High frequency driven semiconductor superlattice oscillators for generation of subterahertz and terahertz radiation
Two novel types of superlattice oscillators, suitable for generation of subterahertz and terahertz radiation are presented They are based on high-frequency driven miniband transport. The first oscillator, the double resonance superlattice parametric oscillator, is for up conversion of radiation. It oscillates simultaneously at the 3rd and 5th harmonic of a pump frequency. Double resonance oscillations at 300GHz and 500GHz in a GaAs/AlAs superlattice are demonstrated. A sub-THz source was built delivering tuneable (~10%), monochromatic radiation around 500 GHz (power~10µW). Used as a frequency multiplier, the superlattice generated radiation at the 11th harmonic at 1.1 THz. A theoretical treatment showed that double-resonance oscillations are in principle possible up to a 5th harmonic frequency of the order of 10 THz. The second oscillator, the THz-field driven Bloch oscillator, is for down conversion of THz-radiation. It is driven by a THz-field of fixed frequency and generates monochromatic radiation which is tunable over a wide frequency range. A theoretical treatment shows that it can generate radiation from almost zero frequency up to the pump frequency with a high conversion efficiency (~5-15%).