Near-field THz imaging and spectroscopy using a multiple subwavelength aperture modulator

We present a near-field, simultaneous multiple pixel subwavelength THz transmission imaging device based on a solid-state THz spatial modulator. Frequency-division multiplexing is used to acquire multiple pixels simultaneously. The modulator was used to acquire THz transmission images with resolution of λ/4 at 118 µm. The image acquisition speed is 16 times greater than that of a comparable single-aperture subwavelength imaging technique. Additionally, spectroscopic THz imaging with subwavelength spatial resolution can be accomplished with the modulator, and the technique is scalable to at least 100 simultaneous pixels

A novel multiplexed THz spatial modulator for fast, sub-wavelength imaging and spectroscopy

We report on the current state of the development of a sub-wavelength THz spatial modulator array – a multi-pixel THz imaging device. The modulator allows fast image acquisition and spectroscopy with greatly improved spatial resolution

Second-order Nonlinear Optical Microscopy of Spider Silk

Asymmetric $\rm \beta$-sheet protein structures in spider silk should induce nonlinear optical interaction such as second harmonic generation (SHG) which is experimentally observed for a radial line and dragline spider silk by using an imaging femtosecond laser SHG microscope. By comparing different spider silks, we found that the SHG signal correlates with the existence of the protein $\rm \beta$-sheets. Measurements of the polarization dependence of SHG from the dragline indicated that the $\rm \beta$-sheet has a nonlinear response depending on the direction of the incident electric field. We propose a model of what orientation the $\rm \beta$-sheet takes in spider silk.Comment: 8 pages, 8 figures, 1 tabl

U-shaped bilayer graphene channel transistor with very high Ion/Ioff ratio

A novel graphene transistor architecture is reported. The transistor has a U-shaped geometry and was fabricated using a gallium focused ion beam (FIB). The channel conductance was tuned with a back gate. The Ion/Ioff ratio exceeded 10E5

Spectral imaging as a potential tool for optical sentinel lymph node biopsies

We investigate the potential use of spectral imaging for performing an optical sentinel lymph node biopsy. Dummy images generated from previously published data are analysed using a spectral angle map and we conclude that there is scope for spectral imaging to form the basis of an optical biopsy technique

Sum frequency generation spectroscopy of the attachment disc of a spider

The pyriform silk of the attachment disc of a spider was studied using infrared-visible vibrational sum frequency generation (SFG) spectroscopy. The spider can attach dragline and radial lines to many kinds of substrates in nature (concrete, alloy, metal, glass, plant branches, leaves, etc.) with the attachment disc. The adhesion can bear the spider's own weight, and resist the wind on its orb web. From our SFG spectroscopy study, the NH group of arginine side chain and/or NH$_{2}$ group of arginine and glutamine side chain in the amino acid sequence of the attachment silk proteins are suggested to be oriented in the disc. It was inferred from the observed doublet SFG peaks at around 3300 cm$^{-1}$ that the oriented peptide contains two kinds of structures.Comment: 21 pages, 8 figure

An electrically driven solid state modulator

Simulation results for the design and fabrication of an electrically driven solid state modulator are presented. The design criteria has identified various trade-offs in the manufacturing of an electrically driven modulator using a p-i-n diode to be made from high purity Ge. The issues relating to the doping, layer thickness and contact material for the diode fabrication are discussed. A compromise between the high 'ON' state transmission and uniformity is required to achieve the optimum performance from the device. Using FEMLAB and ATLAS a p-i-n diode with different apertures has been simulated which clearly show the effects of non-uniformity and the requirement of a mesh-type electrode for a uniform absorption across the large device apertures

Epitaxial growth of high quality ZnS films on sapphire and silicon by pulsed laser deposition

We report for the first time, epitaxial growth of high-quality ZnS films on sapphire and silicon substrates, using pulsed laser deposition. X-ray diffraction results show that at all growth temperatures from 200°C to 680°C, epitaxial wurtzite (002) ZnS films have been successfully grown on (1012) sapphire and (001) silicon substrates. X-ray diffraction data yield full width at half maximum 2theta values of 0.13° for as-grown samples, compared with 28 values or 0.09° and 0.08° for the bare sapphire and silicon substrates respectively