T-Rays Heat Up
A semiconductor terahertz-laser source works at Room Temperature

Source: “Room Temperature Terahertz Quantum Cascade Laser Source Based on Intracavity Difference-Frequency Generation”
Federico Capasso et al.
Applied Physics Letters 92: 201101

Results: Researchers have designed a semiconductor laser that emits terahertz radia­tion–or t-rays–at room temperature.

Why it matters: Terahertz radiation could enable sensitive chemical detection, ultrafast data transmission, and devices that “see through” walls and clothing. Today’s devices for emitting terahertz radiation, however, require expensive liquid-nitrogen cooling systems and are too bulky to be portable. The new terahertz laser source is a tiny semiconductor chip that doesn’t need to be cryogenically cooled.

Methods: On the chip, the researchers built a device called a quantum-cascade laser, which can emit two beams of infrared light at different frequencies. Inside the chip, semiconductors are arranged such that they not only relay the infrared beams but also emit a third beam whose frequency is the difference between those of the first two. The researchers adjusted the device so that the third beam is in the terahertz frequency range.

Next steps: Currently, the terahertz rays shine from the edge of the chip, which limits the total power of the laser. The researchers plan to adapt the device to force the light out of the top surface, which should increase its power.