Lasers have become part of our daily lives, from consumer electronics to telecommunication and medicine, with or without us realizing. The different wavelengths at which lasers operate are what makes them so interesting, and yet not so well researched. For example, the far infrared and terahertz regime, quantum cascade lasers are a source of coherent radiation.
Here, light amplifies through semi-conductor layers, which facilitate the movement of the electric current. A main disadvantage associated with these lasers is the fact that they work only when they are strongly cooled, however between the layers, electrons collide with other particles and consequently heat up the laser.
In their attempt to tackle this, PhD student Kathrin Sandner and Helmut Ritsch decided to test whether this heat can be used to power the laser. Their theory is that avoiding the heat in quantum cascade lasers is not only possible, but if the layers are appropriately modified, this can also be valuable.
According to Sandner, the most critical part is to separate the areas in the laser according to their temperature, because this determines whether the electrons are thermally excited and produce heat, or they are cool and produce photons. This creates a circuit where light is emitted and heat is absorbed. Sander also points out that between each emission of light particles, a photon is absorbed and the laser is cooled.
Ritsch, Sandner’s supervisor from the Institute for Theoretical Physics, University of Innsbruck in Austria, is certain that if this idea works out, their invention will be groundbreaking, although at first sight it seems very challenging. In theory the simplified concept seems feasible and various ways to implement it in an experimental setting has already begun. The idea can present a new way of using heath in microchips, rather than dissipate it by cooling.