Martin Brucherseifer

Label–free THz sensing of genetic sequences: towards ‘THz biochips’

THz–wave–based approaches for the label–free characterization of genetic material are described. Time–resolved THz spectroscopic analysis of genetic sequences (polynucleotides) demonstrate a distinct complex refractive index in the THz frequency range as a function of the binding state of the analysed DNA sequences. By monitoring THz signals, one can thus infer the binding state of oligo– and polynucleotides, enabling the label–free determination of the genetic composition of target polynucleotides by sensing their binding to known probe molecules. Here we review integrated THz sensing array developments exhibiting high sensitivity and single–base mutation detection capabilities. Recent achievements using functionalized biosensing arrays of high–Q resonators are illustrated.

Propagation effects in electro-optic sampling of terahertz pulses in GaAs.

Freely propagating terahertz pulses are detected in the time domain by electro-optic sampling in bulk GaAs. We investigate the influence of dispersion of the near-infrared sampling pulse on the transients by varying the thickness of the GaAs crystal. Pronounced propagation effects are identified that originate from the frequency dependence of the phase-matching condition between the terahertz and the sampling pulse.

THz spectroscopy with ultrahigh sensitivity

Summary form only given.Although THz radiation has been used successfully for several applications the signal-to-noise ratio is mostly restricted to 10/sup 4/ to 10/sup 6/ in intensity. Especially for thin films of material the absorption and time delay of a THz pulse are mostly too low to be detected. We show a new method to enhance the sensitivity of THz spectroscopy to relative changes of 10/sup -10/ in intensity by shaking a sample through the focus of a THz beam and using lock-in detection on the shaking frequency.

Time-Domain Terahertz Spectroscopy and Sensing

Spectroscopy in the terahertz (THz) region of the electromagnetic spectrum is an important and growing field of research with a broad range of applications. The characteristic properties of THz radiation (1 THz = 1012 Hz), localised between the infrared and the microwave frequencies, suggest many applications in the spectroscopy of gases, liquids and condensed matter. As an example, the rotational transitions of small molecules lie in this spectral range, enabling the direct quantitative detection and chemical analysis of gases. Moreover, important semiconductor properties, such as carrier concentration and mobility, lead to resonances in this spectral range, which enables one to derive such information directly from THz-transmission experiments. THz spectroscopy therefore constitutes an important analytical tool complementary to standard characterisation methods which opens up a wide variety of application perspectives.