19 October 2000 Rapid prototyping of optical thin film filters
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In the course of the rapid development of laser technology and modern optics, an ever increasing demand for optical coatings with extraordinary specifications can be observed. In practice, the production of such high quality optics with special requirements in respect to bandwidth, edge steepness or wavelength accuracy regularly requires an extended optimization of the coating process. In many cases, the resulting high production cost delays the development of new promising concepts in laser and optics technology. For the realization of new optical designs, generally two difficulties occur: At first, the physical properties of the coating materials change after completion of the coating process due to environmental influences. Furthermore, the accuracy of the commonly utilized methods for thin films thickness monitoring is not sufficient for a reliable thickness control. In this paper, an ion beam sputtering (IBS) coating process is described for the completely automated fabrication of optical coatings with extremely stable characteristics. In contrast to conventional arrangements with witness glasses, the presented thickness monitoring during the coating process can be directly performed for the optics. The precise transmittance measurement over a bandwidth of one octave is achieved by a fiber-coupled multi-channel spectrophotometer. With this arrangement also very small layer thickness errors are detected and may be compensated by optimizing the subsequent layers in the stack in order to meet the specifications. The combination of the innovative IBS- process with the broad-band spectrophotometric thickness monitoring is the key for new laser applications, e.g. low loss edge filters for high power diode laser wavelength multiplexing or phase-optimized mirrors for ultrashort pulse laser systems.
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Kai Starke, Tobias Grosz, M. Lappschies, Detlev Ristau, "Rapid prototyping of optical thin film filters", Proc. SPIE 4094, Optical and Infrared Thin Films, (19 October 2000); doi: 10.1117/12.404754; https://doi.org/10.1117/12.404754

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