Ultra-fast method to create terahertz radiation advances materials science 

sperm, brain tumours, Common drugs, diabetes, chronic wounds, magnetism, intestinal tumours, molecular scissors, disease, genetic, immune cells, drug development, Diabetes, Antibiotic, hydrogen generation, chronic obstructive pulmonary disease, malaria, photosynthesis, kidney failure, Brain tumours, mental health, blood cancer, cancer, dementia, cancer treatment, antibiotic resistance, blood vessel leakage, quantum simulations, atrial fibrillation, batteries, goiter treatment, terahertz radiation, organic materials , Guild of European Research Intensive Universities, gene copies, social anxiety, blue light screens, ‘Our hope is that these findings will make it possible to discover a way to selectively inhibit the TGF-beta signals that stimulate tumour development without knocking out the signals that inhibit tumour development, and that this can eventually be used in the fight against cancer,’ says Eleftheria Vasilaki, postdoctoral researcher at Ludwig Institute for Cancer Research at Uppsala University and lead author of the study. TGF-beta regulates cell growth and specialisation, in particular during foetal development. In the context of tumour development, TGF-beta has a complicated role. Initially, it inhibits tumour formation because it inhibits cell division and stimulates cell death. At a late stage of tumour development, however, TGF-beta stimulates proliferation and metastasis of tumour cells and thereby accelerates tumour formation. TGF-beta’s signalling mechanisms and role in tumour development have been studied at the Ludwig Institute for Cancer Research at Uppsala University for the past 30 years. Recent discoveries at the Institute, now published in the current study in Science Signaling, explain part of the mechanism by which TGF-beta switches from suppressing to enhancing tumour development. Uppsala researchers, in collaboration with a Japanese research team, discovered that TGF-beta along with the oncoprotein Ras, which is often activated in tumours, affects members of the p53 family. The p53 protein plays a key role in regulating tumour development and is often altered – mutated – in tumours. TGF-beta and Ras suppress the effect of mutated p53, thereby enhancing the effect of another member of the p53 family, namely delta-Np63, which in turn stimulates tumour development and metastasis.

Uppsala physicists have in an international collaboration developed a new method for creating laser pulses which are shorter, have much higher intensity and cover the THz frequency range better than current sources. The study is published today in the authoritative journal Nature Photonics and is of great importance to materials research.

“Many interesting, dynamic phenomena of interest to materials science occur within the so-called terahertz spectral range but it has been difficult so far to generate such short pulses,” says Pablo Maldonado, one of the researchers behind the study.

The THz range has become increasingly important to science and engineering since so many dynamic processes such as molecular vibrations or magnetic spin waves usually vibrate with THz-frequencies. Therefore, there are many important areas of application for THz radiation such as medical diagnostics, security scanning at airports, molecular sensors or even wireless communications. However, it has been difficult to realise THz sources which cover the entire frequency domain and supply ultra-short pulses of sufficient intensity.

In collaboration with researchers from Germany, France and the USA, Uppsala University researchers Pablo Maldonado and Peter Oppeneer have developed a new THz laser emitter which has better properties than every such device so far made. It builds upon principles of ultra-fast spin transport developed by the Uppsala physicists.

Ultra-fast superdiffusion spin currents are generated by laser excitation in a nanometre thin metallic magnetic layer and move through the adjacent layer in less than a picosecond (10-12 seconds). There they induce the extremely short-lived charge currents which emit intensive THz radiation with a pulse width shorter than 0.5 picoseconds. In order to find the best THz emitter, the researchers from Mainz and Greifswald (Germany) synthesised more than 70 different thin metallic layer systems, which were measured in Berlin. The best emitter was found to consist of three different metal layers which together are less than six nanometres thick.

“It was pleasing that our theory of ultra-fast spin currents could be used in this way and that we can not only explain how spin currents are generated but also how they can be applied to create brilliant THz laser pulses,” says Pablo Maldonado.

Article reference:
Efficient metallic spintronic emitters of ultrabroadband terahertz radiation 
T. Seifert1, S. Jaiswal2,3, U. Martens4, J. Hannegan5, L. Braun1, P. Maldonado6, F. Freimuth7,
A. Kronenberg2, J. Henrizi2, In. Radu8, E. Beaurepaire9, Y. Mokrousov7, P.M. Oppeneer6, M. Jourdan2, G. Jakob2, D. Turchinovich10, L.M. Hayden5, M. Wolf1, M. Münzenberg4, M. Kläui2, T. Kampfrath1