting light energy, the core region being surrounded by a cladding that essentially confines the light energy within the core region, the first section of the core region comprising a first length of material whose refractive index increases as temperature increases; The at least one waveguide is temperature-compensating in that and the second section of the core region comprises a second length of material whose refractive index has a sufficient enough difference of the rate of the variation of the index with the temperature, wherein the second section has a plurality of grooves, filled with the material whose refractive index has a sufficient enough difference of the rate of the variation of the index with the temperature, that are designed in a way the effective width of the second section changes between adjacent wave guides.

Few-mode fiber profile

Abstract: A family of fiber profiles is disclosed which exhibit only three well guided modes in the operative “band”. The reduction in the number of modes is accomplished with a change in the refractive index in the core area. The change in refractive index in the core area changes the order of the appearance of the modes, thus leading to fewer guided modes, and less MPI. In one embodiment the refractive index ring comprises an area of depressed refractive index, and the null energy point of one of the guided modes is found therein. In another embodiment, the change in the refractive index in the core is located coincidentally with the null point of a desired mode. In some embodiments negative dispersion on the order of −400 ps/nm/km is experienced, while MPI is minimized. In another embodiment the fiber profile is further characterized by a negative slope suitable for compensating a link of transmission fiber.

Optical fiber with built-in grating and optical fiber for forming grating therein

Abstract: The present invention provides an optical fiber equipped with a grating that functions as a narrow-band loss filter. The optical fiber has a core, an inner cladding, an intermediate cladding, and an outer cladding, which have refractive indexes n0, n1, n2, and n3, respectively, the refractive indexes having a relationship of n0>n3≧n1n2. At least a part of the inner cladding has a grating. The refractive index of the intermediate cladding is lower than the refractive indexes of the inner cladding and the outer cladding such that a recession is formed in the refractive index profile of the clad. The grating is provided on the inner side relative to the recession.

Dispersion-compensating fiber having a high relative dispersion slope

Abstract: Disclosed is a dispersion-compensating (DC) optical fiber 10 that is designed to support the fundamental mode of radiation at 1550 nm. The DC fiber is fabricated from silica glass and has a refractive index profile that includes a core region 51 surrounded by a cladding region 52 having a nominal refractive index n4. The core region includes a central core 511 having a nominal refractive index n1, a “trench” 512 surrounding the central core having a nominal refractive index n2, and a “ridge” 513 surrounding the trench having a nominal refractive index n3. A range of refractive index profiles has been found that provides relative dispersion slopes (RDS) that are greater than 0.012 nm−1 and figures of merit that are greater than 200 ps/(nm·dB). The range is conveniently expressed in terms of index differences and radial dimensions: central core: radius=1.5±0.5 μm, and 0.015

Refractive index of lens fiber membranes in different parts of the crystalline lens

Abstract: Purpose: Local variations in refractive index are an important physical cause of light scattering in the lens. The goal of this study was to further add to the understanding of the process of light propagation in the lens by directly measuring local variations in refractive index by phase contrast microscopy. Methods: Refractive index was estimated by immersion refractometry. Cryo-sections of quick frozen human donor lenses were embedded in a graded series of bovine serum albumin solutions, and in immersion oil. Results: Superficial cortical fiber membranes proved to have a refractive index considerably above values given for cytoplasm at the same location. Nuclear fiber membranes have a refractive index of the same order as given in the literature for nuclear fiber cytoplasm. Conclusion: The large difference in refractive index between fiber membranes and cytoplasm in the lens cortex may be important for optical function and transparency of the lens. Support: Marie Curie Fellowship of the European Community program Quality of Life (QLK6-CT-1999-51159).© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Optical fiber and method of manufacturing the same

Abstract: This invention relates to an optical fiber having a structure that effectively reduces transmission loss and bending loss. An optical fiber according to this invention is an optical fiber mainly comprised of silica and including a core region and a cladding region covering the core region. The core region is doped with chlorine so as to have a refractive index higher than that of pure silica. The cladding region is doped with fluorine so as to have a refractive index lower than that of pure silica. The optical fiber, in particular, is characterized in that a peak value of a relative refractive index difference of the core region with respect to a refractive index of pure silica is 0.05% or more.

Higher-order-mode dispersion compensating photonic crystal fibres

Abstract: The present invention relates to a novel group of cladding and core designs, especially for use in optical fibres, which provides enhanced dispersion compensating properties through waveguiding of higher-order modes. In a first aspect, the present invention relates to an optical fibre comprising: A central region (41) having a centre radius r centre, max and an effective refractive index ncentre.eff • A core region (43), having a core radius rcore-max,a maximum refractive index ncore,max, and an effective refractive index ncore,eff • A cladding region (45, 46) having a cladding radius rciadding,max, a maximum refractive index nclad,max, an effective refractive index nciad,effand/or a resultant geometrical index ng,clad In preferred embodiments, the core region and or the cladding region comprise a photonic crystal structure.

Optical fiber, optical fiber component and optical transmission method

Abstract: An optical fiber comprising a core and a cladding region which covers an outer periphery of the core, having a zero-dispersion wavelength in a wavelength range of 1.4 μm to 1.65 μm, and being in a single mode in that zero-dispersion wavelength, wherein GeO 2 is doped in the core in a quantity such that a relative refractive index difference of the core becomes not less than 1.8%, the cladding region includes first, second, and third cladding regions, and a refractive index of the second cladding region is smaller than those of the first cladding region and the third cladding region.

Reflection preventing film laminated body and method of manufacturing the laminated body

Abstract: An antireflection film laminate comprising a low refractive index film on the surface side and a high refractive index film which is disposed under the low refractive index film in contact therewith, wherein the high refractive index film is formed as a discontinuous layer in the planar direction. If the high refractive index film is formed as a discontinuous layer, the high refractive index film can enter into the low refractive index film to restrain movement of the low refractive index film, and therefore an antireflection film laminate exhibiting superior antiscratching property and transparency can be obtained.

Simultaneous measurement of the nonlinear refractive index and chromatic dispersion of optical fibers by four-wave mixing

Abstract: The simultaneous measurement of the nonlinear refractive index and the chromatic dispersion measurement of dispersion shift fibers are proposed, based on the power determination of the mixing products generated by four pump waves. This method is also used with other low-dispersion chromatic dispersion fiber, such as nonzero dispersion shifted fibers. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 305–307, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10444

Multimode fiber having a refractive index profile

Abstract: The present invention relates to a multimode fiber having a refractive index profile, wherein the area surrounding the center of the fiber has a refractive index profile such that the responses of a DMD (Differential Mode Delay) measurement carried out on a fiber having a length of at least 300 m are obtained without any pulse splitting occurring in the center of the fiber.

Dispersion and dispersion slope compensating fiber and optical transmission system utilizing same

Abstract: A dispersion and dispersion slope compensating optical fiber (10) includes a segmented core (12, 14, 16, 18) and a cladding layer (20) wherein the refractive index profile is selected to provide a dispersion having a maximum deviation of less than 7 ps/nm-km over a wavelength band from 1550 nm to 1610 run. According to a further embodiment of the invention, a dispersion compensating optical fiber is provided having a refractive index profile with a central core segment having a positive relative refractive index; a depressed moat segment on a periphery of the central core segment having a relative refractive index that is more negative than -1.2 %; and an annular ring segment outward from the depressed moat segment having a relative refractive index that is greater than 1.2 %.