The Ultra-Fast Laser At Terahertz Frequencies Is Closer

Researchers from the Nanoscience Institute of the CNR have collaborated with institutions from all over Europe to create a compact and inexpensive "quantum cascade" laser, which exploits the potential of terahertz radiation to generate short pulses. The result opens up prospects for a vast number of applications, from diagnostics to climate science to ultra-fast communications. The study is published in Nature Photonics

A team of researchers from all over Europe, coordinated by Miriam Serena Vitiello of the Nanoscience Institute of the National Research Council of Pisa (Cnr-Nano), has created an innovative miniaturized semiconductor laser, or "quantum cascade" laser, compact and cheap , capable of generating short pulses of radiation at terahertz frequencies.

The invention, described in an article in the journal Nature Photonics , is based on an extremely promising, but still little exploited technology: in fact, unlike traditional lasers, which work continuously by producing a constant beam of radiation, the device created is capable of generating "pulsed" beams, i.e. switched on and off at regular intervals, spontaneously, without the need for an external power supply or complex control electronics, thanks to the mechanism known as "mode-locking", a goal long considered unattainable in terahertz lasers.

Heart of the technology, the innovative combination of quantum cascade laser technology with the optical properties of graphene. Miriam Serena Vitello, research manager of Cnr-Nano and lead author of the study explains: “For a long time it was believed that the generation of short pulses was prevented by the very nature of the emission mechanism of semiconductor lasers. To overcome this limitation, we exploited an innovative device architecture that integrates localized strips of graphene embedded in a very compact semiconductor laser, known as a quantum cascade laser. The resulting configuration is compact, fully electronic and extremely economical”.

Thus, for the first time, self-generated pulses with a duration of 4 picoseconds were obtained - a picosecond is equal to one thousandth of a billionth of a second - and extremely precise timing which makes possible a range of applications in the field of physics, of chemistry and spectroscopy.

"The device born from this collaboration, impulsive and spontaneous, would allow for example to study the ultra-fast processes of interaction between light and matter, taking a sort of 'snapshot'", adds Vitiello. “Furthermore, such a technology could be used for the spectroscopic analysis of gases or complex molecules, also, for example, in the climatic and environmental fields. Or still be exploited in quantum sciences, where fast pulses can bring molecular samples out of equilibrium, as well as in metrology and very high-speed communications”.

Finally, miniaturized terahertz lasers could replace the cumbersome systems currently used in various sectors such as biomedical imaging, security checks, quality control and cultural heritage, also having greater analysis precision.

The result is the result of an extensive scientific collaboration which involved, in addition to Cnr-Nano, the University of Leeds, the Technical University of Munich, the University of Cambridge and the Ecole Normale Supérieure in Paris. The device was conceived and designed in the Nest Laboratory of Cnr-Nano and Scuola Normale Superiore by the team of Miriam Vitiello, which includes Elisa Riccardi and Valentino Pistore, in the context of the ERC Consolidator SPRINT funding, with the collaboration of the groups of Giles Davies and by Edmund Linfield of the University of Leeds and by Andrea C. Ferrari of the University of Cambridge.