Polymeric photorefractive materials have attracted much attention over the past decade due to their potential applications, especially for optical information processing. However, their practical use has until now been limited, the available photosensitizers being efficient only in the visible range. Here, the chemical development and optical investigations of a photorefractive polymeric material active at 1500 nm are described. To our knowledge, this is the first such material to be reported. A conjugated poly[(ethynediyl)(arylene)(ethynediyl)silylene] acts as both an optical chromophore, as well as charge generator and conductor. Its absorption band tails into the near-IR hence providing charge generation at the 1500 nm excitation. The photoconductivity of the composite samples was measured with a dc-method using a 1500 nm diode laser source. The electro-optical coefficient was measured with a simple reflection technique. The photorefractive response was investigated with a two-beam coupling technique. The gain of the probe beam intensity, delivered from the pumping beam, reached 40 cm-1 at the electric field strength of 650 kVcm-1 thus confirming the photorefractive nature of the grating. The gain exceeded the absorption (30 cm-1) that showed a good potential of this material for applications.
Proof of concept narrow-band etalon filters have been fabricated and characterized for the SWIFT instrument program. The Stratospheric Wind Interferometer For Transport studies is a limb viewing satellite instrument which is intended to measure stratospheric horizontal wind velocities in the altitude range of 20 to 40 km. In addition to providing the atmospheric research community with the first direct measurements of stratospheric dynamics on a global scale, continuous global SWIFT data is expected to improve long range weather forecasting in the troposphere. To isolate the single lines required for the Doppler measurement of the SWIFT instrument, two narrow-band germanium etalon filters centered near 9 micrometer and with 0.8 nm and 2.5 nm bandwidths were fabricated and tested. The SWIFT filter testbed consists of a cryogenic dewar and temperature controller for stabilizing and tuning the filters. The SWIFT filter requirements are discussed, as is the filter testbed design. The measured filter characteristics: transmittance as a function of wavelength, temperature and angle of incidence and tandem filter properties are discussed in the context of satellite instrument requirements.
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