Scientists Create World's Most Powerful Terahertz Quantum Cascade Laser

Terahertz radiation sources are becoming more and more important in the technological world. They can be used for diagnostic imaging, analyzing unknown substances and ultrafast communication. Now, scientists have set a new world record by creating the most powerful terahertz quantum cascade laser yet.

Terahertz waves are invisible, but incredibly useful. They can penetrate many materials which are opaque to visible light. In addition, these waves are perfect for detecting a variety of molecules. Terahertz radiation can actually be produced by using tiny quantum cascade lasers. Yet creating stronger lasers has long been a goal for researchers.

For the electrons in each layer of the quantum cascade laser, only certain discrete energy levels are allowed. If the right electrical current is applied, the electrons jump from layer to layer and in each step emit energy in the form of light. This way, the exotic terahertz radiation with wavelengths in the sub-millimeter regime (between microwaves and infrared) can be produced with high efficiency.

In the case of the world record laser, there are more layers. A higher number of layers mean that more photons are produced. In addition, the efficiency was increased due to improved optical properties.  While the previous record for terahertz quantum cascade lasers was around 250 milliwatts, the new laser produces about one watt of radiation--a huge leap forward.

So what can these lasers do? Terahertz radiation can be used for chemical detectors. It also plays an important role for medical imaging; it's a non-ionizing radiation and its energy is considerably lower than that of roentgen radiation, which means that it's not dangerous. In addition, the wavelength is shorter than that of microwave radiation, which means that it can be used to create higher resolution images.

The new laser could be a huge step for the application of terahertz lasers in a variety of technological fields.

The details of the new layer are published in two articles in Applied Physics Letters here and here.