PbS nanosculptured thin film for phase retarder, anti-reflective, excellent absorber, polarizer and sensor applications.

Lead-sulphide (PbS) nanosculptured thin film (nSTF) is prepared using a glancing angle deposition (GLAD) technique and the physical vapour deposition (PVD) process. The morphology of the GLAD films clearly shows that an anisotropic structure is obtained and is composed of micro-sheets with sharp top edges (a few tens of nanometres tip width). Due to this anisotropy, optical birefringence is induced in the nSTF as well as linear dichroism. The structural and optical properties of the PbS nSTF have been characterized by scanning electron microscopy, atomic force microscopy, Raman spectroscopy and transmission measurements. The Raman spectra of PbS nSTF exhibit sharp peaks representative of vibrations in nano-crystalline PbS. Due to the absorption of PbS the nSTF is found to act as a linear polarizer with good extinction and contrast in the near infra-red range. Due to its porosity this nSTF also has the ability to sense fluids, which we demonstrate using ethanol-water solution at different concentrations. The combination of these effects in PbS nSTF is believed to constitute a prime candidate for many desirable device applications in different aspects with the low cost of production in large areas.

Chalcogenide waveguides on a sapphire substrate for mid-IR applications.

We report on the fabrication of arsenic tri-sulfide chalcogenide strip waveguides on a sapphire substrate, suitable for guiding 0.55-5 µm wavelengths. Propagation losses measured using the Fabry-Perot resonator technique are 2.78 dB/cm. The chalcogenide layer refractive index dispersion is evaluated by measuring the transmission as a function of wavelength prior to waveguide fabrication. Numerical simulations are used to compare between silica and sapphire substrates for mid-IR transmittance and to calculate the waveguide's effective refractive index in a suggested design. The use of a low-loss sapphire substrate redefines the mid-IR boundaries of chalcogenide waveguides for linear and nonlinear applications.

Liquid crystal high-resolution optically addressed spatial light modulator using a nanodimensional chalcogenide photosensor.

The fabrication and performance of an optically addressed spatial light modulator (OASLM) based on nematic liquid crystal and nanodimensional amorphous arsenic trisulfide (a-As2S3) chalcogenide glassy films are described. The photoconductive a-As2S3 layers are used both as photoalignment material and as a photosensor. The use of the OASLM as a color converter is demonstrated in the transmission mode. The phase retardation dynamic range is over 3π. Diffraction efficiency measurements show a high resolution (150 lp/mm at 50% MTF). A wide variety of materials from the chalcogenide glass (ChG) family are useful for simple fabrication of high-resolution OASLMs depending on the desired wavelength.