JP2012073415A - Polarization conversion element and method for manufacturing polarization conversion element - Google Patents

Abstract

An object of the present invention is to provide a polarization conversion element capable of converting circularly polarized light into radial polarization without providing a dielectric film, and a method for manufacturing a polarization conversion element with high productivity.
A polarization conversion element that converts right-handed circularly polarized light into radial polarized light, and includes a plurality of quarter-wave plates having a triangular prism shape in which both principal surfaces are isosceles triangles. An angle formed by two equal sides on one main surface of a quarter-wave plate is an apex angle, and a point on one main surface of the quarter-wave plate at which two equal sides touch is a vertex, and a quarter wavelength. When one side of the plate that connects two equal sides is the base, when viewed from the output side, the perpendicular of the optical axis of the quarter wave plate drawn from the apex to the base is 45 ° clockwise. Provided at a position rotated in the plane, the side faces of the quarter wave plate are joined so that the apex angle of the quarter wave plate is 360 °, and both main faces are regular polygons. It is formed in the regular polygonal column shape which becomes.
[Selection] Figure 1

Description

  The present invention relates to a polarization conversion element that converts circularly polarized light into radial polarized light and a method for manufacturing a polarization conversion element that converts circularly polarized light into radial polarized light.

  A polarization conversion element that converts circularly polarized light into radial polarized light is used, for example, in an optical apparatus such as a laser irradiation device or a microscope.

Here, the polarization conversion element is an optical component element that can convert and output the polarization state of incident light.
Further, the circularly polarized light is light in a state where the electric vector draws a circle.
The electric vector is a vibration direction of a transverse wave that vibrates perpendicularly to the light traveling direction.
Further, as shown in FIG. 3, the radial polarization is light that is linearly polarized with a radial electric vector. Accordingly, there are a plurality of radial polarization electric vectors, which are parallel along the radial direction.
Linearly polarized light is light having a constant electric vector.

  In general, an optical apparatus such as a laser irradiation apparatus or a microscope has a structure in which light emitted from a light source is irradiated onto a workpiece.

When the workpiece is irradiated with radially polarized light, the laser irradiation apparatus can improve the processing accuracy, and the optical instrument such as a microscope can improve the measurement sensitivity.
For this reason, an optical apparatus such as a laser irradiation device or a microscope has a structure that can irradiate a workpiece with radial polarized light.

  However, the light source used in the above-described laser irradiation apparatus or optical device such as a microscope generally emits linearly polarized light.

  The laser irradiation apparatus includes, for example, a light source, a quarter wavelength plate, and a polarization conversion element.

  As the light source, for example, a laser oscillator is used, and linearly polarized light is emitted.

The quarter wave plate has a principal surface parallel to the optical axis, and circularly polarized light is emitted when linearly polarized light having an electric vector forming an angle of 45 ° with the optical axis is incident.
The quarter wavelength plate is provided with a quarter wavelength plate so that the linearly polarized electric vector emitted from the light source forms an angle of 45 ° with the optical axis of the quarter wavelength plate.
Accordingly, the quarter wavelength plate plays a role of converting linearly polarized light emitted from the light source into circularly polarized light.

In general, when a linearly polarized light having an electric vector that forms an angle of 45 ° with the optical axis of the ¼ wavelength plate is incident on the ¼ wavelength plate, circularly polarized light is emitted. At this time, when the optical axis is located at a position rotated in the clockwise direction when viewed from the plane from which the electric vector of the incident linearly polarized light is emitted, the circularly polarized light is rotated counterclockwise. Further, when the optical axis is at a position rotated in the counterclockwise direction when viewed from the plane from which the electric vector of the incident linearly polarized light is emitted, the circularly polarized light is rotated to the right.
In addition, when the circularly polarized light is incident on a plane parallel to the optical axis of the quarter-wave plate, the quarter-wave plate emits linearly polarized light having an electrical vector that forms an angle of 45 ° with the optical axis. . At this time, the electric vector of the linearly polarized light that is emitted when the clockwise circularly polarized light is incident is at a position obtained by rotating the optical axis by 45 ° clockwise when viewed from the emergent surface. Further, the electric vector of the linearly polarized light emitted when the counterclockwise circularly polarized light is incident is at a position obtained by rotating the optical axis by 45 ° counterclockwise when viewed from the emergent surface.

  The polarization conversion element includes, for example, an axicon lens and a dielectric film.

The axicon lens is a transparent member having a conical shape.
For example, when the cross section of the axicon lens is viewed, the conical surface of the cone is 45 ° with respect to the perpendicular drawn from the apex of the conical shape to the bottom surface of the conical shape.

The dielectric film is formed on the conical surface of the axicon lens.
Accordingly, when the cross section of the dielectric film is viewed, its main surface is 45 ° with respect to a line drawn perpendicularly from the apex of the conical shape to the conical bottom surface.

  In the polarization conversion element, when circularly polarized light is incident from the cone-shaped apex side of the axicon lens toward the cone-shaped bottom surface side of the axicon lens, radial polarized light is emitted from the bottom surface of the cone of the axicon lens ( For example, see Patent Document 1).

In general, a method for manufacturing a polarization conversion element including a dielectric film includes a dielectric film forming step of forming a dielectric film.
In the dielectric film forming step, for example, a vapor deposition apparatus is used, and the dielectric film is formed obliquely with respect to one main surface of the transparent substrate on one main surface of the transparent substrate through which light is transmitted. It is a process. At this time, the transparent substrate has a rectangular flat plate shape.

  Here, the state in which the dielectric film is formed obliquely with respect to one main surface of the transparent substrate means that the thickness of the dielectric film is not uniform and the one main surface of the transparent substrate is not uniform. In this state, the film thickness increases from one predetermined side toward the side opposite to the one predetermined side.

  In the dielectric film formed in the dielectric film forming step, when circularly polarized light is incident on the principal surface of the transparent substrate at a predetermined angle, the circularly polarized light is incident on the dielectric film at a predetermined angle. Thus, linearly polarized light is emitted (see, for example, Patent Document 2).

  Accordingly, the polarization conversion element as described above is formed by forming a dielectric film on the conical surface of a conical axicon lens, and circularly polarized light is incident from the apex side of the conical shape of the axicon lens. Since circularly polarized light is sometimes incident on the dielectric film at a predetermined angle, when circularly polarized light is incident from the apex of the cone shape of the axicon lens, it is emitted as radial polarized light.

Although the case where the polarization conversion element is used in the laser irradiation apparatus has been described, for example, it is also used in an optical apparatus such as a microscope.
Examples of optical instruments such as a microscope include a second harmonic microscope, a laser fluorescence microscope, a Raman microscope, and a near-field microscope.
In addition, an optical apparatus such as a microscope has a configuration in which, for example, linearly polarized light is emitted from a light source, converted into radial polarized light, and the work is irradiated with radial polarized light.

JP 2010-134328 A Japanese Patent Publication No. 7-3486

However, according to the conventional polarization conversion element, it is composed of a conical axicon lens and a dielectric film formed on the conical surface of the axicon lens. When the polarized light is incident, the dielectric film formed on the conical surface and the circularly polarized light have a predetermined angle. Therefore, if the dielectric film thickness is not uniform, the electric vector is not constant. There is a possibility that the light is emitted radially and the radially polarized light is not emitted.
That is, according to the conventional polarization conversion element, even if circularly polarized light is incident on the apex of the cone shape of the axicon lens, there is a possibility that radial polarized light is not emitted.

In addition, according to the conventional method for manufacturing a polarization conversion element, since the dielectric film is formed on the conical surface of the conical axicon lens, the dielectric film having a uniform film thickness is formed on the conical surface of the axicon lens. There is a possibility that the film cannot be formed.
For this reason, according to the conventional method for manufacturing a polarization conversion element, a structure in which circularly polarized light cannot be incident on the dielectric film at a predetermined angle occurs, and a defect that circularly polarized light cannot be converted into radial polarized light occurs. There is a risk that productivity will deteriorate.

  Therefore, an object of the present invention is to provide a polarization conversion element capable of converting circularly polarized light into radial polarization without providing a dielectric film, and a method for manufacturing a highly productive polarization conversion element.

  In order to solve the above-mentioned problem, a plurality of quarter-wave plates, each of which is a polarization conversion element that converts right-handed circularly polarized light into radial polarized light and has a triangular prism shape in which both principal surfaces are isosceles triangles. An angle formed by two identical sides on one main surface of the quarter-wave plate is defined as an apex angle, and a point at which the two identical sides meet on one main surface of the quarter-wave plate is defined as a vertex. When the side that is one main surface of the quarter-wave plate and connects two equal sides is the base, the optical axis of the quarter-wave plate is from the apex to the base when viewed from the output side. It is provided at a position where the drawn perpendicular line is rotated in the plane by 45 ° in the clockwise direction, and the side surfaces of the quarter-wave plate are joined so that the apex angle of the quarter-wave plate is 360 °. The two main surfaces are formed in a regular polygonal column shape having a regular polygon.

  In addition, in order to solve the above-mentioned problem, a polarization conversion element that converts left-handed circularly polarized light into radial polarized light, and a plurality of quarter wavelengths having a triangular prism shape in which both principal surfaces are isosceles triangles An angle formed by two equal sides on one main surface of the quarter-wave plate, and a point where two equal sides meet on one main surface of the quarter-wave plate. When viewed from the exit side, the optical axis of the quarter-wave plate is from the top when the top is the base and the side connecting two equal sides that is one main surface of the quarter-wave plate. A vertical line drawn on the bottom side is provided at a position rotated in a counterclockwise direction by 45 ° in the plane, and the side surface of the quarter-wave plate is adjusted such that the apex angle of the quarter-wave plate is 360 °. It is formed in the shape of a regular polygonal cylinder that is joined to each other and both main surfaces are regular polygons. And

In addition, in order to solve the above-described problem, a method for manufacturing a polarization conversion element that converts circularly polarized light into radial polarized light, which has a triangular prism shape in which both principal surfaces are parallel to the optical axis and is an isosceles triangle. A quarter-wave plate forming step of cutting a quarter-wave plate wafer provided with a portion to be a four-wave plate to form a plurality of quarter-wave plates, and one main surface of the quarter-wave plate The angle formed by two equal sides is the apex angle, the point at which one of the main surfaces of the quarter-wave plate is in contact with the same two sides is the apex, and one main surface of the quarter-wave plate is A quarter-wave plate joining step of joining the side faces of the quarter-wave plate so that the apex angle of the quarter-wave plate is 360 ° when the side connecting two equal sides is the base. Whether the optical axis of each quarter-wave plate is the exit side in the quarter-wave plate forming step. Viewed perpendicular and quarter-wave plate so that the position rotated in 45 ° plane clockwise or counter-clockwise is formed when the,
The quarter wave plate joined in the quarter wave plate joining step has a regular polygonal prism shape.

According to such a polarization conversion element, the side surfaces of the quarter-wave plates are joined such that the apex angles of a plurality of quarter-wave plates whose both principal surfaces are isosceles triangles are 360 °. Since it is formed in a regular polygonal column shape, perpendiculars drawn from the apex of the quarter-wave plate to the base are radial.
Further, according to such a polarization conversion element, when viewed from the emission side, the optical axis of the ¼ wavelength plate is provided at a position rotated in the plane by 45 ° clockwise around the vertical line drawn from the apex to the base. Therefore, when right-handed circularly polarized light is incident on each quarter-wave plate, linearly-polarized light having an electric vector parallel to the perpendicular is emitted from each quarter-wave plate.
Therefore, according to such a polarization conversion element, the perpendicular line drawn from the apex of the quarter-wave plate to the base is radial, and when clockwise circularly polarized light is incident on each quarter-wave plate. Since linearly polarized light having an electric vector parallel to the normal is emitted, when circularly polarized light is incident on each quarter-wave plate, radial polarized light that is linearly emitted can be emitted.
According to such a polarization conversion element, it is possible to convert right-handed circularly polarized light into radial polarized light without providing a dielectric film.

In addition, according to such a polarization conversion element, the side surfaces of the quarter-wave plate are arranged such that the apex angles of a plurality of quarter-wave plates whose both principal surfaces are isosceles triangles are 360 °. Since they are joined and formed into a regular polygonal prism shape, perpendiculars drawn from the apex of the quarter-wave plate to the base are radial.
Further, according to such a polarization conversion element, when viewed from the output side, a perpendicular line in which the optical axis of the quarter-wave plate is drawn from the apex to the base is provided at a position rotated in a 45 ° counterclockwise direction. Therefore, when left-handed circularly polarized light is incident on each quarter-wave plate, linearly-polarized light having an electric vector parallel to the perpendicular is emitted from each quarter-wave plate.
Therefore, according to such a polarization conversion element, the perpendicular drawn from the apex of the quarter-wave plate to the bottom is radial, and when counterclockwise circularly polarized light is incident on each quarter-wave plate. Since linearly polarized light having an electric vector parallel to the normal is emitted, when circularly polarized light is incident on each quarter-wave plate, radial polarized light that is linearly emitted can be emitted.
According to such a polarization conversion element, it is possible to convert counterclockwise circularly polarized light into radial polarized light without providing a dielectric film.

  According to such a method for manufacturing a polarization conversion element, a quarter-wave plate wafer is cut, and a plurality of triangular prism-shaped quarter-wave plates whose main surface is parallel to the optical axis and isosceles triangles, When formed and viewed from the exit side, the optical axis of the quarter-wave plate is provided at a position where the perpendicular is rotated 45 ° clockwise or counterclockwise, so that a plurality of quarter-wave plates are one in one. / 4 wavelength plate wafer can be easily cut and formed, and productivity can be improved.

According to such a method for manufacturing a polarization conversion element, the side surfaces of the quarter-wave plates are joined so that the apex angles of a plurality of quarter-wave plates are adjusted to 360 °, resulting in a regular polygonal prism shape. The perpendicular line drawn from the apex to the base is radial with respect to the apex.
Further, according to such a method for manufacturing a polarization conversion element, the optical axis of each quarter-wave plate is at a position rotated in the plane by 45 ° clockwise or counterclockwise when viewed from the output side. Since the quarter-wave plate is formed so that circularly polarized light is incident on each quarter-wave plate, linearly polarized light having an electric vector parallel to the perpendicular is emitted from each quarter-wave plate. Is done.
Therefore, according to such a method of manufacturing a polarization conversion element, a plurality of quarter-wave plates having the same shape are formed, and the dielectric films are formed by joining the apex angles so that the apex angles are 360 °. Therefore, it is possible to easily manufacture the polarization conversion element and improve the productivity.

It is a state figure showing an example of a polarization conversion element concerning a first embodiment of the present invention. It is a state figure showing an example of a polarization conversion element concerning a second embodiment of the present invention. It is a conceptual diagram which shows an example of the concept of the electric vector of radial polarization.

  Next, the best mode for carrying out the present invention will be described. In each drawing, the state of each component is exaggerated for easy understanding.

(First embodiment)
The polarization conversion element 100 according to the first embodiment of the present invention is mainly composed of a plurality of quarter-wave plates 111 as shown in FIG.
Here, the polarization conversion element 100 according to the first embodiment of the present invention is formed in, for example, a regular hexagonal prism shape in which both main surfaces are regular hexagons.

In general, an optical component element called a quarter wave plate emits circularly polarized light when linearly polarized light having an electric vector forming an angle of 45 ° with the optical axis is incident. At this time, when the optical axis is located at a position rotated in the clockwise direction when viewed from the plane from which the electric vector of the incident linearly polarized light is emitted, the circularly polarized light is rotated counterclockwise. Further, when the optical axis is at a position rotated in the counterclockwise direction when viewed from the plane from which the electric vector of the incident linearly polarized light is emitted, the circularly polarized light is rotated to the right.
An optical component element called a quarter-wave plate has an electric vector parallel to a line obtained by rotating the optical axis by 45 ° counterclockwise when circularly polarized light is incident on a plane parallel to the optical axis. Linearly polarized light is emitted. At this time, the electric vector of the linearly polarized light that is emitted when the clockwise circularly polarized light is incident is at a position obtained by rotating the optical axis by 45 ° clockwise when viewed from the emergent surface. Further, the electric vector of the linearly polarized light emitted when the counterclockwise circularly polarized light is incident is at a position obtained by rotating the optical axis by 45 ° counterclockwise when viewed from the emergent surface.

Hereinafter, in the present embodiment, a case where, for example, six quarter-wave plates 111 are provided will be described.
Further, the quarter wavelength plate 111 has an isosceles triangle shape on both principal surfaces, and has a triangular prism shape.

Here, an angle formed by two equal sides on one main surface of the quarter-wave plate 111 is defined as an apex angle.
Further, a point on one main surface of the quarter-wave plate 111 where two equal sides contact each other is defined as a vertex.
Further, a side that is one main surface of the quarter-wave plate 111 and connects two equal sides is defined as a bottom side.
A line drawn perpendicularly from the apex of the quarter-wave plate 111 to the bottom is defined as a perpendicular line S.

The quarter-wave plate has an optical axis C that is parallel to both main surfaces.
In the quarter-wave plate, the perpendicular S and the optical axis C form an angle of 45 °. At this time, when viewed from the surface from which the light of the quarter-wave plate is emitted, the optical axis C is parallel to a line obtained by rotating the perpendicular S in the in-plane direction by 45 ° clockwise.

As described above, a quarter-wave plate generally has an electric vector parallel to a line obtained by rotating the optical axis by 45 ° counterclockwise when circularly polarized light that rotates clockwise is incident on a plane parallel to the optical axis. The provided linearly polarized light is emitted.
Accordingly, when the circularly polarized light that rotates clockwise is incident on a plane parallel to the optical axis C, the quarter-wave plate 111 emits linearly polarized light having an electric vector parallel to the perpendicular S.

  The quarter wavelength plate 111 is joined to the side surfaces of the quarter wavelength plate 111 so that the apex angles are 360 °. At this time, the top of the quarter wavelength plate 111 is in contact with one point, and the base is provided on the outer edge side.

  Here, the side surface of the quarter-wave plate 111 is a surface that includes two equal sides of one main surface and is a surface perpendicular to the one main surface.

  Therefore, the joined quarter wavelength plate 111 is provided radially from the point where the perpendicular S drawn from the apex to the base contacts the apex.

  The six quarter-wave plates 111 have, for example, apex angles of 60 °, and the side surfaces of the quarter-wave plates 111 are joined to each other so that the six apex angles are 360 °. As you go, it becomes a regular hexagonal prism.

  The quarter-wave plate 111 is bonded by, for example, atomic diffusion bonding that is performed by providing a metal film (not shown) of 1 nm or less. At this time, since the thickness of the metal film is 1 nm or less, the influence of light absorption and reflection by the metal film can be suppressed as compared with the metal film in the case of bonding by anodic bonding. In addition, it is possible to join with high processing accuracy compared to the case of joining using a resin.

According to the polarization conversion element 100 according to the first embodiment of the present invention as described above, the apex angles of the plurality of quarter-wave plates 111 whose principal surfaces are isosceles triangles are combined to be 360 °. Thus, since the side surfaces of the quarter-wave plate 111 are joined and formed in a regular polygonal column shape, the perpendicular lines S drawn from the apex of the quarter-wave plate 111 to the bottom are radial.
Further, according to the polarization conversion element 100 according to the first embodiment of the present invention, when viewed from the emission side, the perpendicular S in which the optical axis C of the quarter-wave plate 111 is drawn from the apex to the base is shown. Since it is provided at a position rotated clockwise by 45 ° in the clockwise direction, when circularly polarized light that rotates clockwise is incident on each quarter-wave plate 111, the vertical line S extends from each quarter-wave plate 111. Linearly polarized light with parallel electrical vectors is emitted.
Therefore, according to the polarization conversion element 100 according to the first embodiment of the present invention, the perpendicular lines S drawn from the apex of the quarter-wave plate 111 to the base are radial, and each 1/4 is provided. When circularly polarized light that rotates clockwise is incident on the wave plate 111, linearly polarized light having an electric vector parallel to the perpendicular line S is emitted. Therefore, when circularly polarized light that rotates clockwise is incident on each quarter wavelength plate 111, the linearly polarized light is linearly emitted. Radially polarized light whose polarization is radial can be emitted.
According to such a polarization conversion element 100 according to the first embodiment of the present invention, it is possible to convert circularly polarized light that rotates clockwise without providing a dielectric film into radial polarized light.

Next, a method for manufacturing the polarization conversion element according to the first embodiment of the present invention will be described.
Here, the polarization conversion element manufactured by the method for manufacturing the polarization conversion element according to the first embodiment is, for example, a polarization conversion element in which circularly polarized light that rotates clockwise is converted into radial polarized light.

  The method for manufacturing a polarization conversion element according to the first embodiment of the present invention includes a quarter-wave plate forming step and a quarter-wave plate joining step.

(1/4 wavelength plate forming process)
The quarter-wave plate forming step includes a quarter-wave plate wafer provided with a portion to be a quarter-wave plate having a triangular prism shape in which both main surfaces are parallel to the optical axis and are isosceles triangles. This is a step of cutting to form a plurality of quarter-wave plates.

The quarter-wave plate wafer has an optical axis, and the optical axis is parallel to both main surfaces.
In addition, when a right-handed circularly polarized light is incident on one main surface of the quarter-wave plate wafer, for example, linearly polarized light having an electric vector parallel to the optical axis rotated 45 ° counterclockwise is obtained. The light is emitted from the other main surface.
In addition, when a counterclockwise circularly polarized light is incident on the quarter wavelength plate wafer, for example, linearly polarized light having an electric vector parallel to the optical axis rotated 45 ° clockwise is emitted from the other main surface. Is done.

  In the quarter-wave plate forming step, for example, a wire saw cutting device is used.

  The quarter-wave plate formed in the quarter-wave plate forming step has a triangular prism shape in which both main surfaces are isosceles triangles.

Here, the angle formed by two equal sides on one main surface of the quarter-wave plate to be formed is defined as an apex angle.
Moreover, the point which is one main surface of the quarter wave plate to be formed which is in contact with two equal sides is defined as a vertex.
Further, a side that is one main surface of the formed quarter-wave plate and connects two equal sides is defined as a bottom side.
Further, a line drawn perpendicularly from the apex to the bottom side of one main surface of the quarter-wave plate to be formed is defined as a perpendicular line.

The formed quarter-wave plate has both major surfaces parallel to the optical axis.
Further, in the formed quarter-wave plate, for example, a line obtained by rotating a perpendicular 45 ° clockwise is parallel to the optical axis.

In the quarter-wave plate forming step, a plurality of quarter-wave plates having the same shape are formed.
Accordingly, in the quarter wavelength plate forming step, a plurality of quarter wavelength plates can be easily formed simultaneously by cutting in three directions using one quarter wavelength plate wafer.

(1/4 wavelength plate bonding process)
The quarter-wave plate joining step is a step of joining the side faces of the quarter-wave plate so that the apex angles of the quarter-wave plates are 360 °.

  In the quarter wave plate bonding step, bonding is performed using atomic diffusion bonding in which a metal film having a thickness of 1 nm or less is used for bonding. At this time, since the thickness of the metal film is 1 nm or less, the influence of light absorption and reflection by the metal film can be suppressed as compared with the metal film in the case of bonding by anodic bonding. In addition, it is possible to join with high processing accuracy compared to the case of joining using a resin.

In the quarter-wave plate joining step, the side faces of the quarter-wave plate are joined so that the apex angles of the quarter-wave plates are 360 ° to form a regular polygonal prism shape.
Therefore, in the quarter wavelength plate joining process, a plurality of quarter wavelength plates are joined so that the bottom of the quarter wavelength plate is located on the outer edge side while the apex of the quarter wavelength plate is in contact at one point. It becomes.
At this time, the perpendicular lines of the respective quarter-wave plates are provided radially from the apex of the quarter-wave plate.

  Therefore, in the method for manufacturing a polarization conversion device according to the first embodiment of the present invention, linearly polarized light having an electric vector parallel to a perpendicular line is emitted when clockwise circularly polarized light is incident. A four-wave plate is formed, and a plurality of quarter-wave plates are joined so that the perpendicular line is provided radially from the apex.

According to the method for manufacturing a polarization conversion element according to the first embodiment of the present invention, the side surface of the quarter wavelength plate is adjusted such that the apex angles of the plurality of quarter wavelength plates are 360 °. Since they are joined to form a regular polygonal column, the perpendicular drawn from the apex to the base is radial with respect to the apex.
In addition, according to such a method for manufacturing a polarization conversion element, the optical axis of each quarter-wave plate is 1 so that the perpendicular line is rotated clockwise in the plane by 45 ° when viewed from the exit side. Since quarter-wave plates are formed, when circularly polarized light that rotates clockwise is incident on each quarter-wave plate, linearly-polarized light having an electric vector parallel to the perpendicular is emitted from each quarter-wave plate. The
Therefore, according to the method for manufacturing a polarization conversion element according to the embodiment of the present invention, by forming a plurality of quarter-wave plates having the same shape and joining them so that the apex angles are 360 °. In addition, a polarization conversion element can be easily manufactured without forming a dielectric film, and productivity can be improved.

(Second embodiment)
A polarization conversion element 200 according to a second embodiment of the present invention will be described.
The polarization conversion element 200 according to the second embodiment of the present invention is provided at a position where the optical axis of the optical rotation plate 211 is rotated in the plane by 45 ° counterclockwise about the perpendicular S of one main surface of the optical rotation plate 211. This is different from the first embodiment.

The polarization conversion element 200 according to the second embodiment of the present invention is mainly composed of a plurality of quarter wavelength plates 211.
Here, the polarization conversion element 200 according to the second embodiment of the present invention is formed in, for example, a regular hexagonal prism shape in which both main surfaces are regular hexagons.

For example, six quarter-wave plates 211 are provided.
Further, the quarter wavelength plate 211 has an isosceles triangle shape on both principal surfaces, and has a triangular prism shape.

Here, an angle formed by two equal sides on one main surface of the quarter-wave plate 211 is defined as an apex angle.
Further, a point on one main surface of the quarter-wave plate 211 where two equal sides contact each other is defined as a vertex.
Further, a side that is one main surface of the quarter-wave plate 211 and connects two equal sides is defined as a bottom side.
A line drawn perpendicularly from the apex of the quarter-wave plate 211 to the bottom is defined as a perpendicular line S.

The quarter-wave plate 211 includes an optical axis C that is parallel to both main surfaces.
In the quarter-wave plate 211, the perpendicular S and the optical axis C form an angle of 45 °. At this time, when viewed from the surface from which the light of the quarter-wave plate is emitted, the optical axis C is parallel to the line obtained by rotating the perpendicular S in the plane by 45 ° counterclockwise.

As described above, the quarter wave plate generally has an electric vector parallel to a line obtained by rotating the optical axis by 45 ° clockwise when a circularly polarized light that rotates counterclockwise is incident on a plane parallel to the optical axis. The linearly polarized light is emitted.
Accordingly, when the circularly polarized light that rotates counterclockwise is incident on the quarter wavelength plate 211 on a plane parallel to the optical axis C, linearly polarized light having an electric vector parallel to the perpendicular S is emitted.

  The quarter-wave plate 211 is joined to the side surfaces of the quarter-wave plate 211 such that the apex angle is 360 °. At this time, the top of the quarter wavelength plate 211 is in contact with one point, and the base is provided on the outer edge side.

  Here, the side surface of the quarter-wave plate 211 is a surface that includes two equal sides of one main surface and is a surface perpendicular to the one main surface.

  Therefore, the joined quarter wavelength plate 211 is provided radially from the point where the perpendicular line S drawn from the apex to the base contacts the apex.

  The six quarter-wave plates 211 have, for example, vertex angles of 60 °, and the side surfaces of the quarter-wave plates 211 are joined to each other so that the six vertex angles are 360 °. As you go, it becomes a regular hexagonal prism.

  The quarter-wave plate 211 is bonded by, for example, atomic diffusion bonding that is performed by providing a metal film (not shown) of 1 nm or less. At this time, since the thickness of the metal film is 1 nm or less, the influence of light absorption and reflection by the metal film can be suppressed as compared with the metal film in the case of bonding by anodic bonding. In addition, it is possible to join with high processing accuracy compared to the case of joining using a resin.

According to the polarization conversion element 200 according to the second embodiment of the present invention, the apex angles of a plurality of quarter-wave plates 211 whose both principal surfaces are isosceles triangles are 360 °. Thus, since the side surfaces of the quarter wavelength plate 211 are joined and formed in a regular polygonal column shape, the perpendicular lines S drawn from the apex of the quarter wavelength plate 211 to the bottom are radial.
In addition, according to the polarization conversion element 200 according to the first embodiment of the present invention, when viewed from the emission side, the perpendicular line S in which the optical axis C of the quarter-wave plate 211 is drawn from the apex to the base is shown. Since the counterclockwise rotation is provided at a position rotated by 45 ° in the plane, when the circularly polarized light that is rotated counterclockwise is incident on each quarter-wave plate 211, the perpendicular S from each quarter-wave plate 211. Linearly polarized light with an electrical vector parallel to the beam is emitted.
Therefore, according to the polarization conversion element 200 according to the second embodiment of the present invention, the perpendicular lines S drawn from the apex of the quarter-wave plate 211 to the bottom are radial, and each 1/4 is provided. When circularly polarized light that rotates counterclockwise is incident on the wave plate 211, linearly polarized light having an electric vector parallel to the perpendicular line S is emitted. Therefore, when circularly polarized light that rotates counterclockwise is incident on each quarter wavelength plate 211, the linearly polarized light is emitted. Radially polarized light whose polarization is radial can be emitted.
According to the polarization conversion element 200 according to the second embodiment of the present invention, it is possible to convert the circularly polarized light that rotates counterclockwise into radial polarized light without providing a dielectric film.

Next, a method for manufacturing a polarization conversion element according to the second embodiment of the present invention will be described.
In the method for manufacturing a polarization conversion element according to the second embodiment of the present invention, the optical axis of the quarter-wave plate formed in the quarter-wave plate forming step is a line obtained by rotating the perpendicular 45 ° counterclockwise. It differs from the first embodiment in that it is parallel.

The method for manufacturing a polarization conversion element according to the second embodiment differs from the first embodiment in that a polarization conversion element that converts circularly polarized light that rotates counterclockwise into radial polarized light is manufactured.

  The quarter-wave plate forming step includes a quarter-wave plate wafer provided with a portion to be a quarter-wave plate having a triangular prism shape in which both main surfaces are parallel to the optical axis and are isosceles triangles. This is a step of cutting to form a plurality of quarter-wave plates.

The quarter-wave plate wafer has an optical axis, and the optical axis is parallel to both main surfaces.
In addition, when a right-handed circularly polarized light is incident on one main surface of the quarter-wave plate wafer, for example, linearly polarized light having an electric vector parallel to the optical axis rotated 45 ° counterclockwise is obtained. The light is emitted from the other main surface.
In addition, when a counterclockwise circularly polarized light is incident on the quarter wavelength plate wafer, for example, linearly polarized light having an electric vector parallel to the optical axis rotated 45 ° clockwise is emitted from the other main surface. Is done.

  In the quarter-wave plate forming step, for example, a wire saw cutting device is used.

  The quarter-wave plate formed in the quarter-wave plate forming step has a triangular prism shape in which both main surfaces are isosceles triangles.

Here, the angle formed by two equal sides on one main surface of the quarter-wave plate to be formed is defined as an apex angle.
Moreover, the point which is one main surface of the quarter wave plate to be formed which is in contact with two equal sides is defined as a vertex.
Further, a side that is one main surface of the formed quarter-wave plate and connects two equal sides is defined as a bottom side.
Further, a line drawn perpendicularly from the apex to the bottom side of one main surface of the quarter-wave plate to be formed is defined as a perpendicular line.

The formed quarter-wave plate has both major surfaces parallel to the optical axis.
In the quarter wave plate to be formed, for example, a line obtained by rotating a perpendicular 45 ° counterclockwise is parallel to the optical axis.

In the quarter-wave plate forming step, a plurality of quarter-wave plates having the same shape are formed.
Accordingly, in the quarter wavelength plate forming step, a plurality of quarter wavelength plates can be easily formed simultaneously by cutting in three directions using one quarter wavelength plate wafer.

Therefore, the manufacturing method of the polarization conversion element according to the second embodiment of the present invention includes a ¼ wavelength plate from which linearly polarized light having an electric vector parallel to a perpendicular line is emitted when the counterclockwise circularly polarized light is incident. Forming.
In addition, in the method for manufacturing a polarization conversion element according to the second embodiment of the present invention, a quarter-wave plate having a triangular prism shape in which both main surfaces are isosceles triangles is formed, and the quarter-wave plate is joined. It is formed in a regular polygonal column shape. At this time, it has a structure in which perpendiculars are located radially along the apex of the quarter-wave plate.

According to the method for manufacturing a polarization conversion element according to the second embodiment of the present invention, the side surfaces of the quarter-wave plates are adjusted so that the apex angles of the plurality of quarter-wave plates are 360 °. Since they are joined to form a regular polygonal column, the perpendicular drawn from the apex to the base is radial with respect to the apex.
Further, according to the second method for manufacturing a polarization conversion element of the present invention, when the optical axis of each quarter-wave plate is viewed from the emission side, the perpendicular is rotated in the plane by 45 ° counterclockwise. Since the quarter wave plates are formed so as to be in the positions, when the counterclockwise circularly polarized light is incident on each quarter wave plate, an electric vector parallel to the perpendicular line is generated from each quarter wave plate. The provided linearly polarized light is emitted.
Therefore, according to the method for manufacturing a polarization conversion element according to the second embodiment of the present invention, a plurality of quarter-wave plates having the same shape are formed and the apex angles are adjusted to be 360 °. By bonding, a polarization conversion element can be easily manufactured without forming a dielectric film, and productivity can be improved.

  In addition, although the case where the polarization conversion element is composed of six quarter-wave plates is described, if the sum of the apex angles of the quarter-wave plates is 360 °, for example, eight It may be. At this time, the apex angle is 45 °.

  In addition, the case where the polarization conversion element is composed of an even number of six quarter-wave plates is described. If the sum of the apex angles of the quarter-wave plates is 360 °, for example, Nine may be sufficient. At this time, the apex angle is 40 °.

100, 200 Polarization conversion elements 111, 211 ¼ wavelength plate C optical axis S perpendicular

Claims (3)

A polarization conversion element that converts right-handed circularly polarized light into radial polarized light,
A plurality of quarter-wave plates having a triangular prism shape in which both main surfaces are isosceles triangles,
The apex angle is an angle formed by two equal sides on one main surface of the quarter-wave plate, and the apex is a point where two equal sides are touched on one main surface of the quarter-wave plate, When one side of the quarter-wave plate and the side connecting two equal sides is the bottom side,
When viewed from the exit side, the optical axis of the quarter-wave plate is provided at a position rotated in a 45 ° clockwise direction perpendicular to the vertex drawn from the apex to the base,
The quarter-wave plates are joined to each other so that the apex angles of the quarter-wave plates are 360 °, and are formed in a regular polygonal prism shape in which both main surfaces are regular polygons. A polarization conversion element characterized by comprising: A polarization conversion element that converts left-handed circularly polarized light into radial polarized light,
A plurality of quarter-wave plates having a triangular prism shape in which both main surfaces are isosceles triangles,
The apex angle is an angle formed by two equal sides on one main surface of the quarter-wave plate, and the apex is a point where two equal sides are touched on one main surface of the quarter-wave plate, When one side of the quarter-wave plate and the side connecting two equal sides is the bottom side,
When viewed from the output side, the optical axis of the quarter-wave plate is provided at a position rotated in the plane by 45 ° counterclockwise with a perpendicular drawn from the apex to the base,
The quarter-wave plates are joined to each other so that the apex angles of the quarter-wave plates are 360 °, and are formed in a regular polygonal prism shape in which both main surfaces are regular polygons. A polarization conversion element characterized by comprising: A method of manufacturing a polarization conversion element that converts circularly polarized light into radial polarized light,
A plurality of quarter-wave plates are obtained by cutting a quarter-wave plate wafer provided with a portion to be a quarter-wave plate having a triangular prism shape in which both main surfaces are parallel to the optical axis and are isosceles triangles. A quarter-wave plate forming step of forming
The apex angle is an angle formed by two equal sides on one main surface of the quarter-wave plate, and the apex is a point where two equal sides are touched on one main surface of the quarter-wave plate, When one side of the quarter-wave plate and the side connecting two equal sides is the bottom side,
A quarter wavelength plate joining step of joining the side faces of the quarter wavelength plate so that the apex angle of the quarter wavelength plate is 360 °,
With
In the quarter-wave plate forming step, the optical axis of each quarter-wave plate is 1/50 so that the perpendicular line is rotated in the plane by 45 ° clockwise or counterclockwise when viewed from the output side. A four-wave plate is formed,
A method for manufacturing a polarization conversion element, wherein the quarter-wave plate joined in the quarter-wave plate joining step has a regular polygonal prism shape.

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