JP2005181760A - Holding structure for optical element, and optical isolator using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a holding structure for optical elements which can easily be manufactured with a high yield, without causing adhesion of an inorganic adhesive between each optical element, and which can be further miniaturized, as a whole. <P>SOLUTION: The holding structure has a constitution with at least one plate-like polarizer and at least one plate-like Faraday rotator are disposed side-by-side, and both of their end parts are held by a pair of substrates, wherein the main surface of at least one of the substrates has a groove-like recessed part, communicating with the side face, the end parts of the polarizer and the Faraday rotator are held in the recessed parts and fixed by adhesive. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical element holding structure mainly used for optical communication equipment, optical information processing equipment, optical measurement, and the like, and an optical isolator using the same.

  In an optical communication system, light emitted from a semiconductor laser is projected and transmitted to the end face of an optical fiber through a lens, but some light is reflected from the surface of the end face of the lens or optical fiber and returns to the semiconductor laser. turn into. This noise has an adverse effect of destabilizing the operation of the semiconductor laser. Therefore, an optical isolator is used to remove the return light.

  In general, optical isolators are used in optical amplifiers, semiconductor laser devices, and the like. In this optical mechanism component, a relative angle between two polarizers is set to 45 °, and a Faraday rotator having a Faraday rotation angle of about 45 ° is inserted between them and fixed to each other. It has a function of transmitting light and blocking light in the reverse direction. In recent years, there has been a strong demand for miniaturization, mass production, and cost reduction for these optical mechanism components. For example, optical isolators disclosed in Patent Document 1 are actively used and developed as countermeasures. I came.

  FIG. 5 is a perspective view showing a basic configuration of a conventional optical isolator 20. In this optical isolator 20, each optical element is made of an organic adhesive so that the Faraday rotator 22 is arranged between two polarizers 21 in one direction on the same mounting substrate 24 as one arrangement reference. Two magnets 23 that generate a magnetic field to be applied to the Faraday rotator 22 so as to sandwich and fix each optical element in another direction perpendicular to one direction around each optical element on the mounting substrate 24 are bonded and fixed. It has a structure bonded and fixed with an organic adhesive. Here, in the configuration in which the outer shape of each optical element is accurately cut and arranged on the mounting substrate 24, the overall dimensions in the thickness direction of the mounting substrate 24 are reduced, and the overall size and size of the optical element are reduced. In order to achieve cost reduction and high reliability, the shape of the main surface of each optical element is made to be a square, and the interval between the optical elements in the previous period is narrowed.

Of these, a GdBi-based or TbBi-based magnetic garnet thick film is used for the Faraday rotator 22. In such a case, the material of the magnet 23 is usually Sm ₂ Co in order to align the magnetic moment of the magnetic garnet thick film. ₁₇ type or Nd—Fe—B type rare earth magnets are used. While this rare earth magnet has high magnetic properties (residual magnetic flux density, coercive force, etc.), it contains a large amount of rare earth elements, which increases the cost of raw materials and easily oxidizes. Have disadvantages such as being easily deteriorated, being liable to cause scattering of oxide particles, and being difficult to process because the material is hard and brittle. Therefore, when a rare earth magnet is used, there are restrictions on the grinding fluid and immersion time during processing, and in addition, an oxidation resistant coating treatment such as plating is indispensable for mounting on an optical isolator.

Recently, as a material of the magnet 23, a ferrite magnet is used instead of a rare earth magnet. This ferrite magnet is an oxide magnet composed of BaO, SrO and Fe ₂ O _3, and exhibits low magnetic properties when compared with rare earth magnets, but has low raw material costs and extremely high corrosion resistance. And having advantages such as easy processing due to the small crystal grains of the material. Therefore, when a ferrite magnet is used, there are few restrictions on the grinding fluid and immersion time during processing, and no oxidation-resistant coating treatment is required.
JP-A-10-227996

  As described above, according to the present invention, in the case of the above-described existing optical element holding structure and an optical isolator using the same, the overall size in the thickness direction of the mounting substrate is reduced in the manufacturing process, and the entire structure is reduced. In order to achieve miniaturization, cost reduction, and high reliability, the shape of the main surface of each optical element is made square and the distance between each optical element is narrowed. In such a configuration, each optical element is attached. When bonding and fixing to the substrate using an organic adhesive, the organic adhesive may adhere between the optical elements in the previous period, which should not be attached due to surface tension. There is a problem that the yield is deteriorated due to a defective product that blocks the optical path between the optical elements.

  FIG. 6 is a side view of an excerpt of the essential parts shown to explain the problems in manufacturing the optical element holding structure and the optical isolator using the optical element holding structure. Here, when the polarizer 21 and the Faraday rotator 22 are fixed to the mounting substrate 24 using an epoxy resin adhesive 25 as an organic adhesive, the epoxy resin adhesive 25 is rotated by the surface tension. It shows a state of being attached between the children 22. Such an organic adhesive is somewhat distorted at the time of fixing, but when the organic adhesive is sucked by surface tension between the optical elements without escape, it becomes substantially U-shaped as shown in FIG. It becomes easy to form.

  In addition, in the case of the optical element holding structure and the optical isolator using the optical element, the optical element, the magnet, and the mounting substrate basically require three components, and in particular, the optical elements and magnets are arranged. Therefore, there is a problem in that it is difficult to realize further downsizing as a whole because the dimensional area of the mounting substrate for this purpose requires a certain size.

  The present invention has been made in view of such problems, and its technical problem is that it can be easily manufactured with good yield without adhesion of an inorganic adhesive between the optical elements, and further downsizing of the whole is further achieved. It is another object of the present invention to provide an optical mechanism component that can realize low cost and high reliability.

  In order to solve the above problems, the present invention is a structure in which at least one plate-like polarizer and at least one plate-like Faraday rotator are arranged and held at both ends by a pair of substrates, The main surface of one of the substrates has a concave portion with a U-shaped groove communicating with one side surface, and the ends of the polarizer and the Faraday rotator are held in the concave portion and fixed with an adhesive. It is characterized by.

  Furthermore, the present invention is a structure in which at least one plate-like polarizer and at least one plate-like Faraday rotator are arranged side by side and held at both ends by a pair of substrates. The surface has a rectangular recess not communicating with the side, and the end of the polarizer and Faraday rotator is held in the recess and fixed with an adhesive.

  Further, the depth of the groove is 0.05 mm to 0.28 mm.

  Further, the substrate is made of a permanent magnet.

  Further, the present invention is characterized in that an optical isolator is structured using the holding structure of the optical element.

  As described above, according to the optical element holding structure of the present invention and the optical isolator using the optical element holding structure, the existing at least one plate-shaped polarizer and at least one plate-shaped Faraday rotator are arranged side by side. By using a pair of substrates for attaching both ends as opposing substrates, and holding each optical element in a concave portion of the substrate using an inorganic adhesive, the light transmission surface of each optical element has an end surface in the Z-axis direction. As a result, the vertical surface can be positioned with respect to the substrate with the X-axis direction as the side surface. As a result, even when the inorganic adhesive is excessive when producing the holding structure of the optical element, the outflow is prevented by the partition walls of the recesses, or the influence is eliminated because the structure flows into the recesses. In addition, it is possible to realize further miniaturization, cost reduction, and high reliability, and it is possible to easily manufacture with good yield without adhesion of the inorganic adhesive between the optical elements.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. 1 and 3 are perspective views showing a holding structure for an optical element according to an embodiment of the present invention. The optical isolator 10 includes two polarizers 1 with respect to a mounting substrate 3 used as two opposing substrates, and one Faraday rotator 2 disposed between the polarizers 1. A total of three optical elements, each having a light transmission surface as the end surface in the Z-axis direction and a vertical surface A as the side surface in the X-axis direction, combined with the side surface of the substrate 3 and the side surfaces of the optical elements It is constructed by joining and fixing using solder as a.

2 and 4 show cross sections of the joint portion. In the embodiment shown in FIGS. 1 and 2, three groove-shaped recesses 4 having a U-shaped cross section communicating with one side surface are formed on the main surface of the substrate 3, and the end of each optical element is formed in each recess 4. The part is inserted and fixed using an adhesive such as solder 5. As shown in FIG. 2, the recess 4 has widths t ₁ , t ₂ , length H ₀ , and distance l ₁ , a distance l ₀ from the left and right side surfaces in FIG. 2, and a distance from the lower side surface and it has a H _1.

In the example of FIGS. 3 and 4, which is another embodiment, the substrate 3 is formed with a rectangular recess 4 that does not communicate with the side surface. The end of each optical element is inserted into each recess 4, and solder 5 or the like is inserted. It is fixed using an adhesive. As shown in FIG. 4, the recess 4 has widths t ₁ , t ₂ , length H ₀ , and distance l ₁ , a distance l ₀ from the left and right side surfaces in FIG. 2, and a distance from the upper and lower side surfaces. and it has a H _1.

  In any of the embodiments, the substrate 3 itself is preferably made of a permanent magnet such as an Sm-Co magnet.

A Faraday rotator 2 is provided between the two polarizers 1 with a gap size l ₁ , and a GdBi-based or TbBi-based magnetic garnet thick film is conventionally provided on the Faraday rotator 2. in use.

Here, the width t ₁ of the recess 4 that holds the polarizer ₁ is 0.15 mm to 0.25 mm, the width t ₂ of the recess 4 that holds the Faraday rotator ₂ is 0.3 mm to 0.45 mm, and the height H _0. There 0.7mm~1.1mm, _{H 1} is 0.1 mm to 0.5 mm, distance _{l 1} of the recess 4, the distance _{l 0} between the side surface is preferably set to 0.05 mm to 0.2 mm.

  Moreover, it is preferable that the depth of the recessed part 4 shall be 0.05 mm-0.28 mm. By setting it within this range, the solder 5 is not attached between the optical elements 1 and 2 due to surface tension, and as a result, the solder 5 does not block the optical path between the optical elements 1 and 2. It is preferred that the yield be improved.

  In the present invention, as seen in the prior art, the overall size is reduced by having a structure in which each optical element and magnet are not bonded and fixed on a substrate formed of a flat metal material, glass, ceramic or the like. ing.

  That is, in the case of such a configuration, the side surfaces of the optical elements 1 and 2 are attached in the concave portions 4 when the optical element holding structure requiring application of the solder 5 is produced. Since the solder 5 can be prevented from flowing out beyond the partition wall formed between the recess 4 and the adjacent recess 4 (even if the solder 5 is excessive, the partition wall between the recesses 4 prevents outflow). The solder 5 is not adhered between the optical elements, and as a result, the solder 5 becomes a non-defective product that does not block the optical path between the optical elements 1 and 2, and the yield is improved.

As an example of the optical element holding structure of the present invention and an optical isolator using the same, the optical isolator 10 shown in FIGS. Two polarizers 1 and one Faraday rotator 2 are mutually spaced with gap dimensions l ₀ , l ₁ and height H _1, and the widths t ₁ , t of the U-shaped groove 4 at the l ₀ position of the substrate 3. ₂ and height H ₀ were joined.

  Each polarizer 1 has a size of 1 mm × 1 mm × t 0.2 mm, a Faraday rotator 2 has a size of 1 mm × 1 mm × t 0.4 mm, and a substrate (magnet) 3 has a size of 1.39 mm × 1.2 mm × t 0.6 mm. A concave portion 4 is formed at a predetermined position at a depth of 0.25 mm for attaching, bonding, and fixing the side surfaces of the optical elements 1 and 2 with the solder 5.

The gap dimension l ₁ of each of the optical elements 1 and 2 is 0.1 mm, and the gap dimension l ₀ is 0.12 mm. The width t ₁ of each recess 4 is 0.25 mm, the width t ₂ is 0.45 mm, and the height H ₀ is 1.025 mm.

On the other hand, an anti-air reflection film (Al ₂ O ₃ / SiO ₂ ) was applied to each end face of each optical element 1, ₂ . These antireflection films were optimized at a wavelength of 1.55 μm.

  Next, a process of bonding and fixing the optical elements 1 and 2 to the U-shaped groove 4 on the surface of the substrate 3 was performed. First, each U-shaped groove 4 of the substrate 3 was plated with gold so that the solder 5 could be attached. Further, a solder foil (melting point: 280 ° C.) containing 90% gold and 10% tin is placed on each U-shaped groove portion 4 of the substrate 3 where the side surfaces of the optical elements 1 and 2 are fixed. Was melted by heating to 350 ° C. with high frequency heating. When the foil of the solder 5 melts, the high-frequency heating is stopped, and in the process where the temperature of the solder 5 is lowered, the optical elements 1 and 2 are joined and fixed to the U-shaped grooves 4 with the solder 5 melted. Was completed. The length of this optical isolator in the light transmission direction could be 1.10 mm.

  On the other hand, the optical isolator 20 used as a comparative example as shown in FIG. 5 includes these optical elements 21 and 22 and two polarizers 21 in one direction on the same mounting substrate 24 as one arrangement reference. A 45 ° Faraday rotator 22 is provided in between, and it is possible to bond and fix with an epoxy resin adhesive 25. Further, a flat plate made of stainless steel (SUS304) 1.39 mm × 3.2 mm × t0. The dimension is 5 mm. The optical isolator 20 was completed using the optical elements 21 and 22 and the magnet 23 having the same optical elements 1 and 2 and the substrate 3 of the present invention.

The length of the optical isolator 20 in the light transmission direction was 1.22 mm, but this is a dimension for individually bonding and fixing the optical elements 21 and 22 on the substrate 24 without a fixing groove. is there.

  Eleven samples of the optical isolators 10 and 20 of the embodiment of the present invention and the comparative example were produced, and the optical characteristics (forward insertion loss and reverse insertion loss) were measured. The optical characteristics were measured under the conditions of a light wavelength λo of 1550 nm and a laser light output intensity of 0 dBm or 1 mW.

  For the measurement system, measurement was performed using a Hewlett Packard HP8153A optical multimeter as a power meter, a HP81553SM series as a fixed laser light source module, and a HP81531A series as an optical power sensor module.

Table 1 shows the optical property evaluation results of the optical devices of the examples and comparative examples of the present invention under the above measurement conditions.

  Thereby, the average of 11 forward insertion losses of the Example of this invention was 0.10 dB, and the average of backward insertion loss was 45 dB. In addition, the average of 11 forward insertion losses of the comparative example was 0.13 dB, and the average of backward insertion loss was 38 dB. Therefore, it was confirmed that the examples of the present invention had sufficiently better optical characteristics than those of the comparative examples, and those values were also stable.

  As is clear from the above results, when the polarizer and the Faraday rotator are fixed to the mounting substrate using an epoxy resin adhesive as an organic adhesive, the epoxy resin adhesive is rotated by the surface tension. It shows a state of attachment between the children. When the organic adhesive is fixed, some blurring occurs, and when the organic adhesive is sucked by the surface tension between the optical elements without escape, a substantially U-shape as shown in FIG. The shape became easier to form. As a result, the isolation characteristics of the optical mechanism parts were significantly degraded.

  In addition, the value of the reverse insertion loss at which the angular deviation between the polarizer and the Faraday rotator appears remarkably worse than the result of the example, and the values of the individual optical mechanism components also vary widely. This is considered to be because the angle adjustment of the polarizer and the Faraday rotator was shifted by the epoxy resin adhesive.

  Moreover, in the optical mechanism component according to the present invention, it is understood that the optical characteristics are good and stable because the angle adjustment accuracy of the polarizer and the Faraday rotator is ensured.

  Furthermore, since the polarizer and the Faraday rotator are not bonded and fixed on the substrate (stainless steel (SUS304)), it is possible to reduce the size particularly in the light transmission direction.

  As described above, the optical characteristics of long-term stability of the holding structure of the optical element in which each optical element is bonded and fixed to the mounting substrate by the recess are realized.

It is a perspective view which shows the holding structure of the optical element of this invention. It is sectional drawing which shows the holding structure of the optical element of this invention. It is a perspective view which shows the holding structure of the other optical element of this invention. It is sectional drawing which shows the holding structure of the other optical element of this invention. It is a perspective view which shows the conventional optical isolator. It is sectional drawing which shows the conventional optical isolator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 21 Polarizer 2, 22 Faraday rotator 3 Substrate 4 Recessed part 5 Solder 10, 20 Optical isolator 23 Magnet 24 Substrate 25 Epoxy resin adhesive
X side
Z End surface l ₀ Distance between recess and side surface l ₁ Distance between recesses t ₁ , t ₂ Width of recess
H ₀ Distance from substrate side to recess
H ₁ Recess length

Claims (5)

A structure in which at least one plate-like polarizer and at least one plate-like Faraday rotator are arranged side by side and held at both ends by a pair of substrates, and at least one main surface of the substrate has one side surface A holding structure for an optical element, which has a U-shaped groove-shaped concave portion communicating with each other, the ends of the polarizer and the Faraday rotator being held in the concave portion and fixed with an adhesive. A structure in which at least one plate-like polarizer and at least one plate-like Faraday rotator are arranged side by side and held at both ends by a pair of substrates, and communicated with the main surface of at least one of the above-mentioned substrates on the side surface A holding structure for an optical element, which has a rectangular concave portion that is not held, and holds the end portions of the polarizer and the Faraday rotator in the concave portion and is fixed with an adhesive. 3. The optical element holding structure according to claim 1, wherein a depth of the concave portion is 0.05 mm to 0.28 mm. The optical element holding structure according to claim 1, wherein the substrate is made of a permanent magnet. An optical isolator comprising the optical element holding structure according to claim 1.

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