Table 2.
Generation of CW and pulsed THz radiations [61].
| CW THz Radiation | Pulsed THz Radiation | ||
|---|---|---|---|
| Generation approach | Medium | Generation approach | Medium |
| Photomixing | Power cable switch | Transient photoconductive switching | PCAs |
| Difference frequency generation using parametric oscillation | Nonlinear crystal | OR | Dielectrics, semiconductors, organic materials |
| Rotational transitions | Far-infrared gas lasers | Emission from a periodically undulated electron beam | Electron accelerators |
| Streaming motion and population inversion | Semiconductor laser | Surge current | Semiconductor |
| Frequency multiplication of microwaves | Schottky barrier diode | Tunneling of electron wave packet | Quantum semiconductor structures |
| Transitions in superlattice | Quantum cascade lasers | Coherent longitudinal optical phonons | Semiconductors, semimetals, superconductors |
| Electron interactive with a traveling electromagnetic wave | Backward wave oscillator | Optically short-circuiting the switch | High-temperature superconductor bridge |
| Relativistic electron interaction with transverse magnetic field | Free-electron lasers | Nonlinear transmission line | Electronic circuits consisting of NLTL |