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International Conference on UK-China Emerging Technologies (UCET)

Mutual Synchronization of Terahertz Emissions from Multiple Intrinsic Josephson Junction Mesas

Ken Hayama, Shuma Fujita, Yuya Kuriyama, Keiichiro Maeda, Manabu Tsujimoto, Itsuhiro Kakeya

Published Aug 1, 2020• 0 citations
Publisher

Abstract

We present a direct proof of synchronized macroscopic Josephson oscillations excited in two intrinsic Josephson junction stacks formed on a Bi2Sr2CaCu2O8+δsingle crystal. The strong coupling between the Josephson oscillations in the two mesas via the base crystal is detected by polarization analysis of emitted terahertz waves from individually biased mesas and simultaneously biased mesas.

DOI
10.1109/ucet51115.2020.9205454

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We present a direct proof of synchronized macroscopic Josephson oscillations excited in two intrinsic Josephson junction stacks formed on a Bi2Sr2CaCu2O8+δsingle crystal. The strong coupling between the Josephson oscillations in the two mesas via the base crystal is detected by polarization analysis of emitted terahertz waves from individually biased mesas and simultaneously biased mesas.
We examine coupling interactions used to synchronize macroscopic Josephson oscillations induced in intrinsic Josephson junction (IJJ) mesa stacks made of Bi2212 single crystals. Synchronized emissions of terahertz electromagnetic (EM) waves are detected under common voltage and current bias operations of two connected mesas with close individual emission frequencies, while uncoupled and bimodal emissions are frequently observed in two mesas with different individual emission frequencies. Detailed observations of the polarization of the EM wave emitted when two mesas are biased in parallel or series allow us to reveal the coupling matrix components, which include ratios of synchronized IJJs in the mesas and phase retardation between the macroscopic Josephson oscillations. This finding stimulates systematic survey on polarization of EM wave emitted from synchronized multiple mesa devices in order to realize powerful emissions from superconductors.
We examine coupling interactions used to synchronize macroscopic Josephson oscillations induced in intrinsic Josephson-junction (IJJ) mesa stacks made of a Bi2212\mathrm{Bi}2212Bi2212 single crystal. Synchronized radiations of terahertz electromagnetic (EM) waves are detected under common voltage and current bias operations of two connected mesas with close individual radiation frequencies, while uncoupled and bimodal radiations are frequently observed in two mesas with different individual radiation frequencies. Detailed observations of the polarizations of the EM waves emitted when two mesas are biased in parallel or series allow us to reveal the coupling matrix components, which include ratios of synchronized IJJs in the mesas and phase delay between the macroscopic Josephson oscillations. A frequency evolution of the phase delay implies that the coupling between the Josephson oscillations is mediated by the small amplitude Josephson plasmon inside the superconducting substrate. This finding stimulates systematic survey on polarization of EM wave emitted from synchronized multiple mesa devices in order to realize powerful terahertz emissions from superconductors.
We examine coupling interactions used to synchronize macroscopic Josephson oscillations induced in intrinsic Josephson junction (IJJ) mesa stacks made of a Bi2212 single crystal. Synchronized radiations of terahertz electromagnetic (EM) waves are detected under common voltage and current bias operations of two connected mesas with close individual radiation frequencies, while uncoupled and bimodal radiations are frequently observed in two mesas with different individual radiation frequencies. Detailed observations of the polarizations of the EM waves emitted when two mesas are biased in parallel or series allow us to reveal the coupling matrix components, which include ratios of synchronized IJJs in the mesas and phase delay between the macroscopic Josephson oscillations. A frequency evolution of the phase delay implies that the coupling between the Josephson oscillations is mediated by the small amplitude Josephson plasmon inside the superconducting substrate. This finding stimulates systematic survey on polarization of EM wave emitted from synchronized multiple mesa devices in order to realize powerful terahertz emissions from superconductors.
We discuss coupling interactions to synchronize macroscopic Josephson oscillations induced in intrinsic Josephson junction (IJJ) mesa stacks made of Bi2212 single crystals. Synchronized emissions are found under common voltage and current bias operations of connected two mesas with close individual emission frequencies while uncoupled and bimodal emissions are often found in two mesas with different individual emission frequencies. The detailed observations on polarization of the emitted electromagnetic wave when two mesas are biased in parallel or series allow us to reveal the coupling matrix components which includes ratios of synchronized IJJs in the mesas and phase retardation between the macroscopic Josephson oscillations.
high-temperature superconductor represent stacks of atomic scale intrinsic Josephson junctions. They can be used for generation of high-frequency electromagnetic waves. Here we analyze Josephson emission from small-but-high mesas (with a small area, but containing many stacked junctions). We have found strong evidence for tunable terahertz emission with a good efficacy in a record high-frequency span 1-11 THz, approaching the theoretical upper limit for this superconductor. Emission maxima correspond to in-phase cavity modes in the mesas, indicating coherent superradiant nature of the emission. We conclude that terahertz emission requires a threshold number of junctions N ~ 100. The threshold behavior is not present in the classical description of stacked Josephson junctions and suggests importance of laser-like cascade amplification of the photon number in the cavity.
Despite its potential for e.g.e.g.e.g. medical imaging, wireless communication, and ultrasensitive analysis of biological materials, the terahertz frequency range of light cannot be suitably utilized without practical solid-state sources. A naturally formed stack of superconducting junctions emits terahertz radiation, owing to synchronization of macroscopic wave functions, and the authors propose a means to manipulate that synchronization, which is the most promising way to attain a versatile superconducting terahertz source. Their findings also give insight into the quantum physics of entangled photons emitted from superconductors.