What distinguishes terahertz quantum cascade lasers from different lasers is the reality they discharge light in the terahertz range of the electromagnetic range. They have applications in the field of spectroscopy, where they are used in chemical analysis.
The lasers could likewise provide ultra-fast, short-hop wireless connections where massive datasets must be moved across hospital campuses or between research facilities on universities– or in satellite communications.
To be able to send data at these increased speeds, the lasers need to be modulated very rapidly: switching on and off or pulsing about 100 billion times every second.
Engineers and scientists have so far failed to develop a way of achieving this.
Now, a team of scientists from the University of Leeds and the University of Nottingham has made a breakthrough in the control of terahertz quantum cascade lasers, which could lead to the transmission of data at the rate of 100 gigabits per second.
They combined the power of acoustic and light waves.
John Cunningham, Professor of Nanoelectronics at Leeds, said: “This is exciting research. At the moment, the system for modulating a quantum cascade laser is electrically driven – but that system has limitations.“
“Ironically, the same electronics that deliver the modulation usually puts a brake on the speed of the modulation. The mechanism we are developing relies instead on acoustic waves.“
Instead of using external electronics, the researchers used acoustic waves to vibrate the quantum wells inside the quantum cascade laser. The acoustic waves were generated by the impact of a pulse from another laser onto an aluminum film. This caused the film to expand and contract, sending a mechanical wave through the quantum cascade laser.
Tony Kent, Professor of Physics at Nottingham, said, “Essentially, what we did was use the acoustic wave to shake the intricate electronic states inside the quantum cascade laser. We could then see that the acoustic wave was altering its terahertz light output.”
Professor Cunningham added: “We did not reach a situation where we could stop and start the flow completely, but we were able to control the light output by a few percents, which is a great start. We believe that with further refinement, we will be able to develop a new mechanism for complete control of the photon emissions from the laser, and perhaps even integrate structures generating sound with the terahertz laser so that no external sound source is needed.”
The findings are published today in Nature Communications.