Analytic thermal modeling for dc to midrange modulation frequency response for thin film high-Tc superconductive edge-transition bolometers

Cataloged from PDF version of article.Thin-film superconductive edge-transition bolometers are modeled with a one-dimensional analytic thermal model with joule heating, film and substrate materials, and the physical interface effects taken into consideration. The results from the model agree well with the experimental results of samples made of large-meander-line Yba(2)Cu(3)O(7-x) films on crystalline SrTiO3, LaAlO3, and MgO substrates up to 100 kHz, the limits of the experimental setup. Compared with the results of the SrTiO3 substrate samples, the results from the model of the LaAlO3 and the MgO substrate samples deviate slightly from the measured values at very low modulation frequencies (below similar to 10 Hz). The deviation increases for higher thermal-conductive substrate materials. When the model was used, the substrate absorption and the thermal parameters of the devices could also be investigated. (C) 2001 Optical Society of Americ

Control of the responsivity and the detectivity of superconductive edge-transition YBa2Cu3O7-x bolometers through substrate properties

Cataloged from PDF version of article.The detectivity D* limits of YBa2Cu3O7-x bolometer on 0.05-cm-thick crystalline substrates are investigated, and a method to increase D* to greater than 10(9) (cm Hz(1/2))/W at a 20-mu m wavelength is proposed. Because the response increases proportionally with the bias current I-b, whereas the noise near T-c (the transition or critical temperature) of our MgO and SrTiO3 substrate samples does not, an increase in D* of these samples is obtained by an increase in I-b. Another limiting factor is the de thermal conductance G(0) of the device, which, although controlled by the substrate-holder thermal boundary resistance for our samples, can be changed by means of thinning the substrate to increase D*. The optimal amount of thinning depends on the substrate's thermal parameters and the radiation modulation frequency. D* in our samples is also found to follow the spectral-radiation absorption of the substrate material. (C) 1999 Optical Society of America

Analytic thermal modeling for dc-to-midrange modulation frequency responses of thin-film high-Tc superconductive edge-transition bolometers

Thin-film superconductive edge-transition bolometers are modeled with a one-dimensional analytic thermal model with joule heating, film and substrate materials, and the physical interface effects taken into consideration. The results from the model agree well with the experimental results of samples made of large-meander-line Yba2Cu3O7-x films on crystalline SrTiO3, LaAlO3, and MgO substrates up to 100 kHz, the limits of the experimental setup. Compared with the results of the SrTiO3 substrate samples, the results from the model of the LaAlO3 and the MgO substrate samples deviate slightly from the measured values at very low modulation frequencies (below ∼10 Hz). The deviation increases for higher thermal-conductive substrate materials. When the model was used, the substrate absorption and the thermal parameters of the devices could also be investigated. © 2001 Optical Society of America

Superconductivity Transition Dependence of the Thermal Crosstalk in YBa2Cu3O7-x Edge-Transition Bolometer Arrays

The effect of the superconductivity transition on the thermal crosstalk in YBa2Cu3O7-x, edge-transition bolometer arrays is investigated for DC to midrange modulation frequency infrared radiation. The bolometers; in the arrays were designed with various distances on SrTiO3 (100) substrates. We have observed a change in the thermal crosstalk between neighbor devices through the superconductivity transition temperature range. Superconductivity transition dependence of the thermal coupling between the devices was measured by utilizing the thermal conductance measurement methods developed for the bulk material. The knee points in the magnitude of the response versus modulation frequency curves of the devices were also determined by illuminating one of the bolometers in the arrays and measuring the response of the neighbor devices. By using the knee frequency and the distance between the bolometers, the modulation frequency criterion for crosstalk-free response at the transition region in various array structures is found and the results of the thermal coupling measurements are further studied and presented here

Case Study of Decoherence Times of Transmon Qubit

In the past two decades, one of the fascinating subjects in quantum physics has been quantum bits (qubits). Thanks to the superposition principle, the qubits can perform many calculations simultaneously, which will significantly increase the speed and capacity of the calculations. The time when a qubit lives in an excited state is called decoherence time. The decoherence time varies considerably depending on the qubit type and materials. Today, short decoherence times are one of the bottlenecks in implementing quantum computers based on superconducting qubits. In this research, the topology of the transmon qubit is investigated, and the decoherence time caused by noise, flux, and critical current noise is calculated by numerical method.Comment: 7 pages, 5 figure

Temperature dependence of the phase of the response of YBCO edge-transition bolometers: Effects of superconductivity transition and thermal parameters

The variation of the phase of the response of YBCO edge-transition bolometers on crystalline MgO substrate is found to be dependent on the normal-superconducting transition. The phase of the response for T < Tc increased at low modulation frequencies where the thermal diffusion length into the sample substrate from the top absorbing YBCO film is longer than the substrate thickness. The substrate/cold-head boundary resistance mainly dominates the thermal conductance of our samples at low frequencies. This transition-dependent change of the phase of the response is interpreted to be due to the effects of the order parameter of the YBCO material on the phonon spectrum and hence the determining Kapitza boundary resistance. The phase of the response decreased at high modulation frequencies where the thermal diffusion length into the substrate is less than the substrate thickness. The results of our analytical model for the low modulation frequencies agree well with the measured values for temperatures close to the Tc-zero

Analytic modeling of patterned high-Tc superconductive bolometers: Film and substrate interface effects

Superconducting film and substrate interface effects on the response of superconductive edge-transition bolometers are modeled with a one dimensional thermal model in closed form, for samples with large area patterns compared to the substrate thickness. The results from the model agree with experimental results on samples made of meander line patterned granular YBCO films on crystalline substrates, in both the magnitude and phase of the response versus modulation frequency up to about 100 KHz, the limit of the characterization setup. Using the fit of the calculated frequency response curves obtained from the model to the measured ones, values of the film-substrate and substrate-holder thermal boundary resistance, heat capacity of the superconducting film, and the thermal parameters of the substrate materials could be investigated. While the calculated magnitude and phase of the response of the SrTiO3 substrate samples obtained from the model is in a very good agreement with the measured values, the calculated response of the LaAlO3 and MgO substrate samples deviate slightly from the measured values at very low frequencies, increasing with an increase in the thermal conductivity of the substrate material. Using the fit of the calculated response to the measured values, film-substrate thermal boundary resistances in the range of 4.4* 10-3 to 4.4* 10-2 K-cm2-w-1 are obtained for different substrate materials. The effect of substrate optical absorption in the response of the samples is also investigated

Feasibility of electrical-contact free measurement of the response of superconductive bolometer arrays using the thermal crosstalk

We utilized and investigated the unique dependence of the magnitude and phase of the response on the thermal crosstalk between bolometer pixels in an array to measure the response of the devices through fewer monitoring devices. In this study, we show the feasibility of the proposed read-out technique by use of two source pixels in an array, as the image-mapping devices, and one optically shielded pixel as the read-out device. While the sense pixels were electrical-contact free, the read-out device was current biased in 4-probe current-bias configuration. Both the phase and magnitude of the response due to the crosstalk in the array were found to be strongly dependent on the modulation frequency and the distance between the sense and read-out pixels. A series of measurements were designed to extract the response of each single sense-pixel. By combining the measured data, the response of individual pixels could be extracted through the interpolation of the mapped responses. © 2006 IOP Publishing Ltd

Analytical modelling of the interpixel thermal crosstalk in superconducting edge-transition bolometer arrays

We present an analytical thermal model to explain the crosstalk in YBCO edge-transition bolometer arrays. The verification of the model was tested on sample array devices made of 200 and 400 nm YBCO films on LaAlO3 and SrTiO3 substrates. The model presented was able to explain the effects of the various physical parameters of the devices, such as the film thickness, operating temperature, and the device separation, which cause different response behaviours based on the variation of the related thermal crosstalk characteristics. In addition, the model is valid above the crosstalk-free modulation frequencies, where the effects of the thermal crosstalk on the response of the devices are negligible. © 2006 IOP Publishing Ltd

Superconducting and electro-optical thin films prepared by pulsed laser deposition technique

Cataloged from PDF version of article.The pulsed laser deposition (PLD) technique is an excellent method to prepare single crystalline complex oxide thin films. We have successfully grown films for the use in HTS SQUID-devices as well as for thin film optical waveguides. The Josephson junction used in the HTS SQUIDs is formed by a step edge type gain boundary junction. The step preparation is a very critical process in the SQUID preparation to achieve reproducible low 1/f noise devices. We have established a new ion beam etching process to achieve clean and steep edges in LaAlO(3) (100) substrates. The 1/f noise of SQUIDs prepared with the new method is drastically reduced. In the process of developing thin film electro-optical waveguide modulators we investigated the influence of different substrates on the optical and structural properties of epitaxial BaTiO(3) thin films. These films are grown on MgO(1 0 0), MgAl(2)O(4)(1 0 0), SrTiO(3)(1 0 0) and MgO buffered Al(2)O(3)(1 (1) over bar 0 2) substrates. The waveguide losses and the refractive indices were measured with a prism coupling setup. The optical data are correlated to the results of Rutherford backscattering spectrometry/ion channeling (RBS/C), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The dielectric constant, the ferroelectric hysteresis loop and the transition temperature (ferroelectric to paraelectric state) of the BaTiO(3) thin films are measured. (C) 2000 Elsevier Science B.V. All rights reserved