- 著者
- 門脇 和男 中山 諒 折田 尚樹 小池 隆 出口 幸太 Delfanazari Kaveh 辻本 学 Ivanovic Krsto 福屋 翔太 浅井 栄大 山本 卓 柏木 隆成 立木 昌 Klemm Richard A.
- 出版者
- 一般社団法人日本物理学会
- 雑誌
- 日本物理学会講演概要集 (ISSN:13428349)
- 巻号頁・発行日
- vol.65, no.2, 2010-08-18
- 著者
- Sekimoto S. Watanabe C. Minami H. Yamamoto T. Kashiwagi T. Klemm Richard A. Kadowaki K.
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.103, no.18, pp.182601, 2013-10
- 被引用文献数
- 67 5
Using a modified mesa structure of high-Tc superconducting Bi2Sr2CaCu2O8+δ with a thin underlaying base superconductor (∼3 μm), the effective working temperature of the continuous and monochromatic terahertz emitter is extended up to 70 K, and the maximum power of ∼30 μW at 0.44 THz is achieved at the relatively high temperature of T b = 55 K in a low bias current retrapping region. The diverging behavior of the intensity occurring at 55 K in the low current regime without hot spot formation may provide us an important clue for the stronger THz radiation from intrinsic Josephson junction devices.
- 著者
- Klemm Richard A. Delfanazari Kaveh Tsujimoto Manabu Kashiwagi Takanari Kitamura Takeo Yamamoto Takashi Sawamura Masashi Ishida Kazuya Hattori Toshiaki Kadowaki Kazuo
- 出版者
- Elsevier
- 雑誌
- Physica. C, Superconductivity and its applications (ISSN:09214534)
- 巻号頁・発行日
- vol.491, pp.30-34, 2013-08
- 被引用文献数
- 19 3
In order to understand the radiation observed from the intrinsic Josephson junctions in triangular Bi2Sr2CaCu2O8+δ mesas, we calculate the transverse magnetic (TM) electromagnetic modes for thin equilateral cavities. A new set of distinct but degenerate TM modes coexists with the known modes of Helszajn and James, but are expected to lead to distinct radiation angular distribution patterns. Although we have been unable to solve for the exact TM modes of a thin cavity of general acute isosceles triangular shape, we solved exactly the closely related problems of the TM cavity modes of two thin circumscribing “pie-shaped” wedges, which provide highly accurate approximations to very acute isosceles triangular cavities.
- 著者
- Klemm Richard A Kadowaki Kazuo
- 出版者
- IOP Publishing
- 雑誌
- Journal of physics. Condensed matter (ISSN:09538984)
- 巻号頁・発行日
- vol.22, no.37, pp.375701, 2010-08
- 被引用文献数
- 74 36
The angular dependence of the radiation-zone output power and electric polarization of stimulated terahertz amplified radiation (STAR) emitted from a dc voltage applied across cylindrical and rectangular stacks of intrinsic Josephson junctions is calculated. The boundary conditions are obtained from Love's equivalence principles. During coherent emission, a spatially uniform ac Josephson current density in the stack acts as a surface electric current density antenna source, leading to a harmonic radiation frequency spectrum, as in experiment, but absent in all cavity models of cylindrical mesas. Spatial fluctuations of the ac Josephson current allow its fundamental mode to lock onto the lowest finite energy cylindrical cavity mode, causing it to resonate, leading to a non-uniform magnetic surface current density radiation source, and a non-trivial combined fundamental frequency output power with linear polarization for general radiation directions, which may be fully or partially coherent. The higher ac Josephson harmonics do not excite other cylindrical cavity modes. For rectangular mesas, the lowest energy modes are empirically not excited, but the non-uniform ac Josephson current can excite the harmonic sequence of modes with spatial variation across the rectangular widths, leading to combined radiation outputs both for the fundamental and the higher harmonics, which combinations also may be either fully or partially coherent. The superconducting substrate is modeled as a perfect magnetic conductor, greatly reducing the STAR emitter power and modifying its angular dependence, especially parallel to the substrate. Based upon this substrate model, existing Bi2Sr2CaCu2O8 + δ crystals atop perfect electric conductors could have STAR emitter power in excess of 5 mW, acceptable for many device applications.