Abstract: A filter module comprising a lens, three optical fibers, an optical filter, and a mirror, wherein the three optical fibers are arranged a single side of the lens.

Abstract: An optical element using one-dimensional photonic crystal according to the invention includes a multilayer film, which is achieved by an element processed into a triangular prism shape. A phase modulation unit is provided so as to be adjacent or abutting to a light input end surface of the optical element. Input light is phase-modulated by the phase modulation unit in the same period and direction as those of photonic crystal so that only specific high-order band light can be propagated through the optical element. When this optical element is formed in an optical waveguide, a small-size spectroscopic device having high resolving power can be provided.

Abstract: An optical element according to the invention uses a thin film-like two-dimensional photonic crystal having a structure of periodic repetition in two directions perpendicular to each other. When the two periodic directions are Y-axis and Z-axis directions, opposite surfaces of the photonic crystal structure perpendicular to the Z-axis direction and parallel to the Y-axis direction are used as a light input surface and a light output surface respectively. The direction of movement of light rays incident onto the light input surface is decided so that it is parallel to the YZ plane and inclined at a predetermined inclination angle to the Z-axis direction.

Abstract: A phase modulation unit is provided in an end surface of one-dimensional photonic crystal to phase-modulate input light in the same period and direction as those of the photonic crystal and propagate only specific high-order band light in the photonic crystal to thereby increase the intensity of output light emerging from a surface of the one-dimensional photonic crystal used as a spectroscopic device, that is, to thereby improve efficiency in use of the input light. In addition, by the function of a structure added to the photonic crystal, the output light is distributed into one or both of opposite sides of the photonic crystal and the intensity of the output light is adjusted.

Abstract: An optical element according to the invention constituted by a multilayer structure having a periodic structural portion as at least one region constituted by repetition of a predetermined period, wherein an end surface of the multilayer structure not parallel to layer surfaces of the multilayer structure is used as a light input surface whereas one or each of opposite surfaces of the multilayer structure parallel to the layer surfaces is used as a light output surface. The periodic structural portion of the multilayer structure can be regarded as a one-dimensional photonic crystal. Refracted light from the one-dimensional photonic crystal has good directivity and the direction of the refracted light has strong dependence on wavelength. When this wavelength dependence property is used, a spectroscopic device or a polarized light separating device of high resolution can be achieved without increase in device size.

Abstract: A method for producing an aspherical structure according to the invention includes the steps of: forming a layer on a surface of a substrate so that the layer exhibits an etching rate distribution in a direction perpendicular to the surface of the substrate; forming a mask having a predetermined opening shape on the surface of the layer; and etching the layer to thereby form at least one aspherical concave portion. When each concave portion is used as a molding tool so that a resin with which the concave portion is filled is solidified and removed from the concave portions an aspherical lens array can be formed accurately.

Abstract: In the invention, light incident onto an end surface of one-dimensional photonic crystal is phase-modulated in the same period and direction as those of the photonic crystal to thereby propagate only specific high-order band light in the photonic crystal. That is, a phase modulation unit for generating phase-modulated wave having the same period as that of the periodic structure is disposed adjacent or close to a light incident surface of the periodic structure.

Abstract: An optical device is provided, which includes optical fibers and rod lenses with their optical axes all being allowed to coincide, particularly, through optimization of the angles of faces of the rod lenses processed to have slopes, wherein the path of a center light ray entering an input fiber is allowed to coincide with the optical axes.

Abstract: Two lenses are used for forming a collimator parallel pair, in which the distance between the two lenses is substantially made coincident with the maximum distance allowing beam waists to be formed at equal distances from the two lenses respectively.

Abstract: In an optical system in which light output from an optical fiber (11) is collimated into parallel light rays by a gradient index rod lens (13), reflected by a filter (4) and then converged again by the rod lens (13) so that the resulting light is coupled to an optical fiber (12), a principal beam component of the light output from the optical fiber (11) disagrees with an optical axis (32) of the optical fiber (12) to thereby cause a coupling loss.

Abstract: An optical module which satisfies a required insertion loss and can be easily assembled with high productivity. The optical module includes first optical fiber, a first lens, an optical device, a second lens, and second optical fiber. The first lens receives an incident light from the first optical fiber and converts the incident light into a parallel light. The optical device receives the parallel light and performs predetermined optical processing on the parallel light. The second lens receives a transmitted parallel light from the optical device and converge the transmitted parallel light to produce an outgoing light. The second optical fiber receives the outgoing light. An optical axis of the first lens and an optical axis of the second lens are substantially coincident with each other. An optical axis of the first optical fiber and an optical axis of the second optical fiber are substantially parallel with each other and substantially parallel to the optical axes of the first and the second lenses.

Abstract: A graded index lens is obtained by treating a raw glass material having a rod shape by ion exchange using silver to form a refractive index distribution in the radial direction of the rod, wherein the raw glass material comprises a glass composition of the following components: 15<Na2O≦30 mol %; 10<Al2O3≦25 mol %; 27.5≦SiO2≦55 mol %; 3≦B2O3≦18 mol %; 2.5≦MgO≦18 mol %; 0≦Ta2O5≦5 mol %; 0≦La2O3≦3 mol %; 0≦BaO≦3 mol %; and 0≦ZrO2≦3 mol %.

Abstract: The invention provides an optical device using two- or three-dimensional photonic crystal having a repeatedly periodic structure in two or three different directions. The photonic crystal in this optical device is processed into a prism structure or a blazed diffraction grating structure.

Abstract: An SiO2-TiO2-Li2O-Na2O-based glass composition containing no lead oxide having incorporated therein specific amounts of specific components which are selected from oxides of the metal elements having an atomic number of 30 (Y) to 73 (Ta) and which hardly cause coloration of glass. The glass composition has a desirable refractive index, hardly undergoes devitrification, and hardly develops cracks on ion exchanging and is suitable as glass for a graded index lens.

Abstract: An optical imaging system is provided that includes a rod lens array and has the optimum refractive index distribution for achieving a high resolving power.

Abstract: In a method of measuring a radial gradient index distribution of a rod lens by calculating higher-order index distribution coefficients indicating the gradient index distribution, (1) the rod lens is processed so that the optic-axial length of the rod lens is approximately equal to P/2 (in which P represents a paraxial period length (pitch)) or approximately equal to an integer multiple of P/2 and so that opposite end surfaces of the rod lens are shaped like parallel planes, (2) a patterned surface is set as an object surface in the proximity of one end surface of the rod lens, and an image surface is formed in the proximity of the other end surface of the rod lens by irradiating the patterned surface with condensed monochromatic light, (3) the positions of paraxial focal points and the curves of curvature of field are obtained by observing the image surface, and

Abstract: In an optical device using an end surface of a periodic multilayer structure as a beam incidence surface or a beam exit surface, a high-resolving-power spectroscopic apparatus can be achieved without increase in size of the apparatus and by use of good directivity of beam leaked from the periodic multilayer structure and strong wavelength dependence of the angle of the leaked beam. Particularly, by disposing layer surfaces of the multilayer structure perpendicularly to a substrate, optical devices suitable for integration of the devices can be formed.

Abstract: A high performance optical imaging system can be provided by minimizing the overlapping degree m, increasing the quantity of light of the rod lens array and improving the resolving power while taking into account the irregularity of the quantity of light when a dislocation between a sensor and an optical axis of an entire rod lens array occurs. In the optical imaging system, a plurality of rod lenses with a refractive index distribution in the radial direction are arranged in two rows in a rod lens array with their optical axes in parallel to each other. This optical imaging system focuses light from a manuscript plane onto an image plane, the planes being arranged on the two sides of the rod lens array. The overlapping degree m defined as the following equation (Eq. 10) is in a range of 0.91≦m≦1.01; m=X0/2R   (Eq. 10) wherein X0 denotes an image radius that the rod lenses project onto the image plane and 2R denotes a distance between the optical axes of neighboring rod lenses.

Abstract: A wavelength monitoring apparatus according to the present invention constituted by: an optical device made of a periodic multilayer structure; a beam source optically connected to at least one end surface of the multilayer structure, the one end surface being not parallel to layer surfaces of the mutilayer structure; and a beam detecting means provided for detecting beam made to exit from at least one surface of the multilayer structure at a specific angle with respect to a specific wavelength, the one surface being parallel to the layer surfaces of the mutilayer structure.

Abstract: A lens function-including optical lens according to the present invention is constituted by: at least one step-index optical fiber; and at least one gradient index optical fiber having an outer diameter equal to that of the step-index optical fiber and having a periodic length exhibiting a lens function, the gradient index optical fiber being joined or attached to an end surface of the step-index optical fiber. The present invention is especially effective in a single mode optical fiber which is typical of the step-index optical fiber. The gradient index optical fiber can be produced by an ion exchange method.