A Non-contact Optical Technique to Monitor Surface Stress in Sapphire Windows
The present invention provides a non-contact method for evaluating stress in a substrate. The method includes non-uniformly introducing at least one impurity into the crystalline substrate. The crystalline substrate is subjected to physical stress. Fluorescence producing energy is directed at the crystalline substrate. A fluorescence produced by the crystalline substrate is measured. The fluorescence spectrum is correlated with the stress on the crystalline substrate.
The present invention also includes a method for manufacturing a structure for non-contact evaluation of stress in the structure. According to the method at least one impurity is non-uniformly introduced into a crystalline substrate.
Additionally, the present invention provides a structure for non-contact evaluation of stress in the structure. The structure includes a crystalline substrate including at least one impurity non-uniformly distributed in the substrate.
Furthermore, the present invention provides a device for non-contact evaluation of stress in a substrate. The device includes a hollow cylindrical window support operable to support the substrate. A source of fluorescence producing energy is operable to direct the fluorescence producing energy at the substrate. A heat source is operable to subject the substrate to elevated temperature. A mechanical loading assembly is operable to subject the substrate to a mechanical load. A sensor is operable to detect fluorescence emitted from the substrate.
Still further, the present invention provides a non-contact method for evaluating stress in a sapphire window. The method includes subjecting to a physical stress a sapphire window that includes at least one impurity non-uniformly distributed in at least one region in the vicinity of at least one surface of the sapphire window. Fluorescence producing energy is directed at the sapphire window. A fluorescence produced by the sapphire window is measured. The fluorescence spectrum is correlated with the stress on the sapphire window.
Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from a review of the following detailed description. The detailed description shows and describes preferred embodiments of the present invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the present invention is capable of other and different embodiments and its several details are capable of modifications in various obvious respects, without departing from the present invention. Accordingly, the drawings and description are illustrative in nature and not restrictive
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