Abstract
Low power efficiency is one of the main problems of THz sources, colloquially known as the THz gap. In this work we present prototypes of THz devices based on whisker-crystals of a hightemperature superconductor Bi2Sr2CaCu2O8+d with a record high radiation power efficiency of 12% at a frequency of 4 THz. We employ various on- and off-chip detection techniques and, in particular, use the radiative cooling phenomenon for accurate evaluation of the emission power. We argue that such devices can be used for creation of tunable, monochromatic, continuous-wave, compact and power-efficient THz sources.
Highlights
Tunable, monochromatic, cw, compact, and powerefficient sources of terahertz (THz) electromagnetic waves (EMW) are required for a broad variety of applications such as spectroscopy, environmental control, security, nonionizing medical imaging, ultrahigh-speed telecommunication and electronics, as well as for fundamental research in various areas of science [1,2]
In this work we present prototypes of THz devices based on whisker crystals of a high-temperature superconductor Bi2Sr2CaCu2O8+δ with a record high-radiation power efficiency of 12% at a frequency of approximately 4 THz
Despite a significant progress achieved in development of semiconducting quantum cascade lasers (QCLs) [4,5,6], the radiation power efficiency (RPE) of cw QCLs drops from 28% at f 55 THz [7] to a subpercent at 3–4 THz [8,9] and to approximately 0.01% at f 1.3 THz [10]
Summary
The RPE of our devices can reach 12% making a significant step forward towards the theoretical limit of 50%. The boost of efficiency is attributed to good impedance matching with open space, caused by a specific turnstile antennalike geometry of our devices. We conclude that such devices can be used for creation of tunable, and, what is more, power-efficient cw THz sources. The I -V of the generator mesa, with marked bias points, is shown in the top panel of Fig. 2(a).
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