Scientists Make Terahertz Quantum Cascade Laser Control Breakthrough

Researchers have made a breakthrough in the control of terahertz quantum cascade lasers that could lead to the ability to transmit data at 100 gigabits per second. The transmission of data at that speed would be about a thousand times faster than Fast Ethernet operating at 100 Mbps. What sets a terahertz laser apart from other lasers is that the light emitted is in the terahertz range of the electromagnetic spectrum.The lasers have applications in the field of spectroscopy, where they are used in chemical analysis. The lasers also have the potential to provide ultra-fast, short-hop wireless links where large amounts of data must be transferred. This would be beneficial in situations like sending data across hospital campuses or between research facilities on a university campus. It could also be used in satellite communications.

To send data at the increased speed requires the laser to be modulated very rapidly by switching on and off at about 100 billion times per second. Researchers have had no luck developing a method of achieving that rapid modulation so far. A team from the University of Nottingham thinks it has found a way to deliver ultra-fast modulation by combining the power of acoustic and light waves.

The scientists say that a quantum cascade laser is very efficient. As an electron passes through the optical component of the laser, it goes through a series of quantum wells where the energy level of the electron drops, and a photon or pulse of light energy is emitted. One electron can emit multiple protons. That is the process controlled during modulation.

The team used the acoustic wave to shake the intricate electronic states inside the quantum cascade laser. They were then able to see that its terahertz light output was altered by the acoustic wave. Scientists say that the results open a new area for physics and engineering to come together to explore the interaction of terahertz sound and light waves.