Abstract

The development of a compact, continuous wave (CW), room-temperature, broadly-tunable terahertz (THz) laser source is of great interest for a number of applications ranging from biomedical imaging and indoor communication to spectroscopy, security and defence. Among the usually used laser sources, direct quantum cascade lasers (QCLs) and semiconductor mixers of mid-IR QCLs are regarded as most popular sources offering the highest-to-date wall-plug efficiency. However, such lasers require a cryogenic cooling and suffer from the drawbacks in terms of the production complexity, the lack of broad tunability and the limitation of the generated frequencies range to above 2 THz. On the other hand, THz emitters based on photomixing in semiconductor photoconductive antennae are very promising for the development of practical, compact, sufficiently powerful and reasonably-cheap, room-temperature THz sources. In this respect, quantum-dot (QD) semiconductor materials, InAs/GaAs QDs in particular, are of great interest for the use in both the pump laser and the photoconductive antenna for the development of a compact, room-temperature, widely-tunable THz laser source. Such QD-based lasers can offer broad wavelength coverage [1] together with the ability to generate two tunable longitudinal modes simultaneously [2], and InAs/GaAs QD-based antennae are capable of being pumped at high optical intensities of more than 1W [3]. Furthermore, the use of similar InAs/GaAs QD structures in both the pump laser and the antenna is beneficial for the generation of efficient THz radiation, particularly for the pump of the antenna in the vicinity of the QD excited states [3].

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