High-power THz Pulses Research Articles

System for Long-Term Irradiation of Living Cell Culture with High-Intensity THz Pulses

In this paper we present an experimental set up for long-term irradiation of cells with high-power terahertz pulses with intensities of about 23 GW/cm2. The system was shown to be a reliable tool for cell irradiation in single-point irradiation mode as well as in scanning mode. Wharton’s Jelly derived mesenchymal stem cells were exposed to high power THz pulses with a field strength of about 3 MV/cm for 90 min for the first time. Preliminary results on THz radiation effects on cell viability and proliferation were obtained.

Investigation of dynamic optical behavior of CeO2 thin film using terahertz spectroscopy

Dynamic optical behavior of CeO2 thin film has been investigated using Terahertz spectroscopy at room temperature by exciting with different amplitude pulses. The CeO2 thin films have been deposited on Si (100) substrate by RF magnetron sputtering technique. It has been observed that the optical density increases at 0.75 THz on the incident of pulse ≥100 kV/cm indicating that it is possible to induce extremely large amplitude motions in the harmonic potential of the material by direct excitation of CeO2 vibrations with intense THz pulse. This study further shows that it is possible to control the large amplitude motions in the materials using different high power THz pulses, and in turn can control the optical properties, establishing the nonlinear spectroscopy technique for such studies.

Aspects of application of high-power THz pulses for gas detection and recognition on open-space pathways

Aspects of application of high-power THz pulses for gas detection and recognition on open-space pathways

THz Autocorrelators for ps Pulse Characterization Based on Schottky Diodes and Rectifying Field-Effect Transistors

When operating Schottky diodes and rectifying field-effect transistors in the saturation regime, where they show a sublinear response to incident THz power, they can be used as fast autorcorrelators yielding information on the pulse envelope. We report on autocorrelation measurements at 3.41 THz of high-power THz pulses for determination of the pulse duration and pulse structure. By fringe-resolved measurements, the THz frequency of the pulse is also obtained. We develop a theoretical model for the rectification process and compare the performance of an antenna-coupled Schottky diode to a large-area field-effect transistor rectifier. While the Schottky diode saturates earlier and can therefore be used for autocorrelation measurements at lower input power, antenna-less large-area field-effect transistors can be used for highest power levels—even at free electron lasers—and turn out to be very robust.

Ultra-fast transistor-based detectors for precise timing of near infrared and THz signals

A whole class of two-color experiments involves intense, short Terahertz radiation pulses. A fast and moderately sensitive detector capable to resolve both near-infrared and Terahertz pulses at the same time is highly desirable. Here we present the first detector of this kind. The detector element is a GaAs-based field effect transistor operated at room temperature. THz detection is successfully demonstrated at frequencies up to 4.9 THz. The THz detection time constant is shorter than 30 ps, the optical time constant is 150 ps. This detector is ideally suited for precise, simultaneous resolution of optical and THz pulses and for pulse characterization of high-power THz pulses up to tens of kW peak power levels. The dynamic range of the detector is as large as 65±3dB/Hz, enabling applications in a large variety of experiments and setups, also including table-top systems.

Nonlinear ultrafast dynamics of high temperature YBa2Cu3O7–δsuperconductors probed with THz pump / THz probe spectroscopy

High power THz pulses induce near transparency in superconductive YBCO thin films below the critical temperature. THz pump/THz probe measurements reveal a decay of the induced transparency on the time scale of a few picoseconds.

Detection of nanosecond-scale, high power THz pulses with a field effect transistor

We demonstrate detection and resolution of high power, 34 ns free electron laser pulses using a rectifying field effect transistor. The detector remains linear up to an input power of 11 ± 0.5 W at a pulse energy of 20 ± 1 μJ at 240 GHz. We compare its performance to a protected Schottky diode, finding a shorter intrinsic time constant. The damage threshold is estimated to be a few 100 W. The detector is, therefore, well-suited for characterizing high power THz pulses. We further demonstrate that the same detector can be used to detect low power continuous-wave THz signals with a post detection limited noise floor of 3.1 μW/√Hz. Such ultrafast, high power detectors are important tools for high power and high energy THz facilities such as free electron lasers.

Mobile source of high-energy single-cycle terahertz pulses

The Teramobile laser facility was used to realize the first mobile source of high-power THz pulses. The source is based on a tilted-pulse-front pumping THz generation scheme optimized for application of terawatt laser pulses. Generation of 50-μJ single-cycle electromagnetic pulses centered at 0.19 THz with a repetition rate of 10 Hz was obtained for incoming 700-fs 120-mJ near-infrared laser pulses. The corresponding laser-to-THz photon conversion efficiency is approximately 100%.