JPH1114940A - Optical isolator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical isolator which has high yield at the time of cutting. SOLUTION: A proplarizing element of double refraction element and a Faraday rotator have their optical surfaces adhered together with an adhesive which has rubber elasticity at least 10 to 40 deg.C, the adhesion element is cut into chip type adhesion type optical elements having optical surfaces of =<2 mm<2> in area, and those elements are put in a magnetic field to obtain the optical isolator. When the adhesion layer is 10 to 10 μm thick, damage such as the peeling of the adhesion boundary surface is hardly caused even by cutting the adhesion element obtained by adhering the optical surfaces of the polarizing element or birefringent element and Faradary rotator across the rubber elasticity type adhesive of adhesion strength having rubber elasticity almost at room temperature, thereby improving the cutting yield of the stuck type isolator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical isolator capable of obtaining a high yield at the time of cutting in the manufacture of an optical isolator.

[0002]

2. Description of the Related Art In recent years,
With an increase in the amount of information communication, not only a backbone communication network but also an ordinary communication line and an optical cable such as a cable broadcast such as a CATV have been developed. The amount of information on these branch lines is smaller than that of the trunk lines, and it is not easy to recover the investment associated with the use of optical cables. Therefore, efforts are being made to reduce the costs associated with the use of optical cables.

An optical isolator is used to prevent light sent from a laser oscillator from returning to the laser oscillator again, and it is also required to reduce the cost.

However, optical elements used in optical isolators are often expensive members such as oxide single crystals, and the precision in combining the elements must be strictly controlled. The cost of a member such as a holder for holding and fixing the device hinders cost reduction.

[0005] As a means of reducing costs associated with assembly, there is known a method in which optical elements are laminated and bonded in advance and then cut into required dimensions.

FIG. 1 shows a manufacturing flow of such an adhesive type isolator, wherein 1 and 2 denote a polarizing element or a birefringent element, respectively, and 3 denotes a Faraday rotator. The parts 1 and 2 and the Faraday rotator 3 are bonded with an adhesive. Then, the element 4 having a large size as shown in FIG. 1A is cut into a required size to obtain an adhesive element chip 5 as shown in FIG. 1B, which is shown in FIG. 1 (D) is obtained by combining the magnet 6 and the metal holder 7 as shown in FIG.

The inventor of the present invention has made it clear that a resin having rubber elasticity (entropic elasticity) in an operating temperature range of an isolator is effective for forming an isolator excellent in thermal shock as an adhesive used here. This is shown in Japanese Patent Application No. 8-200888. Further, the above adhesive is suitable for obtaining an isolator having an excellent extinction ratio because a large stress is not applied to the optical element. However, since the bonding strength is smaller than that of an adhesive having energy elasticity, when cutting into a desired size after bonding, the bonding interface is easily damaged, which causes a reduction in yield.

[0008] The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide an optical isolator that can obtain a high yield at the time of cutting.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a polarizing or birefringent element and an Faraday rotator having a rubber elasticity at least at 10 to 40 ° C. Glue the optical surfaces together through
This adhesive element is cut to form a chip-type adhesive optical element having an optical surface area of 2 mm ² or less, and an optical isolator obtained by arranging the chip in a magnetic field. An optical isolator having a thickness of 10 to 100 μm is provided.

That is, as described above, when an adhesive having rubber elasticity (entropic elasticity) is used, an adhesive isolator excellent in thermal shock resistance and optical characteristics can be obtained. Is easy to occur. This tendency becomes more pronounced as the cutting size is smaller. In this case, with a normal adhesive, the thinner the adhesive layer, the stronger the adhesive strength. However, when an adhesive having rubber elasticity is used, it is considered that even if the adhesive layer is made thin, the adhesive interface cannot withstand the impact applied from the blade at the time of cutting, and a part or all of the adhesive layer is peeled off. Was.

In order to solve this problem, the relationship between the thickness of the adhesive layer and the cutting yield was examined, and it was found that the cutting yield was improved in a region where the adhesive layer had a certain thickness. The area is 10 to 100 μm, particularly 1 μm.
It has been found that in the range of 5 to 50 μm, a cutting yield exceeding 95% (a yield relating to peeling of the adhesive layer) can be obtained.

It is considered that the relationship between the thickness of the adhesive and the cutting yield appears by the following mechanism. That is, when the adhesive layer is thin, the impact applied from the blade at the time of cutting is concentrated on the adhesive interface without being reduced by the adhesive layer, and as a result, the adhesive interface is broken. When the adhesive layer becomes thick to some extent, the impact at the time of cutting is dispersed and alleviated throughout the adhesive layer, so that the influence on the adhesive interface is reduced and destruction of the adhesive interface is avoided. Further, when the thickness of the adhesive layer is increased, peeling at the time of cutting occurs again frequently because the adhesive force itself is reduced.

Hereinafter, the present invention will be described in more detail. The optical isolator of the present invention is an isolator having a structure in which a polarizing element or a birefringent element and a Faraday rotator are bonded to each other through an adhesive having rubber elasticity at around room temperature, and optical surfaces are bonded to each other.
The thickness of the adhesive is 10 to 100 μm.

Here, as the polarizing element, the birefringent element and the Faraday rotator, a material known as an optical isolator is used.

The adhesive may be used at around room temperature, ie, 1
There is no particular limitation as long as it has rubber elasticity at 0 to 40 ° C, but it is preferable that the resin has rubber elasticity in the operating temperature range of the isolator, and a resin having a glass transition point of -40 ° C or less is preferable. Examples of the resin corresponding to this property include a silicone resin, an epoxy resin, and a (meth) acrylic resin. Among the above resins, silicone resins have rubber elasticity in a wide temperature range and have excellent environmental resistance. Use of a fluorine-modified resin is also effective for improving heat resistance.

Here, in the present invention, the adhesive is applied with the thickness of the adhesive being 10 to 100 μm, and the object of the present invention cannot be achieved outside this range.

In the present invention, after a polarizing element or a birefringent element having a large size, preferably 2 mm × 2 mm to 100 mm × 100 mm, particularly 7 mm × 7 mm to 20 mm × 20 mm, and a Faraday rotator are bonded with the above-mentioned adhesive. , which 2 mm ² or less, and effective particularly when cut into 1 mm ² or less, 10 to 100 [mu] m thickness of the adhesive
By cutting, even when cut into an adhesive element chip having an optical surface area of ² mm
Damage such as peeling of the adhesive interface is unlikely to occur, and the cutting yield is improved.

The chip thus cut is then placed in a magnetic field, for example, inserted into a cylindrical magnet 6 as shown in FIG. 1 (C) to constitute an optical isolator.

[0019]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples and Comparative Examples] As a polarizing glass, a polarizing glass having a polarizer core of 1.3 μm and a size of 15 × 15 mm with an anti-reflection film for air and an anti-reflection film for adhesive was used. As the Faraday rotator, bismuth-substituted rare earth iron garnet (θf = 45 ° at 1.31 μm)
m) A 15 × 15 mm coated anti-reflection film on both sides was used. As the adhesive, a silicone two-component thermosetting resin was used. This adhesive has a glass transition point of −45 ° C. and exhibits rubber elasticity in a range of −45 ° C. to 250 ° C.

The bonding procedure of each optical element was performed as follows. First, the first anti-reflection film surface of the first polarizing glass and the Faraday rotator (FR) were temporarily bonded (thermosetting conditions: 150 ° C., 10 minutes, in the air) with the above-mentioned adhesive to obtain the first polarizing glass / FR. An adhesive element was made. Next, an adhesive was dropped on the anti-reflection film surface of the second polarizing glass with respect to the adhesive, and adhered to the FR surface of the polarizing glass / FR adhesive element to form a first polarizing glass / FR / second polarizing glass structure. . The adhesive is F
After confirming that R and the second polarizing glass had spread over the entire bonding surface, the substrate was thermally cured at 150 ° C. for 6 hours in the air.

According to the above procedure, the thickness of the adhesive is 2 to 200 μm.
A sample was prepared so as to have an arbitrary thickness in between.

The obtained adhesive element was fixed on a glass table with wax, set on a dicer, and cut. The cutting size was 0.49 to ⁴ mm ² . After cutting, the adhesive element was removed from the glass table, and the adhesive interface was observed with a microscope to check for peeling.

As a result, it was confirmed that when the thickness of the adhesive layer was fixed at 5 μm and the cut size was changed, as shown in FIG. 2, the peeling of the adhesive layer increased when the cut size was 2 mm ² or less. . Therefore, chips having cut sizes of 0.49 mm ² and 2 mm ² were cut out at a thickness of the adhesive layer of ² to 200 μm, and peeling of the adhesive interface was confirmed. As shown in FIG. It was confirmed that the cutting yield exceeded 90% in the range of １００100 μm. In the region where the thickness of the adhesive layer was 15 to 50 μm, the cutting yield was 95% or more, and very good results were obtained.

In this embodiment, the polarizing glass is used. However, the present invention is also effective for improving the cutting yield when an isolator is formed by using a birefringent material such as rutile instead of the polarizing glass. .

[0026]

According to the present invention, the thickness of the adhesive layer is 10 to
By setting the thickness of the optical element to 100 μm, the area of the optical surface of the adhesive element obtained by bonding the optical surfaces of the polarizing element or the birefringent element and the Faraday rotator to each other through a rubber elastic adhesive having a small adhesive strength having rubber elasticity at around room temperature is reduced. Even when cut into chips of 2 mm ² or less, damage such as peeling of the bonding interface is less likely to occur, and the cutting yield of the bonded isolator is improved.

[Brief description of the drawings]

1A and 1B show a manufacturing flow of an adhesive type isolator, in which FIG. 1A is a perspective view of a large-sized adhesive element, and FIG.
Is a perspective view of an adhesive element chip obtained by cutting the adhesive element,
(C) is a perspective view showing the assembled state of the chip, (D)
FIG. 3 is a perspective view of an isolator.

FIG. 2 is a graph showing the relationship between the optical surface area of an adhesive element and the rate of occurrence of adhesive layer peeling when the thickness of the adhesive is 5 μm.

FIG. 3 is a graph showing the relationship between the thickness of the adhesive layer and the rate of occurrence of peeling of the adhesive layer.

[Explanation of symbols]

 1, 2 polarizing element or birefringent element 3 Faraday rotator 4 adhesive element 5 adhesive element chip 6 magnet 7 metal holder 8 optical isolator

Claims (1)

[Claims] An optical surface is adhered to a polarizing element or a birefringent element and a Faraday rotator at least at 10 to 40 ° C. via an adhesive having rubber elasticity, and the adhesive element is cut to obtain an area of the optical surface. Is a chip-shaped adhesive optical element having a diameter of ² mm ² or less, and an optical isolator obtained by arranging the adhesive optical element in a magnetic field, wherein the adhesive layer of the adhesive optical element has a thickness of 10 to 100 μm. Optical isolator.