Published in Journal of Superconductivity
A phase-sensitive time-domain terahertz-transmission spectroscopy was carried out on a c-axis oriented underdoped Bi2Sr2CaCu2O8 + δ thin film. We directly extracted the complex refractive index and conductivity at frequencies from 0.3 to 1.5 THz by numerically solving the observed complex transmittance without Kramers–Kronig analysis. The frequency...
We report on what is believed to be the first observation of coherent subterahertz (sub-THz) emission from a 1-m string in the atmosphere. The sub-THz pulse emitted by the filamentary structure from an intense IR femtosecond laser pulse is detected perpendicularly to the laser propagation axis by use of two heterodyne detectors at 94±1 and 118±1GHz...
We investigate the transmittance of thin doped GaAs layers in the terahertz (THz) frequency range taking into account multiple reflections. Our experimental and theoretical study aims at providing a guideline for designing the top-side contact layers for THz emitters and receivers with direct, antenna-free coupling of he radiation. It is shown that...
Published in Journal of Biological Physics
We report the use ofterahertz time-domain spectroscopy for thestudy of two therapeutic bio-molecules:glucose and uric acid. Terahertztransmission spectra of crystalline samplesof both molecules were measured between 0.1–3.0 THz using an evacuated spectroscopysystem. We propose that the stereo-isomersof glucose show spectral featuresoriginating from...
Published in Journal of Biological Physics
We report on a method to obtain asub-wavelength resolution in terahertz time-domain imaging. In our method,a sharp copper tip is used to locallydistort and concentrate the THz electricfield. The distorted electric field, presentmainly in the near field of the tip, iselectro-optically measured in an (100)oriented GaP crystal. By raster scanning the ...
Published in Journal of Biological Physics
The terahertz frequency absorption spectraof DNA molecules reflect low-frequencyinternal helical vibrations involvingrigidly bound subgroups that are connectedby the weakest bonds, including thehydrogen bonds of the DNA base pairs,and/or non-bonded interactions. Althoughnumerous difficulties make the directidentification of terahertz phonon modes i...
Published in Journal of Biological Physics
Modelling the interaction of terahertz(THz) radiation with biological tissueposes many interesting problems. THzradiation is neither obviously described byan electric field distribution or anensemble of photons and biological tissueis an inhomogeneous medium with anelectronic permittivity that is bothspatially and frequency dependent making ita com...
Published in Journal of Biological Physics
We report the production of high power (20watts average, ∼ 1 Megawatt peak) broadbandTHz light based on coherent emission fromrelativistic electrons. Such sources areideal for imaging, for high power damagestudies and for studies of non-linearphenomena in this spectral range. Wedescribe the source, presenting theoreticalcalculations and their exper...
Published in Applied Physics B
Calorimetric measurements of the THz radiation from plasma filaments created in air by intense IR fs laser pulses were performed. The decay kinetics of the THz radiation from this extended plasma source is shown to be different from that of a localized air plasma source produced by the same laser.
We propose a microwave diode based on a modulation-doped GaAs/Al(0.25)Ga(0.75)As structure. The principle of the diode operation relies on a non-uniform heating of the two-dimensional electron gas in microwave electric fields arising due to the asymmetric shape of the device. The voltage sensitivity of the diode at room temperature is dose to 0.3 V...
