Optical detection in thin granular films of Y-Ba-Cu-O at temperatures between 4.2 and 100 K

Leung, M.; Broussard, P. R.; Claassen, J. H.; Osofsky, M. S.; Wolf, S. A.; Strom, U.

doi:10.1063/1.98287

Cited by 126 publications

(17 citation statements)

References 6 publications

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“…The decay time is much longer than the duration (typically 100 ns) of FIR pulsed molecular lasers. This fact and the superlinear power dependence may explain why no bolometric response has been observed [1,6] in measurements with FIR molecular lasers pumped by TEA or Qswitched low-pressure CO2 -lasers. As the response time is larger than the duration of the exciting laser pulse, the peak signal is determined by the deposited energy rather than by the peak intensity of the laser pulse.…”

Section: Discussionmentioning

confidence: 99%

“…Slow signals, with time constants in the range of microseconds to milliseconds, were identified as a bolometric response arising from heating of the film. Fast signals in the far infrared (FIR), with time constants of nanoseconds, were attributed to several non-thermal mechanisms: an optical destruction of wave function coherence [1], the depairing of vortex-antivortex pairs [2], an optically induced charge imbalance in neighbouring superconducting grains [3] or infrared radiation generated currents in Josephson junctions inherent in granular films [4,5]. A drastic variation of the response time with frequency were found in T12Ba2CalCu208 films using FIR molecular lasers pumped by TEA CO2 lasers [6].…”

Section: Introductionmentioning

confidence: 99%

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Far infrared response of thin film Bi2Sr2CaCu2O8 using a free electron laser

Prettl

Lengfellner

Kaminski

et al. 1992

Int J Infrared Milli Waves

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The far infrared response of granular thin-film Bi2Sr~.CaCu208 superconductor has been investigated using long (~ 5/ts) but sharply truncated free electron laser pulses in the fi'equency range between 50 cm -1 and 125cm -1. Under constant current bias, a fast response and a slow bolometric signal component could be identified in this energy range, which is below the BCS energy gap (~ 200 cm-1). Measurements of the power dependences of the signal voltages showed that both the fast and the thermal responses are consistent with the predictions of the resistively shunted Josephson junction model. 1660 Prettl and Lengfellner IntroductionThere has been considerable interest in understanding the optical and infrared response of high-To superconductors.In previous investigations of thin granular films a wide range of response times have been observed. Slow signals, with time constants in the range of microseconds to milliseconds, were identified as a bolometric response arising from heating of the film. Fast signals in the far infrared (FIR), with time constants of nanoseconds, were attributed to several non-thermal mechanisms: an optical destruction of wave function coherence [1], the depairing of vortex-antivortex pairs [2], an optically induced charge imbalance in neighbouring superconducting grains [3] or infrared radiation generated currents in Josephson junctions inherent in granular films [4,5]. A drastic variation of the response time with frequency were found in T12Ba2CalCu208 films using FIR molecular lasers pumped by TEA CO2 lasers [6]. Below a critical frequency uc ~ 100cm -1 only fast signals, with a time constant in the order of lns, were observed. In contrast, above uc a slow response of bolometric character occurred. The transition frequency uc was identified with the energy gap value at the surface of superconducting grains. Recently non-thermal processes have been questioned by an investigation of the thermal boundary resistance of YBa2CuaOT-x films and their substrate materials [7]. It was shown that a bolometric response may occur on a nanosecond time scale: thus thermal and nonthermal effects cannot be distinguished by the time constant alone.In the present paper we report on measurements of the FIR response of thin granular film Bi2Sr2CaCu2Os using the University of California, Santa Barbara,(UCSB) Free Electron Laser (FEL). The sample was irradiated by long laser pulses truncated at the trailing edge by a rapid optical switch. Our results demonstrate that in the FIR both fast and slow signals of very different time constants are present at high powers, indicating two distinct signal generation mechanisms. The slow signal is readily identified as a bolometric response by the non -exponential decay which follows from one dimensional heat flow through the substrate to the cold finger [8]. Both types of signals show a nonlinear dependence on intensity which may be explained by the model of an effective resistively shunted Josephson junction which has the properties of a random array of junctions [9,...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Far infrared response of thin film Bi2Sr2CaCu2O8 using a free electron laser

Prettl

Lengfellner

Kaminski

et al. 1992

Int J Infrared Milli Waves

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“…The interaction of light with superconducting samples is long known to perturb superconductivity [1][2][3][4] , which can be used as a probing mechanism for optoelectronic applications [5][6][7][8][9][10][11][12][13] . In general, photons of energy greater than the Cooper pair binding energy (2∆) can initiate a chain of pair-breaking events resulting in a deviation of the quasiparticle and pair densities from their equilibrium values.…”

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confidence: 99%

Ultrafast linear kinetic inductive photoresponse of YBa2Cu3O7−δ meander-line structures by photoimpedance measurements

Atikian

Ghamsari

Anlage

et al. 2011

Applied Physics Letters

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We report the experimental demonstration of the linear kinetic-inductive photoresponse of thin-film YBa 2 Cu 3 O 7−δ (YBCO) meander-line structures, where the photoresponse amplitude, full-width-halfmaximum (FWHM), and rise-time are bilinear in the incident optical power and bias current. This bilinear behavior reveals a trade-off between obtaining high responsivity and high speed photodetection. We also report a rise-time as short as 29ps in our photoimpedance measurements.The interaction of light with superconducting samples is long known to perturb superconductivity 1-4 , which can be used as a probing mechanism for optoelectronic applications 5-13 . In general, photons of energy greater than the Cooper pair binding energy (2∆) can initiate a chain of pair-breaking events resulting in a deviation of the quasiparticle and pair densities from their equilibrium values. Typically, these distributions depend on temperature, optical power and wavelength, thermal boundary conditions, and material properties such as electron-electron and electron-phonon interactions times, electron density, coherence length, penetration depth, and geometry 6,14 . While determining the spatial and temporal distribution of quasiparticles and pairs under a time-varying optical illumination is a profound problem in non-equilibrium superconductivity, many of the important concepts of such an interaction for device applications can be captured by means of a much simpler and more phenomenological approach, namely the kinetic inductance model 13 . Within the kinetic inductance model the presence of the superconductive condensate, at a macroscopic level, can be adequately modeled by an additional inductive channel for charge transport. The optically initiated pair breaking mechanism, within this framework, should be interpreted as the spatial and temporal variations of the kinetic inductance and the normal resistance of the superconducting specimen.Many researchers have experimentally studied the kinetic inductive photoresponse of superconducting thin films through photoimpedance measurements 6,15 . In photoimpedance measurements, light induced changes in the microwave impedance of the superconducting structure are measured by an external high-frequency circuit. In its simplest form, the specimen is externally biased with a dc current and connected to a fast oscilloscope in series with a high bandwidth amplifier; absorption of optical photons then changes the impedance of the sample and produces a transient voltage response. A number a) Author to whom correspondence should be addressed. Electronic address: haatikia@maxwell.uwaterloo.ca of previous works have reported photoimpedance measurements on different superconductors mainly concluding that: 1) the resistive photoresponse dominates at temperatures well below the critical temperature (T c ), whereas the kinetic inductive response becomes the main mechanism of photoresponse close to T c ; 2) In the kinetic inductive regime the photoresponse could be very fast, with a rise time as low as 50...

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“…Such an effect, observed in current biased YBa2Cu307_~f [7] T1-Ba-Ca-Cu-O [8] and Bi2Sr2CaCuzOs [9] samples, is due to the depression of the critical current Ic by far…”

mentioning

confidence: 99%

“…Such an effect, observed in current biased YBa2Cu307_~f [7] T1-Ba-Ca-Cu-O [8] To date photoresponse studies have mainly been used at frequencies to > 2A to investigate pair-breaking effects and quasiparticle recombination times [11]. We extend the range of these studies to lower frequencies (to < 2A), extracting structural information about the superconductor.…”

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confidence: 99%

Magnetic field dependence of Josephson photoresponse in high-Tc superconductor thin films

Schneider

Huggard

O’Brien

et al. 1994

Solid State Communications

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The Josephson photoresponse of granular high-T~ superconductor films to pulsed far infrared laser radiation has been investigated in magnetic fields of up to 3 T. Its value is strongly influenced by fields less than 50 mT and shows a pronounced hysteresis here. At low bias current densities, jb < 10 A/cm 2, an applied field stimulates the photoresponse, while for Jb > 100 A/cm 2 the photoresponse is depressed. All changes have occured by a field of B < 50 roT: for higher fields the photoresponse remains constant. This dependence is interpreted to arise from micrometre sized grain boundary junctions with a strongly inhomogenous critical current distribution on a sub-nanometre scale.A topic of great current interest is the study of the intergranular interfaces in high Tc superconductors, as the weak links betweek grains determine the materials critical current density jc and most probably its surface resistance. Conventional experimental techniques, such as a.c. susceptibility [1] and transport critical current measurements [2], have been used to study the effects of external magnetic fields on jc. Typically, a magnetic field dependence is observed for B < 50 mT while for larger B a field indepent plateau is reported [2,3]. Additionally, a residual microwave [4,5] and far infrared absorption [6] is found in the superconducting state. These effects are explained by the existence of weak links [4,5], by magnetic flux penetrating at low fields only into the intergranular material [2] and by the effect of intragrain flux pinning on the intergraln flux density [1].We present a novel technique to study the microscopic structure of weak links, utilising the far infrared Josephson photoresponse of granular thin films. Such an effect, observed in current biased YBa2Cu307_~f [7] T1-Ba-Ca-Cu-O [8] and Bi2Sr2CaCuzOs [9] samples, is due to the depression of the critical current Ic by far

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Optical detection in thin granular films of Y-Ba-Cu-O at temperatures between 4.2 and 100 K

Cited by 126 publications

References 6 publications

Far infrared response of thin film Bi2Sr2CaCu2O8 using a free electron laser

Far infrared response of thin film Bi2Sr2CaCu2O8 using a free electron laser

Ultrafast linear kinetic inductive photoresponse of YBa2Cu3O7−δ meander-line structures by photoimpedance measurements

Magnetic field dependence of Josephson photoresponse in high-Tc superconductor thin films

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