Numerical study of Anderson localization of terahertz waves in disordered waveguides

We present a numerical study of electromagnetic wave transport in disordered quasi-one-dimensional waveguides at terahertz frequencies. Finite element method calculations of terahertz wave propagation within LiNbO3 waveguides with randomly arranged air-filled circular scatterers exhibit an onset of Anderson localization at experimentally accessible length scales. Results for the average transmission as a function of waveguide length and scatterer density demonstrate a clear crossover from diffusive to localized transport regime. In addition, we find that transmission fluctuations grow dramatically when crossing into the localized regime. Our numerical results are in good quantitative agreement with theory over a wide range of experimentally accessible parameters both in the diffusive and localized regime opening the path towards experimental observation of terahertz wave localization.

Environment induced variation in the photoconductivity of graphene observed by terahertz spectroscopy

Chemical vapour deposition (CVD) grown graphene sheets were investigated using optical-pump terahertz-probe spectroscopy, revealing a dramatic variation in the photoinduced terahertz conductivity of graphene in different atmospheres. © 2012 IEEE.

Probing the critical electronic properties of III-V nanowires using optical pump-terahertz probe spectroscopy

Optical pump-terahertz probe spectroscopy was used to study the key electronic properties of GaAs, InAs and InP nanowires at room temperature. Of all nanowires studied, InAs nanowires exhibited the highest mobilities of 6000 cm2V-1s-1. InP nanowires featured the longest photoconductivity lifetimes and an exceptionally low surface recombination velocity of 170 cm/s. © 2013 IEEE.

Transient terahertz spectroscopy of mono- and tri-layer CVD-grown MoS 2

Molybdenum disulpide, a novel two-dimensional semiconductor, was studied using optical-pump terahertz-probe spectroscopy. Mono and trilayer samples grown by chemical vapour deposition were compared to reveal their dynamic electrical response. © 2013 IEEE.

Fast, sensitive and low-noise nanowire and graphene field effect transistors for room-temperature detection of Terahertz quantum cascade laser emission

Antenna-coupled field effect transistors have been developed as plasma-wave THz detectors in both InAs nanowire and graphene channel materials. Room temperature operation has been achieved up to 3 THz, with noise equivalent power levels < 10-10 W/Hz1/2, and high-speed response already suitable for large area THz imaging applications. © 2013 IEEE.

Material parameter extraction in THz-TDS using a converging beam transfer function

We demonstrate a parameter extraction algorithm based on a theoretical transfer function, which takes into account a converging THz beam. Using this, we successfully extract material parameters from data obtained for a quartz sample with a THz time domain spectrometer. © 2010 IEEE.

Nanowire and graphene architectures for room temperature THz detection

Antenna-coupled field effect transistors have been developed as plasma-wave THz detectors in both InAs nanowire and graphene channel material. Room temperature operation has been achieved up to frequencies of 1.5 THz, with noise equivalent powers as low as a few 10-11 W/Hz1/2, and high-speed response. © 2012 IEEE.

Dual-layer frequency-selective grid polarizers on thin-film substrates for THz applications

Dual-layer frequency-selective subwavelength grid polarizers on thin-film dielectric substrates are proposed for THz and sub-THz applications. The dual-layer grids possess enhanced (squared) polarizing efficiency at a sequence of discrete frequencies in reflection and within extended frequency bands in transmission as compared to conventional single grids.

W-Band Planar Wide-Angle Scanning Antenna Architecture

This paper proposes a hybrid scanning antenna architecture for applications in mm-wave intelligent mobile sensing and communications. We experimentally demonstrate suitable W-band leaky-wave antenna prototypes in substrate integrated waveguide (SIW) technology. Three SIW antennas have been designed that within a 6.5 % fractional bandwidth provide beam scanning over three adjacent angular sectors. Prototypes have been fabricated and their performance has been experimentally evaluated. The measured radiation patterns have shown three frequency scanning beams covering angles from 11 to 56 degrees with beamwidth of 10?±?3 degrees within the 88-94 GHz frequency range.

Subspace and wavelet-packet algorithms for de-noising and classifying broadband THz transients

The results from a range of different signal processing schemes used for the further processing of THz transients are contrasted. The performance of different classifiers after adopting these schemes are also discussed.

Deconvolution: imaging the unturned page

A custom-built deconvolution technique for pulsed terahertz imaging is presented in this paper. It is examined as a tool for the measurement of thin transparent films. The power of the technique is illustrated by using the impulse response function, calculated in the deconvolution process, to recreate terahertz images of both sides of a piece of paper derived from one single terahertz reflection measurement.

Quantifying user perception of foodstuffs using THz spectrometry

We discuss the potential of using THz spectrometry for the direct observation of phase transitions in foodstuffs, with the aim of quantifying consumer perception. Experimental results from phase transitions using a continuous wave dispersive Fourier transform spectrometer and a cyclotron enhanced liquid helium cooled bolometric detector are reported.

Femto-chemometrics: the signal processing of fast pulse transients

Traditional chemometrics techniques are augmented with algorithms tailored specifically for the de-noising and analysis of femtosecond duration pulse datasets. The new algorithms provide additional insights on sample responses to broadband excitation and multi-moded propagation phenomena.