Some may say that lasers are cool, but very often this is not true as electron movement builds up enough heat to even shut down the laser. To keep these lasers, especially quantum cascade lasers, operating, cooling systems have to be used, but they are not always enough. Researchers at the University of Innsbruck though have found a way to address the heat problem that could end up driving the laser as it works.
In a quantum cascade laser electrons tunnel between semiconductor layers and emit photons as they move. However, as the electrons move between the layers, they bump into each other and these collisions create the heat which can disrupt the laser. Instead of looking to new ways to cool the laser by traditional methods, the researchers looked to the physics involved with the operation of the laser and found that with some modifications, the design itself could keep the laser cool. By controlling the distance between the semiconductor layers, the researchers can create a temperature gradient across the layers. This gradient then encourages the electrons to tunnel from the warm areas to the cooler ones, which are where the photons are emitted. With each photon emitted though, some of the heat leaves the system.
In theory, this approach could be used to power the laser as the thermal energy is converted to laser light. An actual laser that uses this design will have to be created to prove that though.