Imaging at 3.4 THz with a quantum-cascade laser

We have assembled a single-frequency imaging system at 3.4 THz with a quantum-cascade laser. Images of electronic and biological applications are demonstrated. We operate the laser with a peak output power of 2.5 mW at a 7% duty cycle and a 22 K operating temperature. The minimum spot size is 340 μm. The signal is detected with a single-element deuterated triglycine sulfate detector, and images are captured by scanning of the sample.