JPH04360103A - polarizing beam splitter - Google Patents

Abstract

PURPOSE:To provide the polarization beam splitter which is manufactured at extremely low cost and reduce the cost of various devices utilizing this beam splitter. CONSTITUTION:Interference fringes 4 are so formed that when incident light 1 is transmitted through a light transmission type base 2 and made incident on a reflection type hologram 3, the diffraction angle of the incident light and reflected light which satisfy the Bragg conditions is 90 deg., so the S-polarized light component 5 of the incident light 15 diffracted by the interference fringes 4 with nearly 100% efficiency and the P-polarized light component 6 is not diffracted at all and transmitted, so that the incident light 1 can be split into two linear polarized light components.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing beam splitter, and more particularly to a polarizing beam splitter that can be manufactured at low cost using holography technology.

0002

[Prior Art] A polarizing beam splitter has been known as an optical element that separates natural light into linearly polarized light.
As such a polarizing beam splitter, a Nicol prism utilizes the phenomenon that two refracted lights, an ordinary ray and an extraordinary ray, appear when light is incident on a crystal exhibiting optical anisotropy.
By forming a dielectric multilayer thin film between two prisms such as a Rochon prism, Wollaston prism, etc., and setting the incident angle to this multilayer thin film at Brewster's angle, the incident light to the multilayer thin film can be divided into two. A device that separates light into polarized components has been put into practical use.

[0003] Such a polarizing beam splitter is
For example, it is used as a method of optical demultiplexing in the field of optical communications, as a component of an optical isolator, or as a variable beam splitter for optical experiments.

0004

[Problems to be Solved by the Invention] However, since the conventional polarizing beam splitters described above all use expensive optical crystals and dielectric multilayer thin films, the entire beam splitter becomes extremely expensive. This has the disadvantage that the cost of various devices using optical elements increases.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a polarizing beam splitter that can be manufactured at extremely low cost and that enables cost reduction of various devices using such a beam splitter. That is.

[0006]

[Means for Solving the Problems] In order to achieve the above object, a polarizing beam splitter according to the present invention splits incident light into two linearly polarized lights, in which a surface of a light-transmitting support is A reflection hologram is formed which has substantially the same refractive index as the mold support and has interference fringes such that the diffraction angle between the incident light and the reflected light is 90 degrees that satisfies the Bragg condition, so that the incident light is The feature is that the light passes through the transmission type support and enters the reflection type hologram.

[0007]

[Operation] According to the present invention, as shown in the principle diagram of FIG. 1, when the incident light 1 passes through the light transmission support 2 and enters the reflection hologram 3, the hologram 3 satisfies the Bragg condition. Since the interference fringes 4 are formed such that the diffraction angle between the incident light and the reflected light is 90°, the S-polarized component 5 of the above-mentioned incident light 1 is diffracted by the interference fringes 4 with almost 100% efficiency. At the same time, the P-polarized light component 6 is transmitted without being diffracted at all, thereby making it possible to divide the incident light 1 into two linearly polarized light components.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 2 to 11. FIG. 2 shows an embodiment of the polarizing beam splitter A according to the present invention.
It is equipped with two homogeneous right-angle prisms 7 and 7', which are ordinary inexpensive optical systems that do not exhibit optical anisotropy and whose cross section is an isosceles right triangle. has almost the same refractive index as the right angle prism 7,
The diffraction angle between the incident light and reflected light that satisfies the Bragg condition is 90
A reflection-type phase volume hologram 3 having interference fringes (not shown) arranged at an angle of .degree. is formed. Further, on the surface of the hologram 3, the other right angle prism 7'
The right angle prisms 7' are closely arranged so that the slopes 7a' of the right angle prisms 7a' are located, and the hologram 3 is formed on the joining surface of the two right angle prisms 7, 7'.

In such a polarizing beam splitter A, when incident light 1 as random polarized light equally containing S-polarized light and P-polarized light of a predetermined wavelength or wavelength band is incident on the side surface 7b of one right-angle prism 7 at right angles. , this incident light 1
passes through the right-angle prism 7 and enters the hologram 3, and due to the setting of the interference fringes in the hologram 3, the S-polarized light 5 perpendicular to the plane of incidence of the incident light 1 is almost 100% efficient. P-polarized light 6 that is diffracted and parallel to the plane of incidence is transmitted without being diffracted at all. Then, the S-polarized light 5 diffracted by the hologram 3
is emitted at right angles from the side surface 7c of the right-angle prism 7 that is not the incident surface, and the P-polarized light 6 that has passed through the hologram 3 also passes through the other right-angle prism 7' and forms the side surface 7b' of the prism 7'. The incident light 1 can be reliably separated into S-polarized light 5 and P-polarized light 6.

Here, in order to form the polarizing beam splitter A, as shown in FIG. At the same time, the other prism 7' is bonded to the prism 7 on which the hologram emulsion 8 is arranged via a matching liquid, and in this state, the reference light R, which is a plane wave, is incident from the side surface 7b of the one prism 7.
A signal light S, which is a plane wave, is incident on the hologram emulsion 8 from the side surface 7c' of the other prism 7', and a predetermined diffraction angle between the incident light and the reflected light that satisfies the Bragg condition described above is 90°. interference fringes (not shown) are recorded, and then developed and fixed. Further, the hologram emulsion 8 is developed with the prisms 7 and 7' joined together,
If fixing is not possible, after recording predetermined interference fringes on the hologram emulsion 8 as described above, separate the joined prism 7', perform development and fixing in that state, and then record the separated prism 7' again. The beam splitter A is formed by joining the two.

Therefore, in this embodiment, a reflection hologram 3 having predetermined interference fringes, which is easy to manufacture, is formed on the joint surface of ordinary inexpensive right angle prisms 7 and 7' that do not exhibit optical anisotropy. However, since the diffraction effect in the hologram 3 is used to reliably separate the incident light 1 into S-polarized light 5 and P-polarized light 6, it is no longer necessary to use expensive optical system crystals or multilayer thin films as in the past. The beam splitter A can be manufactured at extremely low cost without using the beam splitter A, and the costs of various devices using the beam splitter A can be reduced. In the above description, the right angle prisms 7 and 7' are shown as having an isosceles right triangular cross section, but the same can be said for right angle prisms having a non-isosceles right triangle shape.

FIG. 4 shows another embodiment of the present invention, in which the slope 9a of an ordinary right-angled prism 9 having a non-isosceles right triangular cross section and exhibiting no optical anisotropy has the above embodiment. As in the example, it has almost the same refractive index as the right angle prism 9,
The diffraction angle between the incident light and reflected light that satisfies the Bragg condition is 90
A reflection-type phase volume hologram 3 having interference fringes (not shown) arranged at an angle of .degree. is formed. Further, in this embodiment, the incident light 1 is made to enter from the long side 9b side of the right angle prism 9, and the incident light 1 that passes through the right angle prism 9 is incident on the hologram 3. The angle θ is approximately the Brewster angle.

Also in such a polarizing beam splitter A, the incident light 1 incident at right angles to the long side side surface 9b of the right angle prism 9 is transmitted through the right angle prism 9 and is incident on the hologram 3, and the above-mentioned in this hologram 3 By setting the interference fringes, the S-polarized light 5 is diffracted with almost 100% efficiency, and the P-polarized light 6 is transmitted without being diffracted at all. Then, the S-polarized light 5 diffracted by the hologram 3 is transmitted to the short-side side surface 9 of the rectangular prism 9, which is not the incident surface.
The P-polarized light 6 that is emitted from C at a right angle and transmitted through the hologram 3 is refracted at a predetermined angle and emitted without being reflected at the interface 10 between the hologram 3 and the air. This makes it possible to reliably separate the incident light 1 into S-polarized light 5 and P-polarized light 6.

Here, when forming the polarizing beam splitter A, as shown in FIG. A prism 9', which is the same as the prism 9, is bonded to the prism 9 on which the hologram emulsion 8 is disposed via a matching liquid, and in this state, a signal light S, which is a plane wave, is incident from the side surface 9b of one of the prisms 9. , the reference beam R, which is a plane wave, is incident on the side surface 9c' of the other prism 9' to record the above-mentioned interference fringes (not shown) on the hologram emulsion 8, and then the prism 9' is separated. , development, fixing, etc.

Therefore, in this embodiment as well, a reflection hologram 3 having predetermined interference fringes that is easy to manufacture is formed on a normal, inexpensive right-angle prism 9 that does not exhibit optical anisotropy.
By utilizing the diffraction effect in this hologram 3, the incident light 1
can be reliably separated into S-polarized light 5 and P-polarized light 6, so there is no need to use expensive optical system crystals or multilayer thin films as in the past, and moreover, only one right-angle prism 9 is used. Therefore, the beam splitter A can be manufactured at extremely low cost, and the overall shape of the beam splitter A can be reduced in size. Furthermore, since the angle formed by the separated S-polarized light 5 and the P-polarized light 6 is not a right angle, the direction of separation of the linearly polarized light can be set as appropriate, including the case described later, so the degree of freedom in optical design can be increased. .

Note that it is not necessary to set the incident angle θ strictly to the Brewster's angle, and since this set angle is slightly different, a part of the P-polarized light 6 that passes through the hologram 3 may be at the boundary between the hologram 3 and the air. Even if the reflected light is slightly reflected by the surface 10, there is no problem because the direction of reflection of the P-polarized light 6 is different from the direction of diffraction of the S-polarized light 5 diffracted by the hologram 3. By absorbing the P-polarized light 6 of this portion by a predetermined means, it is possible to reliably separate the incident light 1 into two beams.

Furthermore, when the incident angle θ becomes larger than the Brewster's angle, the reflectance of the P-polarized light 6 at the interface 10 gradually increases. In particular, when the incident angle θ becomes larger than the critical angle, the hologram 3 The P-polarized light 6 that passes through is totally reflected at the boundary surface 10, but in such a case, as shown in FIG.
If the incident light 1 is made to enter at a right angle from the point c, the S-polarized light 5 diffracted by the hologram 3 will exit at right angles from the long-side side surface 9b of the prism 9, and the totally reflected P-polarized light 6 will be emitted from the prism 9 at a right angle. The light is emitted from the long-side side surface 9b at a non-perpendicular angle, and as a result, the diffraction direction of the S-polarized light 5 and the reflection direction of the P-polarized light 6 become completely different, so there is no problem.

However, as shown in FIG. 7, if the cross-sectional shape of the right-angled prism 9 is a right isosceles triangle, the direction of the S-polarized light 5 diffracted by the hologram 3 and the direction of the P-polarized light totally reflected at the boundary surface 10 will be different. Since the direction of the polarized light 6 coincides with that of the polarized light 6, the incident light 1 cannot be separated, and in this case, as in the above embodiment shown in FIG. It is necessary to join prisms of the same shape. Note that each numerical value shown in FIG. 4 was determined assuming that the average refractive index of the right-angle prism 9 and the hologram emulsion 8 is 1.5.

FIG. 8 shows still another embodiment of the present invention, which is a type of polarizing beam splitter A called a so-called polarizing plate, and includes an ordinary flat plate prism 11 that does not exhibit optical anisotropy. As in the above embodiment, the surface 11a has interference fringes (Fig. (not shown) is formed. Also in this embodiment, the incident light 1 passing through the flat prism 11 is
The angle of incidence θ of the beam onto the hologram 3 is approximately the Brewster angle.

In the polarizing beam splitter A as well, the incident light 1 that is refracted at the interface 12 between the air and the flat prism 11 and enters the flat prism 11 passes through the flat prism 11 and enters the hologram 3. By setting the interference fringes in this hologram 3, the S-polarized light 5 is diffracted with almost 100% efficiency, and the P-polarized light 6 is transmitted without being diffracted at all. Then, the S-polarized light 5 diffracted by the hologram 3 is totally reflected at the boundary surface 12 of the flat plate prism 11 and travels inside the prism 11, and is scattered and emitted from the end face of the flat plate (not shown) or is reflected again at the end face. The P-polarized light 6 that has passed through the hologram 3 is refracted at a predetermined angle and emitted without being reflected at the interface 10 between the hologram 3 and the air. This makes it possible to reliably separate the incident light 1 into S-polarized light 5 and P-polarized light 6.

When forming the polarizing beam splitter A, it is impossible to record interference fringes on the hologram 3 if it is a flat plate, so it is necessary to form the polarizing beam splitter A on one surface as shown in FIGS. 9(a) and 9(b). A right angle prism 1 of the same quality as the flat prism 1 is placed on both sides of a flat prism 11 on which a hologram emulsion 8 is arranged.
3 and 13' are joined, and a reference beam R is incident on the hologram 3 so that the incident angle θ is Brewster's angle, and a signal beam S that is orthogonal to this reference beam R is incident to record interference fringes. , Then, the prisms 13 and 13' are separated and developed.
It performs processes such as fixing. Note that the reference numeral 14 in the figure is a black paint layer that serves as a light absorption surface to prevent the reflected light during recording from forming unnecessary interference fringes, and each numerical value in the figure indicates the flat prism 11 and the hologram. The average refractive index of Emulsion 8 was determined as 1.5.

Therefore, in this embodiment as well, a reflection hologram 3 having predetermined interference fringes that is easy to manufacture is formed on an ordinary inexpensive flat prism 11 that does not exhibit optical anisotropy, and the diffraction in this hologram 3 is Since the system uses this function to reliably separate incident light 1 into S-polarized light 5 and P-polarized light 6, it is possible to use a beam splitter without using expensive optical system crystals or multilayer thin films as in the past. A can be manufactured at extremely low cost. Note that if a light absorption surface such as a black paint layer (not shown) is formed on the boundary surface 12 of the flat prism 11, the S-polarized light 5 traveling inside the prism 11 can be absorbed, thereby obtaining only the P-polarized light 6. You can also do it like this.

Furthermore, as shown in FIG. 10, if a transmission hologram 15 is formed on the boundary surface 12 of the flat prism 11, total reflection of the S-polarized light 5 at the boundary surface 12 can be prevented. It is also possible to reliably guide the S-polarized light 5 out of the flat prism 11. In addition, the above-mentioned transmission hologram 1
5, as shown in FIG.
Right angle prisms 17 and 17' of the same quality as the
The direction of the diffraction of the S-polarized light 5 in the hologram 3 is set to be the diffraction direction of the S-polarized light 5, and the signal light S may be set in a direction such that total reflection does not occur during reproduction.

[0024]

Effects of the Invention As described above, the polarizing beam splitter according to the present invention has a surface of a light-transmitting type support that has approximately the same refractive index as the light-transmitting type support, and is capable of separating incident light and light that satisfy the Bragg condition. A reflection hologram having interference fringes with a diffraction angle of 90° with respect to the reflected light was formed, and the incident light was made to pass through the light transmission support and enter the reflection hologram. When incident light enters a reflection hologram, due to the diffraction effect of the hologram, the S-polarized component of the incident light is diffracted with almost 100% efficiency, and the P-polarized component is transmitted without being diffracted at all. , whereby the incident light can be reliably divided into two linearly polarized components.

In addition, without using expensive optical crystals or multilayer thin films as in the past, it is possible to form predetermined interference fringes that are easy to manufacture on a normal, inexpensive light-transmitting support that does not exhibit optical anisotropy. Since a reflection hologram having a beam splitter is formed, the beam splitter can be manufactured at extremely low cost, and the cost of various devices using such a beam splitter can be reduced.

Furthermore, by using various right angle prisms, flat plate prisms, etc. as the light-transmitting support, the separation direction of S-polarized light and P-polarized light can be set appropriately, and the degree of freedom in optical design can be increased. be effective.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention.

FIG. 3 is an explanatory diagram when forming the beam splitter of FIG. 2;

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is an explanatory diagram when forming the beam splitter of FIG. 4;

FIG. 6 is a diagram showing a modification of FIG. 4;

FIG. 7 is a diagram illustrating a case where it does not function as a beam splitter.

FIG. 8 is a diagram illustrating still another embodiment of the present invention.

9A and 9B are explanatory diagrams when forming the beam splitter of FIG. 8. FIG.

FIG. 10 is a diagram showing a modification of FIG. 8;

FIG. 11 is an explanatory diagram when forming the beam splitter of FIG. 10;

[Explanation of symbols]

A Polarizing beam splitter 1
Incident light 2 Light-transmissive support 3
Reflection hologram 4 Interference fringes 5 S-polarized light 6 P-polarized light 7, 9 Right-angle prisms 10, 12 Boundary surface 11 Flat prism

Claims (6)

[Claims] Claim 1: In a polarizing beam splitter that splits incident light into two linearly polarized lights, the surface of a light-transmitting support is provided with:
Forming a reflection hologram having substantially the same refractive index as this light transmission type support and having interference fringes such that the diffraction angle between the incident light and the reflected light is 90° that satisfies the Bragg condition,
A polarizing beam splitter, characterized in that the incident light is transmitted through the light transmission type support and is incident on the reflection type hologram. 2. The light-transmitting support is formed of a right-angle prism, the reflection hologram is formed on the slope of the right-angle prism, and the surface of the reflection hologram is provided with:
2. The polarizing beam splitter according to claim 1, further comprising a prism that is the same as the right-angle prism. 3. The polarized light according to claim 1, wherein the light transmission type support is formed of a right angle prism having a non-isosceles right triangle shape, and the reflection type hologram is formed on the slope of the right angle prism. beam splitter. 4. The incident light according to claim 3, wherein the incident light is incident from a long side surface of the right angle prism, and the incident angle to the reflection hologram is approximately Brewster's angle. Polarizing beam splitter. 5. The incident light according to claim 3, wherein the incident light is incident from the short side side surface of the right angle prism, and the incident angle to the reflection hologram is larger than the Brewster angle. Polarizing beam splitter. 6. The light transmission support is formed of a flat prism, the reflection hologram is formed on the surface of the flat prism, and the transmission hologram is formed on the surface opposite to the surface on which the reflection hologram is formed. The polarizing beam splitter according to claim 1, characterized in that: