4 March 1993 Thermal-optical controllable thin-film device at 10.6 μm
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A sharp spectral rise in reflectance or transmittance of a suitable thin film filter can be used to construct a thermo-optical controllable mirror or phase retarder. A Fabry-Perot filter or a (lambda) /4-multilayer stack are such devices. Because of its comparatively high temperature dependence of refractive index Germanium is used as the active substance. The design wavelength is 10.6 micrometers . Reflectance of the filter can be tuned either in a quasistatic way by temperature variation of the whole device or in a dynamic regime with light pulses of visible spectral range which are strongly absorbed in Germanium. This increases temperature and causes a transmission change by displacing the resonance peak of the Fabry-Perot. Thermal relaxation time is of about 10 microsecond(s) .
© (1993) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
W. Richter, W. Richter, Udo Weinert, Udo Weinert, } "Thermal-optical controllable thin-film device at 10.6 μm", Proc. SPIE 1782, Thin Films for Optical Systems, (4 March 1993); doi: 10.1117/12.141038; https://doi.org/10.1117/12.141038

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