Abstract: A phase type computer hologram has a plurality of cells for applying a predetermined phase to different portions of a wavefront of light, wherein no phase skip larger than &pgr; is present in the cells. Such a phase type computer hologram can be produced by a process of determining phases for a plurality of cells, respectively, smoothening a distribution of the phases of the cells, by shifting the phase of at least one of the cells by 2&pgr;, and forming, on a substrate, the cells whose phase distribution is smoothened in the smoothening step.

Abstract: Method of fabricating an optical waveguide grating having a plurality of grating lines of refractive index variation including (i) repeatedly exposing a spatially periodic writing light pattern onto a photosensitive optical waveguide; and (ii) moving at least one of the writing light pattern and the waveguide between successive exposures of the writing light pattern, so that each of at least a majority of the grating lines is generated by at least two exposures to different respective regions of the writing pattern.

Abstract: The invention relates to the field of optical fiber wavelength division multiplexed transmission, and more particularly to the field of narrow-band optical filters for dense multiplexing. The invention proposes a narrow-band optical filter with a group-delay response that is very flat in the working band, obtained by cascading two Bragg gratings having group delays that are linear as a function of wavelength in the working band, but with their gradients being of opposite signs. The present solution is easier and less costly to implement than the prior art solutions, and it should also offer higher performance.

Abstract: A grating member comprising a diffraction grating having a periodic structure for converting an incident wavefront at the central area into a prescribed wavefront is provided with a light-shielding member comprising a UV-light absorbing material at the periphery of the grating member in order to reduce excess light and scattered light.

Abstract: A surface pattern comprises microscopically fine relief structures that diffract visible light. When the surface pattern is illuminated perpendicularly with white light, the surface pattern appears with bright and dark regions from a first viewing direction. The length and/or position and/or number of bright and dark regions changes as the viewing angle changes. Preferably, the contour of the surface pattern is selected so that the length or position of the bright regions changes markedly when the viewing angle changes.

Abstract: A multilevel diffractive optical element comprising a base and a plurality of phase zones having phase levels of a substantially identical height h, each phase zone being defined by a local modulation depth d and a local number of phase levels &xgr;=d/h, the local number of phase levels &xgr; per phase zone being a real number, an integer of which defines the number of complete levels in the phase zone, which complete levels have identical widths, and a fraction of which, in at least one phase zone, defines an incomplete level which is narrower than the complete levels, said local number of phase levels &xgr;=&xgr;(x, y) varying among different phase zones so as to provide corresponding variation of said local modulation depth d=d(x, y) whereby local diffraction efficiencies and consequently an overall diffraction efficiency of the optical element is arbitrarily controlled.

Abstract: A device for calculating diffraction efficiencies of a diffraction lens divided into a plurality of regions, each region comprising at least one grating ring, comprises a first memory for storing information about diffraction efficiencies of the regions; a second memory for storing information about weights corresponding to the regions; and a first processor for retrieving information from the first and the second memory, and calculating diffraction efficiencies of the entire diffraction lens using the formula E j = ∑ m = 1 M ⁢ W m ⁢ η mj ( 1 )

Abstract: A surface pattern (1) is composed of elements (2 to 5) which are arranged in a mosaic-like fashion and of which at least one pattern is formed from a background element (4) and a pixel (2) with microscopically fine relief structures diffracting visible light. The surface elements (3) and the element portions (5) either contain the microscopically fine relief structures diffracting visible light or they comprise reflecting or scattering surfaces. Arranged in the pixel (2) is a first diffraction grating B1 and arranged in the background element (4) is a second diffraction grating B2, wherein the first diffraction grating B1 and the second diffraction grating B2 are a superimposition of at least two different, microscopically fine relief structures F1 and F2 diffracting visible light. The first diffraction grating B1 and the second diffraction grating B2 differ only by virtue of a relative phase shift &Dgr;&phgr; between the relief structure F1 and the relief structure F2.

Abstract: A waveguide that is operative to produce a reflected optical signal having a spectral profile corresponding to a product of a spectral profile of an input optical signal and a predetermined complex-valued spectral filtering function wherein the waveguide includes a plurality of spatially distinct subgratings each possessing a periodic array of diffraction elements. The subgratings are situated and configured based on the predetermined complex-valued spectral filtering function.

Abstract: An optical beam shaper for production of a uniform sheet of light for use in a parts inspection system having a light source including a coherent light generator, a diffractive beam shaper, and lens elements.

Abstract: Diffraction optical element used in a scanning optical apparatus as a scanning optical element has a diffraction grating formed on a substrate. The diffraction grating has a tilt portion for generating a power and a wall portion connecting one end portion of the tilt portion to the substrate. The wall portion is tilted within a predetermined range with respect to a normal of the substrate surface. The tilt angle of the wall portion of the diffraction grating with respect to the normal of the substrate continuously changes to increase as a distance away from an optical axis of the diffraction optical element becomes large.

Abstract: Diffraction optical element used in a scanning optical apparatus as a scanning optical element has a diffraction grating formed on a substrate. The diffraction grating has a tilt portion for generating a power and a wall portion connecting one end portion of the tilt portion to the substrate. The wall portion is tilted within a predetermined range with respect to a normal of the substrate surface. The tilt angle of the wall portion of the diffraction grating with respect to the normal of the substrate continuously changes to increase as a distance away from an optical axis of the diffraction optical element becomes large.

Abstract: A multilevel diffractive optical element comprising a base and a plurality of phase zones having phase levels of a substantially identical height h, each phase zone being defined by a local modulation depth d and a local number of phase levels &xgr;=d/h, the local number of phase levels &xgr; per phase zone being a real number, an integer of which defines the number of complete levels in the phase zone, which complete levels have identical widths, and a fraction of which, in at least one phase zone, defines an incomplete level which is narrower than the complete levels, said local number of phase levels &xgr;=&xgr;(x, y) varying among different phase zones so as to provide corresponding variation of said local modulation depth d=d(x, y) whereby local diffraction efficiencies and consequently an overall diffraction efficiency of the optical element is arbitrarily controlled.

Abstract: The present invention entails a volume grating for use as an optical coupler and method for creating the same which comprises a predetermined surface grating pattern having a decreasing surface grating period along a waveguide light propagation direction in the volume grating with a plurality of slanted grating fringes having a variable slant angle along the waveguide light propagation direction to focus coupled light in a first dimension with a predetermined light intensity profile along a grating-cover interface plane of the volume grating. In addition, the predetermined surface grating pattern further includes an increasing radius of curvature along the waveguide light propagation direction to focus the light in a second dimension. The present invention further comprises a system and method for designing the volume grating, as well as a system and method for designing an apparatus for fabricating the volume grating.

Abstract: Method for the preparation of holographic diffusers where the holographic diffuser is designed through iterative calculations according to the Fraunhofer theory of diffraction and some constrain conditions. In the iterative calculation some constrain conditions that can change the magnitude of the light passing through the diffuser are used to design the diffuser. A novel iterative calculation is disclosed such that uniformed mixing of colors and high light utilization efficiency of the diffuser may be provided.

Abstract: A multilevel diffractive optical element comprising a base and a plurality of phase zones having phase levels of a substantially identical height h, each phase zone being defined by a local modulation depth d and a local number of phase levels &xgr;=d/h, the local number of phase levels &xgr; per phase zone being a real number, an integer of which defines the number of complete levels in the phase zone, which complete levels have identical widths, and a fraction of which, in at least one phase zone, defines an incomplete level which is narrower than the complete levels, said local number of phase levels &xgr;=&xgr;(x, y) varying among different phase zones so as to provide corresponding variation of said local modulation depth d=d(x, y) whereby local diffraction efficiencies and consequently an overall diffraction efficiency of the optical element is arbitrarily controlled.

Abstract: The invention concerns a structure arrangement that includes surface regions having one or more structures having an optical-diffraction effect, in particular for visually identifiable, optical security elements for value-bearing documents, for example banknotes, credit cards, passes or check documents, or other items to be safeguarded; in order to make it more difficult to forge and in particular copy such a structure arrangement it is proposed in accordance with the invention that the structure arrangement is such that for the production of given items of optical information in given viewing directions in one or more of the surface regions (8, 30) of the structure arrangement there are provided sub-regions (10, 12, 14, 32, 34) with a structure (16, 18, 20; 36, 38) that is identical except for the structural parameter of optical depth and that the optical depth of the structure (16, 20; 36) is constant over the extent of a sub-region (10, 14; 32) but is different from the optical depth of the structure (18;

Abstract: Spatial light modulators (SLMs) can be amplitude-only modulated, phase-only modulated, or the pixel amplitudes can even be a function of phase. However, practical devices providing independently controllable values of phase and amplitude are not expected for some time. It has been possible to design modulation patterns for these limited range SLMs that do produce diffraction patterns similar to those possible from full complex SLMs, but hours of intensive iterative optimization usually have been required. Our approach instead develops and evaluates direct, pixel-by-pixel encoding algorithms that map the limited range modulation properties onto the entire complex plane. The advantage of these algorithms (generally recognized by the name pseudo random encoding) over iterative optimization is that designs can be performed in real-time making systems adaptable to rapidly changing situations.

Abstract: A diffractor for electromagnetic radiation with a spherical stepped geometry constructed under the constant step width conditions (here defined as pseudo-spherical geometry). The diffractor consists of a plurality of spherically curved dispersive elements (oriented monocrystals, crystal surfaces or gratings) that are located on a focal circle. The location on the focal circle of each element is made to guarantee the same Bragg angle for the incident radiation. Thus a diffractor is an array of diffracting elements (“steps”) each one contributing to the total solid angle of the diffractor, that increase the spectral output of the device without decreasing the resolution. Because the steps are spherically curved, they are curved also in the direction perpendicular to the focal circle in order to satisfy Bragg's law for diffraction over a maximum area of the diffractor.

Abstract: A multibeam scanning exposure device includes a light source for emitting a light beam, a multiple beam splitting element that is provided with a diffractive grating for dividing the light beam from the light source into a plurality of beams, a deflector for deflecting exit beams from the multiple beam splitting element, and a scanning lens for converging the deflected beams onto the photosensitive medium to form a plurality of scanning beam spots. The diffractive grating has a corrugated surface having a plurality of periodical patterns arranged in parallel at a predetermined fixed pitch. Since the incident light beam in the multiple beam splitting element from the light source is divided into a plurality of beams at once, there are no influence of the assembling error and therefore the arrangement of the beam spots on the photosensitive medium can be controlled accurately.

Abstract: An optical grating includes a sequence of grating lines, the sequence being such that each grating line is centered on a position which is an integer multiple of a line spacing distance from a datum position on the grating, the sequence of grating lines is non-periodic and the sequence of the grating lines is formed from N concatenated sub-sequences. Each sub-sequence includes a series of one or more instances of a respective grating line pattern. Such an optical grating has a structure that is more amenable to calculation of the grating lines necessary to achieve a desired characteristic. A method of calculating and fabricating such a grating is also disclosed.

Abstract: An apparatus for redirecting physical energy includes a substrate defining a first boundary of a region, a first electrode defining a second boundary of the region, the second boundary disposed opposite to the first boundary, a second electrode adjacent to the first boundary for cooperating with the first electrode to apply a non-uniform electric field to the region, the non-uniform electric field having electrical field intensities simultaneously including a first electric field intensity and a second electric field intensity, and a layer of material disposed in the region, the layer having a variable index of refraction responsive to the electric field intensities of the non-uniform electric field, the variable index of refraction including a first index of refraction in response to the first electric field intensity and a second index of refraction in response to the second electric field intensity.

Abstract: A diffractive collector for an optical scanner includes a wedged-shaped substrate having holographic grating provided on a front surface, a conical-shaped back surface, and at least one detector. Substantially parallel light is made incident upon the front surface of the substrate, and the light is diffracted within the substrate to the back surface. The wedged shaped of the collector and the holographic grating cause the light to reflect back within the substrate at such an angle that the light remains within the substrate as the light propagates to the at least one detector.

Abstract: An optically variable surface pattern includes at least one graphic representation producing an achromatic impression when viewed in visible light over a certain angular range without noticeable color fringes occurring in the adjoining angular ranges. A plane surface portion includes a grating structure which disperses incident light with comparable intensity into a cone within a predetermined angle range regardless of differing wavelength. An overlap of several successive high orders of diffraction results in a recombination of the dispersed light to white light at any diffraction angle within the cone. The surface portion viewed from a direction within the cone reflects white light, in contrast to a simple flat mirror which has a very narrow range of specular reflection. At viewing angles outside the cone, the surface portion is dim or dark grey. The shape of the surface portion is then recognized as an area white lit or dark depending upon a particular viewing angle relative to incident light.

Abstract: An optical arrangement comprising a plurality of cells arranged in a two-dimensional array on, into, or partly into an optical medium, each said cell having a pattern structure comprising a number of grooves which are parallel to each other and which form a grating. The grating of each cells forms at least two sections which are displaced in relation to each other by a predetermined distance in a direction which is essentially perpendicular to the longitudinal direction of the grooves. The grooves of two or more adjacent cells are unaligned with one another for controlling the phase or amplitude of one or more incident optical waves when the cells receive the incident optical waves.

Abstract: An optical viewfinder system comprising two optical elements, and a field stop or a reticle, to provide an image of a scene to a viewer, and further comprising a diffractive optical element to provide a clear, stationary image of the field stop or reticle to the viewer.

Abstract: An encoder has the capability of outputting a stable displacement signal with small distortion. The encoder includes a first scale and a second scale. The first or second scale has a scale pattern in which pattern elements are arranged in such a manner that the spacings between adjacent pattern elements are not constant but vary in phase relative to the reference phase of a reference pattern element by amounts of P/(2.multidot.L), P/(2.multidot.m), P/(2.multidot.n), P/(2.multidot.o), . . . (L, m, n, o, . . . are positive integers, P is the mean pattern period) and by amounts of combinations of sums of these values.

Abstract: A diffractive homogenizer is provided for receiving a beam of laser energy and producing a desired illumination pattern in a target plane. The homogenizer is made up of a plurality of diffractive sub-elements, each of which contributes to all or a portion of the desired image. By combining the contributions of many sub-elements to form the final image, a homogenizing effect is realized. In preferred embodiments, the sub-elements are designed to compensate for the finite spatial coherence of the incident laser beam and to control the numerical aperture distribution of the transmitted light. Each sub-element is composed of a large number of discrete pixels, each of which alters the phase of radiation passing therethrough by a selected amount. The pixel arrangement is chosen, using computer modeling and optimization techniques, such that the interference pattern created by the collective pixels in a sub-element makes up the desired image (or a portion thereof).

Abstract: The invention relates to a semiconductor optical reflector serving in particular for being disposed facing an integrated laser cavity so as to feed light back into said cavity, and enable it to oscillate continuously. The reflector is made up of a plurality of cascaded Bragg reflector sections. More particularly, said sections are of the same length L and have the same coupling coefficient, and the length L of each pair of sections is given by the following relationship:L=.lambda..sup.2 /[(n.sub.i+1 +n.sub.i).times.1.7(n.sub.i+1 .LAMBDA..sub.i+1 -n.sub.i .LAMBDA..sub.i)]where .lambda. is the mean value of the Bragg wavelengths reflected by the reflector;n.sub.i+1 and n.sub.i are the respective effective refractive indices of said adjacent sections; and.LAMBDA..sub.i+1 and .LAMBDA..sub.i are the respective periods of said adjacent sections.The reflector of the invention has a wide spectrum band independent of the value of the coupling coefficient.

Abstract: Method for the preparation of diffractive lens with one single etching step and using one single etching mask. While the widths and intervals of the masked areas of the photo masks are decided under a geometric relation, an etching mask can be prepared on the substrate of the lens where the widths and the intervals of the masked areas can be determined. As the included angle between the etching mask and the plan of the material of the lens is in a certain ratio to the etching efficiency of the etchant to the substrate of the lens, a one step etching process can be developed whereby multilevel diffractive lens with required number, widths and heights of the levels can be obtained. This invention also provides an oxidation-isotropic etching process on the diffractive lens so prepared.

Abstract: The optical head has a light source, a collimating lens, an aperture-limiting element and an objective lens in the mentioned order in the direction of progress of light emitted from the light source, and a photo-detecting system for detecting return light having been transmitted through the objective lens and reflected by an optical disk. The aperture-limiting element includes a plurality of stripe transparent electrodes spaced apart at a predetermined interval on an electro-optical crystal substrate, and a substantially circular non-electrode area lacking the stripe transparent electrodes at a center portion of the substrate. The aperture-limiting element can be constructed with a reduced number of components as compared with the prior art construction.

Abstract: A photographic optical system using a DOE in which color flare is inconspicuous. The photographic optical system has at least one diffractive optical element. Assuming that a wavelength at which the diffraction efficiency of the diffractive optical element reaches a maximum is defined as a design wavelength .lambda..sub.DOE, it satisfies the following condition:0<E.sub.1 (.lambda..sub.DOE)+E.sub.3 (.lambda..sub.DOE)<0.2where E.sub.1 (.lambda..sub.DOE) is the amount of color flare received by a blue photosensitive layer or a blue light-receiving element, and E.sub.3 (.lambda..sub.DOE) is the amount of color flare received by a red photosensitive layer or a red light-receiving element.

Abstract: A diffractive optical element for diffracting non-collimated light includes a base surface and a periodic structure formed on the base surface and having a plurality of diffractive surfaces and a plurality of boundary surfaces. The boundary surfaces are separated into plural zones, and in each zone, the boundary surface is placed substantially parallel to a main portion of a light beam impinging on that zone.

Abstract: A soft aperture allows gradual attenuation of a light beam dependent upon its location away from the center of a diffractive optical element. Such an optical element may be provided by decreasing a number of phase levels, increasing a number of phase levels, increasing a density of metal patches or diffractive gratings, or decreasing a blaze height and/or duty cycle, all radially from the center. Alternatively, the soft aperture may be defined by a photolithographic process. Such a soft aperture is particularly useful in aiding circularizing of an elliptical light beam. The soft aperture may be used alone or integrated with other optical elements.

Abstract: An optical system has a diffractive optical element. A diffractive optical surface of the optical element has a blaze-shaped diffraction grating. The grating heights are smaller in the peripheral region of the grating than in the central region of the grating around its optical axis. The optical element acts as a lenses a result of light rays being deflected by the light-diffracting action of the diffractive optical surface.

Abstract: The invention provides a diffraction grating lens suitable for use as an objective lens for an optical disk recording/reproducing apparatus. This lens includes a light transmissive substrate of which a refractive index is larger than 1, having one plane and the other plane, and a diffraction grating pattern having a lens effect and constituted by a plurality of diffraction gratings formed on one plane of the light transmissive substrate. The diffraction grating pattern is for focusing an incident light beam flux at a focal point provided on a side of the other plane of the light transmissive substrate and is formed so that a numerical aperture, calculated with the focal point as a peak point, becomes larger than 1.

Abstract: A kinoform optical element (KOE) has different surface relief heights in different zones of the kinoform surface, in order to optimize the first order diffraction efficiency in each zone. By increasing the first order diffraction efficiency, noise as well as ghost image problems may be reduced and contrast and resolution may be enhanced. In an exemplary embodiment, each zone, or even different areas of the same zone, has a non-constant step height that is preferably defined by a predetermined relationship between an optimal step height and an associated predominant angle of incidence associated with that particular zone or area. In the case of an optical system having a relatively large aperture and a relatively narrow field of view, each point of the KOE sees the entire image; the associated predominant angle of incidence at that point may be defined by a so-called "marginal" ray from the center of the entire image space (i.e., on the optical axis and at the effective "middle" of the usable depth of field).

Abstract: A high-resolution light-beam scanning apparatus utilizing only mass-producible holograms instead of utilizing auxiliary optical systems, and capable of compensating for disadvantages.

Abstract: A waveguide input/output device for input and output of laser light L into a thin-film waveguide 2 via an input grating or prism 7 and an output or emission grating 8. The height of the emission grating 8 is gradually increased in a travel direction of a light advancing through the waveguide and either the height of the input grating 7 or the height of the output grating 8 is gradually increased in the direction of propagation of the service elastic waves in the waveguide 3 generated by a transducer element 3.

Abstract: In a grating structure for use in a Fourier spectrometer with a series of raised and recessed surfaces of optical quality, a plurality of binary lamellar gratings are provided which have distinct height differences and are arranged on different surface areas to provide a suitable diffractive-optical element.

Abstract: A device for linear beam steering, where a translation of one grating respective the other one results in an increased angular deviation of the light beam. The device includes at least one pair of gratings with parallel lines, different from each other, and each according to a different mathematical formula, spaced at a certain distance parallel one below the other, the spacing of lines in each of the gratings increases from one edge to the other. There can be provided a plurality of such "facets" of gratings arranged one after the other. The double design is compact, inexpensive and essentially aberration free, it has many applications such as scanners for laser range finders, dynamic aiming systems, laser printers and plotters, and many more.

Abstract: An apparatus and method for simultaneous chirp adjustment and frequency conversion of an ultra-short input optical pulse A.sub.1 characterized by a center angular frequency .omega..sub.1,0 in a non-linear optical material with a quasi-phasematching (QPM) grating exhibiting an aperiodic pattern of regions D.sub.j constituting a grating. Passing the ultra-short input optical pulse A.sub.1 through the grating gives rise to a chirp-adjusted and frequency-converted output optical pulse A.sub.2. In the preferred embodiment the non-linear optical material is a Second Harmonic Generator (SHG) such that the output optical pulse A.sub.2 generated from the input optical pulse A.sub.1 is a chirp-adjusted second harmonic of said ultra-short input optical pulse A.sub.1. In the general case the method and apparatus use a transfer function D(.OMEGA.) derived from the equation:A.sub.2 (.OMEGA.)=D(.OMEGA.).multidot.A.sub.1.sup.2 (.OMEGA.),where A.sub.1.sup.2 (.OMEGA.

Abstract: A smooth contoured structure is formed from a planar surface by etching mesas of equal height into the surface and heat treating the structure to mass transport material above the desired contour to fill in voids below the desired contour. In an alternate embodiment, an optical element is formed using a patterned layer of sacrificial material and thermally treating the sacrificial layer to form a precursor contour line. The line is then transformed onto a substrate and smoothed to form the optical element.

Abstract: A tri-focal diffractive lens defining three foci, for viewing a band of light having a representative wavelength of .lambda., including a diffractive surface having a number of optical heights, h.sub.o, wherein the difference between the highest and the lowest optical heights is, modulo .lambda., substantially different from .lambda./2, wherein each of the foci receives at least 20% of light incident on the lens.

Abstract: A scale and encoder are capable of stably outputting a displacement signal with less distortion. The scale has grating pattern lines arranged successively, and the widths of the pattern lines of a second scale are not P/2 but are determined to remove high-order distortion components on the grating pattern. For example, for removing the third and fifth order distortion components, the scale is made to include two slits in which pattern line widths are 17P/30 and 23P/30.

Abstract: A diffractive optical element, ("DOE"), and particularly a diffractive lens having annular zones about an optical axis and known as a Fresnel zone plate or kinoform lens, is athermalized so that its effective focal length ("EFL") does not shift substantially with temperature over a temperature range by, respectively, increasing and decreasing the zone widths with respect to widths which are optimized to focus at the EFL at room temperature. Half of the zones (alternate, adjacent zones) provide the correct EFL for the expanded condition of the lens at the hot end of the temperature range; the other half of the zones provide correct EFL for the contracted condition of the lens at the cold end of the temperature range.

Abstract: A diffractive optical device includes a substrate for allowing transmission therethrough of light to be diffracted; and a grating section located on the substrate and including a plurality of grating elements each having multiple discrete phase levels. The plurality of grating elements are arranged at different grating periods in different areas of a surface of the substrate and have the phase levels in different numbers in accordance with the grating period.

Abstract: An optical system for use in a relatively wide wavelength range including a plurality of diffractive optical elements whose diffraction efficiencies are optimized for different wavelengths within said predetermined wavelength range. A diffractive optical element for use in a wide wavelength range includes a light transmissive substrate having a plurality of surface regions and a plurality of surface relief diffractive gratings are formed in said surface regions such that diffraction efficiencies of these gratings are optimized for different wavelengths within said predetermined wavelength range. A diffractive optical element is formed by a single optical element having a light transmissive substrate which reveals a given spectral transmittance and a surface relief diffractive grating formed in a surface of said substrate such that a wavelength dependency of said grating provides a desired spectral transmittance together with said spectral transmittance of the substrate.

Abstract: A focus detecting optical system for detecting a focus condition of an image of an object to be picked-up by an image forming lens including a condenser lens arranged in a vicinity of a predetermined focal plane of the image forming lens, aperture stop having a plurality of apertures, a plurality of image reforming lenses and a plurality of light receiving element arrays. At least one diffractive optical element having a lens function due to a diffraction is provided on a surface of the condenser lens or image reforming lenses. The diffractive optical element may be formed by kinoform or binary optical element having a step-wise configuration. The diffractive optical element may be formed in a surface of an infrared cut filter.

Abstract: An improved Bragg grating for an optical waveguide comprising a core and a cladding. The grating includes refractive index perturbations formed within the waveguide. It has a bandwidth in reflection having a full width at half-maximum greater than 12 nm, a total intrinsic optical loss less than 0.2 dB, and a total peak optical extinction, measured in transmission, greater than 20 dB.