Continuous wave terahertz radiation from an InAs/GaAs quantum-dot photomixer device

Abstract

Generation of continuous wave radiation at terahertz (THz) frequencies from a heterodyne source based on quantum-dot (QD) semiconductor materials is reported. The source comprises an active region characterised by multiple alternating photoconductive and QD carrier trapping layers and is pumped by two infrared optical signals with slightly offset wavelengths, allowing photoconductive device switching at the signals’ difference frequency ~1 THz

Quantum dot materials for terahertz generation applications

“…In addition to pulsed THz signals, CW THz radiation by heterodyne conversion [37] may be generated. We have already demonstrated the CW THz emission by photomixing of ∼850 nm laser diodes pump in optimised QD structures [13]. With the implementation of broadly tunable QD semiconductor lasers as pump sources, the generated signal can be also tunable.…”

“…All these applications take advantage of the distinctive properties of QDs, such as high thermal and optoelectronic efficiency and short charge carrier lifetime [11], properties that are also crucial for effective operation of photoconductive (PC) THz devices. Recently, research into efficient ultrafast PC materials and structures for THz [12][13][14] applications has included the investigation of optically-pumped QD-based semiconductor structures with the primary function of utilising layers of implanted QDs as the photocarrier lifetime shortening mechanism [4,8]. This could potentially allow the production of a highly efficient, ultrafast device without introducing compromises between factors such as carrier mobility, PC gain, resistivity and carrier lifetimes as would normally be made in bulk-type PC THz materials.…”

Towards realisation of an efficient continuous wave terahertz source using quantum dot devices

“…The rise of semiconductor lasers and the appreciable properties of quantum dot gain media in semiconductor lasers has paved the way for widely tunable high power semiconductor lasers, moreover, the external cavity diode lasers provides narrow-linewidth that is suitable for CW terahertz emission. CW THz signals can be generated using semiconductor materials with sub-picosecond carrier lifetimes optically pumped by a beat signal composed of two distinct narrow line width signals a few nanometres apart [5].…”

Photoelectric Properties of InAs/GaAs Quantum Dot Photoconductive Antenna Wafers

“…Recently, QD based PCAs have been demonstrated to successfully generate coherent THz radiation in the pulsed [6], [20] and CW [5], [6], [21] regimes. THz generation was achieved both within a Ti:Sapphire (GaAs bandgap) and a compact QD-based laser diode (QD bandgap) pumps.…”