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Molecular beam epitaxy has been used to grow SrF 2 thin films on Si͑001͒. The growth modes have been investigated by atomic force microscopy, electron diffraction, and photoemission. Two principal growth regimes have been identified: ͑i͒ when deposition is carried out with the substrate held at a temperature of 700-750°C, SrF 2 molecules react with the substrate giving rise to a Sr-rich wetting layer on top of which three dimensional bulklike fluoride ridges develop; ͑ii͒ when deposition is carried out with the substrate held at 400°C, a nanopatterned film forms with characteristic triangular islands. Results are compared to the growth mode of CaF 2 on Si͑001͒ under analogous deposition conditions. Morphological and structural differences between the two systems are associated with the larger lattice parameter of SrF 2 with respect to CaF 2 , resulting in a larger mismatch with the Si substrate.

We present the results of calculation and experimental testing of an achromatic polarization converter and a composite terahertz waveplate (WP), which are represented by sets of plane-parallel birefringent plates with in-plane birefringence axis. The calculations took into account the effect of interference, which was especially prominent when plates were separated by an air gap. The possibility of development of a spectrum analyzer design based on a set of WPs is also discussed.

The growth of MnF2 and ZnF2 layers on Si(001) and Si(111) substrates was studied by molecular-beam epitaxy. Calcium fluoride buffer layers with (001), (110), and (111) orientations were used to prevent chemical interaction of MnF2 and ZnF2 molecules with the Si substrate. The analysis of x-ray and reflection high-energy electron-diffraction (RHEED) patterns showed that MnF2 layers grow on all of these planes in the orthorhombic α-PbO2-type crystal phase observed earlier only at high pressures and temperatures. Atomic force microscopy revealed a strong dependence of the surface morphology on the buffer orientation and growth temperature. The best-ordered MnF2 growth occurred at 500 °C on a CaF2 (110) buffer layer. The diffraction analysis enabled us to find the epitaxial relations at the MnF2∕CaF2 interface. A careful analysis of the RHEED patterns of the films grown on CaF2(001) showed a similarity in the structure and growth modes between MnF2 and ZnF2 layers, with ZnF2 tending to form multiphase layers. These findings are in agreement with the x-ray diffraction measurements.