Deutschetelekom Ag

Matthias Falk

Karsten Buse

Daniel Haertle

Michael Koesters

Theo Woike

Konrad Peithmann

Method for preparing a purified crystal for use in an optical component, from an impure crystal having impurities or crystal defects capable of causing a specific absorption of incident light, includes heating the impure crystal to a temperature at which ions in the crystal are mobile and provide conductivity. A part of the crystal is illuminated with an electromagnetic purifying beam having a frequency in or near a visible frequency range so as to optically excite and migrate charges in the crystal, the charges being compensated by a counter-migration of the ions so as to be fixed in place thereafter so as to provide a purified crystal zone. The crystal is cooled to a future operating temperature.

Optical purification of crystals

Method for treating a nominally pure crystal having non-linear optical properties. The nominally pure crystal contain foreign atoms at a residual concentration of less than 20 ppm so as to provide specific absorption of incident light. The method includes determining, based on testing on a specifically doped reference crystal of same type as the nominally pure crystal, a threshold value. The threshold value is defined by a temperature at which a migration of ions in the nominally pure crystal to the surface of the nominally pure crystal ceases. The foreign atoms are transformed to a higher valance state by a thermally-supported oxidation process including heating the nominally pure crystal at a heating rate that increases by less than 3 &#xb0; C. per minute to a maximum temperature above the threshold value and below a Curie temperature of the nominally pure crystal. An electrical voltage is applied so as to eliminate electrons released during the oxidation process from the nominally pure crystal.

Treatment of crystals for the prevention of optical damage

A method for the treatment of a crystal, such as a lithium niobate crystal or lithium tantalate crystal, having nonlinear optical properties. The crystal comprises foreign atoms which bring about specific absorption of radiated light. The foreign atoms are transformed into a lower valent state by means of oxidation. Electrons, which are released during oxidation, are discharged from the crystal with the aid of an external power source.

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Los Altos Hills, CA, United States of America

Matthias Falk