Ultrafast terahertz (THz) spectroscopy is a potent tool for studying the fundamental properties of matter. Limitations of current THz sources, however, preclude the technique being applied in certain advanced configurations or in the measurement of, e.g., strongly absorbing samples. In response to this problem, here we demonstrate the generation of 1.38 mW broadband THz radiation at 10 MHz repetition rate by combining the highly efficient nonlinear organic crystal HMQ-TMS with ultrafast pump pulses generated using a simple and stable external pulse compression of a high power, near-infrared (NIR) femtosecond ytterbium-doped fiber (Yb:fiber) laser. Utilizing spectral broadening in a large core, polarization maintaining photonic crystal fiber and a pair of SF11 prisms, we achieve a tenfold pulse compression of the Yb:fiber laser, yielding compressed 0.35 µJ pulses with a full-width at half maximum pulse duration of 22 fs, exerting a peak power of 13.8 MW at a repetition rate of 10 MHz. THz generation through optical rectification of the NIR pulses is explored in two distinct thicknesses of the organic crystal, leading to a maximum conversion efficiency of ∼5.5 · 10⁻⁴, an order of magnitude higher than that achieved with inorganic nonlinear crystals, e.g., gallium phosphide, for similar pump parameters. The focused THz beam has a peak on-axis field strength greater than 6.4 kV cm⁻¹ in unpurged atmosphere. We believe that our moderately strong-field THz source is well suited to a variety of applications in ultrafast THz spectroscopy, in particular THz-enabled scattering-type near-field, and scanning tunneling spectroscopy, where multi-MHz repetition rate sources are required.

We demonstrate the first megahertz (MHz) repetition-rate, broadband terahertz (THz) source based on optical rectification in the organic crystal HMQ-TMS driven by a femtosecond Yb:fibre laser. Pumping at 1035 nm with 30 fs pulses, we achieve few-cycle THz emission with a smooth multi-octave spectrum that extends up to 6 THz at -30 dB, with conversion efficiencies reaching 10⁻⁴ and an average output power of up to 0.38 mW. We assess the thermal damage limit of the crystal and conclude a maximum fluence of ∼1.8 mJ·cm⁻² at 10 MHz with a 1/e² pump beam diameter of 0.10 mm. We compare the performance of HMQ-TMS with the prototypical inorganic crystal gallium phosphide (GaP), yielding a tenfold electric field increase with a peak on-axis field strength of 7 kV·cm⁻¹ and almost double the THz bandwidth. Our results further demonstrate the suitability of organic crystals in combination with fibre lasers for repetition-rate scaling of broadband, high-power THz sources for time-domain spectroscopic applications.

The German Climate Action Plan targets an electric vehicle fleet of 6 million by 2030. However, from today’s perspective, we are far away from a path that is steep enough to reach this goal. In order to identify how different policy instruments can stimulate e-mobility diffusion in Germany, we build and calibrate an agent-based simulation model (ABM). The model allows for the consideration of the rich dynamics of social influence as well as the heterogeneity of actors and is flexible enough to be applied with other technologies. We simulate different policy scenarios against a business as usual (BAU) scenario. We show that with the currently implemented set of policies (BAU scenario), it is very unlikely that the envisaged goals in terms of e-mobility diffusion can be reached. Moreover, we suggest additional measures such as a carbon tax on fuel, more charging points, and higher direct subsidies, which are as a combined package likely to have a significantly positive effect on the diffusion of electric cars.

A novel lightwave‐driven detector that combines photomultiplier tube (PMT) technology with structured metasurfaces is presented to enable efficient detection of long‐wavelength radiation in the mid‐infrared (mid‐IR) to terahertz (THz) range. This overcomes the limitations of conventional PMT technology, which cannot efficiently detect wavelengths longer than 1.7 m. The approach utilizes the long‐wavelength radiation's instantaneous electric field to facilitate field‐driven electron emission from metasurfaces, which allows it to cover the entire THz to mid‐IR range by geometric scaling. This enables a novel class of lightwave‐driven detectors with the benefits and performance characteristics known from the established PMT technology, such as fast response times and low noise, while expanding the operational wavelength range vastly. It is shown that the amount of field‐emitted electrons depends on the THz electric field in a highly nonlinear manner, generally following the Fowler–Nordheim relation. Furthermore, the THz‐PMT can determine specific lightwave characteristics of the incident field, including its peak field strength and absolute polarity, due to its sensitivity to the sign of the electric field. With a field sensitivity as low as a few kV cm⁻¹, the THz‐PMTs provide a versatile tool for high sensitivity detection across various fields of interest in science and technology.

Editorial: Responsible Research and Innovation as a toolkit: indicators, application, and context

Although lagging behind the USA in biologics, German firms are forging ahead in the emerging field of biosimilars. This development confirms earlier explanations of the differences in these industries given by the Varieties of Capitalism approach. With the recent differentiation in biopharmaceuticals, again, the differences in the institutional environment on both sides of the Atlantic are responsible for different dynamics. However, this time German companies are in the better position: the industry refers to a tradition of engineering capabilities in chemicals and pharmaceuticals. Additionally, European regulation introduced the world’s first regulatory framework, which moreover is designed in a progressive way concerning market admission.