WO2006029872A1

WO2006029872A1 - Radiotransparent component and method for the production thereof

Info

Publication number: WO2006029872A1
Application number: PCT/EP2005/009943
Authority: WO
Inventors: Ulrich Bismayer; Dmytro Ivanovych Savytskii; Oleg Anatoliyvych Buryy
Original assignee: Universität Hamburg
Priority date: 2004-09-17
Filing date: 2005-09-15
Publication date: 2006-03-23
Also published as: EP1789823A1

Abstract

The invention relates to a radiotransparent, particularly optical, component, especially a polarizing apparatus, and a method for producing a polarizing apparatus, above all a polarizing prism (5). The inventive component comprises a crystal (10, 11) with a twin boundary (12) and at least one first and a second crystal area (10, 11) that are interconnected by means of the twin boundary (12). The inventive method is characterized by the following steps: a seed crystal (17) is provided that encompasses a twin boundary (12) and two monocrystalline crystal areas (10, 11); a crystal (10, 11) is grown based on the seed crystal (17) using a Czochralski process.

Description

Radiolucent component and method for producing the same

description

The invention relates to a radiolucent, in particular opti¬ cal, component, in particular a polarizing device, and a method for producing the same.

From W. Kleber, Introduction to Crystallography, VEB Verlag Technik Berlin, 16th edition, 1985, page 254, 255, a Nicolian prism is provided for the polarization of light, which consists of two Pris¬ halves halves, which are glued together so as to provide a wall between the two halves of the prism allowing total reflection of the ordinary refracted beam and passing the extraordinary beam. There are also corresponding prisms of the Senarmon type which are also relatively expensive to manufacture. In addition, the polarization intensity ratios are relatively poor due to the use of prism clipped halves and prism components, respectively. To produce such a polarization prism, optical polishing of the connecting wall between the prism components and ensuring their planarity is required. In addition, a special adhesive having a refractive index between the ordinary and extraordinary ray values is needed. Finally, the adsorption behavior of the adhesive interferes. It comes to a light scattering on defects and non-homogeneity of the glued edges or surfaces and the

Adhesive layer. Due to the elaborate production of such prisms, these are also correspondingly expensive.

It is an object of the present invention, at low cost an optical device and a method for the manufacture of this device to specify, can be made available by means of the light with a high degree of polarization in the broadest possible frequency spectrum.

This object is achieved by a, in particular optical, Bau¬ element, in particular a polarization device comprising a crystal with a twin boundary and at least one Ers¬ th and a second crystal region, which are interconnected by the twin boundary. This is in particular a naturally grown twin border. By Erfin dung modern optical component, a very high degree of pola¬ risiertem light can be generated, in particular linear polarisier¬ tes light having a polarizing intensity ratio of 6 x 10 ^"6 or smaller.

The extraordinary and ordinary ray is preferably separated at a domain wall. The twin boundary or wall is atomically small, so that the wavefronts of the transmitted light are practically not deformed. In view of the atomically small wall thickness is a particularly high degree of miniaturization of the optical

Component or component possible. In particular, a ferroic domain wall is used as connecting wall or twin boundary used between the two geometrically reoriented crystal regions or prism components.

The two crystal regions of the crystal are preferably monocrystalline, so that the crystal is preferably a bicrystal. However, according to the invention, it may also be sufficient to have a crystal which only emanates from the region necessary for the electromagnetic radiation for the use of the device monocrystalline regions separated by a twin border,

Preferably, the optical axis of the first crystal region and the optical axis of the second crystal region are not parallel to each other. Preferably, the angle between the optical axes of the first and second crystal regions is between 30 ° and 90 °, in particular 45 ° and 75 ° and in particular approximately

65, 5 °, wherein the last value applies in particular with lithium niobate as Ma material. A particularly preferred embodiment of the optical component is present when the twin boundary is oriented substantially perpendicular to the plane which is spanned by the two optical axes. The optical component is preferably a prism, in particular in the form of a rectangular parallelepiped. In this case, the outer surfaces of the parallelepiped or prisms are preferably designed such that an incident beam can be aligned with the first crystal region parallel to the optical axis of the first crystal region, the optical axis preferably being perpendicular to the entrance surface of the prism of the light beam to be polarized.

Preferably, the crystal is or substantially comprises an anisotropic material. Preferably, the crystal is anisotropic. In a particularly preferred embodiment, this is Material optically uniaxial, especially tetragonal, hexagonal or rhombohedral. If the material has no phase transition under the growth conditions, a particularly high degree of polarization and a very high quality of the crystal are present. The twin wall or the possible twin walls can preferably have a paraelastic-ferroelastic phase transition. In the case of lithium niobate (LiNbOa), this is, for example, the cubic rhombohedral phase transition, so that the preferred twin boundaries or twin planes from the family (1 0 2), (10 0), or generally (1 0 2n) where n is a natural Number is, come.

In addition, ytrium vanadate (YVO ₄ ) is preferred as the preferred material. Preferably, the twin boundary is a (1 0 2n), (1 0 -1 2n), (n 0 n) plane, where n is a natural number. For ytrium vanadate, the (1 0 1) plane is particularly suitable.

The object is further achieved by a method for producing a polarization device, in particular a polarization prism with the following method steps:

- Providing a crystal nucleus with a

Twin boundary and two crystal regions, which are preferably each monocrystalline,

Drawing a crystal based on the crystal nucleus using a Czochralski culture method.

By means of the method according to the invention, an efficient and cost-effective production of corresponding polarization devices is possible since two parts of the polarization device do not have to be conventionally cut and polished and glued to one another, but the intermediate surface in the polarization device naturally grows can, so the elaborate Procedural steps can be avoided accordingly. In addition, this produces a qualitatively very high-quality polarization device.

Preferably, the seed has a size of more than 1 x 1 x

2 mm ³ , in particular more than 2 x 2 x 4 mm ³ , in particular more than 3 x 3 x 10 mm ³ . In the case of lithium niobate, the seed crystal preferably has a size of approximately 4 × 4 × 20 mm ³ .

To first provide a very first seed, preferably two single crystals are appropriately cut and put together in twin configurations to then draw a corresponding bicrystal of two single crystal halves and a twin wall using the Czochralski method and the Czochralski method, respectively. Subsequently, a part of the cultivated or pulled bicrystal can then be cut out and act as a seed crystal. The bicrystal is drawn with the known growth parameters, such as monocrystalline material, for example in the case of lithium niobate and also in the case of ytrium vanadate. The crystallization seed should have a special twin wall. In addition, the person skilled in the art then has to control or control the spatial orientation of both parts of the crystallization nucleus, which should be parallel to the growth direction of the bicrystal.

Preferably, the growth or growth of the crystal occurs in the direction of an axis of symmetry of the crystal.

Finally, the outer walls necessary for the desired polarization device are finally cut, ground and / or polished.

The invention can drastically improve optical design elements are made available by using a naturally formed inner wall (ferroic domain wall or twin wall) in a polarization onsprisma or other optical components. There are fewer costly production steps, for example, no mechanical processing of the inner connecting wall is required any more. Optimal planarity and optical quality are obtained by the growth of the crystals according to the invention alone. In addition, no adhesive is required, which results in a low absorption of the light rays. Finally, miniaturization on an atomic scale is possible because the wall thickness is only a few atomic layers. In addition, a favorable polarization intensity ratio is possible since there is almost no deformation of the wavefront at the twin boundary. In addition, light can be polarized in a large frequency spectrum, for example in the case of lithium niobate, between 350 and 5000 nm. For lithium niobate, the optical axes of the two crystal regions or prism halves separated by the domain wall preferably have an angle of approximately 65.5 °.

The device according to the invention, in particular optical, is preferably used in a laser optics, e.g. as polarizer or modulator, in crystal optics, in optical projectors (monitors), in optical data transfer, e.g. used in CD and DVD players, etc., in ellipsometry, in acousto-optic and electro-optical applications, and in photospectrometry. The incident electromagnetic beam, in particular the light beam, preferably falls into the component essentially parallel to the plane which is spanned by the optical axes of the two crystal regions.

The invention will be described below without limiting the general concept of the invention by means of exemplary embodiments Referring to the drawings described. With respect to all details of the invention not explained in detail, reference is expressly made to the drawings. Show it:

5 is a copy of a photograph of a seed of two defined oriented lithium niobate single crystals,

Fig. 2 is a schematic side view of an inventive erfindungsge¬ optical device.

10

In the following figures, in each case identical or similar elements or corresponding parts with the same reference numbers are provided, so that a corresponding renewed idea is disregarded.

15

Fig. 1 shows a nucleus of two defined oriented lithium niobate single crystals in the form of a first single crystal 10 and a second single crystal 1 1 for growing the prism material with natural partition wall 12 in the form of a twin wall. The crystallization seed 20 17 is arranged on a holder 13. From this germ, a corresponding larger bicrystal is grown with a Czochralski method under normal growth conditions for lithium niobate single crystals, which can be used as a radiolucent, in particular optical, component according to the invention.

25

FIG. 2 shows a schematic side view of a polarizer 5 according to the invention. This is a two-beam polarization prism. In the case of a two-beam polarization prism, the orientation of the prismatic elements, ie the angle between the optical axes of the prism portions or the first single crystal 10 and the second single crystal 11, is greater than 0 °, which in particular ensures that the ordinary and the extraordinary Beam at the connecting wall, in this case, the twin wall 12 are deflected differently.

A single-beam polarization prism would be present if one of the two beams (ordinary or extraordinary) is reflected at the intermediate wall of the prism portions, which are preferably triangular prisms in cross section, or total reflection prevails. Such a configuration would gem. the invention possible. In Fig. 2, however, an example of a double-beam prism is shown.

In order to generate two beams in the form of a regular beam 15 and an extraordinary beam 16 from the incident beam 14, the incident beam 14 is to be aligned so that it lies in the plane passing through the optical axis c of the first single crystal 10 and the optical axis c ^{1 of} the second single crystal 11 is clamped.

In the case of an incident beam which lies outside this plane spanned by the optical axes, four outgoing beams may also occur.

In this embodiment, the angle φ between the opti¬'s axes c and c 'is less than 90 °. He can also be 90 °. For lithium niobate and a (1 0 2) plane as a twin wall 12, the angle is preferably 65.5 °. There exists an angle β between the incident rays in the form of the ordinary ray 15 and the extraordinary ray 16.

The twin boundary 12 or the twin wall 12 is an ideal flat boundary of the connection of the two parts of the optical crystal or polarizer 5. The width or depth of this boundary is significantly smaller than the wavelength of the electromagnetic light of the optical region of the crystal used for example, lithium niobate. The flatness and atomic size of the twin wall makes it possible to reduce the light losses and to increase the polarization ratio of the output beams 15 and 16. The absence of an adhesive makes it possible to increase the spectral range of the prism into the transparency range of the optical crystal used for prism production ,

This range can be very large, for example for lithium nitrate between 350 and 5000 nm.

The two beam polarization prism according to the invention and according to Fig. 2 is realized in the form of a rectangular parallelepiped comprising two parts of an optical anisotropic crystal connected by a twin boundary. The optical axes of the two parts of the prism are twisted against each other, i. have an angle between them, which is not equal to 0 or 180 °, wherein preferably the plane which is spanned by the two optical axes, is aligned perpendicular to the twin wall 12 and parallel to the direction of propagation of the incident and unfolding rays. If the two-beam polarization prism is realized on the basis of a uniaxial lithium niobate crystal, the angle between the optical axes of both parts 10 and 1 1 to the twin boundary 12 along the (1 0 -1 2) plane is equal to 32.75 °, so that the angle φ is 65.5 °. The two-beam polarization prism 5 shown in Fig. 2 has a divergence angle β of 5.9 ° at a wavelength of 0.66782 μm. The lattice structure of lithium niobate is perovskite-like, so that the width of the twin boundary

12 is in the range of some lattice parameters of a Perovskitzelle, ie at 1 to 2 nm. The preferred domain wall or twin wall 12 at Ytriumvanadat (YVO ₄ ) is (1 0 1) according to the cubic tetragonal relationship. The surface of the first crystal region 10, which is hit by the incident beam 14, is preferably the Z-axis.

Level (0001). This level is easy to orient and to cut. LIST OF REFERENCES

5 polarizer

10 1. Single crystal

1 1 2. Single crystal

12 twin wall

13 holders

14 incident beam

15 ordinary ray

16 extraordinary ray

17 crystallization germ

C optical axis c ¹ optical axis φ angle between the optical axes ß angle between the ordinary and extraordinary beam

Claims

Radiolucent component and method of making the same patent claims

Radiation-permeable, in particular optical, component, in particular polarization device (5), comprising a crystal (10, 11) with a twin boundary (12) and at least a first and a second crystal region (10, 11) passing through the twin boundary (12) connected to each other.

2. Radiolucent component (5) according to claim 1, da¬ characterized in that the optical axis (c) of the first crystal region (10) and the optical axis (c ¹ ) of the second crystal region (11) are not parallel to each other.

3. Radiolucent component (5) according to claim 2, da¬ characterized in that the angle (φ) between the optical axes (c, c ') of the first and the second crystal region (10, 11) between 30 ° and 90 °, in particular 45 ° and 75 °, in particular at about 65.5 °.

4. Radiolucent component (5) according to claim 2 or 3, characterized in that the twin boundary (12) is oriented substantially perpendicular to the plane defined by the two optical axes (c, c ').

5. Radiolucent component (5) according to one of claims 1 to 4 An¬, characterized in that it is a prism, in particular in the form of a rectangular parallelepiped.

6. Radiolucent component (5) according to any one of An¬ claims 1 to 5, characterized in that the crystal (10, 11) is made of an anisotropic material.

7. Radiolucent component (5) according to claim 6, character- ized in that the material is optically uniaxial, in particular tetragonal, hexagonal or rhombohedral.

8. Radiolucent component (5) according to claim 6 or 7, characterized in that the material during the growth of the crystal has no phase transition.

9. Radiolucent component (5) according to any one of An¬ claims 6 to 8, characterized in that the material is LiNbO ₃ or YVO ₄ .

10. Radiolucent component according to one of claims 7 to 9, characterized in that the twin boundary (12) is a (1 0 2n), (1 0 -1 2n), (n 0 n) plane, where n is a natural number ,

1 1. A process for producing a polarizing device, in particular a polarization prism (5) with the following Steps:

Providing a crystal nucleus (17) with a twin boundary (12) and two crystal areas (10, 1 1),

Drawing a crystal (10.1 1) on the basis of Kristallkei¬ mes (17) with a Czochralski breeding method.

12. The method according to claim 1 1, characterized in that the seed crystal (17) has a size of more than 1 x 1 x 2 mm ³ , in particular greater than 2 x 2 x 4 mm ³ , in particular greater than 3 x 3 x 10 mm ³ has ,

13. The method of claim 1 1 or 12, characterized gekennzeich¬ net, that for providing the seed crystal (17), in particular a first seed crystal (17), two single crystals (10, 1 1) are cut and brought together in twin configuration become.

14. The method according to claim 13, characterized in that a subsequent crystal nucleus (17) from a ers¬ th crystal nucleus (17) pulled crystal (10, 1 1) is cut.

15. The method according to any one of claims 1 1 to 14, characterized ge indicates that finally cut for the desired Po larizationvorrichtung (5) outer walls geschnit¬, ground and / or polished.

16. The method according to any one of claims 11 to 15, characterized ge indicates that the crystal regions (10, 1 1) each one are crystalline.

17. Use of a, in particular optical, component (5) according to one of claims 1 to 10, in a laser optics, in optical projectors, for optical data transfer, in the

Ellipsometrie, in acousto-optical or electro-optical applications or in photospectrometry, wherein an ein¬ falling electromagnetic beam, in particular Licht¬ beam, substantially parallel to the plane passing through the optical axes, (c, c ') of the two Crystal regions (10, 1 1) is spanned, is provided.