JP2006251046A - Optical waveguide substrate, optical surface mounting waveguide element, and their manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide substrate and an optical surface mounting waveguide element that cause no deterioration of optical connection efficiency through difference in positional accuracy or refractive index, in an optical path switching technology, and also to provide their manufacturing method. <P>SOLUTION: The manufacturing method of the optical waveguide substrate is characterized in that; by preparing a clad block composed of a clad material on a temporary substrate, coating the entire surface with a core material and removing unnecessary parts, a block is produced comprising the core material and the clad material; that, by further overcoating the clad material, a plurality of reverse U-shaped waveguides are formed in parallel on the temporary substrate, wherein two waveguide vertical parts are faced vertically to the temporary substrate; and that, by forming a mirror, sticking the substrate, and removing the temporary substrate, a plurality of U-shaped optical waveguides with the mirror are arranged in parallel on the substrate. The invention also refers to the optical waveguide substrate and the optical surface mounting waveguide element manufactured by the above method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a structure of an optical surface mount waveguide element for optically coupling arrayed surface light emitting elements and light receiving elements, and a method for manufacturing the same.

  In recent years, with the increase in speed and capacity of information communication equipment, a shortage of capacity of electrical wiring in the apparatus has become a problem. Therefore, studies are underway to replace part of the electrical wiring with optical fibers or optical waveguides. In particular, an array type surface light emitting device or a combination of a light receiving device and an optical waveguide is advantageous for high density and high speed, and is being studied actively. In this case, since the array-type surface light-emitting element or light-receiving element and the optical waveguide are not on the same optical axis, there is an increasing demand for an element and method for coupling them with high efficiency and low cost.

  In response to this requirement, a technique has been studied in which a 45-degree mirror is provided on the end face of the optical waveguide and the light-receiving / emitting element can be coupled by performing a 90-degree optical path change (see, for example, Non-Patent Document 1). However, in this optical path conversion method, a surface emitting laser is installed on the surface of the waveguide several tens of microns away. Therefore, if the 45-degree mirror processing accuracy technique and the waveguide film thickness control are insufficient, the optical signal spreads and is reflected. More light leaks outside the surface. In addition, in order to suppress light leakage to other than the reflective surface, it is possible to reduce the distance between the surface light emitting element and the reflective surface by reducing the thickness of the cladding layer. There is. Furthermore, since there is a clad layer having a low refractive index between the reflective surface and the surface light emitting element, mode conversion cannot be avoided.

As means for solving this problem, inclined surfaces provided on two or more optical fibers having a transmission path structure composed of a core and a clad are joined to each other, and the optical fiber transmission path structure is connected to another optical fiber. A technique has been proposed in which an optical path conversion component characterized by having a micromirror that propagates light to a transmission path structure is embedded in a through hole of an optical waveguide, and an optical signal transmitted through the optical waveguide reaches a photoelectric element ( For example, see Patent Document 1). This conventional optical path conversion technology is used to reduce the light connection efficiency between the light emitting element and the optical waveguide due to the light emitted from the light emitting element into the space and the light emitted from the optical waveguide into the space having a radiation angle. The optical connection efficiency between the optical waveguide and the light receiving element can be prevented from decreasing. Further, the same structure is used both when light is incident on the optical waveguide from the surface light emitting element (photoelectric conversion element) via the micromirror and when light is emitted from the optical waveguide toward the light receiving element (photoelectric conversion element). Thus, optical connection between the photoelectric conversion element and the optical waveguide can be performed. In addition, since the optical path conversion component itself has a transmission path structure that matches the refractive index of the optical waveguide, it has a structure that can eliminate mode conversion.
JP 2004-191903 A Ichimura et al. “Polymer waveguide with 45 ° mirror for optical surface mounting”, Journal of Circuit Packaging Society, 1998 Vol. 13, No2, p. 97-102

  In this conventional optical path conversion technique, it is necessary to manufacture a light conversion component with a micromirror for each photoelectric conversion element, which complicates the manufacturing process and cannot reduce the cost. In addition, it is difficult to process through holes formed in optical printed circuit boards, and the clearance between the through holes and optical conversion components is several tens of μm to minimize optical path deviation in the vertical, horizontal, and depth directions. Therefore, the optical connection efficiency between the optical waveguide and the optical path conversion component is lowered. Furthermore, since the optical path conversion component and the waveguide are separately manufactured, a difference in refractive index occurs, causing a decrease in optical connection efficiency. Further, when the photoelectric conversion elements are arranged, an array type optical path conversion component is required, but it is difficult to accurately manufacture all the core positions and mirror positions, resulting in an increase in cost.

  In the present invention, a clad block made of a clad material is produced on a temporary substrate, a core material is coated on the entire surface, and unnecessary portions are removed to produce a block made of the core material and the clad material. By coating, a plurality of inverted U-shaped waveguides in which two waveguide vertical portions are perpendicular to the temporary substrate are formed in parallel on the temporary substrate, mirror formation, substrate bonding, and temporary substrate removal are performed. A method of manufacturing an optical waveguide substrate, wherein a plurality of U-shaped optical waveguides with mirrors are arranged in parallel on a substrate.

  Further, the optical waveguide substrate is manufactured by the above method.

  Furthermore, after forming electrodes and markers on the above optical waveguide substrate, a plurality of U-shaped optical waveguides with mirrors are arranged in parallel by cutting out in an element shape, and both end faces of the core are arranged in the same plane An optical surface-mounting waveguide element manufacturing method comprising a multi-channel waveguide element and a core end face provided with markers and electrodes that enable surface-emitting elements and light-receiving elements to be passively mounted.

  Further, it is an optical surface mount waveguide device manufactured by the above method.

  According to the present invention, all the cores of the optical waveguide vertical part and the horizontal part are integrally formed, that is, the optical path conversion part and the optical waveguide are integrally formed. Loss due to optical coupling does not occur and propagation loss is low. Further, since the optical characteristics of the waveguide portion and electrode formation can be formed in a substrate shape, an optical surface mount waveguide element is provided at a low cost.

  The point of the present invention is that an optical waveguide substrate in which a plurality of U-shaped optical waveguides with mirrors are arranged on a substrate in parallel on the substrate with lithography accuracy can be manufactured. The optical characteristics of multiple optical surface mount waveguide elements can be evaluated at once on the substrate for what was required to be evaluated for each waveguide element, and electrodes and markers can be formed on the substrate with lithography accuracy. Therefore, it is possible to provide an optical surface mount waveguide element that enables optical coupling of an array type surface light emitting element and a light receiving element with high efficiency at a low cost.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a method for producing an optical waveguide according to the present invention. A clad layer 4 made of a clad material is formed on the temporary substrate 9 and processed to form a clad block 4A (ac). The core material 2 is further coated thereon, and unnecessary portions are removed to produce a block made of the core material and the clad material (d, e). Further, by overcoating the clad material 4B, 2A becomes an inverted U-shaped waveguide (f). Further, this is processed into an inverted V shape, the mirror 3 is formed, the clad material 4C is overcoated, the substrate 1 is bonded, and the temporary substrate 9 is removed to obtain a U-shaped optical waveguide with a mirror (g˜). k). By forming a plurality of clad blocks 4A in parallel in the initial stage, a plurality of U-shaped optical waveguides with mirrors can be formed in parallel.

  FIG. 2 is a diagram for explaining the optical path changing operation of the U-shaped optical waveguide with a mirror according to the present invention.

  FIG. 3 is a perspective view schematically showing an optical waveguide substrate in which a plurality of U-shaped optical waveguides with mirrors are formed in parallel in the present invention. In FIG. 3, since both ends of the core are arranged with the lithography accuracy on the same plane of the optical waveguide substrate, light is inserted from one end of the core on the substrate, and the light intensity emitted from the core at the other end is measured. It is possible to measure the optical insertion loss of a plurality of multi-channel waveguide elements arranged inside. For example, it is possible to measure the optical characteristics of all the waveguides in the substrate at once by using a fiber array that has the number of cores corresponding to the number of cores in the substrate and that matches the core pitch of the optical waveguide substrate. Selection is possible, and the cost of the optical surface-mounted waveguide element can be reduced. Further, since both ends of the core are arranged on the same plane with lithography accuracy, electrodes and markers for mounting the surface light emitting element array and the light receiving element array can be collectively formed with lithography accuracy in the state of the substrate.

The optical waveguide material may be either an inorganic material or a polymer material. In the present invention, a polymer waveguide is preferable, and the difference in refractive index between the core and the clad is 0.3 to 2.0%. The shape of the core constituting the optical waveguide is rectangular, and the size is preferably 5 to 100 μm. The distance between the vertical portions of the waveguide is preferably 5 to 100 μm, and if it is 5 μm or less, the propagation loss of the horizontal portion of the waveguide is adversely affected. Further, the distance between the horizontal portions is not particularly limited as long as a pattern can be formed by lithography.
As the material of the optical waveguide, for example, deuterated methacrylate, epoxy resin, silicone resin, fluorinated polyimide, and the like are preferable, and epoxy resin, silicone resin, and fluorinated polyimide are particularly preferable in view of their solder heat resistance and optical characteristics.

  The waveguide pattern is made by depositing aluminum on the waveguide material, then patterning with lithography technology, and then obtaining the waveguide pattern by reactive ion etching, etc., and imparting photosensitivity to the waveguide material itself A method of directly forming a waveguide pattern by a lithography technique and a method of patterning a resist on a waveguide material by lithography and then using that as an index to create a waveguide pattern can be considered. If it is a method to do, it will not specifically limit.

  Further, the temporary substrate and the substrate material are preferably inorganic materials in order to stably achieve the positional accuracy of lithography, and in particular, silicon, quartz, and general plate glass are preferable because of their workability.

  FIG. 4 is a perspective view schematically showing an optical surface mount waveguide device of the present invention. FIG. 5 is a schematic view of mounting the array type surface light emitting element and the light receiving element on the element shown in FIG. In FIG. 4, the optical surface mount waveguide element is manufactured by embedding four U-shaped cores 2 </ b> A serving as optical paths in a clad. It is formed by the end faces of the core and clad and the mirror surface 3 for optical path conversion. The core end face is formed at the same end, and the pitch is arranged with the accuracy of lithography at the pitch of the surface light emitting element array and the light receiving element array. Further, since the waveguide vertical portion and the waveguide horizontal portion of the core are formed at a time, mode conversion and coupling loss between the waveguides do not occur. Moreover, since the marker 6 for mounting the electric wiring and the array type surface light emitting element and the light receiving element is formed with the positional accuracy of lithography, the surface light emitting element and the light receiving element can be optically coupled with high efficiency only by passive mounting. Achieve.

  It is conceivable that the form shown in FIG. 4 is produced by bonding a plurality of single U-shaped waveguide chips as in the existing technology, but it is very difficult to bond the waveguides with high accuracy, for example, pasting Even if the matching can be carried out, it is necessary to evaluate the optical characteristics of the elements one by one, which increases the cost.

  Hereinafter, an example explains.

A cladding layer was formed on a 4-inch BK7 temporary substrate. Epoxy resin was used for the clad material, and spin coating was used for film formation. The thickness of the clad material implemented is 70 μm. After film formation, a flattening process was performed by grinding, polishing, etc., and a clad block in which a block using a clad material was formed was produced. For the block production, a mask material was formed on the clad material and patterned by photolithography. Al was used as the mask material, and unnecessary portions of the cladding material were removed by O ₂ -RIE. Next, the core layer was formed by spin coating. Epoxy resin was used for the core material. The thickness of the implemented core material is 40 μm from the top of the cladding block. After film formation, planarization was performed by grinding, polishing, or the like. Thereafter, a mask material was formed on the clad material and patterned by photolithography. Al was used for the mask material. Further, unnecessary portions of the clad material were removed by O ₂ -RIE, and a block made of the core material and the clad material was produced. Thereafter, the entire surface of the substrate was filled with a clad material. A spin coat method was used for filling, and a flattening process of grinding and polishing was performed. Thereafter, a V groove was formed with a dicing saw to form a mirror film. The mirror was formed by magnetron sputtering so that an Au film was formed only in the V-groove portion. After forming the mirror surface, the V-groove was filled with a clad layer, and after filling, a flattening process of grinding and polishing was performed. Thereafter, BK7 was attached to the upper surface of the substrate using an epoxy adhesive, and the temporary substrate was removed by polishing to produce an optical waveguide substrate on which a plurality of multichannel waveguides were disposed.

  The produced optical waveguide substrate can measure the optical insertion loss and the like in the state of the substrate, and the result by the butt joint method using the multimode fiber array is 4 ± 1 dB at the measurement wavelength of 850 nm, and has excellent characteristics and distribution in the substrate. I confirmed it was small. In addition, the core position accuracy was all ± 2.5 dB in the substrate, and it was confirmed that there was no problem in practical use.

  Subsequently, electrical wiring and markers were formed by the lift-off method and sputtering. Then, the optical surface mount waveguide element was produced by chip-izing with a dicer. A gold-tin bump was formed on the optical surface mount waveguide substrate using micro punches, and the array type surface light emitting element and the light receiving element were passively mounted and connected to a driver and a receiver by wire bonding. The transmission speed was achieved, and it was proved that the low-cost optical surface waveguide device manufactured by the present invention optically connects the array type surface light emitting device and the light receiving device with high efficiency.

It is a schematic diagram which shows the preparation methods of the optical waveguide board | substrate of this invention. It is a figure explaining optical path changing operation of the optical waveguide of the present invention. It is a perspective view showing typically an optical waveguide board which created a plurality of U-shaped optical waveguides with a mirror in parallel in the present invention. It is a perspective view which shows an optical surface mount waveguide element typically. It is a schematic diagram which mounts an array type surface light emitting element and a light receiving element to the element shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Core layer 2A Waveguide core 3 Mirror 4 Clad layer 4A Clad block 4B Clad layer 4C Clad layer 5 Electrode 6 Marker 7 Array type surface light emitting element 8 Array type light receiving element 9 Temporary substrate 10 V groove

Claims (4)

A clad block made of a clad material is produced on a temporary substrate, a core material is coated on the entire surface, unnecessary portions are removed to produce a block made of a core material and a clad material, and further, the clad material is overcoated. A plurality of inverted U-shaped waveguides whose two waveguide vertical portions are perpendicular to the temporary substrate are formed on the temporary substrate in parallel, mirrors are formed, the substrates are bonded together, and the temporary substrate is removed to provide a plurality of mirrors. A method of manufacturing an optical waveguide substrate, comprising arranging U-shaped optical waveguides in parallel on a substrate. An optical waveguide substrate produced by the method according to claim 1. After forming electrodes and markers on the optical waveguide substrate according to claim 1, a plurality of U-shaped optical waveguides with mirrors are arranged in parallel by cutting out in an element shape, and both end faces of the core are arranged in the same plane A method for producing an optical surface-mounted waveguide element, comprising: a multi-channel waveguide element; and a marker and an electrode that enable passive mounting of a surface light-emitting element and a light-receiving element on a core end surface portion. An optical surface mount waveguide device manufactured by the method according to claim 3.