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We designed and characterized a microstrip pattern of planar patch antennas compatible with a cuprate high-Tc superconducting terahertz emitter. Antenna parameters were optimized using an electromagnetic simulator. We observed repeatable sub-terahertz emissions from each mesa fabricated on identical Bi2Sr2CaCu2O8+δ base crystals in a continuous frequency range of 0.35-0.85 THz. Although there was no significant output power enhancement, a plateau behavior at a fixed frequency was observed below 40 K, indicating moderate impedance matching attributable to the ambient microstrip pattern. A remarkably anisotropic polarization at an axial ratio of up to 16.9 indicates a mode-locking effect. Our results enable constructing compactly assembled, monolithic, and broadly tunable superconducting terahertz sources.
RESUMO
The radiation intensity from the intrinsic Josephson junction high-Tc superconductor Bi2Sr2CaCu2O8+δ terahertz emitters (Bi2212-THz emitters) is one of the most important characteristics for application uses of the device. In principle, it would be expected to be improved with increasing the number of intrinsic Josephson junctions N in the emitters. In order to further improve the device characteristics, we have developed a stand alone type of mesa structures (SAMs) of Bi2212 crystals. Here, we understood the radiation characteristics of our SAMs more deeply, after we studied the radiation characteristics from three SAMs (S1, S2, and S3) with different thicknesses. Comparing radiation characteristics of the SAMs in which the number of intrinsic Josephson junctions are N⼠1300 (S1), 2300 (S2), and 3100 (S3), respectively, the radiation intensity, frequency as well as the characteristics of the device working bath temperature are well understood. The strongest radiation of the order of few tens of microwatt was observed from the thickest SAM of S3. We discussed this feature through the N2-relationship and the radiation efficiency of a patch antenna. The thinner SAM of S1 can generate higher radiation frequencies than the thicker one of S3 due to the difference of the applied voltage per junctions limited by the heat-removal performance of the device structures. The observed features in this study are worthwhile designing Bi2212-THz emitters with better emission characteristics for many applications.
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We study the transverse magnetic (TM) electromagnetic cavity mode wave functions for an ideal equilateral triangular microstrip antenna (MSA) exhibiting C 3v point group symmetry. When the C 3v operations are imposed upon the antenna, the TM(m,n) modes with wave vectors [Formula: see text] are much less dense than commonly thought. The R 3 operations restrict the integral n and m to satisfy [Formula: see text], where [Formula: see text] and [Formula: see text] for the modes even and odd under reflections about the three mirror planes, respectively. We calculate the forms of representative wave functions and the angular dependence of the output power when these modes are excited by the uniform and non-uniform ac Josephson current sources in thin, ideally equilateral triangular MSAs employing the intrinsic Josephson junctions in the high transition temperature T c superconductor Bi2Sr2CaCu2 [Formula: see text], and fit the emissions data from an earlier sample for which the C 3v symmetry was apparently broken.
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Using recently-developed THz emitters constructed from single crystals of the high-Tc superconductor Bi2Sr2CaCu2O8+δ, we performed three prototype tests of the devices to demonstrate their unique characteristic properties for various practical applications. The first is a compact and simple transmission type of THz imaging system using a Stirling cryocooler. The second is a high-resolution Michelson interferometer used as a phase-sensitive reflection-type imaging system. The third is a system with precise temperature control to measure the liquid absorption coefficient. The detailed characteristics of these systems are discussed.
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Stacks of intrinsic Josephson junctions in Bi2Sr2CaCu2O8+δ emit intense and coherent terahertz waves determined by the internal electromagnetic cavity resonance. We identify the excited transverse magnetic mode by observing the broadly tunable emissions from a nearly square stack and simulating the scattering spectrum. We employ a wedge-type interferometer to measure spatially-integrated power independently of the far-field pattern. The simulation results are in good agreement with observed resonance behaviors as a function of frequency.
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Continuous, coherent subterahertz radiation arises when a dc voltage is applied across a stack of the many intrinsic Josephson junctions in a Bi2Sr2CaCu2O(8+δ) single crystal. The active junctions produce an equal number of I-V characteristic branches. Each branch radiates at a slightly tunable frequency obeying the Josephson relation. The overall output is broadly tunable and nearly independent of heating effects and internal cavity frequencies. Amplification by a surrounding external cavity to allow for the development of a useful high-power source is proposed.
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In this paper, we report intense electromagnetic wave emissions generated by the rectangular mesa structure of intrinsic Josephson junctions with high-T(c) superconducting Bi2Sr2CaCu2O(8+δ). The radiated power is an order of magnitude stronger than that of the previously observed power of a few µW. Two emission regions, reversible (R-type) and irreversible (IR-type), with comparable intensities can be observed at different I-V curve locations in the same mesa. We find peculiar temperature dependences of the emission power in both the R- and IR-type radiations, suggesting that a non-equilibrium thermodynamic state may be realized through the dc input current. The R-type emission is quite stable, whereas the IR-type emission is rather unstable. Although the emitted frequency for both cases obey the cavity resonance conditions, this sharp contrast in emission stability is indicative of two different states in a multi-stacked intrinsic Josephson junction system.
RESUMO
Subterahertz radiation emitted from a variety of short rectangular-, square-, and disk-shaped mesas of intrinsic Josephson junctions fabricated from a Bi(2)Sr(2)CaCu(2)O(8+δ) single crystal was studied from the observed I-V characteristics, far-infrared spectra, and spatial radiation patterns. In all cases, the radiation frequency satisfies the conditions both for the ac Josephson effect and for a mesa cavity resonance mode. The integer higher harmonics observed in all spectra imply that the ac Josephson effect plays the dominant role in the novel dual-source radiation mechanism.
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A 61-year-old man was referred to our department because of painless and stony hard mass beside the left testis. Serum levels of lactate dehydrogenase, alpha-fetoprotein and human chorionic gonadotropin were within normal ranges. The ultrasonography of the mass showed almost homogenous and relatively low intensity echogram. The mass which derived from the left spermatic cord and was partially surrounded by fat-like soft and yellow tissue, was removed with the left testis by usual orchiectomy. Histopathological diagnosis was liposarcoma, whose subtype was dedifferentiated type derived from well differentiated type. Postoperatively, a para-aortic mass, which resembled lymphnode metastasis, was pointed by computed tomographic scan and was removed surgically. However, it was histopathologically diagnosed as neurogenicganglioma irrelevant to liposarcoma. He has been free of disease for about 1 year without any adjuvant therapy.
Assuntos
Neoplasias dos Genitais Masculinos/diagnóstico , Lipossarcoma/diagnóstico , Cordão Espermático , Neoplasias dos Genitais Masculinos/patologia , Humanos , Lipossarcoma/patologia , Masculino , Pessoa de Meia-IdadeRESUMO
We report on a case of renal cell carcinoma (RCC) with hemorrhagic cyst formation in a 4-year-old boy. The patient presented with asymptomatic macrohematuria. Abdominal ultrasound, computed tomography and magnetic resonance imaging demonstrated a left renal complicated cyst, 18 mm in diameter. Renal malignancy was suspected, and left radical nephrectomy was performed. Pathological diagnosis was a complicated cyst filled with bloody clots, with a wall composed of RCC. No metastases to the regional lymph nodes or other organs were found. This is an extremely rare occurrence of such a small RCC that developed a hemorrhagic cyst in a boy of this young age. The boy is being followed-up without any additional treatment.