Terahertz Amplifier with Optical Threshold

Amplifiers of Terahertz (THz) radiation are quite useful, because in this spectral range radiation is normally weak and sensitive detectors are hard to get. Monolithically integrated master-oscillator power-amplifier (MOPA) [1] , [2] as well as free-space amplifiers [3] have been demonstrated by using Quantum Cascade laser (QCL) structures with amplifications in the range of 3 – 12 dB. Although these devices are very promising, they all provide a linear amplification. However, for most telecommunication applications an amplification only above a certain threshold is advantageous, since this avoids the amplification of noise.