With the increasing complexity of optical designs flown on satellites, specialty thin film and multilayer filter coatings
are being implemented more often. Unfortunately, very little ionizing radiation testing has actually been performed on
such coatings, and certainly not completed to very high doses as might be experienced by an unshielded space optic in
orbit for many years. In this paper we present results of gamma irradiation testing on the transmission properties of
selected multilayer filters and optical coatings performed in an inert argon environment.
NASA's Goddard Space Flight Center (GSFC) cooperatively with Sandia National Laboratories completed a series of tests on three separate configurations of multi-fiber ribbon cable and MTP connector assemblies. These tests simulate the aging process of components during launch and long-term space environmental exposure. The multi-fiber ribbon cable assembly was constructed of non-outgassing materials, with radiation-hardened, graded index 100/140-micron optical fiber. The results of this characterization presented here include vibration testing, thermal vacuum monitoring, and extended radiation exposure testing data.
This paper discusses the use of laterally deformable optical nanoelectromechanical systems (NEMS) grating transducers for sensor applications. For very small changes in the spacing of the nanostructured grating elements, a large change in the optical reflection amplitude is observed, making this an ideal transducer element for detecting very small amounts of relative motion. These devices are also very sensitive to wavelength, and could thus be used as tunable elements for spectrometry, as well as communications or inertial sensing. This anomalous diffraction property was predicted in previous work; here, we experimentally verify operation of these devices and demonstrate a motion detection sensitivity of 10 fm/Hz<sup>1/2</sup>, comparable to the most sensitive MEMS transducer. As optical devices, these sensors have additional advantages over electrical sensors, including high immunity to electromagnetic interference and the possibility of integration with fiber optics to create a network of sensors with a single remote optical source and detector.
We have experimentally demonstrated operation of a laterally deformable optical NEMS grating transducer. The device is fabricated in amorphous diamond on a silicon substrate with standard lithographic techniques. For small changes in the spacing of the grating elements, a large change in the optical reflection amplitude is observed. An in-plane motion detection sensitivity of 160 fm/√Hz has been measured, which agrees well with theoretical models. This sensitivity compares favorably to that of any other MEMS transducer. Calculations predict that this sensitivity could be improved by up to two orders of magnitude in future designs. As well as having applications to the field of accelerometers and other inertial sensors, this device could also be used as a modulator for optical switching.