In situ generation of surface plasmon polaritons using a near-infrared laser diode

We demonstrate a semiconductor laser-based approach which enables plasmonic active devices in the telecom wavelength range. We show that optimized laser structures based on tensile-strained InGaAlAs quantum wells-coupled to integrated metallic patternings-enable surface plasmon generation in an electrically driven compact device. Experimental evidence of surface plasmon generation is obtained with the slit-doublet experiment in the near-field, using near-field scanning optical microscopy measurements.     

Non-aqueous solution processed ZnO thin film transistors

Zinc oxide based thin film transistors (TFT) fabricated by a non-aqueous sol-gel solution process with a zinc neodecanoate precursor are demonstrated. X-ray diffraction measurement reveals that the ZnO films adopt a hexagonal structure with a random crystal orientation. Atomic force microscope and scanning electron microscope characterizations show that the films are closely packed and consisted of particles with an average size of 45 nm. The devices exhibit an n-channel enhancement mode behavior, with saturation mobility in the range of 0.95-1.29 cm² V⁻¹ s⁻¹, drain current on-to-off ratios higher than 10⁷ and threshold voltages between 5.3 and 16.8 V in an ambient environment. The results imply that high-performance ZnO TFTs produced by a simple and low-cost technique could be applicable to electronic devices.     

Dynamic range criterion of THz spectrum for amino acids measurements

Terahertz (THz) absorption spectra have been applied to measure the compositions of amino acid samples.Because the concentration information about a specific composition is involved in its spectrum, keeping the spectrum length and dynamic range as wide as possible is essential for precise measurements.It is well known that a spectrum is always contaminated by apparatus noises.In this paper, we present a criterion for noise cutting based on wavelet transform, which usually extends the range determined by traditional threshold criterion.Finally, theimprovement on measurement precision shows the validity of the new criterion.     

Broad spectrum measurement of the birefringence of an isothiocyanate based liquid crystal

Tunable materials with high anisotropy of refractive index and low loss are of particular interest in the microwave and terahertz range. Nematic liquid crystals are highly sensitive to electric and magnetic fields and may be designed to have particularly high birefringence. In this paper we investigate birefringence and absorption losses in an isothiocyanate based liquid crystal (designed for high anisotropy) in a broad range of the electromagnetic spectrum, namely 0.1-4 GHz, 30 GHz, 0.5-1.8 THz, and in the visible and near-infrared region (400 nm-1600 nm). We report high birefringence (Δn = 0.19-0.395) and low loss in this material. This is attractive for tunable microwave and terahertz device applications.     

Quantitative measurements of amino acids by terahertz time-domain transmission spectroscopy

The quantitative analysis of amino acids by terahertz (THz) time-domain absorption spectroscopy is demonstrated. The optical densities of the amino acids were found to be linearly proportional to the concentration. The molar absorption coefficients of L-glutamic acid (L-Glu), L-glutamic acid sodium salt (Na-L-Glu), L-glutamic acid hydrochloric salt (HCl-L-Glu), L-cysteine (L-Cys), and L-histidine (L-His) were calculated by averaging the THz spectra of the amino acids at several different concentrations in approximately the 0.2-1.0 mol L(-1) range. The concentrations of L-Glu, L-Cys, and L-His mixed samples were successfully calculated with errors of less than 11% and 20% when their concentrations were higher than 0.45 and 0.22 mol L(-1), respectively, by using the obtained molar absorption coefficient.