Abstract-Superconducting Emitter Powered at 1.5 Terahertz by an External Resonator

Y. Ono, H. Minami, G. Kuwano, T. Kashiwagi, M. Tsujimoto, K. Kadowaki, and R. A. Klemm

https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.13.064026

A different type of terahertz emitter is made by coupling a source mesa fabricated from the intrinsic Josephson junctions present in single-crystalline high-$T_c$ superconducting ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{Ca}\mathrm{Cu}}_2{O}_{8+\delta }$ ($\mathrm{Bi}2212$) to a much larger and impedance-matched external resonator with resonance frequencies up to 1.5 THz. The lateral dimensions of the source mesa are only $20\times 20\mu m^2$, about 0.5%–3% of those of conventional $\mathrm{Bi}2212$ mesas, but its thickness of $2\mu m$ is comparable to them. The observed emission frequencies that lie near to 1.5 THz match very well the resonance frequencies of the external resonator. This result ensures that the functions of resonator and antenna are separated from that of the THz current source in the $\mathrm{Bi}2212$ mesa structure. These facts allow for much greater flexibility in the emitter design to achieve higher power and higher frequency THz wave sources.

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Abstract-Observation of a two-mode resonant state in a B i 2 S r 2 CaC u 2 O 8 + δ mesa device for terahertz emission

T. M. Benseman, A. E. Koshelev, V. Vlasko-Vlasov, Y. Hao, U. Welp, W.-K. Kwok, B. Gross, M. Lange, D. Koelle, R. Kleiner, H. Minami, M. Tsujimoto, and K. Kadowaki

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.100.144503

Using low-temperature scanning laser microscopy (LTSLM), we have studied the cavity resonance behavior of a rectangular $B{i}_{2}S{r}_2\mathrm{CaC}{u}_2{O}_{8+\delta }$ mesa THz device containing $N=640$ stacked intrinsic Josephson junctions. Our results show that this microscopy technique is an effective means of mapping electromagnetic resonances in this type of device, and we present a detailed analysis of the mechanisms underlying contrast formation in scanning laser microscopy. The LTSLM images reveal that the THz excitation of the stacked junctions contains more than one mode with components along both the long and short axes of the mesa. Thermoluminescent mapping of the same device shows that the mesa temperature is uniform demonstrating that the features seen in LTSLM are electromagnetic in origin, not thermal. Our results also imply that for the purposes of maximizing the THz emission power from $B{i}_{2}S{r}_2\mathrm{CaC}{u}_2{O}_{8+\delta }$ mesas, it is important to design devices that are capable of being excited in a single, purely transverse mode.

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Abstract-Terahertz emission from the intrinsic Josephson junctions of high-symmetry thermally-managed Bi2Sr2CaCu2O8+δ microstrip antennas

Klemm, R and Davis, A and Wang, Q and Yamamoto, T and Cerkoney, D and Reid, C and Koopman, M and Minami, H and Kashiwagi, T and Rain, J and Doty, C and Sedlack, M and Morales, M and Watanabe, C and Tsujimoto, M and Delfanazari, Kand Kadowaki, K

http://publications.eng.cam.ac.uk/959268/

We show for high-symmetry disk, square, or equilateral triangular thin microstrip antennas of any composition respectively obeying C∞v, C4v, and C3v point group symmetries, that the transverse magnetic electromagnetic cavity mode wave functions are restricted in form to those that are one-dimensional representations of those point groups. Plots of the common nodal points of the ten lowest-energy non-radiating two-dimensional representations of each of these three symmetries are presented. For comparison with symmetry-broken disk intrinsic Josephson junction microstrip antennas constructed from the highly anisotropic layered superconductor Bi2 Sr2 CaCu2 O8+δ (BSCCO), we present plots of the ten lowest frequency orthonormal wave functions and of their emission power angular distributions. These results are compared with previous results for square and equilateral triangular thin microstrip antennas.

Abstract-Terahertz emission from pie-shaped wedge microstrip antennas of the high-Tc superconductor Bi2Sr2CaCu2O8+δ

Wang, Q and Doty, C and Klemm, R and Delfanazari, K and Cerkoney, D and Yamamoto, T and Tsujimoto, M and Kadowaki, K and Watanabe, C and Minami, H and Kashiwagi, T and Morales, M

http://publications.eng.cam.ac.uk/880368/

We calculate the standing wave functions for pie-shaped wedge microstrip antennas of various wedge angles ϕ0. We then calculate the emission distributions from the uniform Josephson current and from the excitation of a cavity mode generated from the stand wave functions. For a narrow dieter's pie slice, quantitative fits to the experimental data on a Bi2Sr2CaCu2O8+δ narrow isosceles triangular mesa are shown.