DD287108A5 - METHOD FOR PRODUCING RADIATION-RESISTANT GRID STRUCTURES, ESPECIALLY FOR HOLOGRAPHIC GRIDS - Google Patents

Abstract

The invention relates to a method for producing radiation-resistant grating structures, in particular for holographic gratings. The invention is applicable to holographic grating structures in optical systems with high light powers and as Praegematrize. The method according to the invention is characterized in that the surface of a lattice structure of a lattice structure produced in a known manner, which is provided with a conductive layer, is inverted into a layered metal layer. The application of the metal layer by means of a galvanic bath in several Arbeitsgaengen. The described method achieves an improvement in the radiation resistance of the lattice structures with a relatively low scattered light component, higher damage thresholds and better possibilities of adaptation and variability of the structure depths. Fig. 1 {holographic grating, radiation-resistant; inversion; Metal layer, good conducting; galvanic bath}

Description

For this 2 pages drawings

Field of application of the invention

The invention is applicable to lattice structures, in particular holographic gratings used in high power optical systems, e.g. in beam guidance systems for lithographic processes or laser-induced thermonuclear fusion, but also in material testing and material control as well as for effect lighting and as an embossing die.

Characteristic of the known state of the art

When using grating structures, the disperse and the imaging effect of these components is exploited. Therefore, grating structures are used as disperse elements in spectrometers, in laser resonators for frequency stabilization and bandwidth narrowing and for imaging optics.

Lattice structures can mechanically by scribing, holographically by the action of an interference fringe system on a

Photoresist layer and made by etching over masks werdon.

Scribe and etched grid structures destroy the surface of the lattice girder and therefore lead to high levels of stray light in the diffracted light. Holographically produced lattice structures have sinusoidal profiles or sinusoidal profiles, the surface of the lattice girder remains smooth. The scattered light component of these grating structures is two to three orders of magnitude below that of the scribed grating structures.

Another advantage of the holographically produced lattice structures is that ζ. B. by choosing their groove depths and the location of their structures their properties can be influenced.

A disadvantage of the holographic grating structures is that even at average radiation power- from about

2 r ~ destruction of the Rcsistschicht occurs. Therefore, attempts have been made by applying

dielectric layers to increase the Strahlungsfesiigkeit.

(See L.A. Godfrey, Opt., Comm., 34 (1980 | 108).) However, the method shown leads to a reduction in diffraction efficiency, and the resulting radiation resistance of these structures is slightly higher than that of scribed lattice structures of comparable line frequency.

In the long-wave spectral range (around ΙΟ, βμπι) radiation-resistant grating structures of YVCN-JOBIN, company catalog, are described, which were scratched or etched in Kup'jr or steel beam. The proportion of scattered light is considerable, v. iz & this me'.iiode in the visible and in particular in the short-wave Spvvctralberoich not applicable.

in DE-PS 2715089 ζ jm making money cards eir, galvanically produced metal deduction of diffraction gratings small line frequency (200 and 300 L / mm) is shown, which is soldered to a metal stamp. In this procedure will be

no particular demands made on the dimensional accuracy of the inverted grid structure. Essential is only the maintenance of the line frequency. This method can not be adopted for the production of radiation-resistant grating structures, since the form fidelity of the surface and the lattice structures itself is not preserved.

Object of the invention The aim of the invention is to improve the radiation resistance, in particular in holographically produced lattice structures. Explanation of the essence of the invention The invention has for its object to provide a method that makes it possible without sacrificing quality in the

surface texture and diffraction efficiency as well as the scattered light behavior to increase the radiation resistance at Gitterst'.ukturenzen.

According to the invention the object is achieved in that provided with a conductive layer surface of a Lattice structure of a holographic lattice produced in a known manner in a layered metallic Layer of good thermal conductivity is inverted. The individual process steps are the following: For applying a first metallic layer, the grid is lying, with upwardly directed grid structure in a

dip galvanic bath. Due to the horizontal position of the grid unwanted flow contours on the

Surface of the layer largely avoided. After applying the first layer, the grid is in distilled water

rinsed and thrown dry. To prevent the detachment of this first layer, the edges are sealed to the lattice girder. For applying a second metallic layer, the grid is placed with the already coated side up in a container and dipped together with this again in the meantime carefully filtered galvanic bath.

The inclusion of the grid in a container causes a constant specific conductance of the galvanic bath over the Grid surface and thus a uniform settling of the metallic layer. Also this layer is distilled with Water rinsed and thrown dry. Thereafter, the surface of this second layer with a second carrier, the one

Having flat surface, firmly connected and separated in a last step, the layer according to the invention prepared by the first carrier.

Suitable materials for the metallic coating are, for example: for the conductive layer silver or gold and as

first and second electroplated layer of copper or as conductive layer silver or gold and as first and second

Layer of nickel. The method according to the invention can be applied to lattice structures that are both flat and on

curved surfaces are located.

For lattice structures on curved surfaces, prior to performing the method described, a copy of the lattice structure

to make in a known manner on a suitable surface.

The inventive method is also applicable to mesh of electromechanically-convertible material. By applying the method according to the invention, the desired radiation resistance is achieved. The achieved Layer thicknesses are about 30 pm. In addition, there are the following advantages:

a lower proportion of stray light compared to scribed or etched grating structures,

- higher destruction thresholds due to the defect-free smooth surface compared to scribed grids,

- more possibilities of adaptation and variability by choosing the depth of the lattice structures and their course over the support,

- Better tunability of the lattice constants while maintaining the diffraction efficiency and freedom from stray light when using gratings made of electromechanically-convertible material.

'exemplary

The inventive solution will be explained below using an exemplary embodiment. Show it Fig. 1: a grid in a galvanic bath Fig. 2: a sealed grid structure 3 shows the structure for a grid produced according to the invention with first and second carrier. As an example, a holographically produced planar linear grating G with a ridge density of 2100 lines / mm, a Diameter of 40mm and a sinusoidal groove profile chosen. The grating structure GS is in a known manner

a support T ₁ , for example made of glass, applied and finally provided with a conductive layer SL, in the example silver.

The thickness of the silver layer is about 100 nm. According to the invention, the surface of the lattice structure GS obtained in this way is converted by further process steps into a

layered metal layer of good thermal conductivity inverted. The most important procedural steps are the following:

1. application of a first Cu layer S ₍

2. Seal this layer

3. Application of a second Cu layer S]

4. Separate the inverted layer

5. Post-treatment

In Fig. 1, the galvanic copper sulfate B is shown with the grid G therein. For applying the first copper layer Si, the grating G is placed horizontally in the galvanic bath B. Due to the horizontal position unwanted flow structures on the surface of the grid G are excluded. It is achieved a uniform deposition of the copper layer S ₁ . The copper cathode K is applied to the conductive layer SL and is connected to the negative pole of the voltage source. The anode A is connected to the positive pole of the voltage source. She is made of pure copper. The required for coating galvanic copper sulfate B is always the same and is composed as follows:

CuSO ₂ 200 g H ₂ SO ₄ 70g

C ₆ H ₆ OH 50ml

H ₂ O ad 11

The bath temperature is between 20 and 30 ° C

 The deposition is increasing, and indeed

15Sbei100mA / dm '15Sbei300mA / dm * 60 S at 5A / dm ²

A copper layer S _t of about 1 pm is deposited. After this process, the grid G is rinsed with distilled water and spun dry.

In order to avoid unrolling of the copper layer Si, it is sealed, as shown in FIG. 2, on the outer edge of the carrier Ti, in the example by immersion in liquid paraffin P. However, any other material which does not attack the lattice structures can also be used.

For applying a second copper layer S ₂ , the grid is placed with the copper side up, with it attached electrode as the cathode K in a PVC container and brought together with this in the carefully filtered galvanic copper sulfate B. The anode A is located outside the container in the copper sulphate B. It is important to ensure that the container of about 1 to 3cm of the sulphate bath B is covered.

The inclusion of the grating G in a container has proved to be useful for realizing a constant specific conductance of the copper sulfate solution over the surface of the grating structure GS. This achieves a uniform settling of the second copper layer S ₂ , combined with good layer properties.

In a time of 25 minutes at a current density of 5 A / dm ² , a copper layer S _{2 is achieved} up to a thickness of 30μηι.

The finished layer is rinsed again in distilled water and dried.

Thus, the process of producing the radiation-resistant layer itself is substantially completed.

In order to be able to use this layer as intended, detachment from the carrier T _(is necessary.

As shown in Fig. 3, in the example to the second copper layer S ₂ insoluble another carrier T ₂ with a flat surface ( ^x to) attached and then the carrier Ti, in whose layer the lattice structure was introduced, separated. The non-detachable connection of the carrier T ₂ with the second copper layer S ₂ can be carried out with a commercial adhesive Kl, such as EGK 19 or EP 40 in the prescribed mixing ratio in vacuum at a pressure of 10 ~ ³ to 10 ~ ⁴ Torr.

The detachment of the carrier T _t , for example, by cooling with liquid nitrogen.

As a result of the different coefficients of expansion of glass and copper, the carrier T _{1 separates} from the grating structure GS.

In a final treatment, the protruding part of the second copper layer S _{2 is} removed, the edge is sizing and sealed (eg ECG). The still adherent grid structure GS is removed with a paint solvent. The grid is rinsed with reagent-grade solvent and spun dry.

In order to improve the diffraction efficiency, a reflection layer which is advantageous for the working wavelength range is vapor-deposited onto the conductive layer SL produced according to the invention by the proven method.

Claims (6)

1. A process for the production of radiation-resistant grating structures, in particular for holographic grids by making lattice copies by means of galvanic processes, characterized in that provided with a conductive layer (SL) surface of a lattice structure (GS) of a holographic grating produced in a known manner (G) is inverted in a layered metal layer with high thermal conductivity in such a way that the grid (G) for applying a first metal layer (Si) lying, with upwardly directed lattice structure (GS) introduced into a galvanic bath (B) and then with distilled Water is rinsed and dried, then the edges of this first metal layer (S ₁ ) on the support (Ti) of the grid (G) are sealed, then for applying a second layer (S ₂ ) which is now in a container located grid (G) again immersed in the galvanic bath (B), rinsed again and dried, the surface This second layer (S ₂ ) is inextricably linked to a support (T ₂ ) and finally a separation of the layer according to the invention from the first support (Ti) takes place. 2. The method according to claim 1, characterized in that as materials for the coating, for example, for the conductive layer (SL) silver, gold or copper and as first and second layer (Si and S ₂ ) copper or nickel are selected. 3. The method according to claim 1, characterized in that it can be used for both planar and curved grid structures. 4. The method according to claim 1, characterized in that it can be used for carriers of electromechanischwandelbarem material. 5. The method according to claim 1, characterized in that the permanent connection of the zweiton layer (S ₂ ) with the carrier (T ₂ ), for example by gluing or soldering. 6. The method according to claim 1, characterized in that as the material for the coating according to the invention, for example, as the conductive layer (SL) silver or gold and as the first and second layer (Si and S ₂ ) are selected copper.