JP7221320B2 - Broadband retarder, measuring device and optical attenuator provided with broadband retarder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a retarder, and more particularly to a broadband retarder that can be used in a wide band, a measuring device having the broadband retarder, and an optical attenuator.

A wave plate is an optical element that changes the state of incident polarized light by giving a predetermined phase difference (optical path difference) to two orthogonal polarized light components. In general, two types of wave plates are commonly used: a half-wave plate (λ/2 plate) and a quarter-wave plate (λ/4 plate).

A half-wave plate (HWP) is a wave plate that gives a 1/2 phase difference to an incident light beam. Specifically, λ It is an optical element that provides a phase difference of /2 (180°). A half-wave plate is used to give a phase difference of λ/2 (180°) to an incident light beam and rotate linearly polarized light to emit the light.

A quarter-wave plate (QWP) is a wave plate that gives a 1/4 phase difference to an incident light beam. Specifically, λ It is an optical element that provides a phase difference of /4 (90°). A quarter-wave plate is used to give a phase difference of λ/4 (90°) to an incident light beam to convert linearly polarized light into circularly polarized light or circularly polarized light into linearly polarized light.

Patent Documents 1 and 2 disclose three half-wave plates, one half-wave plate and two quarter-wave plates with crystal axes of birefringent wave plates such as crystal. Pankaratnam-type broadband waveplates are described that are staggered and combined to form a broadband waveplate.

S.PANCHARATNAM, "ACHROMATIC COMBINATIONS OF BIREFRINGENT PLATES PartI. An Achromatic Circular Polarizer", Proc. Indian Acad. Sci., A41, p.130-, 1955. S.PANCHARATNAM, "ACHROMATIC COMBINATIONS OF BIREFRINGENT PLATES PartII. An Achromatic Quarter-Wave Plate", Proc. Indian Acad. Sci., A41 P.137-, 1955.

Polarization measurement is an effective method for analyzing film materials and foreign substances. Among them, spectroscopic polarization measurement is one of the useful analysis prescriptions that can investigate the dispersion characteristics of materials, etc. by adding the parameter of wavelength. be. In addition, there are many substances that have polarization-dependent absorption and scattering properties, not only natural substances and artificial substances, so they are also useful for physics and chemistry.

Spectral polarimetry is also effective for angle measurement, shape analysis of a black object, and other measurements that utilize the difference in reflectance between p-wave and s-wave. For this reason, broadband retarders, which have a wide wavelength band and can convert the polarization state, have been devised and used in many structures and methods. There were almost no elements in which the change in phase difference was small (in other words, the wavelength dependence of the phase difference was small).

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical element that can be used in a broadband and, in particular, has less wavelength dependence of phase difference than a conventional broadband retarder. An object of the present invention is to provide a measuring device and an attenuator provided with an optical element.

As a result of intensive research to solve the above problems, the present inventors have found a broadband wave plate combining a conventionally known birefringent λ/2 plate and a λ/4 plate, and a broadband retarder. The present invention was completed by finding a combination of Fresnel rhombs.

According to the broadband phase shifter of the present invention, the above problem is provided with a first phase difference generating section, a second phase difference generating section, and a third phase difference generating section, and the incidence of the second phase difference generating section The first phase difference generator is arranged on the surface side, the third phase difference generator is arranged on the output surface side of the second phase difference generator, and the second phase difference generator has a wavelength of 200 to 2600 nm. gives a phase difference of 1 80° ± 10% between the p-wave and the s-wave by total reflection at the wavelength of 200 to 2600 nm . A phase difference of 90 ° ± 10% is given between the wave and the s-wave, and the incident surface of the second phase difference generating portion is the first phase difference generating portion and the third phase difference generating portion with the incident light beam axis as the rotation axis. The first phase difference generating part, the second phase difference generating part, and the third phase difference generating part are arranged to rotate with respect to the incident surface of the phase difference generating part, and the first phase difference generating part, the second phase difference generating part, and the third phase difference generating part are composed of Fresnel rhombs. The optical axes of the light beam and the emitted light beam are coaxial, and the first phase difference generating section provides a phase difference of 90° ± 10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm. Having a Fresnel rhomb, the second phase difference generating unit has a second Fresnel rhomb that gives a phase difference of 180° ± 10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm, and the third The phase difference generator has a third Fresnel rhomb that gives a phase difference of 90°±10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm. The plane of incidence of the Fresnel ROM is rotated by 67.5°±10% with respect to the planes of incidence of the first Fresnel ROM and the third Fresnel ROM. °±5° .
Further, according to the broadband phase shifter of the present invention, the above-mentioned problem is provided with a first phase difference generating section, a second phase difference generating section, and a third phase difference generating section, and the second phase difference generating section The first phase difference generator is arranged on the incident surface side of the second phase difference generator, the third phase difference generator is arranged on the exit surface side of the second phase difference generator, and the second phase difference generator has a wavelength of 200 A phase difference of 180° ± 10% is given between the p-wave and the s-wave by total reflection at ~2600 nm, and the first phase difference generating section and the third phase difference generating section are generated by total reflection at a wavelength of 200 to 2600 nm. A phase difference of 180°±10% is given between the p-wave and the s-wave, and the incident surface of the second phase difference generating section is the first phase difference generating section and the third phase difference generating section, with the incident light beam axis as the rotation axis. The first phase difference generating part, the second phase difference generating part, and the third phase difference generating part are arranged to rotate with respect to the incident surface of the phase difference generating part, and the first phase difference generating part, the second phase difference generating part, and the third phase difference generating part are composed of Fresnel rhombs. The optical axes of the light beam and the emitted light beam are coaxial, and the first phase difference generating section is a first Fresnel rhomb that provides a phase difference of 180°±10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm. and the second phase difference generator has a second Fresnel rhomb that gives a phase difference of 180° ± 10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm, and the third The phase difference generator has a third Fresnel lobe that provides a phase difference of 180°±10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm, and the second Fresnel lobe with the axis of the incident light beam as the axis of rotation. is rotated by 60°±10% with respect to the incident surfaces of the first Fresnel ROM and the third Fresnel ROM, and the phase difference of the emitted light with respect to the incident light is 180°±5 at a wavelength of 200 to 2600 nm. ° is resolved by

In this way, by combining a broadband Fresnel rhomb phase shifter with a broadband structure, it has ultra-wideband characteristics that can be used in the wavelength region from vacuum ultraviolet to near infrared, and can rotate linearly polarized light, Circularly polarized light with high precision can be produced, and broadband retarders with coaxial input and output beams can be provided.

At this time, the Fresnel rhombs constituting the first phase difference generating portion, the second phase difference generating portion, and the third phase difference generating portion are made of at least one material selected from the group consisting of quartz, _CaF2, and LiF. It is good to be formed with.
At this time, it is preferable that the Fresnel rhombs constituting the first phase difference generating portion, the second phase difference generating portion, and the third phase difference generating portion have a multilayer film formed on at least one or more total reflection surfaces. .

Moreover, according to the measuring apparatus of this invention, the said subject is solved by providing said wide-band retarder.
Moreover, according to the optical attenuator of the present invention, the above object is solved by providing the broadband phase shifter.

According to the broadband retarder of the present invention, it can be used in the vacuum ultraviolet to near infrared wavelength range (for example, 200 to 2600 nm), and can rotate linearly polarized light or create highly accurate circularly polarized light. It becomes possible.

In addition, since the Fresnel ROM of the present invention has the above characteristics, it can be applied to various measurement devices, such as measurement devices, analysis devices, inspection devices, and observation devices. Various polarization measurements can be performed. Furthermore, by applying the Fresnel rhomb of the present invention to an optical attenuator, it becomes possible to adjust the light intensity of the oscillation light of the laser device and the light intensity of the white light.

FIG. 2 is a schematic diagram of a broadband wave plate with a pancalatnam structure; 4 is a graph showing retardation characteristics of a λ/4 plate (QWP) that constitutes the Pankaratnam structure. 4 is a graph showing retardation characteristics of a λ/2 plate (HWP) that constitutes the Pankaratnam structure. 4 is a graph showing retardation characteristics of a λ/4 broadband waveplate with a pancalatnam structure. 4 is a graph showing ellipticity characteristics of a λ/4 broadband wave plate with a pancalatnam structure; 4 is a graph showing the polarization axis directions of a λ/4 broadband waveplate with a pancalatnam structure; FIG. 4 is a graph showing retardation characteristics of a λ/2 broadband waveplate with a pancalatnam structure; FIG. 2 is a graph showing ellipticity characteristics of a pancalatnam structure λ/2 broadband waveplate. 4 is a graph showing polarization axis directions of a λ/2 broadband wave plate with a pancalatnam structure; 1 is a schematic diagram of a standard λ/4 Fresnel ROM (manufactured by BK-7); FIG. 1 is a schematic diagram of a standard λ/2 Fresnel ROM (manufactured by BK-7); FIG. 10 is a graph showing the relationship between the angle of incidence from BK-7 to air and the phase difference. 4 is a graph showing the relationship between the angle of incidence from quartz to air and the phase difference. 4 is a graph showing the wavelength dependence of the phase difference of a BK-7 Fresnel rhomb (λ/4). 2 is a graph showing the wavelength dependence of the phase difference of a BK-7 Fresnel rhomb (λ/2). 4 is a graph showing the wavelength dependence of the retardation of a Fresnel rhomb (λ/4) made of quartz. 4 is a graph showing the wavelength dependence of the retardation of a Fresnel rhomb (λ/2) made of quartz. FIG. 2 is a schematic diagram showing the structure of a Pankaratnam-type λ/4 Fresnel rhomb. FIG. 3 is a schematic diagram showing the structure of a Pankaratnam-type λ/2 Fresnel rhomb. 4 is a graph showing retardation characteristics of a Pankaratnam-type quartz λ/4 Fresnel rhomb. 4 is a graph showing ellipticity characteristics of a Pankaratnam-type quartz λ/4 Fresnel rhomb. 4 is a graph showing the polarization axis direction of a Pankaratnam-type quartz λ/4 Fresnel rhomb. 4 is a graph showing retardation characteristics of a Pankaratnam-type quartz λ/2 Fresnel rhomb. 4 is a graph showing ellipticity characteristics of a Pankaratnam-type quartz λ/2 Fresnel rhomb. 2 is a graph showing the polarization axis direction of a Pankaratnam-type quartz λ/2 Fresnel rhomb. 1 is a schematic diagram showing the structure of a crystal Fresnel prism; FIG. 4 is a graph showing an example of the circular polarization separation angle of a quartz Fresnel prism. FIG. 4 is a schematic diagram showing 90° rotation of linearly polarized light due to reflection; FIG. 2 is a schematic diagram showing the structure of a Pankaratnam-type quartz λ/4 Fresnel rhomb (Example 1). 4 is a graph showing phase difference characteristics of the element of Example 1. FIG. 4 is a graph showing ellipticity characteristics of the element of Example 1. FIG. 4 is a graph showing the polarization axis directions of the element of Example 1. FIG. FIG. 2 is a schematic diagram showing the structure of a Pankaratnam-type quartz λ/2 Fresnel rhomb (Example 2). 10 is a graph showing retardation characteristics of the element of Example 2. FIG. 10 is a graph showing the ellipticity characteristics of the device of Example 2. FIG. 7 is a graph showing the polarization axis directions of the device of Example 2. FIG. 10 is a graph showing retardation characteristics of the element of Example 3. FIG. 10 is a graph showing the ellipticity characteristics of the element of Example 3. FIG. 10 is a graph showing the polarization axis directions of the element of Example 3. FIG. 10 is a graph showing phase difference characteristics of the element of Example 4. FIG. 10 is a graph showing the ellipticity characteristics of the element of Example 4. FIG. 10 is a graph showing the polarization axis directions of the element of Example 4. FIG. FIG. 10 is a schematic diagram showing the structure of a king-type Pankaratnam-type quartz-made λ/4 Fresnel rhomb with an optical film (Example 5). 10 is a graph showing retardation characteristics of the element of Example 5. FIG. 10 is a graph showing the ellipticity characteristics of the element of Example 5. FIG. 10 is a graph showing the polarization axis directions of the element of Example 5. FIG. 10 is a graph showing phase difference characteristics of the element of Example 6. FIG. 10 is a graph showing the ellipticity characteristics of the device of Example 6. FIG. 10 is a graph showing the polarization axis directions of the device of Example 6. FIG.

A broadband retarder according to an embodiment of the present invention (hereinafter referred to as the present embodiment) will be described below with reference to FIGS. 1 to 21C. The broadband retarder according to this embodiment is a broadband retarder in which the wavelength dependence of the phase difference is small in the vacuum ultraviolet to near-infrared wavelength region.

In the present specification, ◯ nm to Δnm mean ◯ nm or more and Δ nm or less.
As used herein, approximately means a numerical value of ±10%, preferably ±5%, more preferably ±3%, even more preferably ±2%, and particularly preferably ±1%.
As used herein, the term “contact” refers to a pair of adjacent Fresnel rhombs (prism elements, rhombohedrons) arranged in contact with each other. It also includes splicing.
Further, in this specification, Fresnel rhombs (prism elements, rhombohedrons) "facing" means optical contacts that are directly bonded, and bonding that is bonded with something interposed, such as an adhesive. The case includes the case where an air layer is interposed.

[1. basic ideas]
The broadband retarder according to the present embodiment is a combination of a broadband wavelength plate that combines a conventionally known birefringent λ/2 plate and a λ/4 plate and a Fresnel rhomb known as a broadband retarder. be. First, a broadband wavelength plate that combines a birefringent λ/2 plate and a λ/4 plate will be described.

(1) Broadband wave plate (pankaratnam structure wave plate) combining three birefringent wave plates
FIG. 1 and Table 1 show a structural diagram (arrangement diagram) of a Pankaratnam-type broadband wavelength plate. As shown in FIG. 1 and Table 1, it consists of three wave plates. The first and third wave plates are the same wave plate, and the second wave plate has a phase difference of 180°. It is a wave plate configured in an axial direction different from that of the wave plate. The wave plate may be a single wave plate made of a birefringent material, or a wave plate made of a combination of a plurality of birefringent material plates. With such a configuration, a wave plate with a wider band can be produced.

FIG. 2A and FIG. 2B show the wavelength dependence of the phase difference of the wave plates with a phase difference of 90° and 180°, which are combined elements of quartz and MgF ₂ crystal. The optical properties of these combined Pankaratnam-type retarders are shown in FIGS. 2C-2H. 2C and 2F show the wavelength dependence of the phase difference, but the Pankaratnam type retarder cannot express the output polarization state by the phase difference. The output polarization state is represented by the ellipticity in FIGS. 2D and 2G and the polarization axis directions in FIGS. 2E and 2H. As can be seen from FIGS. 2C to 2H, the Pankaratnam type is a device that exhibits rather excellent performance as a λ/2 plate.

(2) Fresnel rom Figs. 3A and 3B show the shape of a standard Fresnel rom. FIG. 3A is a schematic diagram of a λ/4 Fresnel ROM (manufactured by BK-7), and FIG. 3B is a schematic diagram of a λ/2 Fresnel ROM (manufactured by BK-7).

As shown in FIG. 3A, the first rhombohedron 10 forming the λ/4 Fresnel rhomb has a first incident end face 11, a first exit end face 12 arranged parallel to the first incident end face 11, and a first incident end face 11 and the first output end face 12, and a second total reflection surface 14 arranged parallel to the first total reflection surface 13. As shown in FIG.

In the first rhombohedron 10, the first entrance end face 11 and the first exit end face 12 are parallel to each other, and the first total reflection surface 13 and the second total reflection surface 14 are parallel to each other. Further, in the first rhombohedron 10, the angles between the first incident end surface 11 and the first total reflection surface 13 and between the first exit end surface 12 and the second total reflection surface 14 are less than 90 degrees each other. They intersect at an angle (wedge angle α). Further, in the first rhombohedron 10, the angles between the first incident end surface 11 and the second total reflection surface 14 and between the first output end surface 12 and the first total reflection surface 13 are greater than 90 degrees to each other. intersect at an angle.

As shown in FIG. 3B, the λ/2 Fresnel Rhomb has a structure (roof-shaped Fresnel Rhomb) in which two parallelogram-shaped prism elements are combined. Specifically, the λ/2 Fresnel rhomb has a parallelogram-shaped cross section (a cross section parallel to the surface of FIG. 3B, that is, a cross section orthogonal to each incident end face, outgoing end face, and total reflection surface described later). A first rhombohedron 10 and a second rhombohedron 20 are provided. The first rhombohedron 10 and the second rhombohedron 20 have the same shape and are made of an isotropic material.

The second rhombohedron 20 has a second incident end face 21, a second exit end face 22 arranged parallel to the second incident end face 21, and a third total reflection surface intersecting the second incident end face 21 and the second exit end face 22. 23 and a fourth total reflection surface 24 arranged parallel to the third total reflection surface 23 .

In the second rhombohedron 20, the second entrance end face 21 and the second exit end face 22 are parallel to each other, and the third total reflection surface 23 and the fourth total reflection surface 24 are parallel to each other. Further, in the second rhombohedron 20, the angles between the second incident end surface 21 and the third total reflection surface 23 and between the second exit end surface 22 and the fourth total reflection surface 24 are less than 90 degrees to each other. They intersect at an angle (wedge angle α). Further, in the second rhombohedron 20, the angles between the second incident end surface 21 and the fourth total reflection surface 24 and between the second output end surface 22 and the third total reflection surface 23 are greater than 90 degrees. intersect at an angle.

The first rhombohedron 10 and the second rhombohedron 20 are arranged to face each other such that the first emission end face 12 of the first rhombohedron 10 and the second incident end face 21 of the second rhombohedron 20 are parallel to each other. ing. The first emission end face 12 and the second incidence end face 21 are preferably directly joined by optical contact. It is also possible to place

As described above, the first incident end surface 11 and the first total reflection surface 13 (the first output end surface 12 and the second total reflection surface 14) of the first rhombohedron 10 form a wedge angle α. The second entrance end surface 21 and the third total reflection surface 23 (the second exit end surface 22 and the fourth total reflection surface 24) of the rhombohedron 20 also form a wedge angle α. Here, the wedge angle α can be appropriately set according to the type of isotropic material that constitutes the first rhombohedron 10 and the second rhombohedron 20. When the isotropic material is BK-7, , the wedge angle α=55°, for quartz the wedge angle α=54°, and for the isotropic material _CaF2 the wedge angle α=54°.

As described above, the Fresnel rhomb is made of an isotropic material that does not have birefringence, but is a phase shifter that utilizes the phase difference between the p-wave and s-wave generated during total internal reflection. Total internal reflection is a phenomenon that occurs when light is incident from a high refractive material to a low refractive material at an angle equal to or greater than the critical angle. 4A and 4B show the relationship between the angle of incidence on the reflecting surface and the generated phase difference when the materials are BK-7, which is a typical optical glass, and quartz.

From FIGS. 4A and 4B, it can be seen that normal reflection below the critical angle does not produce a phase difference. Also, it can be seen that the generated phase difference differs depending on the angle even if the critical angle is exceeded. It can also be seen that the maximum value of the generated phase difference differs depending on the refractive index of the ROM material (difference in refractive index between incident and outgoing media).

When the ROM material is BK-7, the phase difference is about 45° when the incident angle is about 55°. Therefore, by total reflection twice, a phase difference of 90° can be obtained, and by total reflection four times, a phase difference of 180° can be obtained.

5A and 5B show the wavelength dependence of the retardation of Fresnel rhombs made of BK-7. Also, FIG. 6A and FIG. 6B show the wavelength dependence of the phase difference of the Fresnel rhomb made of quartz. From FIGS. 2, 5A and 5B, and 6A and 6B, it can be seen that the wavelength dependence of the Fresnel rhomb phase difference is small.

(3) Pankaratnam type Fresnel rhomb (broadband retarder of this embodiment)
The broadband phase shifter 1 according to this embodiment has a structure in which the above two wideband phase shifters are combined. By constructing a Fresnel Rhomb retarder with a broadband characteristic with a broadband structure, an unprecedented ultra-wideband characteristic can be obtained.

As an example of the broadband phase shifter 1 according to this embodiment, FIGS. 7A and 7B show a pancalatnam-type Fresnel rhomb made of quartz. In addition, output polarization parameters such as phase difference are shown in FIGS. 8A to 8C. Although the polarization direction of emitted light has wavelength dependence in the same way as a wave plate with a pancalatnam structure, this device exhibits characteristics similar to those of a relatively general wave plate.

The basic structure is as shown in FIGS. 7A and 7B, in which total reflection occurs between two phase shifters with a phase difference of 90° or 180° between the p-wave and s-wave. It has a structure in which a phase shifter, in which a phase difference of 180° is provided between the p-wave and the s-wave by reflection, is rotated by a predetermined angle around the axis of the light beam (incident light beam axis) as the rotation axis.

It is not necessary to generate a phase difference of about 180° or about 90° between the p-wave and the s-wave in one total reflection, and in the example of FIGS. 7A and 7B , it is generated in one total reflection. The phase difference is about 45°, total reflection is repeated four times to generate a phase difference of about 180°, and total reflection is repeated twice to generate a phase difference of about 90°.

In Figures 7A and 7B each rom (criscohedral block) is butted, but need not be. Also, when bonding each ROM, an adhesive may be used as long as it is transparent in the operating band. However, since there are few adhesives that are transparent in the deep ultraviolet region, it is preferable to join them by optical contact. When joining, it is necessary to be careful not to apply stress to the isotropic material of the rom material and not to cause anisotropy.

An AR film (antireflection film) may be applied to the end faces, and it is preferable that the transmittance can be improved over the entire operating band. However, for example, when the material of the element of the present invention is quartz, the usable wavelength band is λ=180 to 2600 nm, and it is generally difficult to form an effective anti-reflection film over this entire band. There is a method using a MgF ₂ single layer film, although it cannot be greatly reduced. There is also a method of applying a special antireflection film with a moth-eye structure. Of course, the antireflection film may not be applied. Again, no significant effect on the output polarization occurs. The end face refers not only to the incident/exit surface but also to the incident/exit surface of each ROM when each ROM is not joined.

In FIGS. 7A and 7B, the three ROMs have the same shape. If they are combined, there is an effect of widening the band. Also, the number of reflections does not have to be a combination of four and two. By applying an optical multilayer film to the total reflection surface and using a broadband ROM, the band can be broadened and the accuracy of the output circularly polarized light can be improved.

As shown in FIGS. 8C and 9C, the retarder of this structure changes the polarization axis direction of emitted light depending on the wavelength. This is also the case with Pankaratnam structures using birefringent materials. This is not a problem when circularly polarized light is generated from linearly polarized light with a Pankaratnam-type λ/4 Fresnel Rhomb (product with a phase difference of 90°), but when linearly polarized light is generated from circularly polarized light, the direction of linearly polarized light changes depending on the wavelength. It may become In the Pankaratnam-type λ/2 Fresnel rhomb (product with a phase difference of 180°), the polarization axis direction has some wavelength dependence, but it is not large. Therefore, depending on the intended use, it can be used without any problem.

(4) Advantages and Disadvantages of the Broadband Retarder According to the Present Embodiment The advantage of the broadband retarder according to the present embodiment is that linearly polarized light can be rotated in a wide wavelength range, and linearly polarized light can be converted into circularly polarized light. It can be done, the incident light beam and the output light beam are coaxial, and the fabrication is easy. A disadvantage of the broadband retarder according to this embodiment is its relatively large size. As described above, the broadband phase shifter according to the present embodiment has advantages and disadvantages, and is characterized by its ability to rotate linearly polarized light and convert linearly polarized light into highly accurate circularly polarized light in a wide wavelength band. It is an element that

[2. Conventional technology]
Broadband λ/4 phase shifters and circular polarizers are shown below as prior art. As described above, the Pankaratnam structure has better broadband characteristics than the original λ/2 retarder and λ/4 retarder, and is a structure that can create a retarder with characteristics similar to those of a λ/2 plate and a λ/4 plate. is. Therefore, if the wavelength dependence of the original phase shifter is small, a phase shifter having a phase difference with less wavelength dependence can be manufactured.

As is conventionally known, Fresnel rhombs have less wavelength dependence than λ/2 plates and λ/4 plates using birefringent materials. It is clear that a retarder with a wider band than the conventional Fresnel Rhomb can be obtained by using a retarder with a wider band than the conventional Fresnel Rhomb.

In addition, even a retarder with a pancalatnam structure that uses a birefringent film to widen the wavelength band is not transparent in the ultraviolet region because it is made using an organic substance. There are characteristic absorption lines even in the infrared region, and it is not a retarder that covers the ultraviolet to infrared region.

Although not a retarder, there is a Fresnel prism as a broadband circular polarizer with a completely different structure. This is, for example, a circular polarizer that separates left and right circularly polarized light at the joint surface by combining a right-handed crystal and a left-handed crystal.

FIG. 10 shows a schematic diagram of a crystal Fresnel prism. FIG. 11 shows an example of the wavelength dependence of the separation angles of right-handed and left-handed circularly polarized light. The Fresnel prism is an element that can obtain almost perfect circularly polarized light in a wide band, but the material that can obtain a large separation angle has not been found, and the element is of poor practical use. In addition, since incident linearly polarized light cannot be changed from linearly polarized light to circularly polarized light, it cannot be used in the same way as a λ/4 plate.

The broadband phase shifter according to this embodiment can be made of any isotropic material with a wide transmission band, and can change the phase difference or rotate the linear light to an arbitrary angle. It is a highly practical retarder that can be used in a manner similar to a conventional wave plate. As a method of rotating linear light by 90° in a wide wavelength band, a method of arranging a mirror as shown in FIG. 12 is known. There are drawbacks such as not being able to choose.

[3. Detailed description of the structure of the broadband phase shifter 1 of the present embodiment]
The broadband retarder 1 of this embodiment has a structure in which a λ/4 Fresnel rhomb (λ/4 part Q in FIG. 3A) and a λ/2 Fresnel rhomb (λ/2 part H in FIG. 3B) are combined. It is an optical element in which the optical axis of the emitted light E is coaxial.

The broadband phase shifter 1 of the present embodiment includes a first phase difference generator (λ/2 part H or λ/4 part Q) composed of Fresnel rhombs and a second phase difference generator (λ/2 part H). , and a third phase difference generator (λ/2 part H or λ/4 part Q). A first phase difference generator is arranged on the incident surface side of the second phase difference generator, and a third phase difference generator is arranged on the exit surface side of the second phase difference generator (FIGS. 13 and 15). .

Here, the second phase difference generator is a λ/2 part H that gives a phase difference of approximately 180° between the p-wave and the s-wave by total reflection, and the first phase difference generator and the third phase difference generator The part is either a λ/4 part Q that gives a phase difference of approximately 90° between the p-wave and the s-wave due to total internal reflection, or a λ/2 part H that gives a phase difference of approximately 180°.

In the broadband phase shifter 1 of the present embodiment, the incidence plane of the second phase difference generator is at a predetermined angle ( θ ₂ −θ ₁ ) are rotated.

(1) Pankaratnam-type λ/4 Fresnel Rhomb When the broadband retarder 1 of the present embodiment is a Pankaratnam-type λ/4 Fresnel Rhomb, as shown in FIGS. has a first Fresnel rhomb FR1 (λ/4 part Q) that provides a phase difference of approximately 90° between the p wave and the s wave, and the second phase difference generator has a total reflection between the p wave and the s wave has a second Fresnel rhomb FR2 (λ/2 part H) that gives a phase difference of approximately 180° to the The incident surface of the second Fresnel rhomb FR2 (λ/2 part H) is the first Fresnel rhomb FR1 (λ/4 part Q). and the third Fresnel rhomb FR3 (.lambda./4 portion Q).

More specifically, with the incident ray axis as the rotation axis, the incident surface of the second Fresnel Rhomb FR2 (λ/2 part H) is the first Fresnel Rhomb FR1 (λ/4 part Q) and the third Fresnel Rhomb FR3 (λ/4 part Q ) is rotated by approximately 67.5° (θ ₂ −θ ₁ ) with respect to the incident surface of ), the phase difference of the outgoing light beam E with respect to the incident light beam I is approximately 90°.

When the broadband phase shifter 1 of this embodiment is a Pankaratnam-type λ/4 Fresnel Rhomb, as shown in FIG. It has a first Fresnel rhomb FR1 that provides a phase difference of approximately 90° between waves, and a second phase difference generator (λ/2 portion H) produces a phase difference of approximately 180° between the p-wave and the s-wave due to total reflection. It has a second Fresnel rhomb FR2 that provides a phase difference, and a third phase difference generator (λ/4 part Q) provides a phase difference of approximately 90° between the p-wave and the s-wave by total reflection. It has Fresnel Rhom FR3. With the incident light beam axis as the axis of rotation, the incident surface of the first Fresnel ROM FR1 is arranged to substantially coincide with the incident surface of the third Fresnel ROM FR3. The incident plane of the second Fresnel ROM FR2 is rotated by approximately 67.5° with respect to the incident planes of the first Fresnel ROM FR1 and the third Fresnel ROM FR3, with the axis of incident light as the axis of rotation.

The incident light ray I incident on the first incident end face 11 of the first Fresnel rhomb FR1 (first rhombohedron 10) constituting the λ/4 portion Q is totally reflected eight times (reflected light ray R), resulting in λ/ The emitted light E is emitted from the third Fresnel ROM FR3 constituting the fourth part Q. FIG. When the broadband retarder 1 is a pancalatnam-type λ/4 Fresnel rhomb, it is approximately 90° (specifically, 90°±5°, preferably 90° 90°±2°, more preferably 90°±1°) is emitted.

(2) Pankaratnam-type λ/2 Fresnel rhomb)
When the broadband phase shifter 1 of this embodiment is a Pankaratnam-type λ/2 Fresnel Rhomb, as shown in FIGS. 15 and 7B, the first phase difference generator generates a It has a first Fresnel rhomb FR1 (λ/2 part H) that gives a phase difference of approximately 180°, and a second phase difference generator gives a phase difference of approximately 180° between the p-wave and the s-wave by total reflection. The second Fresnel ROM FR2 (λ/2 part H) is provided, and the third phase difference generator provides a phase difference of approximately 180° between the p-wave and the s-wave by total reflection. portion H), and with the axis of incident light as the axis of rotation, the incident surface of the second Fresnel Rhomb FR2 (λ/2 portion H) is the first Fresnel Rhomb FR1 (λ/2 portion H) and the third Fresnel Rhomb FR3 (λ/2 It is arranged rotated with respect to the plane of incidence of part H).

More specifically, with the incident ray axis as the rotation axis, the incident surface of the second Fresnel Rhomb FR2 (λ/2 part H) is the first Fresnel Rhomb FR1 (λ/4 part Q) and the third Fresnel Rhomb FR3 (λ/4 part Q ) is rotated by approximately 60° (θ ₂ −θ ₁ ) with respect to the incident surface of ), the phase difference of the outgoing light beam E with respect to the incident light beam I is approximately 180°.

When the broadband retarder 1 of the present embodiment is a Pankaratnam-type λ/2 Fresnel Rhomb, as shown in FIG. It has a first Fresnel rhomb FR1 that provides a phase difference of approximately 180° between the waves, and a second phase difference generator (λ/2 portion H) produces a phase difference of approximately 180° between the p-wave and the s-wave due to total reflection. It has a second Fresnel rhomb FR2 that provides a phase difference, and a third phase difference generator (λ/2 part H) provides a phase difference of approximately 180° between the p-wave and the s-wave by total reflection. It has Fresnel Rhom FR3. With the incident light beam axis as the axis of rotation, the incident surface of the first Fresnel ROM FR1 is arranged to substantially coincide with the incident surface of the third Fresnel ROM FR3. The incident surface of the second Fresnel ROM FR2 is rotated by approximately 60° with respect to the incident surfaces of the first Fresnel ROM FR1 and the third Fresnel ROM FR3, with the axis of incident light as the axis of rotation.

The incident light ray I incident on the first incident end face 11 of the first Fresnel rhomb FR1 (first rhombohedron 10) constituting the λ/2 portion H is totally reflected 12 times (reflected light ray R), resulting in λ/ The emitted light E is emitted from the third Fresnel ROM FR3 constituting the second part H. When the broadband retarder 1 is a pancalatnam-type λ/2 Fresnel rhomb, it is approximately 180° (specifically, 180°±5°, preferably 180° An output light beam E having a phase difference of ±3°, more preferably 180°±2°, and even more preferably 180°±1° is emitted.

Each of the Fresnel roms constituting the λ/2 part H and the λ/4 part Q is made of an isotropic material, and the above-described FIGS. 7A and 7B show the case of using quartz as the isotropic material. (wedge angle α=54°). The isotropic material may be any material that transmits a wavelength region from vacuum ultraviolet to near infrared. It is preferable to use at least one material selected from the group consisting of CaF ₂ (refractive index n=1.44@546 nm) and lithium fluoride (LiF: refractive index n=1.39@600 nm). As for the isotropic material to be used, it is also important that there are no material defects or distortions that deteriorate the phase difference, and it is preferable to use quartz (fused quartz) rather than CaF ₂ .

(Multilayer film M)
The Fresnel rhombs forming the λ/2 portion H and the λ/4 portion Q preferably have a multilayer film M formed on at least one or more total reflection surfaces. Specifically, the first total reflection surface 13 of the first rhombohedron 10, the second total reflection surface 14, the third The total reflection surface 23 and the fourth total reflection surface 24 are coated with a multilayer film M having a refractive index different from that of the isotropic material forming the first rhombohedron 10 and the second rhombohedron 20. and is suitable.

Here, the multilayer film M includes a high refractive index film _MH formed of a high refractive index material having a higher refractive index than the isotropic material forming the first rhombohedron 10 and the second rhombohedron 20; Low refractive index films _ML made of a low refractive index material having a lower refractive index than the isotropic material forming the first rhombohedron 10 and the second rhombohedron 20 are alternately laminated. The order of lamination of the high refractive index film _MH and the low refractive index film _ML is even if the high refractive index film _MH and the low refractive index film _ML are laminated in this order on the isotropic material serving as the substrate. Alternatively, a low refractive index film M _L and a high refractive index film M _H may be laminated in this order on an isotropic material that serves as a substrate.

The incident light I is totally reflected by each total reflection surface, and at the same time a phase difference occurs between the p-polarized light and the s-polarized light. Generally, the phase difference caused by total reflection increases as the wavelength becomes shorter. Therefore, in each Fresnel rhomb, a high refractive index film MH having a higher refractive index than the isotropic material (quartz or CaF ₂ ) constituting the first rhombohedron 10 and the second rhombohedron 20 and a low refractive index film _MH having a small refractive index It is preferable to apply a multi-layered film _M in which two kinds of film materials consisting of a dielectric film ML are alternately laminated on the total reflection surface.

As high refractive index materials constituting the high refractive index film _MH , gadolinium fluoride (GdF ₃ : refractive index n = 1.59 @ 550 nm), lanthanum fluoride (LaF ₃ : refractive index n = 1.59 @ 550 nm ) and neodymium fluoride (NdF ₃ : 1.61@550 nm), but are not limited to these materials. Further, magnesium fluoride (MgF ₂ : refractive index n=1.38 to 1.40 @ 550 nm) is exemplified as a low refractive index material constituting the low refractive index film _ML , but is limited to this. not a thing

The high refractive index film _MH and the low refractive index film _ML can be formed by methods such as vacuum deposition, CVD, and sputtering. The thickness of the high refractive index film _MH and the low refractive index film _ML depends on the type of material, and may be, for example, 100 Å or more and 650 Å or less, but is not limited to this range.

The λ/4 part Q and the λ/2 part H in the broadband phase shifter 1 of this embodiment are not limited to the configurations shown in FIGS. 7A and 7B. For example, as shown in FIG. 19, two king-type Fresnel roms with a phase difference of 90° are arranged in the direction of the beam axis and regarded as a 180° Fresnel rom (λ/2 part H), and a king-type Fresnel rom 1 with a phase difference of 90° It is also possible to adopt a structure in which each king-type Fresnel rom is rotated and arranged by regarding one as a Fresnel rom with a phase difference of 90° (λ/4 part Q).

[4. Application example of the broadband phase shifter of the present embodiment]
An application example of the broadband phase shifter of this embodiment is shown below. The broadband retarder of this embodiment can be applied to a measuring device. Here, the "measurement device" includes various measurement devices, analysis devices, inspection devices, and observation devices.

A semiconductor inspection apparatus is an apparatus for inspecting a fine area, and since it actively uses ultraviolet light, it is preferable to use the broadband retarder of this embodiment, which can be used in the wavelength region from vacuum ultraviolet to near infrared. be. The broadband retarder of this embodiment can be used in semiconductor inspection equipment that utilizes polarization of white light.

Also, the broadband retarder of this embodiment can be applied to an observation device for observing a minute area. Contrast can sometimes be improved by controlling polarization. In order to observe finer details, observation using a short wavelength is necessary, so there is an advantage in using the broadband retarder of this embodiment.

Furthermore, in order to detect foreign matter, an observation device or an inspection device that utilizes the characteristic that the polarization state of the scattered light from the foreign matter is different from that of the normal portion is used. Specifically, the polarization state of the wiring pattern on the semiconductor wafer is observed. The broadband retarder of this embodiment can be applied to a device for detecting foreign matter. Depending on the device, the method of using polarized light differs. By combining it with the element, various polarization measurements are possible.

Also, the broadband retarder of this embodiment can be applied to a film thickness meter. Film thickness gauges are mainly used for inspection during semiconductor processes, but they are also used for inspection of other film-like objects, such as measuring film thickness, coating thickness, and the like. There are various measurement principles of film thickness meters, but there are devices that measure film thickness by ellipsometry similar to ellipsometers.

Alternatively, the broadband retarder of this embodiment can be used in place of a depolarizer to reduce instrument polarization. In a reflective optical system, since the reflectances of p-polarized light and s-polarized light are different, when the polarization state of incident light is different or fluctuates, the transmittance also differs or fluctuates. In order to prevent this, the polarization state of the incident light may be made constant, or the polarization state of the outgoing light from the optical system may be made constant. In the case of a device for precise measurement, it is necessary to keep the polarization state of the incident light beam and the outgoing light beam constant. By combining the broadband retarder of this embodiment with a retarder with a phase difference of 90° (λ/4), any polarization state can be created. becomes.

Also, the broadband retarder of this embodiment can be applied to an optical attenuator. Light intensity adjustment of the oscillation light of the laser device is sometimes performed by an optical attenuator combining a wave plate and a polarizer outside the laser device in order to ensure stability. By using the broadband phase shifter of the present embodiment as the wave plate used in this optical attenuator, it is possible to adjust the amount of light. In addition, by combining the broadband phase shifter of this embodiment with a broadband polarizer, a broadband optical attenuator capable of dimming light from the vacuum ultraviolet to the infrared region together, which could not be realized in the past, can be created. It is configurable.

The broadband phase shifter of the present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

<Example 1: Pankaratnam type quartz λ/4 fresnel rom>
In the Pankaratnam-type quartz λ/4 Fresnel ROM of Example 1, the phase difference between the first ROM (Q portion) and the third ROM (Q portion) is 90°, and the phase difference between the second ROM (H portion) is 180°. The angles of the incident surfaces of the first, third and second ROMs are rotated by 67.5° (θ ₂ - _{θ 1} = 67.5° - 0°) about the axis of the incident light beam. 90° retardation of the structure (FIG. 13, Table 2).

All Fresnel rhombs are made of quartz and have no optical thin film on the reflective surface. The second Fresnel rom is a roof-type Fresnel rom with a phase difference of 180 degrees, and has a structure in which two roms with a phase difference of 90 degrees are arranged. Therefore, in a structure in which four Fresnel ROMs with a phase difference of 90° are arranged, it can be seen that the second and third ROMs are rotated by 67.5° with respect to the first and fourth ROMs.

All ROM boundaries may or may not be bonded, and if bonded, they may be bonded with an adhesive as long as they are transparent in the wavelength band used. Naturally, they may be joined by optical contact. In the case of not bonding to the light-incident/outgoing surface, it is preferable that the light-incident/outgoing plane of each ROM is coated with an antireflection film. , there is no significant effect on the retardation characteristics. 14A to 14C show the optical characteristics of the Pankaratnam-type quartz λ/4 Fresnel rhomb of Example 1. FIG.

<Example 2: Pankaratnam type quartz λ/2 fresnel rom>
The pancalatnam-type quartz λ/2 Fresnel rom of Example 2 has a phase difference of 180° between the first to third Fresnel roms, and the second Fresnel rom is 59 degrees with respect to the first and third Fresnel roms, with the axis of incident light as the axis of rotation. It is a phase shifter with a phase difference of 180° arranged rotated by 0.5° (θ ₂ -θ ₁ =104.5°-45°) (Fig. 15, Table 3).

Since each Fresnel ROM with a phase difference of 180° has a structure in which Fresnel ROMs with a phase difference of 90° are arranged side by side, it can be regarded as a ROM in which six ROMs with a phase difference of 90° are arranged. No optical thin film is applied to the slope. The material of each ROM is quartz, and the total reflection angle is 54°. The joint portion and the anti-reflection film on the surface from which light rays enter and exit are the same as those in the first embodiment.

16A to 16C show the optical characteristics of the Pankaratnam-type quartz λ/2 Fresnel rhomb of Example 2. FIG. From FIGS. 16A to 16C, the ellipticity of the output polarized light (linearity, ellipticity is 0 for linearly polarized light and 1 for circularly polarized light), phase difference, and wavelength dependence of the direction of linearly polarized light are excellent. , it can be used in the same way as a general wavelength plate, and has excellent retardation performance (the degree of linear polarization of outgoing polarized light when linearly polarized light is incident) in a very wide band.

<Example 3: λ/4 Fresnel rom made of Pankaratnam type _CaF2 >
The Pankaratnam type CaF ₂ made λ/4 Fresnel rom of Example 3 has a phase difference of 90° between the first and third Fresnel roms, and a phase difference of 180° between the second Fresnel roms. This is a phase shifter with a phase difference of 90°, in which two Fresnel rhombs are rotated by 67.5° (θ ₂ -θ ₁ =67.5°-0°) about the incident light axis (Table 4).

The material of all Fresnel rhombs is _CaF2 and there is no optical thin film on the reflective surface. The second Fresnel rom is a roof-type Fresnel rom with a phase difference of 180 degrees, and has a structure in which two roms with a phase difference of 90 degrees are arranged. Therefore, in a structure in which four Fresnel ROMs with a phase difference of 90° are arranged, it can be seen that the second and third ROMs are rotated by 67.5° with respect to the first and fourth ROMs.

Since CaF ₂ crystal is an isotropic material that is transparent in the range of λ=130 to 6000 nm, it can be used as a phase shifter with little change in phase difference in a particularly wide wavelength band. The bonding method and the antireflection film are the same as in the first embodiment.

17A to 17C show the optical characteristics of the Pankaratnam-type CaF ₂ λ/4 Fresnel ROM of Example 3. FIG. From FIG. 17B, it can be seen that circularly polarized light with an ellipticity close to 1 can be obtained in a wide wavelength band. The shape of the element is the same as in FIG.

<Example 4: λ/2 Fresnel rom made of Pankaratnam type _CaF2 >
The Pankaratnam-type CaF ₂ λ/2 Fresnel rom of Example 4 has a phase difference of 180° between the first to third Fresnel roms, and the second Fresnel rom is rotated with respect to the first and third Fresnel roms with the incident light axis as the axis of rotation. It is a phase shifter with a phase difference of 180° arranged rotated by 59° (θ ₂ -θ ₁ =104°-45°) (Table 5).

Since each Fresnel ROM with a phase difference of 180° has a structure in which Fresnel ROMs with a phase difference of 90° are arranged side by side, it can be regarded as a ROM in which six ROMs with a phase difference of 90° are arranged. No optical thin film is applied to the slope. The material of each ROM is _CaF2 and the total reflection angle is 54°. The joint portion and the antireflection film on the surface from which light rays enter and exit are the same as those in the third embodiment.

Since CaF ₂ crystal is an isotropic material that is transparent in the range of λ=130 to 6000 nm, it can be used as a phase shifter with little change in phase difference in a particularly wide wavelength band. The bonding method and the antireflection film are the same as in the first embodiment.

18A to 18C show the optical properties of the Pankaratnam-type CaF ₂ λ/2 Fresnel ROM of Example 4. FIG. From FIGS. 18A to 18C, the ellipticity of the emitted polarized light (linearity, ellipticity is 0 for linearly polarized light and 1 for circularly polarized light), phase difference, and wavelength dependence of the direction of linearly polarized light are excellent. , it can be used in the same way as a general wavelength plate, and has excellent retardation performance (the degree of linear polarization of outgoing polarized light when linearly polarized light is incident) in a very wide band.

<Example 5: King type Pankaratnam type quartz λ/4 fresnel rom with optical film>
The king-type pancalatnam-type quartz λ/4 fresnel rhomb with an optical film of Example 5 has the widest usable wavelength band among conventionally known ones, is made of quartz with an ellipticity close to 1, and has a total reflection angle of 72°. Four king-type Fresnel roms with an optical thin film applied to the slanted surface to be used are arranged in the direction of the beam axis. , the last one is regarded as a Fresnel rhombus with a phase difference of 90°, and a Fresnel rhombus with a phase difference of 180° is 67.5° (θ ₂ −θ ₁ =67.5°−0° ) is a rotated structure (Fig. 19, Table 6).

As in Example 1, each king-type Fresnel rom may or may not be joined. No choice of method. Although it is preferable to apply an antireflection film to the surface through which light rays pass, it is not necessary to apply an antireflection film.

20A to 20C show the optical characteristics of the king-type pancalatnam-type quartz λ/4 Fresnel rom with the optical film of Example 5. FIG. From FIGS. 20A-20C, the output polarization properties are superior to any conventional Fresnel rhomb. Since the structure further enhances the performance of the component phase shifter, it can be seen that when the performance of the component is high, higher characteristics are exhibited.

In this embodiment, as the retardation and ellipticity characteristics increase, the wavelength dependence of the polarization axis decreases. It is possible to freely change between polarized light and circularly polarized light.

<Example 6: King type Pankaratnam type quartz λ/2 fresnel rom with optical film>
The king-type pancalatnam-type quartz λ/2 fresnel rhomb with an optical film of Example 6 has the widest usable wavelength band among conventionally known ones, is made of quartz with an ellipticity close to 1, and has a total reflection angle of 72°. Six king-type Fresnel roms with an optical thin film applied to the slanted surface to be used are arranged in the direction of the beam axis. Regarded as a second Fresnel Rhomb with a phase difference of 180°, the last two are regarded as a third Fresnel Rhomb with a phase difference of 180°, and the second Fresnel Rhomb is rotated by 60° (θ ₂ - θ ₁ = 105° −45°) is a rotated configuration (Table 7).

As in Example 1, each king-type Fresnel rom may or may not be joined. No choice of method. Although it is preferable to apply an antireflection film to the surface through which light rays pass, it is not necessary to apply an antireflection film.

21A to 21C show the optical characteristics of the king-type pancalatnam-type quartz λ/2 Fresnel rom with the optical film of Example 6. FIG. From FIGS. 21A-21C, the output polarization properties are superior to any conventional Fresnel rhomb. Since the structure further enhances the performance of the component phase shifter, it can be seen that when the performance of the component is high, higher characteristics are exhibited.

In this example, as the retardation and ellipticity characteristics are increased, the wavelength dependence of the polarization axis is greatly reduced, and it can be seen that there is no difference from a general λ/2 wavelength plate. It can be seen that the phase difference and the ellipticity hardly depend on the wavelength, and the optical characteristics of an ideal broadband λ/2 plate are exhibited.

1 broadband retarder H λ/2 part (H part)
Q λ/4 part (Q part)
FR1 First Fresnel ROM (first phase difference generator)
FR2 Second Fresnel ROM (second phase difference generator)
FR3 Third Fresnel ROM (third phase difference generator)
10 first rhombohedron 11 first incident end face 12 first exit end face 13 first total reflection face 14 second total reflection face 20 second rhombohedron 21 second entrance end face 22 second exit end face 23 third total reflection face 24 second Four total reflection surfaces M multilayer film θ incident angle α wedge angle α1 total reflection angle 100 first wave plate 100a first wave plate optical axis 200 second wave plate 200a second wave plate optical axis 300 third wave plate 300a Optical axis of three-wave plate I Incident ray Ia Incident polarization direction R Reflected ray E Emitted ray X Optical axis MR Mirror

Claims (6)

A first phase difference generator, a second phase difference generator, and a third phase difference generator,
The first phase difference generator is arranged on the incident surface side of the second phase difference generator,
The third phase difference generator is arranged on the exit surface side of the second phase difference generator,
The second phase difference generating section gives a phase difference of 1 80° ± 10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm ,
The first phase difference generating section and the third phase difference generating section give a phase difference of 90 ° ±10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm ,
The incident surface of the second phase difference generating portion is arranged to rotate with respect to the incident surfaces of the first phase difference generating portion and the third phase difference generating portion with the axis of incident light as a rotation axis,
The first phase difference generating section, the second phase difference generating section, and the third phase difference generating section are composed of Fresnel rhombs,
The optical axes of the incident light beam and the output light beam are coaxial,
The first phase difference generator has a first Fresnel rhomb that gives a phase difference of 90° ± 10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm,
The second phase difference generator has a second Fresnel rhomb that provides a phase difference of 180° ± 10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm,
The third phase difference generator has a third Fresnel rhomb that gives a phase difference of 90°±10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm,
The incident surface of the second Fresnel ROM is rotated by 67.5°±10% with respect to the incident surfaces of the first Fresnel ROM and the third Fresnel ROM with the axis of the incident light beam as the axis of rotation,
A broadband phase shifter characterized in that the phase difference of an output light beam with respect to an incident light beam is 90°±5° at a wavelength of 200-2600 nm . A first phase difference generator, a second phase difference generator, and a third phase difference generator,
The first phase difference generator is arranged on the incident surface side of the second phase difference generator,
The third phase difference generator is arranged on the exit surface side of the second phase difference generator,
The second phase difference generating section gives a phase difference of 1 80° ± 10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm ,
The first phase difference generating section and the third phase difference generating section give a phase difference of 1 80° ± 10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm ,
The incident surface of the second phase difference generating portion is arranged to rotate with respect to the incident surfaces of the first phase difference generating portion and the third phase difference generating portion with the axis of incident light as a rotation axis,
The first phase difference generating section, the second phase difference generating section, and the third phase difference generating section are composed of Fresnel rhombs,
The optical axes of the incident light beam and the output light beam are coaxial,
The first phase difference generator has a first Fresnel rhomb that gives a phase difference of 180° ± 10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm,
The second phase difference generator has a second Fresnel rhomb that provides a phase difference of 180° ± 10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm,
The third phase difference generator has a third Fresnel rhomb that gives a phase difference of 180° ± 10% between the p-wave and the s-wave by total reflection at a wavelength of 200 to 2600 nm,
The incident surface of the second Fresnel ROM is rotated by 60°±10% with respect to the incident surfaces of the first Fresnel ROM and the third Fresnel ROM with the axis of the incident light beam as the axis of rotation,
A broadband phase shifter characterized by having a phase difference of 180°±5° between an emitted light beam and an incident light beam at a wavelength of 200 to 2600 nm . The fresnel rhombs constituting the first phase difference generating portion, the second phase difference generating portion and the third phase difference generating portion are made of at least one material selected from the group consisting of quartz, _CaF2 and LiF. 3. A broadband retarder according to claim 1 or 2 , characterized in that: The fresnel rhombs constituting the first phase difference generating section, the second phase difference generating section, and the third phase difference generating section are characterized in that a multilayer film is formed on at least one or more total reflection surfaces. A broadband retarder according to any one of claims 1 to 3 . A measuring apparatus comprising the broadband retarder according to any one of claims 1 to 4 . An optical attenuator comprising the broadband retarder according to any one of claims 1 to 4 .

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