Elasto-optic behaviour in epitaxial films of perovskite oxide ferroelectrics

ABSTRACT

Large variations of refractive index in the visible spectral range are obtained in epitaxial perovskite oxide ferroelectric films experiencing lattice strain. The strain is imposed by substrates, on top of which the films are grown. The optical constants are determined using the spectroscopic ellipsometry. As a reference and for comparison, also prototype single crystals are inspected. The variations in refraction are related to the lattice strain in the films. Elasto-optic coefficient is formally estimated using the out-of-plane lattice elongation or shrinkage in the films compared to bulk. The obtained elasto-optic coefficients exceed significantly those previously reported for ferroelectric materials.     

Uncooled Detectors Challenges for THz/sub-THz Arrays Imaging

Some problems and challenges for applications of uncooled or slightly cooled detectors (not deeper than to 77 K) for sub-THz and THz (terahertz) arrays are briefly discussed. The possibilities to involve detectors based on plasmon resonance FETs (field effect transistors) and those based on warm electron effect narrow-gap semiconductor bolometers are speculated, as they seem to be promising for using in large format broadband arrays of low-cost systems, though they are still in the stage of research and optimization.     

Nanoamorphous carbon as a blackbody source in plasmonic thermal emitters

Ag/dielectric/Ag-type plasmonic thermal emitters (PTEs) following a hexagonal lattice were fabricated, and their plasmonic emission spectrums were characterized with Fourier transform infrared spectroscopy. Nanoamorphous carbon (NAC) is used as a dielectric layer. Doping NAC with various materials over a wide range of levels enables control of the resistivity of the composite films where MoSi(2) was selected as the dopant. Wavelength tuning in the range of 4-7 μm is demonstrated by changing the conductivity of the composite films as well as the lattice periodicity of the hexagonal lattice. We also tested the mechanical stability of the PTEs under mechanical strains.