Terahertz Emitter Using Resonant-Tunneling Diode and Applications

A compact source is important for various applications utilizing terahertz (THz) waves. In this paper, the recent progress in resonant-tunneling diode (RTD) THz oscillators, which are compact semiconductor THz sources, is reviewed, including principles and characteristics of oscillation, studies addressing high-frequency and high output power, a structure which can easily be fabricated, frequency tuning, spectral narrowing, different polarizations, and select applications. At present, fundamental oscillation up to 1.98 THz and output power of 0.7 mW at 1 THz by a large-scale array have been reported. For high-frequency and high output power, structures integrated with cylindrical and rectangular cavities have been proposed. Using oscillators integrated with varactor diodes and their arrays, wide electrical tuning of 400-900 GHz has been demonstrated. For spectral narrowing, a line width as narrow as 1 Hz has been obtained, through use of a phase-locked loop system with a frequency-tunable oscillator. Basic research for various applications-including imaging, spectroscopy, high-capacity wireless communication, and radar systems-of RTD oscillators has been carried out. Some recent results relating to these applications are discussed.

Automated summary

This paper reviews recent progress in resonant-tunneling diode (RTD) terahertz (THz) oscillators, which are compact semiconductor THz sources, including principles and characteristics of oscillation, studies addressing high-frequency and high output power, a structure which can easily be fabricated, frequency tuning, spectral narrowing, different polarizations, and select applications. Fundamental oscillation up to 1.98 THz and output power of 0.7 mW at 1 THz by a large-scale array have been reported, with structures integrated with cylindrical and rectangular cavities proposed for high-frequency and high output power. Wide electrical tuning of 400-900 GHz has been demonstrated using oscillators integrated with varactor diodes and their arrays. A line width as narrow as 1 Hz has been obtained for spectral narrowing through use of a phase-locked loop system with a frequency-tunable oscillator. Basic research for various applications of RTD oscillators has been carried out, with discussion of recent results related to imaging, spectroscopy, high-capacity wireless communication, and radar systems.