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Takashi Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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effect of bias electrode position on terahertz radiation from pentagonal Mesas of superconducting hbox bi _ 2 hbox sr _ 2 hbox cacu _ 2 hbox o _ 8 delta
IEEE Transactions on Terahertz Science and Technology, 2015Co-Authors: Kaveh Delfanazari, Manabu Tsujimoto, Takashi Yamamoto, Hidehiro Asai, Takanari Kashiwagi, T Kitamura, Richard A Klemm, Wade Wilson, Toshiaki Hattori, K KadowakiAbstract:We examined the effect of the bias current position on the radiation of intense and coherent terahertz electromagnetic waves from the intrinsic Josephson junctions (IJJs) in regular pentagonal Mesas of single crystalline high- $T_{\rm c}$ superconducting ${\hbox{Bi}}_{2}{\hbox{Sr}}_{2}{\hbox{CaCu}}_{2}{\hbox{O}}_{8+\delta}$ . The emission from Sample 1, a mesa with a current bias feed on its middle, is strong and sharply peaked at 0.47 THz, whereas that from Sample 2, a mesa with its feed along an edge, shows a comparably strong, sharp peak at 0.43 THz. The common backbending in the current-voltage characteristics due to Joule heating was seen for Sample 1 but almost not for Sample 2. The experimental results are in good agreement with numerical simulations and calculations, both for the cavity resonances and the angular emission patterns. The resonance peaks obtained from these pentagonal Mesas are both stronger and narrower than those found previously from differently shaped Mesas fabricated by focused ion beam milling. The overall devices are small enough to be cooled to their operational temperatures by Stirling refrigerators, so that properly designed devices could be held in one hand as for laser pointers. Therefore, our IJJ-based emitter devices are promising candidates to fill the THz gap with compact, continuous-wave quantum solid-state sources.
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tunable terahertz emission from the intrinsic josephson junctions in acute isosceles triangular bi 2 sr 2 cacu 2 o 8 δ Mesas
Optics Express, 2013Co-Authors: Kaveh Delfanazari, Manabu Tsujimoto, Takashi Yamamoto, Hidehiro Asai, Takanari Kashiwagi, T Kitamura, M Sawamura, Kazuya Ishida, Chiharu Watanabe, S SekimotoAbstract:In order to determine if the mesa geometry might affect the properties of the coherent terahertz (THz) radiation emitted from the intrinsic Josephson junctions in Mesas constructed from single crystals of the high-temperature superconductor, Bi2Sr2CaCu2O8+δ, we studied triangular Mesas. For equilateral triangular Mesas, the observed emission was found to be limited to the single mesa TM(1,0) mode. However, tunable radiation over the range from 0.495 to 0.934 THz was found to arise from an acute isosceles triangular mesa. This 47% tunability is the widest yet observed from the outer current-voltage characteristic branch of such Mesas of any geometry. Although the radiation at a few of the frequencies in the tunable range appear to have been enhanced by cavity resonances, most frequencies are far from such resonance frequencies, and can only be attributed to the ac-Josephson effect.
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interferometer measurements of terahertz waves from bi2sr2cacu2o8 d Mesas
Superconductor Science and Technology, 2012Co-Authors: F Turkoglu, H Koseoglu, Y Simsek, Lutfi Ozyuzer, Yasemin Demirhan, Sascha Preu, Stefan Malzer, Paul Müller, Takashi Yamamoto, Kazuo KadowakiAbstract:We fabricated rectangular mesa structures of superconducting Bi2Sr2CaCu2O8+d (Bi2212) using e-beam lithography and Ar ion beam etching techniques for terahertz (THz) emission. c-axis resistance versus temperature (R?T), current?voltage (I?V) characteristics and bolometric THz power measurements were performed to characterize Bi2212 Mesas. The emission frequency of Mesas was determined using a Michelson interferometer setup which also demonstrates polarized emission. Interference patterns of THz radiation from Bi2212 Mesas were detected by various detectors such as a liquid helium cooled silicon composite bolometer, a Golay cell and a pyroelectric detector. An emitted power as high as 0.06?mW was detected from Bi2212 Mesas. For the first time, most of the pumped power was extracted as THz emission from a Bi2212 mesa. The radiation at 0.54?THz was detected using the Michelson interferometric setup.
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Interferometer measurements of terahertz waves from Bi2Sr2CaCu2O8+d Mesas
Superconductor Science and Technology, 2012Co-Authors: F Turkoglu, H Koseoglu, Y Simsek, Lutfi Ozyuzer, Yasemin Demirhan, Sascha Preu, Stefan Malzer, Paul Müller, Takashi Yamamoto, Kazuo KadowakiAbstract:We fabricated rectangular mesa structures of superconducting Bi2Sr2CaCu2O8+d (Bi2212) using e-beam lithography and Ar ion beam etching techniques for terahertz (THz) emission. c-axis resistance versus temperature (R?T), current?voltage (I?V) characteristics and bolometric THz power measurements were performed to characterize Bi2212 Mesas. The emission frequency of Mesas was determined using a Michelson interferometer setup which also demonstrates polarized emission. Interference patterns of THz radiation from Bi2212 Mesas were detected by various detectors such as a liquid helium cooled silicon composite bolometer, a Golay cell and a pyroelectric detector. An emitted power as high as 0.06?mW was detected from Bi2212 Mesas. For the first time, most of the pumped power was extracted as THz emission from a Bi2212 mesa. The radiation at 0.54?THz was detected using the Michelson interferometric setup.
K Kadowaki - One of the best experts on this subject based on the ideXlab platform.
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effect of bias electrode position on terahertz radiation from pentagonal Mesas of superconducting hbox bi _ 2 hbox sr _ 2 hbox cacu _ 2 hbox o _ 8 delta
IEEE Transactions on Terahertz Science and Technology, 2015Co-Authors: Kaveh Delfanazari, Manabu Tsujimoto, Takashi Yamamoto, Hidehiro Asai, Takanari Kashiwagi, T Kitamura, Richard A Klemm, Wade Wilson, Toshiaki Hattori, K KadowakiAbstract:We examined the effect of the bias current position on the radiation of intense and coherent terahertz electromagnetic waves from the intrinsic Josephson junctions (IJJs) in regular pentagonal Mesas of single crystalline high- $T_{\rm c}$ superconducting ${\hbox{Bi}}_{2}{\hbox{Sr}}_{2}{\hbox{CaCu}}_{2}{\hbox{O}}_{8+\delta}$ . The emission from Sample 1, a mesa with a current bias feed on its middle, is strong and sharply peaked at 0.47 THz, whereas that from Sample 2, a mesa with its feed along an edge, shows a comparably strong, sharp peak at 0.43 THz. The common backbending in the current-voltage characteristics due to Joule heating was seen for Sample 1 but almost not for Sample 2. The experimental results are in good agreement with numerical simulations and calculations, both for the cavity resonances and the angular emission patterns. The resonance peaks obtained from these pentagonal Mesas are both stronger and narrower than those found previously from differently shaped Mesas fabricated by focused ion beam milling. The overall devices are small enough to be cooled to their operational temperatures by Stirling refrigerators, so that properly designed devices could be held in one hand as for laser pointers. Therefore, our IJJ-based emitter devices are promising candidates to fill the THz gap with compact, continuous-wave quantum solid-state sources.
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cavity mode waves during terahertz radiation from rectangular bi 2 sr 2 cacu 2 o 8 δ Mesas
Journal of Physics: Condensed Matter, 2011Co-Authors: Richard A Klemm, Manabu Tsujimoto, Takanari Kashiwagi, Erica R Laberge, Dustin Morley, K KadowakiAbstract:We re-examined the angular dependence of the radiation from the intrinsic Josephson junctions in rectangular Mesas of Bi2Sr2CaCu2O8+δ, in order to determine if the cavity mode part of the radiation arises from waves across the width w or along the lengthof the Mesas, associated with 'hot spots' (Wang et al 2010 Phys. Rev. Lett. 105 057002). We derived analytical forms for the angular dependence expected in both cases for a general cavity mode in which the width of the mesa corresponds to an integer multiple of one-half the wavelength of the radiation. Assuming the coherent radiation from the ac Josephson current source and the cavity magnetic surface current density source combine incoherently, fits to the data of Kadowaki et al (2010 J. Phys. Soc. Japan 79 023703) on a mesa with mean �/w = 5.17 for both wave directions using two models for the incoherent combination were made, which correspond to standing and traveling waves, respectively. The results suggest that the combined output from the uniform ac Josephson current source plus a cavity wave forming along the rectangle length is equally probable as that of the combined output from the uniform ac Josephson current plus a cavity wave across the width. However, for Mesas in which n�/ 2w is integral, where n is the index of the rectangular TM z,0 mode, it is shown that standing cavity mode waves along the length of the mesa do not radiate in the xz plane perpendicular to the length of the mesa, suggesting experiments on such Mesas could help to resolve the question. (Some figures in this article are in colour only in the electronic version)
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cavity mode waves during terahertz radiation from rectangular bi _2 sr _2 cacu _2 o _ 8 delta Mesas
arXiv: Superconductivity, 2010Co-Authors: Richard A Klemm, Manabu Tsujimoto, Takanari Kashiwagi, Erica R Laberge, Dustin Morley, K KadowakiAbstract:We re-examined the angular dependence of the radiation from the intrinsic Josephson junctions in rectangular Mesas of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, in order to determine if the cavity mode part of the radiation arises from waves across the width $w$ or along the length $\ell$ of the Mesas, associated with ``hot spots'' [Wang {\it et al.}, Phys. Rev. Lett. {\bf 105}, 057002 (2010)]. We derived analytic forms for the angular dependence expected in both cases for a general cavity mode in which the width of the mesa corresponds to an integer multiple of one-half the wavelength of the radiation. Assuming the coherent radiation from the $ac$ Josephson current source and the cavity magnetic surface current density source combine incoherently, fits to the data of Kadowaki {\it et al.} [J. Phys. Soc. Jpn. {\bf 79}, 023703 (2010)] on a mesa with mean $\ell/w=5.17$ for both wave directions using two models for the incoherent combination were made, which correspond to standing and traveling waves, respectively. The results suggest that the combined output from the uniform $ac$ Josephson current source plus a cavity wave forming along the rectangle length is equally probable as that of the combined output from the uniform $ac$ Josephson current plus a cavity wave across the width. However, for Mesas in which $n\ell/2w$ is integral, where $n$ is the index of the rectangular TM$^z_{n,0}$ mode, it is shown that standing cavity mode waves along the length of the mesa do not radiate in the $xz$ plane perpendicular to the length of the mesa, suggesting experiments on such Mesas could help to resolve the question.
Kaveh Delfanazari - One of the best experts on this subject based on the ideXlab platform.
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effect of bias electrode position on terahertz radiation from pentagonal Mesas of superconducting hbox bi _ 2 hbox sr _ 2 hbox cacu _ 2 hbox o _ 8 delta
IEEE Transactions on Terahertz Science and Technology, 2015Co-Authors: Kaveh Delfanazari, Manabu Tsujimoto, Takashi Yamamoto, Hidehiro Asai, Takanari Kashiwagi, T Kitamura, Richard A Klemm, Wade Wilson, Toshiaki Hattori, K KadowakiAbstract:We examined the effect of the bias current position on the radiation of intense and coherent terahertz electromagnetic waves from the intrinsic Josephson junctions (IJJs) in regular pentagonal Mesas of single crystalline high- $T_{\rm c}$ superconducting ${\hbox{Bi}}_{2}{\hbox{Sr}}_{2}{\hbox{CaCu}}_{2}{\hbox{O}}_{8+\delta}$ . The emission from Sample 1, a mesa with a current bias feed on its middle, is strong and sharply peaked at 0.47 THz, whereas that from Sample 2, a mesa with its feed along an edge, shows a comparably strong, sharp peak at 0.43 THz. The common backbending in the current-voltage characteristics due to Joule heating was seen for Sample 1 but almost not for Sample 2. The experimental results are in good agreement with numerical simulations and calculations, both for the cavity resonances and the angular emission patterns. The resonance peaks obtained from these pentagonal Mesas are both stronger and narrower than those found previously from differently shaped Mesas fabricated by focused ion beam milling. The overall devices are small enough to be cooled to their operational temperatures by Stirling refrigerators, so that properly designed devices could be held in one hand as for laser pointers. Therefore, our IJJ-based emitter devices are promising candidates to fill the THz gap with compact, continuous-wave quantum solid-state sources.
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tunable terahertz emission from the intrinsic josephson junctions in acute isosceles triangular bi 2 sr 2 cacu 2 o 8 δ Mesas
Optics Express, 2013Co-Authors: Kaveh Delfanazari, Manabu Tsujimoto, Takashi Yamamoto, Hidehiro Asai, Takanari Kashiwagi, T Kitamura, M Sawamura, Kazuya Ishida, Chiharu Watanabe, S SekimotoAbstract:In order to determine if the mesa geometry might affect the properties of the coherent terahertz (THz) radiation emitted from the intrinsic Josephson junctions in Mesas constructed from single crystals of the high-temperature superconductor, Bi2Sr2CaCu2O8+δ, we studied triangular Mesas. For equilateral triangular Mesas, the observed emission was found to be limited to the single mesa TM(1,0) mode. However, tunable radiation over the range from 0.495 to 0.934 THz was found to arise from an acute isosceles triangular mesa. This 47% tunability is the widest yet observed from the outer current-voltage characteristic branch of such Mesas of any geometry. Although the radiation at a few of the frequencies in the tunable range appear to have been enhanced by cavity resonances, most frequencies are far from such resonance frequencies, and can only be attributed to the ac-Josephson effect.
Manabu Tsujimoto - One of the best experts on this subject based on the ideXlab platform.
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mutual synchronization of terahertz emissions from multiple intrinsic josephson junction Mesas
2020 International Conference on UK-China Emerging Technologies (UCET), 2020Co-Authors: Ken Hayama, Shuma Fujita, Yuya Kuriyama, Keiichiro Maeda, Manabu Tsujimoto, Itsuhiro KakeyaAbstract:We present a direct proof of synchronized macroscopic Josephson oscillations excited in two intrinsic Josephson junction stacks formed on a Bi 2 Sr 2 CaCu $_{2} \mathrm{O}_{{8+} {\delta }}$ single 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.
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effect of bias electrode position on terahertz radiation from pentagonal Mesas of superconducting hbox bi _ 2 hbox sr _ 2 hbox cacu _ 2 hbox o _ 8 delta
IEEE Transactions on Terahertz Science and Technology, 2015Co-Authors: Kaveh Delfanazari, Manabu Tsujimoto, Takashi Yamamoto, Hidehiro Asai, Takanari Kashiwagi, T Kitamura, Richard A Klemm, Wade Wilson, Toshiaki Hattori, K KadowakiAbstract:We examined the effect of the bias current position on the radiation of intense and coherent terahertz electromagnetic waves from the intrinsic Josephson junctions (IJJs) in regular pentagonal Mesas of single crystalline high- $T_{\rm c}$ superconducting ${\hbox{Bi}}_{2}{\hbox{Sr}}_{2}{\hbox{CaCu}}_{2}{\hbox{O}}_{8+\delta}$ . The emission from Sample 1, a mesa with a current bias feed on its middle, is strong and sharply peaked at 0.47 THz, whereas that from Sample 2, a mesa with its feed along an edge, shows a comparably strong, sharp peak at 0.43 THz. The common backbending in the current-voltage characteristics due to Joule heating was seen for Sample 1 but almost not for Sample 2. The experimental results are in good agreement with numerical simulations and calculations, both for the cavity resonances and the angular emission patterns. The resonance peaks obtained from these pentagonal Mesas are both stronger and narrower than those found previously from differently shaped Mesas fabricated by focused ion beam milling. The overall devices are small enough to be cooled to their operational temperatures by Stirling refrigerators, so that properly designed devices could be held in one hand as for laser pointers. Therefore, our IJJ-based emitter devices are promising candidates to fill the THz gap with compact, continuous-wave quantum solid-state sources.
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tunable terahertz emission from the intrinsic josephson junctions in acute isosceles triangular bi 2 sr 2 cacu 2 o 8 δ Mesas
Optics Express, 2013Co-Authors: Kaveh Delfanazari, Manabu Tsujimoto, Takashi Yamamoto, Hidehiro Asai, Takanari Kashiwagi, T Kitamura, M Sawamura, Kazuya Ishida, Chiharu Watanabe, S SekimotoAbstract:In order to determine if the mesa geometry might affect the properties of the coherent terahertz (THz) radiation emitted from the intrinsic Josephson junctions in Mesas constructed from single crystals of the high-temperature superconductor, Bi2Sr2CaCu2O8+δ, we studied triangular Mesas. For equilateral triangular Mesas, the observed emission was found to be limited to the single mesa TM(1,0) mode. However, tunable radiation over the range from 0.495 to 0.934 THz was found to arise from an acute isosceles triangular mesa. This 47% tunability is the widest yet observed from the outer current-voltage characteristic branch of such Mesas of any geometry. Although the radiation at a few of the frequencies in the tunable range appear to have been enhanced by cavity resonances, most frequencies are far from such resonance frequencies, and can only be attributed to the ac-Josephson effect.
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cavity mode waves during terahertz radiation from rectangular bi 2 sr 2 cacu 2 o 8 δ Mesas
Journal of Physics: Condensed Matter, 2011Co-Authors: Richard A Klemm, Manabu Tsujimoto, Takanari Kashiwagi, Erica R Laberge, Dustin Morley, K KadowakiAbstract:We re-examined the angular dependence of the radiation from the intrinsic Josephson junctions in rectangular Mesas of Bi2Sr2CaCu2O8+δ, in order to determine if the cavity mode part of the radiation arises from waves across the width w or along the lengthof the Mesas, associated with 'hot spots' (Wang et al 2010 Phys. Rev. Lett. 105 057002). We derived analytical forms for the angular dependence expected in both cases for a general cavity mode in which the width of the mesa corresponds to an integer multiple of one-half the wavelength of the radiation. Assuming the coherent radiation from the ac Josephson current source and the cavity magnetic surface current density source combine incoherently, fits to the data of Kadowaki et al (2010 J. Phys. Soc. Japan 79 023703) on a mesa with mean �/w = 5.17 for both wave directions using two models for the incoherent combination were made, which correspond to standing and traveling waves, respectively. The results suggest that the combined output from the uniform ac Josephson current source plus a cavity wave forming along the rectangle length is equally probable as that of the combined output from the uniform ac Josephson current plus a cavity wave across the width. However, for Mesas in which n�/ 2w is integral, where n is the index of the rectangular TM z,0 mode, it is shown that standing cavity mode waves along the length of the mesa do not radiate in the xz plane perpendicular to the length of the mesa, suggesting experiments on such Mesas could help to resolve the question. (Some figures in this article are in colour only in the electronic version)
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cavity mode waves during terahertz radiation from rectangular bi _2 sr _2 cacu _2 o _ 8 delta Mesas
arXiv: Superconductivity, 2010Co-Authors: Richard A Klemm, Manabu Tsujimoto, Takanari Kashiwagi, Erica R Laberge, Dustin Morley, K KadowakiAbstract:We re-examined the angular dependence of the radiation from the intrinsic Josephson junctions in rectangular Mesas of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, in order to determine if the cavity mode part of the radiation arises from waves across the width $w$ or along the length $\ell$ of the Mesas, associated with ``hot spots'' [Wang {\it et al.}, Phys. Rev. Lett. {\bf 105}, 057002 (2010)]. We derived analytic forms for the angular dependence expected in both cases for a general cavity mode in which the width of the mesa corresponds to an integer multiple of one-half the wavelength of the radiation. Assuming the coherent radiation from the $ac$ Josephson current source and the cavity magnetic surface current density source combine incoherently, fits to the data of Kadowaki {\it et al.} [J. Phys. Soc. Jpn. {\bf 79}, 023703 (2010)] on a mesa with mean $\ell/w=5.17$ for both wave directions using two models for the incoherent combination were made, which correspond to standing and traveling waves, respectively. The results suggest that the combined output from the uniform $ac$ Josephson current source plus a cavity wave forming along the rectangle length is equally probable as that of the combined output from the uniform $ac$ Josephson current plus a cavity wave across the width. However, for Mesas in which $n\ell/2w$ is integral, where $n$ is the index of the rectangular TM$^z_{n,0}$ mode, it is shown that standing cavity mode waves along the length of the mesa do not radiate in the $xz$ plane perpendicular to the length of the mesa, suggesting experiments on such Mesas could help to resolve the question.
Takanari Kashiwagi - One of the best experts on this subject based on the ideXlab platform.
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effect of bias electrode position on terahertz radiation from pentagonal Mesas of superconducting hbox bi _ 2 hbox sr _ 2 hbox cacu _ 2 hbox o _ 8 delta
IEEE Transactions on Terahertz Science and Technology, 2015Co-Authors: Kaveh Delfanazari, Manabu Tsujimoto, Takashi Yamamoto, Hidehiro Asai, Takanari Kashiwagi, T Kitamura, Richard A Klemm, Wade Wilson, Toshiaki Hattori, K KadowakiAbstract:We examined the effect of the bias current position on the radiation of intense and coherent terahertz electromagnetic waves from the intrinsic Josephson junctions (IJJs) in regular pentagonal Mesas of single crystalline high- $T_{\rm c}$ superconducting ${\hbox{Bi}}_{2}{\hbox{Sr}}_{2}{\hbox{CaCu}}_{2}{\hbox{O}}_{8+\delta}$ . The emission from Sample 1, a mesa with a current bias feed on its middle, is strong and sharply peaked at 0.47 THz, whereas that from Sample 2, a mesa with its feed along an edge, shows a comparably strong, sharp peak at 0.43 THz. The common backbending in the current-voltage characteristics due to Joule heating was seen for Sample 1 but almost not for Sample 2. The experimental results are in good agreement with numerical simulations and calculations, both for the cavity resonances and the angular emission patterns. The resonance peaks obtained from these pentagonal Mesas are both stronger and narrower than those found previously from differently shaped Mesas fabricated by focused ion beam milling. The overall devices are small enough to be cooled to their operational temperatures by Stirling refrigerators, so that properly designed devices could be held in one hand as for laser pointers. Therefore, our IJJ-based emitter devices are promising candidates to fill the THz gap with compact, continuous-wave quantum solid-state sources.
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tunable terahertz emission from the intrinsic josephson junctions in acute isosceles triangular bi 2 sr 2 cacu 2 o 8 δ Mesas
Optics Express, 2013Co-Authors: Kaveh Delfanazari, Manabu Tsujimoto, Takashi Yamamoto, Hidehiro Asai, Takanari Kashiwagi, T Kitamura, M Sawamura, Kazuya Ishida, Chiharu Watanabe, S SekimotoAbstract:In order to determine if the mesa geometry might affect the properties of the coherent terahertz (THz) radiation emitted from the intrinsic Josephson junctions in Mesas constructed from single crystals of the high-temperature superconductor, Bi2Sr2CaCu2O8+δ, we studied triangular Mesas. For equilateral triangular Mesas, the observed emission was found to be limited to the single mesa TM(1,0) mode. However, tunable radiation over the range from 0.495 to 0.934 THz was found to arise from an acute isosceles triangular mesa. This 47% tunability is the widest yet observed from the outer current-voltage characteristic branch of such Mesas of any geometry. Although the radiation at a few of the frequencies in the tunable range appear to have been enhanced by cavity resonances, most frequencies are far from such resonance frequencies, and can only be attributed to the ac-Josephson effect.
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cavity mode waves during terahertz radiation from rectangular bi 2 sr 2 cacu 2 o 8 δ Mesas
Journal of Physics: Condensed Matter, 2011Co-Authors: Richard A Klemm, Manabu Tsujimoto, Takanari Kashiwagi, Erica R Laberge, Dustin Morley, K KadowakiAbstract:We re-examined the angular dependence of the radiation from the intrinsic Josephson junctions in rectangular Mesas of Bi2Sr2CaCu2O8+δ, in order to determine if the cavity mode part of the radiation arises from waves across the width w or along the lengthof the Mesas, associated with 'hot spots' (Wang et al 2010 Phys. Rev. Lett. 105 057002). We derived analytical forms for the angular dependence expected in both cases for a general cavity mode in which the width of the mesa corresponds to an integer multiple of one-half the wavelength of the radiation. Assuming the coherent radiation from the ac Josephson current source and the cavity magnetic surface current density source combine incoherently, fits to the data of Kadowaki et al (2010 J. Phys. Soc. Japan 79 023703) on a mesa with mean �/w = 5.17 for both wave directions using two models for the incoherent combination were made, which correspond to standing and traveling waves, respectively. The results suggest that the combined output from the uniform ac Josephson current source plus a cavity wave forming along the rectangle length is equally probable as that of the combined output from the uniform ac Josephson current plus a cavity wave across the width. However, for Mesas in which n�/ 2w is integral, where n is the index of the rectangular TM z,0 mode, it is shown that standing cavity mode waves along the length of the mesa do not radiate in the xz plane perpendicular to the length of the mesa, suggesting experiments on such Mesas could help to resolve the question. (Some figures in this article are in colour only in the electronic version)
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cavity mode waves during terahertz radiation from rectangular bi _2 sr _2 cacu _2 o _ 8 delta Mesas
arXiv: Superconductivity, 2010Co-Authors: Richard A Klemm, Manabu Tsujimoto, Takanari Kashiwagi, Erica R Laberge, Dustin Morley, K KadowakiAbstract:We re-examined the angular dependence of the radiation from the intrinsic Josephson junctions in rectangular Mesas of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, in order to determine if the cavity mode part of the radiation arises from waves across the width $w$ or along the length $\ell$ of the Mesas, associated with ``hot spots'' [Wang {\it et al.}, Phys. Rev. Lett. {\bf 105}, 057002 (2010)]. We derived analytic forms for the angular dependence expected in both cases for a general cavity mode in which the width of the mesa corresponds to an integer multiple of one-half the wavelength of the radiation. Assuming the coherent radiation from the $ac$ Josephson current source and the cavity magnetic surface current density source combine incoherently, fits to the data of Kadowaki {\it et al.} [J. Phys. Soc. Jpn. {\bf 79}, 023703 (2010)] on a mesa with mean $\ell/w=5.17$ for both wave directions using two models for the incoherent combination were made, which correspond to standing and traveling waves, respectively. The results suggest that the combined output from the uniform $ac$ Josephson current source plus a cavity wave forming along the rectangle length is equally probable as that of the combined output from the uniform $ac$ Josephson current plus a cavity wave across the width. However, for Mesas in which $n\ell/2w$ is integral, where $n$ is the index of the rectangular TM$^z_{n,0}$ mode, it is shown that standing cavity mode waves along the length of the mesa do not radiate in the $xz$ plane perpendicular to the length of the mesa, suggesting experiments on such Mesas could help to resolve the question.