A modified version of a conventional optical-contact procedure has been found to facilitate alignment of optical components. The optical-contact procedure (called simply "optical contacting" in the art) is a standard means of bonding two highly polished and cleaned glass optical components without using epoxies or other adhesives. In its unmodified form, the procedure does not involve the use of any foreign substances at all: components to be optically contacted are dry. The main disadvantage of conventional optical contacting is that it is difficult or impossible to adjust the alignment of the components once they have become bonded.
In the modified version of the procedure, a drop of an alcohol-based optical cleaning solution (isopropyl alcohol or similar) is placed at the interface between two components immediately before putting the components together. The solution forms a weak bond that gradually strengthens during a time interval of the order of tens of seconds as the alcohol evaporates. While the solution is present, the components can be slid, without loss of contact, to perform fine adjustments of their relative positions.
After about a minute, most of the alcohol has evaporated and the optical components are rigidly attached to each other. If necessary, more solution can be added to enable resumption or repetition of the adjustment until the components are aligned to the required precision.
This work was done by Daniel Shaddock and Alexander Abramovici of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Physical Sciences category.
NPO-30731
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Solution-Assisted Optical Contacting
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Overview
The document discusses a novel technique for optical contacting developed by researchers at NASA's Jet Propulsion Laboratory (JPL), specifically Daniel Shaddock and Alexander Abramovici. This method enhances the traditional optical contacting process, which is used to bond highly polished glass optical components without adhesives. The conventional method, while effective, has a significant drawback: once the components are bonded, it is challenging to adjust their alignment.
The innovative approach involves the application of an alcohol-based optical cleaning solution, such as isopropyl alcohol, at the interface between the two components just before they are brought into contact. This solution creates a weak bond that allows for fine adjustments of the components' positions while they remain in contact. The bond gradually strengthens as the alcohol evaporates over a period of tens of seconds. This feature enables the components to be slid into the desired alignment without losing contact, which is crucial for applications requiring high precision.
The document highlights the motivation behind this development, particularly in the context of constructing an interferometer made entirely from ultra-low expansion (ULE) titanium silicate glass. The interferometer's beamsplitters must be aligned with extreme precision—better than 1 arcminute in orientation and within 100 microns in position. The traditional optical contacting method does not allow for such fine adjustments due to its instant bonding nature.
By using the alcohol solution, the researchers were able to facilitate the alignment process, allowing the optical components to be adjusted for about a minute before the bond became rigid. This breakthrough significantly improves the ability to achieve the necessary precision in optical assemblies, which is essential for advanced scientific instruments like interferometers.
The document also includes references to related publications and emphasizes that the work was conducted under the auspices of NASA, with no endorsement of specific commercial products. Overall, this technique represents a significant advancement in optical contacting technology, providing a practical solution to a longstanding challenge in the field of optical engineering.
