At&t Bell Laboratories

David L Windt

Warren Kazmir Waskiewicz

Donald M Tennant

Kathleen R Early

Richard E Howard

John C Bean

The invention in one aspect involves a method for repairing an optical system. The optical system includes at least one optical element which comprises, in turn, a substrate having a principal surface, and a multilayer coating overlying the principal surface. The substrate comprises a first material, and the multilayer coating comprises plural second and at least third material layers in alternation. The method includes the steps of removing the multilayer coating from the substrate, and redepositing a new multilayer coating on the substrate. The old multilayer coating is removed in a single etching step while preserving the quality of the principal surface to such an extent that the peak reflectivity of the new multilayer coating is at least 80% the reflectivity of the old multilayer coating. In a second aspect, the invention involves a method for repairing an optical system of the kind described above, in which the optical element comprises a substrate having a principal surface, a layer of chromium overlying the principal surface, and a first layer of iridium overlying the chromium layer. The method comprises the steps of removing the first iridium layer from the substrate; and forming a second iridium coating on the substrate. The iridium layer is removed by exposing the iridium and chromium layers to an aqueous solution comprising potassium ferricyanide and sodium hydroxide, resulting in substantial dissolution of the chromium layer.

Method for repairing an optical element which includes a multilayer

In one aspect, the invention involves an optical element in an x-ray imaging system. The element comprises a substrate overlain by a multilayer coating. The multilayer coating comprises plural first and at least second material layers in alternation. This coating is soluble in at least one etchant solution at an etching temperature less than 100.degree. C. The optical element further comprises a barrier layer intermediate the substrate and the multilayer coating. The barrier layer is relatively insoluble in the etchant solution at the etching temperature. In a second aspect of the invention, the optical element comprises a substrate and a multilayer coating as described above, and further comprises a release layer that underlies the multilayer coating. The release layer comprises a material that is relatively soluble in at least one etchant solution at an etching temperature less than 100.degree. C. In contrast to release layers of the prior art, the inventive release layer comprises germanium.

X-ray optical element including a multilayer coating

We have found a way to, e.g., substantially increase the number of layers in a pseudomorphic strained layer semiconductor mirror over the number obtainable in an analogous conventional mirror, making it possible to obtain pseudomorphic strained layer mirrors of increased reflectance. Such a pseudomorphic mirror consists of alternating layers of a first and a second semiconductor material (e.g., Ge.sub.x Si.sub.1-x /Si), of thickness t.sub.1 and t.sub.2, and refractive index n.sub.1 and n.sub.2, respectively, with the number of layer pairs chosen such that the mirror thickness is less than or equal to the 'critical thickness' L.sub.c. For thicknesses &gt;L.sub.c the mirror will contain dislocations. An article according to the invention comprises a mirror whose layer thicknesses are chosen such that n.sub.1 t.sub.1 .noteq.n.sub.2 t.sub.2, with n.sub.1 t.sub.1 +n.sub.2 t.sub.2 =p.lambda./2, (p being an odd integer, typically 1). In other words, the optical thickness of the layers is not the conventional p.lambda./4. The thicknesses are also chosen such that the average lattice mismatch between substrate and mirror is reduced, compared to the analogous conventional (.lambda./4) mirror. Mirrors according to the invention can be advantageously used in optoelectronic devices such as surface emitting lasers and p-i-n photodetectors.

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Springfield, NJ, United States of America

David L Windt