Showing papers on "Step-index profile published in 2011"
TL;DR: In this article, the optical absorption coefficients and refractive index changes in a two-electron quantum dot with oscillating and linear confining terms are obtained by using compact-density matrix approach and exact analytical method.
Abstract: Analytical expressions of the optical absorption coefficients and refractive index changes in a two-electron quantum dot with oscillating and linear confining terms are obtained by using compact-density matrix approach and exact analytical method. Numerical results on typical GaAs/AlGaAs materials show that, an increase of the confinements blueshifts the peak positions of absorption coefficients and refractive index changes. Additionally, an increase of the optical intensity and relaxation time considerably changes the absorption coefficients as well as the refractive index changes.
82 citations
Patent•
04 May 2011TL;DR: An optical member including high refractive index layers having a great as discussed by the authors and low as discussed by the authors having a small as discussed by the authors, which are each relatively thin as compared with an optical length, disposed alternately in the lateral direction as to an optical axis.
Abstract: An optical member including high refractive index layers having a great refractive index and low refractive index layers having a small refractive index, which are each relatively thin as compared with an optical length, disposed alternately in the lateral direction as to an optical axis. Each width of the high refractive index layers and the low refractive index layers is equal to or smaller than the wavelength order of incident light.
80 citations
TL;DR: A simple refractive index sensor based on a step-index fiber with a hollow micro-channel running parallel to its core that becomes waveguiding when filled with a liquid of index greater than silica, causing sharp dips to appear in the transmission spectrum at wavelengths where the glass-core mode phase-matches to a mode of the liquid-core.
Abstract: We present a simple refractive index sensor based on a step-index fiber with a hollow micro-channel running parallel to its core. This channel becomes waveguiding when filled with a liquid of index greater than silica, causing sharp dips to appear in the transmission spectrum at wavelengths where the glass-core mode phase-matches to a mode of the liquid-core. The sensitivity of the dip-wavelengths to changes in liquid refractive index is quantified and the results used to study the dynamic flow characteristics of fluids in narrow channels. Potential applications of this fiber microstructure include measuring the optical properties of liquids, refractive index sensing, biophotonics and studies of fluid dynamics on the nanoscale.
75 citations
TL;DR: Simple design rules for dispersion controlled fibers are derived, based on which an algorithm for the automatic dispersion optimization is proposed, implemented and used to design various nonlinear fibers for all-optical processing and supercontinuum generation.
Abstract: We investigate a novel approach to obtain highly nonlinear fibers with a tailored group velocity dispersion around a desired wavelength region of interest. Rather than exploiting longitudinal holes to control the average refractive index of the cladding and hence the fiber's waveguide dispersion, as in holey fibers, we propose using an all-solid cladding with a suitably chosen refractive index difference relative to the core. We demonstrate numerically that this solution allows a large freedom in the manipulation of the overall fiber dispersive properties, while enabling, in practice, a much more accurate control of the fiber's structural properties during fabrication. Effectively single mode guidance over a broad wavelength range can be achieved through the use of a second outer cladding forming a W-type index profile. We derive simple design rules for dispersion controlled fibers, based on which an algorithm for the automatic dispersion optimization is proposed, implemented and used to design various nonlinear fibers for all-optical processing and supercontinuum generation. Fabrication of a lead silicate fiber with flattened dispersion at telecoms wavelengths confirms the potential of these new fibers.
60 citations
TL;DR: The effective indices of the cladding modes of optical fibers depend on the refractive index of the medium surrounding the fiber as discussed by the authors, and it has been shown experimentally and theoretically that while claddings with similar effective indices normally have similar refractometric sensitivities, the addition of a 50 nm thick gold sheath enhances the sensitivity of some EH modes by more than one order of magnitude.
Abstract: The effective indices of the cladding modes of optical fibers depend on the refractive index of the medium surrounding the fiber We show experimentally and theoretically that while cladding modes with similar effective indices normally have similar refractometric sensitivities, the addition of a 50 nm thick gold sheath enhances the sensitivity of some EH modes by more than one order of magnitude while nearly completely suppressing the sensitivity of neighbouring HE modes (by three orders of magnitude, down to insignificant levels) A differential sensitivity of ∼1000 nm/(refractive index unit) is experimentally reported between adjacent EH and HE grating resonances
53 citations
TL;DR: Measurements on thermally evaporated AMTIR2 thin films confirmed that the film deposition process provides thin films with reduced index compared to that of the bulk glass used as a target, and it is possible to locally increase the refractive index of the chalcogenide glass using laser exposure at 632.8 nm.
Abstract: The prism coupling technique has been utilized to measure the refractive index in the near- and mid-IR spectral region of chalcogenide glasses in bulk and thin film form. A commercial system (Metricon model 2010) has been modified with additional laser sources, detectors, and a new GaP prism to allow the measurement of refractive index dispersion over the 1.5-10.6 μm range. The instrumental error was found to be ±0.001 refractive index units across the entire wavelength region examined. Measurements on thermally evaporated AMTIR2 thin films confirmed that (i) the film deposition process provides thin films with reduced index compared to that of the bulk glass used as a target, (ii) annealing of the films increases the refractive index of the film to the level of the bulk glass used as a target to create it, and (iii) it is possible to locally increase the refractive index of the chalcogenide glass using laser exposure at 632.8 nm.
49 citations
Patent•
29 Dec 2011
TL;DR: In this article, an optocoupler, an optical interconnect and method of manufacture providing same are provided for coupling an optical signal between a high refractive index waveguide of an integrated circuit and a waveguide external to the integrated circuit.
Abstract: An optocoupler, an optical interconnect and method of manufacture providing same are provided for coupling an optical signal between a high refractive index waveguide of an integrated circuit and a waveguide external to the integrated circuit. The optocoupler includes a thinned high refractive index waveguide having a thickness configured to exhibit an effective refractive index substantially matching a refractive index of the external waveguide.
45 citations
Patent•
31 Jan 2011
TL;DR: A non-zero dispersion shifted optical fiber (NZDSF) includes a central core, an inner cladding, and an outer cladding as discussed by the authors, and the inner claddings include a first intermediate cladding and a buried trench.
Abstract: A non-zero dispersion shifted optical fiber (NZDSF) includes a central core, an inner cladding, and an outer cladding. The central core has an outer radius r1 and a maximum refractive index difference Dn1 with respect to the outer cladding. The inner cladding includes a first intermediate cladding and a buried trench. The first intermediate cladding has an outer radius r2 and a refractive index difference Dn2 with respect to the outer cladding. The buried trench has an outer radius r3, a width w3, and a negative refractive index difference Dn3 with respect to the outer cladding. In some embodiments, the inner cladding includes a second intermediate cladding having an outer radius r4 and a refractive index difference Dn4 with respect to the outer cladding. For a radius of curvature of 30 millimeters at a wavelength of 1625 nanometers, the optical fiber typically exhibits bending losses of about 0.5 dB/100 turns or less. At a wavelength of 1550 nanometers, the optical fiber's effective area is typically about 95 μm2 or greater.
44 citations
TL;DR: In this article, a simple, compact, and robust refractive index sensor is developed, by twisting a pair of silica microfibers to form a coupling device, and the transmission spectrum of the device is highly sensitive to the surrounding this article.
Abstract: A simple, compact, and robust refractive index sensor is developed, by twisting a pair of silica microfibers to form a coupling device. The transmission spectrum of the device is highly sensitive to the surrounding refractive index and the highest sensitivity obtained is -2377 nm/refractive index unit (RIU), at the refractive index value of - 1.3680, for the fibers with diameter of ~4.2 μm, and the sensitivity can be further increased to - 2735 nm/RIU for a smaller fiber diameter of ~2.8 μm. Such a device is easy to construct, of low cost, and compatible with the optical fiber system.
41 citations
TL;DR: In this paper, the authors evaluated the refractive index variation of injection-molded polymethylmethacrylate optical lenses under different levels of packing pressure using a Shack-Hartmann wavefront sensor-based metrology system.
Abstract: In this study, refractive index variation in injection-molded polymethylmethacrylate optical lenses under different levels of packing pressure was evaluated using a Shack–Hartmann wavefront sensor-based metrology system. The experimental results showed that optical polymer's refractive index exhibits a considerable amount of variation for the lenses molded under different packing pressures. Specifically, within the range investigated in this study, refractive index variation is more uniform when higher packing pressure was used but less so for lower packing pressure. Refractive index variation is believed to be the result of density variation, which itself is caused by shrinkage variation at different packing conditions. In addition, using density information in the plastic lenses predicted by finite element simulation, refractive index variation was numerically determined using the differential Lorentz–Lorenz equation and the results were in good agreement with the experiments conducted in this research. © 2011 Wiley Periodicals, Inc. Adv Polym Techn 30:51–61, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20211
40 citations
Patent•
05 Dec 2011
TL;DR: In this paper, the index profile of the inner cladding region is graded with a slope of γn core /R b, where n core is the refractive index of the core region, R b is the bend radius, and γ= 0.6-1.2.
Abstract: A LMA, single-mode optical fiber comprises a core region, an inner cladding region surrounding the core region, and an outer cladding region surrounding the inner cladding region. The inner cladding region is configured to provide bend compensation. In one embodiment the index profile of the inner cladding region is graded with a slope of γn core /R b , where n core is the refractive index of the core region, R b is the bend radius, and γ= 0.6-1.2. In addition, the inner cladding is annular and the ratio of its outer radius to its inner radius is greater than 2. In a preferred embodiment this ratio is greater than 3. The overall index profile may be symmetric or asymmetric.
TL;DR: In this article, the optical band gap, refractive index and oscillator parameters of amorphous semiconductor Se70S30−Sb x thin films with x = 0, 18, 12 and 30 at.
Abstract: The optical band gap, refractive index and oscillator parameters of amorphous semiconductor Se70S30− x Sb x thin films with x = 0, 18, 12 and 30 at. % deposited by electron-beam evaporation were investigated by optical spectrophotometry. The energy gap decreases from 2.25 to 1.08 eV with increasing Sb content introduced at the expense of S, which is explained in terms of chemical bond and cohesive energy approaches. The method proposed by Swanepoel is applied to extract the refractive index n. It was found that the refractive index is strongly related to the change in the concentration of Sb, which is related to the increase density of the film material with increasing Sb content, and is interpreted in terms of polarisability and the mean coordination number. The ratio of the refractive indices of (Se70Sb30)/(Se70S30) is ≈ 1.32 at a wavelength λ ≈ 1600 nm and increases to 1.48 at λ ≈ 950 nm. Such a refractive index contrast could be used to fabricate a distributed Bragg reflector (DBR) stack with limited ...
Patent•
24 Jan 2011
TL;DR: In this paper, a non-zero dispersion shifted optical fiber (NZDSF) includes a central core, an inner cladding, and an outer cladding including a first intermediate cladding and a buried trench.
Abstract: A non-zero dispersion shifted optical fiber (NZDSF) includes a central core, an inner cladding, and an outer cladding. The central core has an outer radius r1 and a maximum refractive index difference Dn1 with respect to the outer cladding. The inner cladding includes a first intermediate cladding and a buried trench. The first intermediate cladding has an outer radius r2 and a refractive index difference Dn2 with respect to the outer cladding. The buried trench has an outer radius r3, a width w3, and a negative refractive index difference Dn3 with respect to the outer cladding. In some embodiments, the inner cladding includes a second intermediate cladding having an outer radius r4 and a refractive index difference Dn4 with respect to the outer cladding. For a radius of curvature of 30 millimeters at a wavelength of 1625 nanometers, the optical fiber typically exhibits bending losses of about 0.5 dB/100 turns or less. The optical fiber's 22-meter cable cutoff wavelength (22 m-λcc) and effective cutoff wavelength at two meters are typically less than 1150 nanometers.
TL;DR: A highly sensitive miniature photonic crystal fiber refractive index sensor based on field mode excitation is presented and is shown to be insensitive to environmental temperature.
Abstract: A highly sensitive miniature photonic crystal fiber refractive index sensor based on field mode excitation is presented. The sensor is fabricated by melting one end of a photonic crystal fiber into a rounded tip and splicing and collapsing the other end with a single-mode fiber. The rounded tip is able to induce cladding mode excitation, which resulted in an additional phase delay. Linear response of 262.28 nm/refractive index unit in the refractive index range of 1.337 to 1.395 is obtained for the physical length of a 953 μm sensor. The sensor is also shown to be insensitive to environmental temperature.
TL;DR: An automated demodulation technique is presented that measures the surrounding refractive index by comparing the differential amplitude of resonance peaks near the plasmon attenuation for two orthogonal amplitude spectra recorded in the same operating conditions.
Abstract: The generation of near-IR surface plasmon resonance in gold-coated tilted fiber Bragg gratings is strongly dependent on both the polarization state of the transmission light and the property of confining materials (including the coating materials and surrounding media). These dependencies can be advantageously used to demodulate the amplitude spectrum and retrieve the surrounding refractive index. In this paper, we present an automated demodulation technique that measures the surrounding refractive index by comparing the differential amplitude of resonance peaks near the plasmon attenuation for two orthogonal amplitude spectra recorded in the same operating conditions. A mean sensitivity of more than 500 nm per refractive index unit is reported. This new refractive index measurement method is shown to be accurate to 5×10(-5) over a full range of 0.01 in water solutions.
TL;DR: In this paper, an asymmetrical twin-core fiber based Michelson interferometer is reported as a refractive index sensor, where one core locates at the fiber center and the other core is 26 μ m away from the central core.
Abstract: An asymmetrical twin-core fiber based Michelson interferometer is reported as a refractive index sensor. One core of the twin-core fiber locates at the fiber center and the other core is 26 μ m away from the central core. Part of the cladding of the twin-core fiber over a small length is removed by chemical etching to make the effective refractive index of the fundamental mode of the side core is sensitive to the ambient refractive index. Therefore, the interference spectrum between the central core and the side core shifts with the variation of the ambient refractive index. The sensitivity of such a Michelson interferometer is ~ 270 nm/RIU in the range of 1.34-1.38.
TL;DR: In this paper, a nanolayer was applied to the optical fiber to increase the sensitivity of the LPG to changes of the refractive index of the external media relatively to variations of wavelength and in transmission.
Abstract: In this work is studied the response of optical fiber long period grating (LPG) to changes of the refractive index of the external media relatively to variations of wavelength and in transmission. The response of the LPG to refractive index greater and lesser than to cladding is investigated. A nanolayer was deposited onto the fiber to increase the sensitivity of the LPG to refractive index of the external media higher than cladding. The film modifies the rates of effective modes of cladding, thus improving the response of the changes in the refractive index of the external media higher than that in the refractive index of the cladding (ncl ≈ 1.457). The Langmuir–Blodgett technique was used for the deposition of the nanolayer.
TL;DR: In this article, a miniaturized metal-dielectric-hybrid fiber tip grating (FTG) using a focused ion beam (FIB) method with high accuracy for refractive index sensing applications is presented.
Abstract: We fabricate a miniaturized metal-dielectric-hybrid fiber tip grating (FTG) using a focused ion beam (FIB) method with high accuracy for refractive index sensing applications. It is the smallest fiber grating by now (nearly 10 μm in length located at the fiber tip of 3 μm in radius) and it has strong surface corrugations with notches periodically. The grating shows refractive index sensitive [125 nm/refractive index unit (RIU)] and insensitive (nearly zero) properties for reflection channels of different resonant modes by metal-dielectric cladding structure. It can be used as a multichannel sensor for simultaneous refractive index and temperature/pressure measurements. Taking advantage of its flexible design, tiny size, unique modal and spectral characteristics, the metal-dielectric-hybrid FTG has great potential in fast-response detection of ultrasmall objects.
TL;DR: In this paper, two routes can be considered for the elaboration of a single mode fiber: the first method consists in preparing a classical step index fiber (SIF) with a core-clad configuration.
Abstract: Chalcogenide glasses are known for their large transparency in the mid infrared, which includes the two atmospheric windows lying from 3–5 μm and 8–12 μm. Chalcogenide single mode fibers present numerous potential applications in the IR field, such as military countermeasures, LIDAR spectroscopy and spatial interferometry. Two routes can be considered for the elaboration of a single mode fiber. The first method consists in preparing a classical step index fiber (SIF) with a core-clad configuration. This procedure is based on two glass compositions (core and clad) with compatible thermal and optical properties and having a refractive index difference allowing the single mode propagation. The second route is based on the design of a microstructured optical fiber (MOF) in which the guiding function is ensured by the refractive index contrast between the core glass and the air contained in the capillaries surrounding the core. Two kinds of fibers exhibiting single mode propagation were fabricated; the first one is a SIF with a 22 μm core diameter and the second one is a three rings of holes MOF. The geometry of the MOF shows a d/Λ around 0.35 and a 40 μm core diameter. In both cases the optical losses in the 2 to 12 μm region were measured and compared.
Patent•
24 May 2011
TL;DR: In this paper, a method is proposed to measure a first transmitted wavefront in a first medium having a first refractive index and a second transmitted wave front in a second medium having an orientation different from the first one.
Abstract: A method includes the steps of measuring a first transmitted wavefront in a first medium having a first refractive index and a second transmitted wavefront in a second medium having a second refractive index different from the first refractive index, and obtaining a refractive index distribution projected value of the object in each orientation by removing a shape component of the object utilizing measurement results of the first transmitted wavefront and the second transmitted wavefront and each transmitted wavefront of a reference object that has the same shape as that of the object and a specific refractive index distribution and is located in one of the first medium and the second medium with the same orientation as that of the object, and calculating a three-dimensional refractive index distribution of the object based on a plurality of refractive index distribution projected values corresponding to the plurality of orientations.
13 Nov 2011
TL;DR: In this paper, a temperature sensor using a singlemode tapered fiber coated by thermo-sensitive material is presented, which works on the multimode interference influenced by the small change of the ambient refractive index.
Abstract: A temperature sensor using a single-mode tapered fiber coated by thermo-sensitive material is presented. It works on the multimode interference influenced by the small change of the ambient refractive index. To better understand the tapered optical fiber, simulations that change parameters such as the taper waist diameter and the ambient refractive index are performed using RSOFT BeamPROP. It is illustrated that optical losses vary with the ambient refractive index, and reduce diameter within a certain range can increase the sensitivity. In our experiment, with the high thermo-sensitive coefficient of material, a good temperature sensing result was achieved. The range of temperature measured is from ∼20°C to 80°C. The results show that the temperature sensor has high temperature sensitivity and good repeatability.
TL;DR: In this paper, a theoretical investigation of coupling optics involving a laser diode and single mode circular core graded index fiber via a hyperbolic microlens on the fiber tip in absence and presence of any possible transverse and angular misalignments is presented.
Abstract: With an aim to explore the suitable refractive index profile for maximum coupling, we present a theoretical investigation of coupling optics involving a laser diode and single mode circular core graded index fiber via a hyperbolic microlens on the fiber tip in absence and presence of any possible transverse and angular misalignments. By employing Gaussian field distributions for both the source and the fiber and also ABCD matrix for hyperbolic microlens under paraxial approximation, we formulate analytical expressions for the concerned coupling efficiencies. The investigations are performed for two different light-emitting wavelengths of 1.3 and 1.5 μm for such fibers with different profile exponents in refractive index profile. Further, it is observed that out of the studied refractive index profiles, the triangular index profile having the dispersion-shifted merit comes out to be the most suitable profile to couple laser diode to single mode circular core graded index fiber for two wavelengths of practical interest. The analysis should find use in ongoing investigations for optimum launch optics for the design of hyperbolic microlens either directly on the graded index circular core single mode fiber tip or such fiber attached to single mode fiber to achieve a long working distance.
Patent•
13 Sep 2011
TL;DR: In this article, a solid-state light-emitting element with a structure body having a property of transmitting visible light and an uneven structure on each of the top side and the bottom side of the structure body is considered.
Abstract: A solid-state light-emitting element includes a structure body having a property of transmitting visible light and an uneven structure on each of the top side and the bottom side thereof; a high refractive index material layer provided on one surface of the structure body; and a light-emitting body with a refractive index of greater than or equal to 1.6 provided over the high refractive index material layer. One surface of the high refractive index material layer is flatter than the other surface thereof which is in contact with the structure body. The refractive index of the high refractive index material layer is greater than or equal to 1.6. The refractive index of the structure body is greater than 1.0 and less than that of the high refractive index material layer.
TL;DR: In this article, an extensive theoretical treatment of an optical waveguide sensor consisting of thin dielectric film surrounded by an aqueous cladding and an ideal nonabsorbing plasma substrate is presented, where the authors consider the case when the frequency of the guided light is greater than the plasma frequency so that the refractive index of the substrate is less than unity.
Abstract: This paper presents an extensive theoretical treatment of an optical waveguide sensor consisting of thin dielectric film surrounded by an aqueous cladding and an ideal nonabsorbing plasma substrate. We consider the case when the frequency of the guided light is greater than the plasma frequency so that the refractive index of the substrate is less than unity. This structure provides a reverse symmetry configuration in which the refractive index of the substrate is less than that of the cladding. The sensitivity of the effective index of the proposed structure to changes in the refractive index of the aqueous cladding is studied with different parameters of the structure. The results show considerable enhancement of the sensitivity compared to a conventional optical waveguide structure with normal symmetry using a glass substrate. The effect of the plasma substrate on the Goos?H?nchen shift, on the effective index of the structure, and on the power flow in the waveguide structure is investigated.
TL;DR: In this article, the authors studied the intersubband optical absorption coefficients and the refractive index changes in a V-groove quantum wire and used analytical expressions for these properties obtained by the compact-density matrix formalism.
Abstract: In this paper, the intersubband optical absorption coefficients and the refractive index changes are studied in a V-groove quantum wire. We use analytical expressions for these properties obtained by the compact-density matrix formalism. In this regard, the linear, nonlinear and total intersubband absorption coefficients and refractive index changes are investigated as a function of the bend width wire (b), the incident optical intensity (I), and the angle θ. According to the results obtained from the present work, it is deduced that: (i) The linear terms in the refractive index changes and absorption coefficients dose not change with incident optical intensity whereas nonlinear terms depend on incident optical intensity; (ii) The total refractive index changes and the absorption coefficients reduce as the incident optical intensity increases; (iii) The total absorption coefficient and refractive index changes increase and also shift toward higher energies as the bend width wire increases; and (iv) The total refractive index changes and absorption coefficients shift toward higher energies as the angle θ increases.
TL;DR: The calculation results indicate that the index valley surrounding each core works properly for preventing the power coupling from the cladding modes to the propagation modes, and consequently, very low inter-channel crosstalk is realized with W-shaped index profiles.
Abstract: For applications in high-density and high-speed optical interconnections, we propose to utilize polymer parallel optical waveguides (PPOWs) with so-called W-shaped refractive index profile in the core area. A W-shaped index profile is composed of a parabolic index distribution surrounded by a narrow index valley, followed by a cladding with a uniform refractive index. We expect that W-shaped index profiles contribute to decreasing the inter-channel crosstalk due to mode conversion in the waveguides. In this paper, we investigate how much the index difference of the index valley improves the crosstalk value. First, we fabricate polymer waveguides with various index profiles by changing the composition of the copolymer for cladding. We show the results that a 1-m long W-shaped profile PPOW has not only low propagation loss (0.027 dB/cm), but an inter-channel crosstalk (~-40 dB) lower than those of graded index (GI) core PPOW we previously fabricated. Next, we theoretically analyze the propagation loss and inter-channel crosstalk in polymer waveguides with different index profiles by means of a ray tracing model in which the light scattering effect is included. The calculation results indicate that the index valley surrounding each core works properly for preventing the power coupling from the cladding modes to the propagation modes, and consequently, very low inter-channel crosstalk is realized with W-shaped index profiles.
Patent•
21 Jun 2011
TL;DR: In this paper, an optical fiber with a glass core and a glass cladding surrounding and in direct contact with the glass core is shown to have a DGD of less than or equal to about 150 ps/km at a wavelength of 1550 nm.
Abstract: Few moded optical fibers with small delay differences between the propagating modes are disclosed. In one embodiment, an optical fiber includes a glass core and a glass cladding surrounding and in direct contact with the glass core. The glass core may include a radius R 1 from about 8 μm to about 13 μm; a graded refractive index profile with an alpha value between about 1.9 and 2.1 at a wavelength of 1550 nm; and a maximum relative refractive index Δ 1MAX from about 0.6% to about 0.95% relative to the glass cladding. The effective area of the LP01 mode at 1550 nm may be between 80 μm 2 and 105 μm 2 such that the core supports the propagation and transmission of an optical signal with X LP modes at a wavelength of 1550 nm, wherein X is an integer greater than 1 and less than 10. The glass cladding may include a maximum relative refractive index Δ 4MAX such that Δ 1MAX >Δ 4MAX . The optical fiber has DGD of less than or equal to about 150 ps/km at a wavelength of 1550 nm.
Patent•
20 Oct 2011
TL;DR: In this article, the polymeric layer does not increase an effective refractive index of the optical article by greater than 10%. But it does not decrease the number of interconnected voids.
Abstract: An optical article includes an optical element, a low refractive index layer disposed on the optical element having an effective refractive index of 1.3 or less and a polymeric protective layer disposed on the low refractive index layer. The low refractive index layer includes a binder, a plurality of metal oxide particles dispersed in the binder, and a plurality of interconnected voids. The polymeric protective layer does not increase an effective refractive index of the optical article by greater than 10%.
24 Mar 2011
TL;DR: The optimization of length of an optical fiber grating for maximum reflectivity and minimum side lobe strength is presented and the optimized parameters are obtained.
Abstract: This paper presents the optimization of length of an optical fiber grating for maximum reflectivity and minimum side lobe strength. The performance of fiber Bragg grating mainly depends on grating length and change in refractive index. Change in refractive index plays a crucial role in side lobe strength; it increases with increase in change in refractive index. It is mainly due to abrupt change in refractive index at the two edges of the grating. The wavelength chosen for analysis is from the third window to minimize the attenuation. The reflection spectra with different lengths and change in refractive index were analyzed. The simulations are based on solving coupled mode equations by transfer matrix method and the optimized parameters are obtained.
TL;DR: In this paper, transverse techniques for measuring the refractive index profile and spontaneous emission of high-power optical fibers are described, particularly for measuring fiber samples incorporating axial variations, such as mode transformers, gratings, fusion splices, tapers, taps, or couplers.
Abstract: Novel transverse techniques for measuring the refractive index profile and spontaneous emission of high-power optical fibers are described. These techniques are particularly attractive for measuring fiber samples incorporating axial variations, such as mode transformers, gratings, fusion splices, tapers, taps, or couplers. Computerized tomography of spontaneous emission is demonstrated as the first nondestructive method for estimating the spatial distribution of gain in a rare earth-doped fiber, which can be particularly useful when exploiting a spatially inhomogeneous dopant profile.