The research, from the University of Leeds, has focused on ways to control terahertz quantum cascade lasers. This technology is considered by physicists as the key to increase data transmission rates to 100 gigabits per second. To put this into context, these types of speeds are some thousand times faster than is possible using Ethernet (which operates at 100 megabits a second).
Terahertz quantum cascade lasers are capable of emitting light in the terahertz range of the electromagnetic spectrum. Terahertz waves are invisible, and have a number of potential applications, such as being able to penetrate materials that are opaque to visible light. In the field of chemistry, the lasers are capable of detecting a variety of molecules.
With the new study, the research was undertaken with a view of this type of laser providing so-termed ultra-fast, short-hop wireless links. This type of technology is seen as important for the transfer of large datasets, such as between universities or for satellite communications.
For this to happen, the main technical challenge is with the modulation of the lasers, which requires them to be switched on and off so that they pulse at a rate of 100 billion times each second. To achieve this, electrons are directed through the optical component of the laser, as this happens each electron passes through a series of ‘quantum wells’. Here the energy level of the electron falls and a photon (as a pulse of light energy) is emitted. Since an individual electron can emit multiple photons, the state of modulation can be achieved.
With the sound aspect, acoustic waves are produced through the impact of a pulse from a separate laser directed at aluminium film. As the film expands and contracts, this pushes a mechanical wave at the quantum cascade laser. the acoustic wave disrupts the electronic states inside the quantum cascade laser, altering the terahertz light output and laying the basis for ultra-fast data transmission.
Further trials will take place to adjust the process and towards achieving full control over the photon emissions from the laser.
The study has been published in the journal Nature Communications, where the research paper is titled “High-speed modulation of a terahertz quantum cascade laser by coherent acoustic phonon pulses.”
