JP2000214328A - Polarization composite element and polarization composite module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make production easy and improve stability after production higher than heretofore. SOLUTION: This element has a parallel plane plate 31 having first and second surfaces 31a and 31b facing each other. The partial region of the first surface is provided with a film which is a first antireflection film 33, is made incident with (s) polarized light at an incident angle of a Brewster angle from the outside of the parallel plane plate and allows the transmission thereof. The partial region inclusive of a point P1 at which the (s) polarized light transmitted through the first reflection film arrives is provided with a reflection film or a first polarizing film 35 for reflecting the (s) polarized light. The partial region inclusive of a point P2 at which the (s) polarized light reflected by the film 35 arrives is provided with a film which is a second polarizing film 37 and is made incident with the incident (s) polarized light described above and the (p) polarized light of parallel rays at the point P2. The film 37 is, however, is the film which allows transmission of the (p) polarized light and reflects the (s) polarized light arriving at the point P2 from the film 35. The partial region inclusive of a point P3 of the second surface at which the (p) polarized light transmitted through the film 37 and the (s) polarized light reflected by the film 37 arrive is provided with a second antireflection film 39.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to s-polarized light and p-polarized light.
The present invention relates to a polarization combining element for combining polarized light and a polarization combining module using the element.

[0002]

2. Description of the Related Art For example, in order to increase the pumping light power of an optical amplifier using pumping light, it has been considered to use light obtained by combining s-polarized light and p-polarized light as pumping light. Further, in order to increase the capacity of optical communication, it has been considered that information is superimposed on each of s-polarized light and p-polarized light, and these polarized lights are combined and transmitted through a transmission path. In order to realize these, a polarization combining element that combines s-polarized light and p-polarized light is required.

An example of an optical element that can be used as a polarization combining element is disclosed in, for example, FIG. 1 of JP-A-61-186903. FIG. 6 is a cross-sectional view illustrating this optical element (hereinafter, referred to as a conventional polarization combining element 10).

[0004] This conventional polarization combining element 10 comprises a substrate 11
And a light reflecting film 13, a light transmitting layer 15, and a polarizing beam split layer 17 formed in this order on the substrate 11, and a cover glass 19 overlaid on the polarizing beam split layer 17. 2nd page upper right column 1-6
line).

The polarizing beam splitting layer 17 is a layer that transmits p-polarized light and reflects s-polarized light (page 2, upper right column, lines 8 to 11 in the above publication).

The polarized light Ls is incident on the conventional polarization combining element 10 from outside through one of two different points of the cover glass 19 and the p-polarized light Lp is incident on the other at an incident angle θi. Then, the p-polarized light Lp passes through the polarizing beam splitting layer 17 and the light transmitting layer 15 and is reflected by the light reflecting film 13, and then passes through the light transmitting layer 15, the polarizing beam splitting layer 17, and the cover glass 19 and exits outside. On the other hand, the s-polarized light Ls is
After being reflected by, it goes out through the cover glass. The p-polarized light Lp and s-polarized light Lp and s are reflected such that the p-polarized light Lp reflected by the light reflecting film 13 and reaching the polarized beam split layer 17 and the s-polarized light Ls reflected by the polarized beam split layer 17 pass substantially the same optical path. By adjusting the incident angle of the polarized light Ls, the thickness of the cover glass 19, the thickness of the light transmitting layer 15, and the like, the p-polarized light Lp and the s-polarized light Ls can be combined, so that the combined light L can be obtained. .

The polarization combining device disclosed in the above publication has the advantage that the drawbacks (for example, the drawbacks such as poor durability) of the polarization combining device using crystals such as calcite can be solved.

[0008]

By the way, when the above-mentioned polarization combining element 10 is used, typically, as shown in FIG. A structure is adopted in which optical fiber connectors 21a and 21b for supplying the polarized light Lp and s-polarized light Ls to the element 10 and an output optical fiber connector 23 for extracting the combined light L from the element 10 are assembled in a predetermined relationship.

However, the polarization combining element 10 is
0, the position of the polarization combining element 10 with respect to the housing 20 depends on the incident angle θi
In the case where the light is shifted so as to cause a phenomenon that the light is shifted, the conventional polarization combining element 10 has a problem that the combined light L is likely to be unable to be extracted.

This problem will be described in more detail with reference to FIG. FIG. 8 shows the polarization combining element 10.
(However, in the figure, the element 10 is replaced by the light transmitting layer 13 for simplicity.) The case where the p-polarized light Lp and the s-polarized light Ls are incident at the regular incident angle θ1 and the case 20 of the element 10
The element 10 has a p-polarized light L
Incidence angle θ2 where p and s polarizations Ls are not regular incidence angles
FIG. 7 is a ray drawing for the case where light is incident.

As can be understood from FIG. 8, the output position and output direction of the combined light L obtained when the polarization combining element 10 is arranged at a regular position of the housing 20 from the polarization combining element 10. On the other hand, the output position and output direction from the polarization combining element 10 of the combined light L2 obtained when the polarization combining element 10 is rotationally shifted by α from the normal position of the housing 20 may be largely shifted. I understand. Therefore, the combined light L2 cannot enter the output optical fiber connector 23.

If the output position and the output direction are small in displacement, the combined light L2 is output from the output optical fiber connector 2.
Even if the light beam can be incident on the third light source, another problem as described below occurs. That is, generally, the output optical fiber connector 2
3, a lens (collimator lens) is provided at the end on the polarization combining element 10 side (not shown). The end face of the optical fiber for output light is located at the focal point of this lens. However, since the combined light L2 has an angle with respect to the regular combined light L, the combined light L2 enters the collimator lens at an angle (incidents with respect to the optical axis). Therefore, the combined light L2 is focused to a position different from the expected focal position, that is, a position different from the end surface position of the output light optical fiber. Therefore, problems such as the occurrence of coupling loss with respect to the output optical fiber occur.

In order to avoid the above-mentioned problems in the conventional polarization combining element 10, it is necessary to strictly control the positional accuracy of mounting the polarization combining element 10 to the housing 20. Also,
It is also necessary to strictly take measures against positional changes after mounting.
That is, the conventional polarization combining element 10 is difficult to manufacture, and it is difficult to obtain stability after manufacturing.

[0014] The present invention has been made in view of the above points, and it is therefore an object of the present invention to provide a structure that does not use crystals such as calcite, which is easier to manufacture than the conventional one and has a higher stability after manufacture. An object of the present invention is to provide a polarization combining element having excellent characteristics.

[0015]

In order to achieve the above-mentioned object, according to the polarization combining element of the present application, the polarization combining element has first and second surfaces facing each other in a parallel relationship and is transparent to light to be handled. Plane plate made of various materials, a first antireflection film, a reflection film or a first polarizing film, a second polarizing film, and a first antireflection film provided on the parallel plane plate as described below. And a second antireflection film.

The first antireflection film is provided on a part of the first surface of the plane-parallel plate, and has an incident angle of Brewster's angle or an angle near the Brewster's angle from outside the plane-parallel plate.
The film receives polarized light and transmits the input s-polarized light.

The angle near the Brewster's angle is
The angle is mainly determined in consideration of the later-described incident loss of p-polarized light to the parallel flat plate and the difficulty of adjusting the incident angle. Preferably, the angle is as close to the Brewster's angle as possible.

The reflection film or the first polarizing film is provided in a part of the second plane of the plane-parallel plate including a point where the s-polarized light transmitted through the first antireflection film reaches, This is a film that reflects the s-polarized light that has arrived in the plane-parallel plate. The special effect when the first polarizing film is used appears particularly when the polarization combining device of the present invention is used as a polarization demultiplexing device. That is, when used as a polarization splitter, the effect of improving the quality of s-polarized light obtained by splitting is exhibited.
If you do not consider the use as a polarization splitter,
It is preferable to form a reflection film without providing the polarizing film. This is because light loss can be easily reduced.

The second polarizing film is provided in a part of the first plane of the plane-parallel plate including a point where the s-polarized light reflected by the reflecting film or the first polarizing film reaches, A film on which p-polarized light whose optical axis is parallel to the incident s-polarized light is incident from the outside of the plane-parallel plate at or near the position corresponding to the s-polarized light arrival point. Of course, it is a film that transmits the p-polarized light and reflects the reflected s-polarized light into a parallel plate. In addition, the vicinity near the position corresponding to the s-polarized light arrival point refers to a range in which p-polarized light can be combined with s-polarized light.

The second antireflection film receives the s-polarized light reflected by the second polarizing film and the p-polarized light transmitted through the second polarizing film on the second surface of the plane-parallel plate. It is a film provided in a partial area including a point.

According to the polarization-combining element of the present invention, the p-polarized light is incident on the plane-parallel plate at the Brewster's angle or at an angle near the p-polarized light at the portion of the second polarizing film, so that there is substantially no transmission loss. In this state, it is incident on the plane-parallel plate. On the other hand, the s-polarized light enters the plane-parallel plate via the first antireflection film,
The s-polarized light also enters the plane-parallel plate with little loss.

Further, in the case of the present invention, the s-polarized light is reflected by the reflecting film or the first polarizing film and the second polarizing film.
Since the s-polarized light is less dependent on the incident angle of the reflection loss than the p-polarized light, it is easier to reduce the light loss in the polarization combining element than in the case where the p-polarized light is reflected in the parallel plane plate.

Further, in the case of the present invention, since the second antireflection film is provided, the s-polarized light and the p-polarized light, that is, the combined light, are output from the parallel plane plate to the outside with low loss.

Further, in the case of the present invention, the details will be described later with reference to FIG. 2. However, when the position where the polarization combining element is attached to the housing or the like slightly deviates from the normal position (when the incident angle of the polarized light is Even if there is a positional deviation slightly deviating from the predetermined angle), the output direction of the output position of the combined light at that time is the output direction of the combined light when the polarization combining element is attached to a regular position of the housing. Is parallel to Of course, the displacement of the output position is also sufficiently smaller than the conventional one (the one described with reference to FIGS. 6 to 8). This means that the tolerance of the mounting accuracy when attaching the polarization combining element to the housing etc. can be made wider than before, and even if the position shift occurs after the mounting, the tolerance is higher than before. It means that it can be widened. Therefore, it is possible to realize a polarization combining element which is easy to manufacture and has excellent stability after manufacturing, even though the structure does not use crystals such as calcite.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. However, the drawings used in the following description merely schematically show the dimensions, shapes, arrangement relations, and the like of the components so that the present invention can be understood. Further, in each of the drawings used for the description, the same components are denoted by the same reference numerals, and the duplicate description thereof may be omitted.

1. First Embodiment FIG. 1 is a plan view illustrating a polarization combining element 30 according to a first embodiment. However, the polarization combining element 30 is assembled into the housing 40 together with the first to third input / output units 51, 53, 55, that is, as the polarization combining module 60 of the first embodiment, Is shown.

The polarization combining element 30 includes a plane parallel plate 31 and
A first anti-reflection film 33, a reflection film or a first polarizing film 35, a second polarizing film 37, and a second anti-reflection film 39, which are provided on the parallel plane plate 31 in a predetermined relationship described later.
And

The plane-parallel plate 31 has a first surface 31a and a second surface 31b facing each other in a parallel relationship. Needless to say, it is made of a material transparent to at least the light to be polarized. The parallel flat plate 31 can be typically formed of a parallel flat plate made of optical glass.

The details will be described later with reference to FIG.
As the thickness t of the parallel plane plate 31 is increased, the distance between input points when s-polarized light and p-polarized light are input to the parallel plane plate 31 can be increased. The element 3 at the output position of the combined light output from the combining element 30
The incident angle dependence of p-polarized light and s-polarized light to zero can be reduced. Therefore, when determining the thickness of the plane-parallel plate 31, the above points should be considered.

The first antireflection film 33 is provided on a part of the first surface 31a of the plane-parallel plate 31. Here, the partial region is a region including a point where the s-polarized light Ls is to be incident, and is a region that does not hinder the formation of the second polarizing film 37. The s-polarized light is incident on the first antireflection film 33 from outside the plane-parallel plate 31 at an incident angle at or near the Brewster's angle. This first anti-reflection film 33
Transmits this s-polarized light. This first anti-reflection film 33
Is typically a dielectric multilayer film, which can transmit the s-polarized light used as efficiently as possible.

The reflecting film or the first polarizing film 35 is
The second plane 31b of the plane-parallel plate 31 is provided in a partial area including the point P1 where the s-polarized light transmitted through the first antireflection film 33 reaches. Here, the partial region is a region that does not hinder the formation of the second antireflection film 39. The reflection film or the first polarizing film 35 reflects the s-polarized light transmitted through the first antireflection film 33 into the parallel plane plate 31.
The reflection film or the first polarizing film 35 is typically a dielectric multilayer film, and is formed of a film capable of reflecting the s-polarized light to be used with as high a reflectance as possible.

Further, the second polarizing film 37 is provided on the parallel plane plate 3.
The reflection film or the first polarizing film 35 on the first surface 31a
Are provided in a partial area including the point P2 where the s-polarized light reflected by the light reaches. Moreover, this second polarizing film 37
A film on which a p-polarized light Lp parallel to the incident s-polarized light Ls from the outside of the parallel plane plate 31 is incident at or near the position corresponding to the point P2. Needless to say, the second polarizing film 37 is a film that transmits the p-polarized light Lp and reflects the s-polarized light that has reached the point P2 into the parallel plane plate 31. The second polarizing film 37 is typically a dielectric multilayer film, and reflects the s-polarized light to be used with as high a reflectance as possible and uses the p-polarized light to be used.
It is composed of a film that can transmit polarized light with as high a transmittance as possible.

The second antireflection film 39 is provided on the second surface 31b of the plane-parallel plate 31 as s-polarized light reflected by the second polarizing film 37 and p-polarized light transmitted through the second polarizing film 37. Is provided in a partial area including the point P3 where the vehicle reaches. The second antireflection film 39 converts the s-polarized light and the p-polarized light, that is, the combined light, into the parallel flat plate 31 with as low a reflectance as possible.
This is a film that is emitted to the outside of the device. This second anti-reflection film 39
Is typically a dielectric multilayer film that is capable of emitting s-polarized light and p-polarized light, that is, combined light, to the outside of the plane-parallel plate 31 with as low a reflectance as possible.

A housing 40 in which the polarization combining element 30 is mounted.
Is made of a housing of any suitable material and shape according to the specifications of the polarization combining module. Typically, the housing is made of metal and has a rectangular outer shape.

Each of the first to third input / output units 51, 53, 55 attached to the housing 40
Further, it is for connecting an external optical waveguide means, specifically, for example, an optical fiber, typically a single mode optical fiber or a polarization maintaining optical fiber.

The first input / output unit 51 can be composed of, for example, an optical component including an optical fiber connector 51a and a collimator lens 51b. The second input / output unit 53 can be composed of, for example, an optical component including an optical fiber connector 53a and a collimator lens 53b. The third input / output unit 55 includes, for example, an optical fiber connector 55a and a collimator lens 55.
b. First input / output unit 51
Is connected to the optical fiber 51c from the s-polarized light source. An optical fiber 53 from a p-polarized light source is
c, and the third input / output unit 55 is connected to an optical fiber 55c for extracting combined light. When the polarization combining module 60 is used as a polarization demultiplexing module, an optical fiber from a light source to be separated is connected to the third input / output unit 55, and the first input / output unit 51 is connected to the s. It is used for extracting polarized light, and the second input / output unit 53 is used for extracting p-polarized light.

The polarization combining element 30 and the first to third
The input / output units 51 to 55 can be attached by any method such as a method using an adhesive or a method using brazing.

Next, the effect of the polarization combining element 30 of the first embodiment will be described. FIG. 2 is a diagram for this explanation. Specifically, the p-polarized light Lp
And the s-polarized light Ls is incident at the regular incident angle θ1, and the mounting position of the element 30 to the housing 40 is shifted (that is, the element 30 is rotationally shifted by α with respect to the predetermined position). FIG. 9 is a ray diagram when Lp and s-polarized light Ls are incident at an incident angle θ2 that is not a regular incident angle.

As is apparent from a comparison between FIG. 2 and FIG. 8 relating to the conventional device, according to the polarization combining element 30 of the present invention, the polarization combining element 30 is displaced from the normal position of the housing 40. Even if the output position and the output direction of the combined light L2 (the light beam shown by the broken line in FIG. 2) output from the polarization combining element 30 at this time, the polarization combining element 30 is positioned at the regular position of the housing 40. Of the combined light L (light shown by the solid line in FIG. 2) obtained when the
It can be seen that there is almost no difference with respect to the output position and output direction from. In detail, it can be seen that the output positions of the combined light L and the combined light L2 are slightly shifted, but the output directions remain parallel to each other. Needless to say, it can be seen that the deviation of the output position is extremely small as compared with the related art, and can be reduced as the thickness of the parallel flat plate 31 is reduced.
Therefore, the combined light L2 can enter the third input / output unit 55. Since the combined light L2 is parallel to the regular combined light L, it is incident on the collimator lens 55b (see FIG. 1) in a state parallel to the optical axis. Therefore, the combined light L2 is narrowed down to the position of the end face of the output optical fiber 55c in the same manner as the combined light L.
Link to 5c as desired. That is, the coupling loss that occurs in the case of FIG. 8 and when the combined light L2 enters the connector 23 does not occur in the present invention.

As described above, according to the present invention, it is possible to realize a polarization combining element which has a structure without using a crystal such as calcite, and which is easier to manufacture than the conventional one and has excellent stability after manufacturing. I understand.

2. Second Embodiment In the case of the polarization combining device of the first embodiment described above, the s-polarized light incident on the parallel plane plate 31 is reflected by the reflection film or the first polarization film 35 and the second polarization film. 37, the element reaches the second antireflection film 39 after being reflected once each. However, after the s-polarized light incident on the parallel plane plate 31 is reflected two or more times by the reflection film or the first polarization film 35 and the second polarization film 37, the second anti-reflection film is formed. A polarization combining element may be configured to reach 39. The second embodiment is an example.

FIG. 3 is a diagram showing a polarization combining module 80 including the polarization combining element 70 according to the second embodiment.

The polarization combining module 80 includes a housing 91
And the polarization combining element 70 and the first to third input / output units 93 and 95 of the second embodiment incorporated in the housing 91.
97.

The housing 91 can be constituted by, for example, the same as the housing 40 of the first embodiment, and the first to third input / output units 9 are provided.
3, 95 and 97 are, for example, the first to third parts of the first embodiment.
And the input / output units 51, 53, and 55 of FIG. For example, optical fibers 93c, 95c, and 97c are connected to the first to third input / output units 93, 95, and 97, respectively.

The polarization combining element 7 of the second embodiment
0 denotes a parallel plane plate 71, a first antireflection film 73, a reflection film or a first polarizing film 75, a second polarizing film 77,
A second antireflection film 79.

The plane-parallel plate 71 can be constructed, for example, of the same type as the plane-parallel plate 31 in the first embodiment. First
The anti-reflection film 73 of the first embodiment can be constituted by the same material as the first anti-reflection film 33 in the first embodiment.

Further, a reflecting film or a first polarizing film 75,
The second polarizing film 77 means that the s-polarized light Ls transmitted through the first anti-reflection film 73 is equal to or more than two times (FIG. 3).
Is reflected twice), the second anti-reflection film 7
9, except that the reflection film or the first polarization film 35 and the second polarization film 3 in the first embodiment are arranged.
7 can be constituted.

Further, the second anti-reflection film 79 can be constituted by, for example, the same one as the second reflection film 39 in the first embodiment.

The polarization combining element 70 according to the second embodiment
In this case, the number of times of reflection of the s-polarized light Ls in the parallel plane plate 71 can be increased even number times as compared with the case of the element 30 of the first embodiment. By increasing the number of reflections, the inter-beam distance X1 between the p-polarized light and the s-polarized light incident on the polarization combining element can be made wider than in the first embodiment. Therefore, the distance between the first input unit 93 and the second input unit 95 should be wider than the distance between the first input unit 51 and the second input unit 53 in the first embodiment. Can be. Therefore, it becomes easier to mount the first and second input units 93 and 95 on the housing 91 as compared with the first embodiment.

Further, since the number of reflections to be increased is an even number, the effect of the device of the present invention, that is, even if the incident angle is shifted, the output light is parallel to the normal output light and the deviation of the emission position is also reduced. The effect of being small can be maintained.

In FIG. 3, the first polarizing film 75 and the second
The structure in which the polarizing film 77 and the second polarizing film 77 reflect the s-polarized light twice and then reach the second antireflection film 79 has been described, but the first polarizing film 75 and the second polarizing film 77 reflect the s-polarized light three times. Of course, a structure that reflects each of the above may be used. However, as the number of reflections increases, the loss also increases. Therefore, it is better to design the element in consideration of this point. Further, in FIG. 3, the first polarizing film 75 is a continuous film between the respective reflection positions, but the first polarizing film 75 may be an independent film for each of the reflection positions. The same applies to the second polarizing film 77.

3. Third Embodiment Next, a first example of a polarization combining module including a polarization combining element and an inter-beam distance expanding element will be described. FIG. 4 is an explanatory diagram for that purpose.

The polarization combining module 100 of the third embodiment includes an inter-beam distance expanding section 101 on the optical path of the polarization combining element 30 on which the p-polarized light is incident.

The inter-beam distance enlarging unit 101 is a second parallel plane plate transparent to p-polarized light, and the p-polarized light is applied to the first surface 101a of the second parallel plane plate at Brewster's angle or its Brewster angle. Incident at a near angle of incidence, and
P output from the second surface 101b of the second plane-parallel plate
It is composed of a second plane-parallel plate arranged so that polarized light enters the p-polarized light incident point P2 of the polarization combining element 30. Second
Can be made of, for example, optical glass. Also,
The second plane-parallel plate may be provided with an optical film such as an anti-reflection film.

When the inter-beam distance enlarging unit 101 is provided,
The inter-beam distance Xb between the p-polarized light and the s-polarized light incident on the polarization combining element 30 on the light source side of the polarized light can be widened. Therefore, the first and second input / output units 51 and 53 can be mounted on the housing 40 at wider intervals than in the first embodiment.
The effect that the input / output units 51 and 53 are easily mounted on the housing 40 is obtained.

As the inter-beam distance expanding section 101, the optical path length of p-polarized light in the polarization combining module 100 is set equal to or close to the optical path length of s-polarized light in the polarization combining module 100. It is preferable that the enlarged portion has an optical path length. Specifically, from the first input / output unit 51, the point P2
The optical path length of s-polarized light up to the point P
The magnifying section 10 has an optical path length that is equal to or substantially equal to the optical path length of the p-polarized light up to 2.
It is good to design 1. Specifically, it is preferable to consider the thickness of the second parallel flat plate. By doing so, the optical loss in the third input / output unit 55 can be reduced as compared with the case where this is not the case. In addition, the degree of the case where they are substantially equal may be determined in consideration of the degree to which the optical loss is allowed and the like.

In the third embodiment, the example in which the polarization combining element 30 is used has been described.
The polarization combining module may be configured by combining the beam splitter 101 and the inter-beam distance expanding unit 101.

4. Fourth Embodiment Next, another example of a polarization combining module including a polarization combining element and an inter-beam distance expanding element will be described. FIG.
(A) and (B) are explanatory diagrams therefor.

The polarization combining module 110 according to the fourth embodiment includes an inter-beam distance expanding section 111 on the optical path of the polarization combining element 30 on which the p-polarized light is incident.

The inter-beam distance enlarging unit 111 includes the member 11
3 and the reflection film 11 provided at a predetermined position of the member 113.
5 and 117. However, the member 113
Correspond to the first and second surfaces 113a, 113
3b and the first surface 113a at an angle of 45 degrees,
Third surface 113 contacting the second surface at an angle of 135 degrees
c, a fourth surface 113d parallel to the third surface 113c and in contact with the first and second surfaces, and made of a material transparent to p-polarized light. Further, the reflection film 115 is made of a third material.
The reflection film 117 is provided on the fourth surface 11c.
3d. The first of the inter-beam distance enlargement unit 111
P-polarized light is perpendicularly incident on the surface 113a. Then, the p-polarized light is reflected by the reflection film 115 on the third surface, further reflected by the reflection film 117 on the fourth surface, and then reflected by the second surface 11.
Go outside from 3b. The enlarged portion 111 is coupled to the polarization combining element 3 so that the p-polarized light output from the second surface 113b is incident on the p-polarized light incidence point P2 of the polarization combining element 30.
Arrange for 0.

By providing this inter-beam distance expanding section 111,
The inter-beam distance Xb between the p-polarized light and the s-polarized light incident on the polarization combining element 30 on the light source side of the polarized light can be widened. Therefore, the first and second input units 51 and 53 can be mounted on the housing 40 at wider intervals than in the first embodiment, so that the first and second input / output units 51 and 53 can be mounted on the housing 40. The effect that it is easy to mount it on the device is obtained.

The optical path length of the p-polarized light in the polarization combining module 110 is set equal to or close to the optical path length of the s-polarized light in the polarization combining module 110. It is preferable that the enlarged portion has an optical path length. Specifically, from the first input / output unit 51, the point P2
The optical path length of s-polarized light up to the point P
The enlargement section 111 may be designed to have an optical path length equal to or substantially equal to the optical path length up to 2. Specifically, the thickness between the first and second surfaces 113a and 113b of the member 113 should be considered. In this case, compared to the case without this, the third
The optical loss at the input / output unit 55 can be reduced. In addition, the degree of the case where they are substantially equal may be determined in consideration of the degree to which the optical loss is allowed and the like.

The inter-beam distance enlarging unit 1 in the third embodiment
In the case of 01, a volume for adjusting the optical path length is mainly required along the direction connecting the second input / output unit 53 and the third input / output unit 55 (hereinafter, the length direction of the housing). On the other hand, in the case of the inter-beam distance expanding section 111 of the fourth embodiment, a volume for adjusting the optical path length is required mainly along the direction perpendicular to the vertical direction (the width direction of the housing). It is convenient from the viewpoint of module design to use the inter-beam distance enlarging unit of the third or fourth embodiment according to the shape of the housing.

In the fourth embodiment, the example using the polarization combining element 30 has been described.
The polarization combining module may be configured by combining the beam splitter 111 and the inter-beam distance expanding unit 111.

Further, in the configuration of the polarization combining module described with reference to FIG.
Instead of 1, an inter-beam distance enlarging unit 120 as shown in FIG. 5B may be provided. That is, the first and second surfaces 121a and 121b opposed in parallel and the first surface 12
A third surface 121c that contacts the first surface 1a at an angle of 45 degrees and contacts the second surface 121b at an angle of 135 degrees, and a fourth surface 121c that is parallel to the third surface 121c and contacts the first and second surfaces. A member 121 made of a material transparent to p-polarized light, an antireflection film 123 provided on the first surface 121a, and an antireflection film 125 provided on the fourth surface 121d. , A so-called 45-degree parallelogram prism;
20 may be provided.

[0066]

As is clear from the above description, according to the polarization combining element of the present invention, the parallel plane plate, the first antireflection film provided in a predetermined relationship with the plane parallel plate, and the reflection film or the reflection film are provided. A first polarizing film, a second polarizing film, and a second antireflection film.

For this reason, even if the incident angles of the p-polarized light and the s-polarized light to the polarization combining element deviate from the normal incident angles, the output light can be output in parallel with the output light at the normal incident angle. The displacement can be made smaller than before. Therefore, it is possible to realize a polarization combining element which is easy to manufacture and has excellent stability after manufacturing, even though the structure does not use crystals such as calcite.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a polarization combining element and a polarization combining module according to a first embodiment.

FIG. 2 is a diagram illustrating the effect of the polarization combining element of the present invention.

FIG. 3 is a diagram illustrating a polarization combining element and a polarization combining module according to a second embodiment.

FIG. 4 is a diagram illustrating a polarization combining module according to a third embodiment.

FIG. 5 is a diagram illustrating a polarization combining module according to a fourth embodiment.

FIG. 6 is a diagram illustrating a conventional polarization combining element.

FIG. 7 is a diagram illustrating a problem of a conventional polarization combining element.

FIG. 8 is a diagram illustrating in detail the problems of the conventional polarization combining element.

[Explanation of symbols]

 30: Polarization combining element of the first embodiment 31: Parallel plane plate 31a: First surface 31b: Second surface 33: First antireflection film 35: Reflection film or first polarizing film 37: Second polarizing film 39: Second anti-reflection film 40: Housing 51: First input / output unit 51a: Optical fiber connector 51b: Collimator lens 53: Second input / output unit 53a: Optical fiber connector 53b: Collimator Lens 55: Third input / output unit 55a: Optical fiber connector 55b: Collimator lens 60: Polarization combining module of the first embodiment 70: Polarization combining element of the second embodiment 71: Parallel plane plate 73 : First antireflection film 75: Reflection film or first polarizing film 77: Second polarization film 79: Second antireflection film 80: Polarization combining module of second embodiment 91: Housing 93 : First entry Power unit 95: Second input / output unit 97: Third input / output unit 100: Polarization combining module of the third embodiment 101: Inter-beam distance expanding unit 101a: First surface 101b: Second surface 110: Polarization combining module of the fourth embodiment 111: Inter-beam distance enlargement unit 113a to 113d: First to fourth surfaces 115, 117: Reflective film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shin Shin Higashi 1-13-13 Wada, Suginami-ku, Tokyo F-term (reference) 2H049 BA05 BA43 BB03 BB65 BC25 2H099 AA01 BA17 CA02

Claims (8)

[Claims] 1. A parallel flat plate having first and second surfaces facing each other in a parallel relationship and made of a material transparent to light to be handled, provided in a partial area of the first surface, S-polarized light is incident from the outside of the plane-parallel plate at an incident angle of Brewster's angle or an angle close to the Brewster's angle, and a first anti-reflection film transmitting the s-polarized light; and a first reflection of the second surface A reflecting film or a first polarizing film, which is provided in a partial area including a point where the s-polarized light transmitted through the prevention film reaches, and reflects the s-polarized light reaching the inside of the parallel plane plate, and the first surface A second polarizing film provided in a partial area including a point at which the s-polarized light reflected by the reflection film or the first polarizing film reaches, at or near a position corresponding to the s-polarized light reaching point The incident s from the outside of the plane parallel plate
A second polarizing film that receives p-polarized light parallel to the polarized light and transmits the p-polarized light and reflects the reflected s-polarized light into the parallel plane plate; and A second antireflection film provided in a partial area including a point at which the s-polarized light reflected by the second polarizing film and the p-polarized light transmitted through the second polarizing film reach. A polarization combining element. 2. The polarization combining device according to claim 1, wherein said plane-parallel plate is made of glass. 3. The polarization combining device according to claim 1, wherein the s-polarized light transmitted through the first anti-reflection film is a reflection film or a first polarization film and a second polarization film. The arrangement area of the reflective film or the first polarizing film and the second polarizing film is determined so that the light is reflected once and reaches the second anti-reflection film. Characteristic polarization combining element. 4. The polarization combining device according to claim 1, wherein the s-polarized light transmitted through the first anti-reflection film is a reflection film or a first polarization film and a second polarization film. Then, an arrangement area of the reflection film or the first polarization film and the second polarization film is determined so that the reflection film or the first polarization film reaches the second antireflection film after being reflected two or more times by the same number. A polarization combining element. 5. The polarization combining device according to claim 1, wherein the polarization combining device is provided on an optical path of the p-polarized light input to the polarization combining device. A polarization beam splitter for widening the distance between the polarized light and the p-polarized light when the polarized light and the p-polarized light are incident on the light source side of the polarized light. Wave synthesis module. 6. The polarization combining module according to claim 5, wherein the inter-beam distance enlarging element sets the optical path length of the p-polarized light in the polarization combining module to the s-polarized light in the polarization combining module. A polarization combining module having an optical path length equal to or close to the optical path length of the polarization combining module. 7. The polarization combining module according to claim 5, wherein the inter-beam distance expanding element is a second plane-parallel plate transparent to the p-polarized light, The p-polarized light is incident on the first surface of the face plate at an incident angle at or near the Brewster angle, and the p-polarized light output from the second surface of the second plane-parallel plate is polarized. A polarization combining module comprising an optical component including a second parallel plane plate arranged so as to be incident on the p-polarized light incident point of the wave combining element. 8. The polarization combining module according to claim 5, wherein the inter-beam distance enlarging element is provided with first and second surfaces facing in parallel, and 45 ° with respect to the first surface. A third surface contacting at an angle and contacting the second surface at an angle of 135 degrees; and a third surface parallel to the third surface and the first surface.
A member made of a material transparent to p-polarized light and having a fourth surface in contact with the second surface, wherein p-polarized light is perpendicularly incident on the first surface, and a third surface and Polarization combining comprising: an optical component arranged so that the p-polarized light output from the second surface after passing through the fourth surface is incident on the p-polarized light incidence point of the polarization combining device. module.