We present the characterization of a Zero-bias Schottky diode-based Terahertz (THz) detector up to 5.56 THz. The detector was operated with both a table-top system until 1.2 THz and at a Free-Electron Laser (FEL) facility at singular frequencies from 1.9 to 5.56 THz. We used two measurement techniques in order to discriminate the sub-ns-scale (via a 20 GHz oscilloscope) and the ms-scale (using the lock-in technique) responsivity. While the lock-in measurements basically contain all rectification effects, the sub-ns-scale detection with the oscilloscope is not sensitive to slow bolometric effects caused by changes of the IV characteristic due to temperature. The noise equivalent power (NEP) is 10 pW/$\sqrt{\mathrm{Hz}}$ in the frequency range from 0.2 to 0.6 THz and 17 pW/$\sqrt{\mathrm{Hz}}$ at 1.2 THz and increases to 0.9 $\mathsf{\mu }$W/$\sqrt{\mathrm{Hz}}$ at 5.56 THz, which is at the state of the art for room temperature zero-bias Schottky diode-based THz detectors with non-resonant antennas. The voltage and current responsivity of ∼500 kV/W and ∼100 mA/W, respectively, is demonstrated over a frequency range of 0.2 to 1.2 THz with the table-top system.

We demonstrate a free space two-port photonic vector network analyzer capable of measuring the scattering parameters of devices and materials in the terahertz range with a frequency coverage of 0.2 - 2 THz in a single system. It is based on photoconductive terahertz sources and detectors driven by a telecom-wavelength femtosecond laser. Being able to cover a bandwidth of one order of magnitude, the system is capable of performing S-parameter measurements deep into the terahertz range, beyond frequencies reachable by their electronic counterparts. We demonstrate high performance at three application examples, namely S-parameter measurements of a split ring resonator array and a distributed Bragg reflector, as well as material parameter extraction of several materials.

THz time-domain spectroscopy (TDS) is a promising tool for quality control purposes in industrial applications, but the high cost and the relatively large laser sources still make it difficult to use the full potential of the technology for a decent price. In this work, a THz TDS system, which uses a commercially available Fabry–Perot laser diode emitting at 1550 nm, is presented. By dispersion compensation, pulses with a duration of 544 fs were generated, resulting in THz radiation with a bandwidth of 1.4 THz and a peak dynamic range of 56 dB with state-of-the-art ErAs:In(Al)GaAs photoconducting antennas. These results are compared with those of a conventional and expensive fiber laser system with a 90 fs pulse duration.

Introduction of electro-optical circuit board (EOCB) technologies based on embedded glass waveguides in the system enclosure of current data storage, compute, or switch platforms will be instrumental in accommodating the prohibitive bandwidth densities projected in exascale data centers, access networks, and high-performance computing environments in future. The main focus of this paper is, therefore, on the realization of large EOCB backplanes (350 × 465) mm ² with passive dual-star interconnect topologies. The waveguides are embedded inside glass panels using a two-step thermal ion exchange process. The fabricated embedded waveguides are then characterized for propagation and coupling losses across different wavelength ranges and for different coupling arrangements. The fabrication process for these large panels is briefly explained accompanied by the lamination process of four separate glass panels. The connectivity between backplane and peripheral cards is addressed using fiber flex termination with two possible waveguide interfaces-actively assembled pluggable interface and passively assembled adhesive bonded interface. A demonstration platform is also finally reported and the viability evaluated for optical connectivity and system efficiency is tested for the whole system containing fiber flex termination.

High-power coherent terahertz (THz) radiation from accelerator facilities such as free-electron lasers (FELs) is frequently used in pump-probe experiments where the pump or probe (or both) signals are intense THz pulses. Detectors for these applications have unique requirements that differ from those of low-power table-top systems. In this study, we demonstrate GaAs antenna-coupled field effect transistors (FETs) as a direct THz detector operating across a broad frequency spectrum ranging from 0.2 THz to 29.8 THz. At approximately 0.5 THz, the maximum current responsivity (ℜ _I ) of 0.59 mA/W is observed, signifying a noise equivalent power (NEP) of 2.27 nW/√Hz. We report an empirical roll-off of f⁻³ for an antenna-coupled GaAs TeraFET detector. Still, NEP of 0.94 μW/√Hz and a current responsivity ℜ _I = 1.7μA/W is observed at 29.8 THz, indicating that with sufficient power the FET can be used from sub-mm wave to beyond far-infrared frequency range. Current and voltage noise floor of the characterized TeraFET is 2.09 pA and 6.84 μV, respectively. This characteristic makes GaAs FETs more suitable for applications requiring higher frequencies, ultra-broadband capabilities and robustness in the THz domain, such as beam diagnostics and alignment at particle accelerators.

We demonstrate a spectrometer capable of measuring terahertz time domain transmission and reflection spectroscopy simultaneously in a single setup. This facilitates highly accurate determination of optical material parameters and the geometric thickness by taking advantage of both geometries. The system is also suitable for parameter extraction for materials when data from transmission geometry cannot be extracted and for characterizing non-time-invariant devices such as optical isolators.