1514 results about "Refractive index profile" patented technology

An apparatus generates femtosecond pulses from laser amplifiers by nonlinear frequency conversion. The implementation of nonlinear frequency-conversion allows the design of highly nonlinear amplifiers at a signal wavelength (SW), while still preserving a high-quality pulse at an approximately frequency-doubled wavelength (FDW). Nonlinear frequency-conversion also allows for limited wavelength tuning of the FDW. As an example, the output from a nonlinear fiber amplifier is frequency-converted. By controlling the polarization state in the nonlinear fiber amplifier and by operating in the soliton-supporting dispersion regime of the host glass, an efficient nonlinear pulse compression for the SW is obtained. The generated pulse width is optimized by utilizing soliton compression in the presence of the Raman-self-frequency shift in the nonlinear fiber amplifier at the SW. High-power pulses are obtained by employing fiber amplifiers with large core-diameters. The efficiency of the nonlinear fiber amplifier is optimized by using a double clad fiber (i.e., a fiber with a double-step refractive index profile) and by pumping light directly into the inner core of this fiber. Periodically poled LiNbO3 (PPLN) is used for efficient conversion of the SW to a FDW. The quality of the pulses at the FDW can further be improved by nonlinear frequency conversion of the compressed and Raman-shifted signal pulses at the SW. The use of Raman-shifting further increases the tuning range at the FDW. For applications in confocal microscopy, a special linear fiber amplifier is used.

Examples of the present invention include a gradient index element formed from a material such as a metamaterial, the material having an index profile and an index gradient profile, where the index profile includes at least one discontinuity and the index gradient profile is substantially continuous.

Systems and methods for measuring the stress profile of ion-exchanged glass are disclosed, based on the TM and TE guided mode spectra of the optical waveguide formed in the ion-exchanged glass. The method includes digitally defining from the TM and TE guided mode spectra positions of intensity extrema, and calculating respective TM and TE effective refractive indices from these positions. The method also includes calculating TM and TE refractive index profiles n_TM(z) and n_TE(z) using either an inverse WKB calculation or a fitting process that employs assumed functions for n_TM(z) and n_TE(z). The method also includes calculating the stress profile S(z)=[n_TM(z)−n_TE(z)]/SOC, where SOC is a stress optic coefficient for the glass substrate. Systems for performing the method are also disclosed.

Disclosed is an optical fiber comprising a center core which forms a passageway for transmitting optical signals and has a refractive index N₁, and a cladding which encloses the center core and has a refractive index N₀. The optical fiber further comprises an upper core, which has a distribution of refractive indices increased starting from a refractive index N₂ (>N₀) at its outer circumference to the refractive index N₁ at its internal circumference, and a minutely depressed refractive index region, which is interposed between said upper core and cladding and has a refractive index N₃. The refractive index N₃ is lower than the refractive index N₀.

A bending-resistant large core diameter high numerical aperture multimode fiber includes a core and a cladding surrounding the core. The core has a radius R1 in a range of 28 to 50 microns, a refractive index profile of a parabola shape with α being in a range of 1.9 to 2.2, and a maximum relative refractive index difference Δ1% max being in a range of 1.9% to 2.5%. The cladding includes an inner cladding and/or a trench cladding, and an outer cladding disposed from the inner to the outer in sequence. The radius R2 of the inner cladding is in a range of 28 to 55 microns, and the relative refractive index difference Δ2% is −0.1% to 0.1%. The radius R3 of the trench cladding is in a range of 28 to 60 microns, and the relative refractive index difference Δ3% is in a range of −0.15% to −0.8%.

Broad band cylindrical lens antenna based on novel artificial electromagnetic materials is formed by arranging a series of novel artificial electromagnetic materials in definite regulation, composing equivalent artificial medium with gradient refractive index. The novel lens antenna includes a cylindrical lens 2 based on novel artificial electromagnetic material 1, feed source 3 used as excitation, reflector 4 for repressing backward radiation. Specific structure 5 of one printed circuit board in the novel artificial electromagnetic material 1 is a series of 'I' shaped units 6 printed on medium substrate arranged according to specific regulation. Regulating size of the 'I' shaped structure to obtain the lens needed refractive index distribution. Selecting suitable and ideal reflector 4 and disposing it back of the feed source 3 for reducing backward radiation generated by the feed source, so as to improve gain and directivity of the antenna. The invention is provided with advantages of high gain, broadband, high directivity, easy manufacture, low cost, light weight and convenient integration.

A transverse closed-loop fiber resonator (10) includes an inner cladding (102) having a surface (300) peripherally forming a closed-loop shape for confining light to the surface (300). The inner cladding has a first diameter thickness (104) and a first index of refraction profile in a cross-sectional portion of the transverse closed-loop fiber resonator (10). A ringed-core (120) corresponding to the closed-loop shape is disposed on the corresponding surface of the inner cladding (102). The ringed-core (120) has a second thickness (124) of material thinner than the first diameter thickness (104), and a second index of refraction profile greater than the first index of the inner cladding by an index delta in the cross-sectional portion of the transverse closed-loop fiber resonator such that the ringed-core can guide light within the ringed-core traversely around the closed-loop shape.

The present wavelength multiplexed optical system includes a multimode optical fiber that transmits wavelength multiplexed optical signals and a plurality of multimode modal dispersion compensation optical fibers. Each modal dispersion compensation optical fiber can transmit one of the multiplex wavelengths, and each modal dispersion compensation optical fiber has an optimized index profile such that the modal dispersion for the transmitted wavelength is approximately inversely equal to the modal dispersion induced in the multimode optical fiber. The wavelength multiplexed optical system facilitates an increased bitrate without reducing bandwidth.

A tunable acoustic gradient index of refraction (TAG) lens and system are provided that permit, in one aspect, dynamic selection of the lens output, including dynamic focusing and imaging. The system may include a TAG lens and at least one of a source and a detector of electromagnetic radiation. A controller may be provided in electrical communication with the lens and at least one of the source and detector and may be configured to provide a driving signal to control the index of refraction and to provide a synchronizing signal to time at least one of the source and the detector relative to the driving signal. Thus, the controller is able to specify that the source irradiates the lens (or detector detects the lens output) when a desired refractive index distribution is present within the lens, e.g. when a desired lens output is present.

A system designs a thin and relatively flat microwave focusing lens that can produce multiple simultaneous beams, using readily-available isotropic dielectric materials, and having a gradient-index (GRIN) profile. The design optimizes the lens to achieve beam scanning and/or multiple beams over a wide field of regard (FOR) with broad bandwidth and a very short focal length compared with conventional lenses. The lens can be used individually or as an element in a more complex antenna having multiple lenses in various orientations that are independently switched, selected and/or excited simultaneously as elements in a phased array. The antenna terminal incorporates such lens into an array of lenses along with one or more feeds to produce single or multiple beams covering a broad field of regard for such applications as satellite communications on-the-move, cellular, broadband point-point or point-multipoint and other terrestrial or satellite communications systems. The lens and array design support multiple simultaneous independently steerable beams as well as null placement for interference cancellation.

A bend-loss tolerant multimode fiber transmission system is provided. The system includes: a transmission fiber having a core and a cladding, and a mode-launching system for selectively exciting only a useful portion of the transmission modes, that portion corresponding to high effective refractive indices relative to a refractive index of the cladding the useful portion corresponding to a substantial number of modes. The mode-launching system may include a lead-in fiber, coupled to the transmission fiber, supporting a number of lead-in modes substantially corresponding to the number of transmission modes in the useful portion. The transmission fiber may have a refractive index profile, within a region of its core that is aligned with the lead-in fiber core, which has a shape that matches a refractive index profile shape in the lead-in fiber core. The transmission fiber core may have a graded refractive index profile that is parabolic or nearly parabolic or truncated.

Optical elements are made using micro-jet printing methods to precisely control the type, position and amount of polymer deposited onto a substrate. In preferred embodiments, the proportions of two or more different polymer compositions are varied over the course of the deposition process to deposit adjoining polymer pixels in the form of a film on the substrate surface. The optical properties of each adjoining polymer pixel can be selected to provide a predetermined optical property, including a specific value of index of refraction. Preferably, the film has a radially non-monotonic refractive index profile and/or an angularly non-monotonic refractive index profile.

An optical device which can be fabricated without any axial alignment by optical measurement and can therefore be produced at a remarkably decreased cost, and which is composed of an optical waveguide part (1) obtained by perpendicularly cutting an optically-transparent polymer film having a glass substrate attached thereto and having a refractive index distribution formed, in a predetermined position measured from the position of the refractive index distribution as a reference, and a holder part (2) for holding the optical waveguide part (1) in a predetermined position, the holder part (2) having a horizontal guide surface (2H) and a vertical guide surface (2V), the optical waveguide part (1) having a glass substrate surface or a polymer film surface coherently attached to the horizontal guide surface (2H) of the holder part (2), and the optical waveguide part (1) having a perpendicularly cut surface coherently attached to the vertical guide surface (2V) of the holder part (2).

An apparatus and method for compensating for mode-profile distortions caused by bending optical fibers having large mode areas. In various embodiments, the invention micro-structures the index of refraction in the core and surrounding areas of the inner cladding from the inner bend radius to the outer bend radius in a manner that compensates for the index changes that are otherwise induced in the index profile by the geometry and/or stresses to the fiber caused by the bending.

An optical fiber that exhibits reduced mode distortions as the fiber is bent is formed by properly defining its refractive index profile during fabrication. The as-fabricated profile is defined as a “pre-distorted” profile that takes into account the gradient introduced by bending the fiber. A parabolic index profile is one exemplary bend-resistant profile that exhibits a quadratic form. A raised-cone index is another profile that may be used as the “as-fabricated” profile. In any properly configured form, factors such as bend loss and mode distortion are significantly reduced, since the profile undergoes a shift of essentially constant gradient as a bend is introduced. The resultant effective area of the inventive fiber is substantially improved over state-of-the-art fiber that is subjected to bending during installation. The as-fabricated profile may be incorporated into various types of fibers (birefringent, photonic bandgap, etc.), and is particularly well-suited for use in a fiber amplifier arrangement.

A method of producing an active optical waveguide having asymmetric polarization, said method comprising the steps of (a) providing an active optical waveguide (10) comprising: (i) a transverse refractive index profile (21) comprising a guiding region (11), an intermediate region (13), and a non-guiding region (12); (ii) a transverse photorefractive dopant profile (31) comprising a constant or graded photorefractive dopant concentration within at least one of the guiding, non-guiding and intermediate regions, except that the photorefractive dopant is not located solely in the guiding region; and (iii) exhibiting in said guiding region, intermediate region, or both, light guiding modes having different polarizations; and (b) exposing at least a part (10a, 10b) of the active optical waveguide to an effective transverse illumination of light (20) reacting with the photorefractive dopant and modifying said transverse refractive index profile; said part of the active optical waveguide being exposed to a fluence selectively suppressing the propagation of the light guiding modes having different polarizations so that the propagation of one mode is less suppressed than the propagation of the other mode(s). Such an active optical waveguide, single polarization mode optical waveguide lasers and multi-wavelength single polarization mode optical waveguide lasers comprising such an active optical waveguide, methods of their production, and their uses in telecommunications, in spectroscopy, in sensors and in absolute calibrated laser light sources.