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1.
We propose a novel terahertz-wave source through the four-wave mixing effect in a conventional single-mode optical fiber pumped by a dual-wavelength laser whose difference frequency lies in the terahertz range. Surface-emitted geometry is employed to decrease absorption loss. A detailed derivation of the terahertz-wave power expression is presented using the coupled-wave theory. This is a promising way for realizing a reasonable narrow-band terahertz-wave source. 相似文献
2.
研究了嵌入Fabry-Perot谐振腔的高温超导双晶约瑟夫森结阵列毫米波相干辐射的实验结果.相干辐射是通过约瑟夫森结阵列与基片(作为一个介质谐振器)和Fabry-Perot(FP)谐振器的共同作用实现的.由166个高温超导双晶约瑟夫森结串联阵列在77 K温度下产生的相干辐射,辐射峰的中心频率为75.84 GHz,功率大约为10 pW.
关键词:
高温超导薄膜
Fabry-Perot谐振腔
约瑟夫森结
毫米波辐射 相似文献
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太赫兹波光谱特性分析 总被引:3,自引:0,他引:3
目前太赫兹技术的研究主要集中在它的产生、探测机理研究上。由于太赫兹波处于微波和可见光之间的频率范围,已有的微波和光波理论是否能适用于太赫兹波或者具有某些共同的特性仍需实验验证。通过实验分析验证了太赫兹波在空气介质中在垂直于传播方向的平面内场振幅是服从高斯函数分布的,测量给出了太赫兹波的能量分布图。根据测试数据推导出太赫兹波在空气介质中能量衰减公式,利用法布里-珀罗(F-P)干涉仪原理设计出太赫兹波长仪,对美国Corehent公司SIFIR-50THz太赫兹激光器发射的1~3THz波长进行了测量。讨论分析了远场发射角、光束入射角度、机械振动、温度波动和折射率n波动等相关因素对测量精度的影响。 相似文献
5.
An achromatically injection-seeded terahertz-wave parametric generator was constructed with MgO:LiNbO (3) crystals and a tunable seeder in a stationary dispersion-compensated optical arrangement. Without readjusting the mirrors, we obtained smooth tuning of the terahertz wave over the 0.6-2.6 THz range by adjusting the seeder wavelength alone. We have successfully demonstrated the feasibility of this system for terahertz-wave absorption measurements over a wide frequency range by using low-pressure water vapor. 相似文献
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We developed a continuous-spectrum light beam from Compton backscattering by using coherent synchrotron radiation in an L-band linac at the Kyoto University Research Reactor Institute. The ratio of Compton backscattered photons to background photons when coherent synchrotron radiation was used was three times larger than when coherent transition radiation was used. The transmission spectrum of a polystyrene film in the terahertz-wave region was evaluated by measuring the spectrum of the Compton backscattered photons and it roughly agreed with that measured by a Martin–Puplett-type interferometer. The spectrophotometry using Compton backscattering shows promise as a new tool for investigations in terahertz-wave science. 相似文献
8.
Tunable terahertz-wave generation from DAST crystal by dual signal-wave parametric oscillation of periodically poled lithium niobate 总被引:3,自引:0,他引:3
The first known demonstration of tunable terahertz-wave generation by difference-frequency generation of dual signal-wave quasi-phase-matched optical parametric oscillation was performed with periodically poled LiNbO(3) (PPLN) with a series of gratings. An organic ionic salt, 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST), was used as a nonlinear crystal. A compact terahertz-wave source resulted, and changing the temperature of the PPLN permitted the wavelength to be varied from 120 to 160 mum. The wavelength could be tuned from 100 to 700 mum by proper selection of combinations of periodically poled gratings. 相似文献
9.
We measure current fluctuations of mesoscopic devices in the quantum regime, when the frequency is of the order of or higher than the applied voltage or temperature. Detection is designed to probe separately the absorption and emission contributions of current fluctuations, i.e. the positive and negative frequencies of the Fourier transformed nonsymmetrized noise correlator. It relies on measuring the quasiparticles photon assisted tunneling current across a superconductor-insulator-superconductor junction (the detector junction) caused by the excess current fluctuations generated by quasiparticles tunneling across a Josephson junction (the source junction). We demonstrate unambiguously that the negative and positive frequency parts of the nonsymmetrized noise correlator are separately detected and that the excess current fluctuations of a voltage biased Josephson junction present a strong asymmetry between emission and absorption. 相似文献
10.
《Current Applied Physics》2001,1(4-5):341-348
High-Tc cuprate superconductors like Bi2Sr2CaCu2O8+y (Bi-2212) show very large anisotropy in the electrical conduction. Inside the CuO2 plan the conduction looks like that in good metals, while the block layers located between CuO2 planes behave like insulating barriers. Thus, neighboring CuO2 layers are linked by the Josephson coupling in superconducting states, and the Bi-2212 single crystal can be regarded as a natural serial array of Josephson junctions along the c-axis. It has been found out that in such a system a unique excitation mode called the collective Josephson plasma exists. The mode collectively oscillates along the c-axis, while it propagates along any direction ranged from the ab-plane to the c-axis. If the mode can be coherently excited, the system should be very useful as a device generating strong electromagnetic wave emission. In this paper we review a theoretical framework describing the Josephson plasma modes. The Josephson vortex penetrates into the sample under the magnetic field parallel to the CuO2 plane and it moves along the ab-plane under an external current parallel to the c-axis. In the vortex flow state, the vortex speed can reach and exceed the propagating velocities of the Josephson plasma modes due to very weak dissipation. Then, the vortices strongly couple with the plasma modes and change their flowing lattice configurations into patterns dependent on the interacting plasma mode profiles. Among many expected flow patterns, we pay attention to a special state resonating with a plasma mode in-phase along the c-axis because all junctions synchronize in such a state. Large-scale numerical simulations by Machida et al. confirmed that the special state characterized by the rectangular lattice stably appears in a wide range of I–V characteristics. In this paper, we report their recent simulation results. 相似文献
11.
We measure the high-frequency emission of a single Cooper pair transistor (SCPT) in the regime where transport is only due to tunneling of Cooper pairs. This is achieved by coupling on chip the SCPT to a superconductor-insulator-superconductor junction and by measuring the photon assisted tunneling current of quasiparticles across the junction. This technique allows a direct detection of the ac Josephson effect of the SCPT and provides evidence of Landau-Zener transitions for proper gate voltage. The emission in the regime of resonant Cooper pair tunneling is also investigated. It is interpreted in terms of transitions between charge states coupled by the Josephson effect. 相似文献
12.
Alexey V. Ustinov Boris A. Malomed Edward Goldobin 《Physica B: Condensed Matter》2000,280(1-4):239-240
Resonant interaction of a soliton (Josephson fluxon) with its self-generated Josephson plasma waves is studied experimentally, numerically, and analytically. An externally applied magnetic field H forms a cos-like potential relief for the soliton in the annular junction. Soliton motion under the influence of the bias current leads to an emission of plasma waves, which gives rise to a resonance at a certain soliton velocity. This resonance on the current–voltage characteristics shows a clear backbending accompanied by a negative differential resistance. Our analysis quantitatively explains the observed effect. 相似文献
13.
M. Tarasov A. Shul’man O. Polyanskii A. Vystavkin E. Kosarev D. Golubev E. Stepantsov M. Darula O. Harnack Z. Ivanov 《JETP Letters》1999,70(5):340-345
A Josephson high-temperature superconducting (HTSC) submillimeter-wave spectrometer is designed, built, and experimentally
investigated. The integrated detection structure of the spectrometer includes a YBCO Josephson junction on a bicrystalline
boundary, a double-slot or log-periodic antenna, and a low-inductance resistive shunt. The selective detector response and
the response at an intermediate frequency of 1.4 GHz are measured under the action of a signal in the frequency range 350–1250
GHz. Three methods of spectroscopy are investigated using this setup: 1) a method of Hilbert spectroscopy with processing
of the detector response is implemented; 2) it is found that for a wide Josephson line at intermediate frequency (IF) the
response has the same form as the detector response, making it possible to obtain a spectrum and the width of the generation
line from IF response measurements; 3) for a narrow Josephson line the IF response corresponds to the regime of conversion
with self-pumping. A new method is proposed for calculating the emission spectrum. The method consists of simple shift, summation,
and subtraction operations. The advantages of the method are simplicity, high sensitivity, and high resolution.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 5, 338–343 (10 September 1999) 相似文献
14.
In his thesis, Josephson asserts that pair transfer accompanied by spontaneous photon emission does not demand the existence of a definite phase relationship between the two superconductors. In this letter we demonstrate the validity of this statement. 相似文献
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For Josephson junctions in sandwich geometry and in thin-film geometry we formulate the equations of nonlocal electrodynamics
which take account of the influence of normal electrons in superconductors. On the basis of these equations we examine the
spectrum and decay of generalized Swihart waves. We find that the decay of these waves by normal electrons becomes especially
prominent in the short-wavelength region. Comparison of various dissipation mechanisms has revealed the conditions for efficient
emission of electromagnetic waves from Josephson structures with finite dimensions.
Fiz. Tverd. Tela (St. Petersburg) 41, 1160–1167 (July 1999) 相似文献
17.
The characteristics of a coherent tunable terahertz-wave source have been experimentally investigated in detail. By using
a difference frequency generation as a result of stimulated Raman scattering by polaritons in MgO:LiNbO3 crystals, the signal wave was continuously tuned in the range of 1.069–1.075 μm, which corresponded to a terahertz-wave in
the wide range from 227 to 104 μm (1.3 to 2.9 THz). The highest output signal pulse energy at the pumping level of 44 mJ/pulse
was 1.8 mJ/pulse with 20 mW seeder injection, and the terahertz peak power was 139 mW at the wavelength of 143 μm. This source
has the advantages of simple alignment, simplicity of tuning, and compactness that makes the device more attractive. 相似文献
18.
在s波超导体绝缘层dx2-y2波超导体结(sId)中,考虑到结界面粗糙散射,运用BogoliubovdeGennes(BdG)方程和FurusakiTsukada(FT)电流公式,计算超导结中的准粒子传输系数和直流Josephson电流.结果表明:sId超导结的直流Josephson电流随温度以及结两侧的相位差变化的关系曲线强烈地依赖于d波超导体的晶轴方位;结界面的粗糙散射对Josephson电流有抑制作用
关键词:
s/I/d超导结
dx2-y2波超导体
直流Josephson电流 相似文献
19.
Using a quantum detector, a superconductor-insulator-superconductor junction, we probe separately the emission and absorption noise in the quantum regime of a superconducting resonant circuit at equilibrium. At low temperature the resonant circuit exhibits only absorption noise related to zero point fluctuations, whereas at higher temperature emission noise is also present. By coupling a Josephson junction, biased above the superconducting gap, to the same resonant circuit, we directly measure the noise power of quasiparticles tunneling through the junction at two resonance frequencies. It exhibits a strong frequency dependence, consistent with theoretical predictions. 相似文献
20.
《Physics letters. A》1987,123(9):459-468
New results concerning emission of radiation (quasi-linear waves) from kinks described by various versions of a perturbed sine-Gordon equation are presented. Considered physical problems pertain to condensed matter physics and nonlinear optics. In perticular, intensities of Swihart wave emission from a fluxon in a long dc driven Josephson junction, and of spin wave emission from a domain wall in a weak ferromagnet driven by external constant magnetic field are calculated. A general estimate for an exponentially small intensity of emission from a kink oscillating near a bottom of an effective potential wall is obtained. A system of coupled double sine-Gordon equations describing a double DNA helix is briefly investigated. It is demonstrated that a collision of a bi-kink (a bound state of two 2Π-kinks belonging to different subsystems) with a 4Π-kink belonging to either subsystem may result in excitation of large-amplitude internal oscillations of both the colliding solitons, and the rate of radiative damping of those oscillations is found. At last, radiative effects accompanying motion of a stimulated-Raman-scattering soliton in a dissipative medium are studied. 相似文献