Effects of the superconductivity transition on the response of YBCO edge transition bolometers

Abstract

Dependence of the phase and magnitude of the response of Y-Ba-Cu-O edge transition bolometers on the superconducting transition is studied. The responses of both large and small area devices were investigated and several anomalies are observed. The response of small area LaAlO 3 devices considerably differed from that expected based on the dR/dT curve. This discrepancy is observed to be strongly dependent on the superconducting transition. Both the phase and magnitude/(dR/dT) of the response of the devices showed abrupt changes for below the T c-onset when measured versus temperature, while the phase variation also showed strong dependence on the modulation frequency. We present the analysis and propose mechanisms responsible for the modulation frequency dependence of the response characteristics versus temperature, within the superconductivity transition region of the devices.

Substrate and Device Pattern Dependence of the Thermal Crosstalk in Y Ba$_2$Cu$_3$O$_{7-\delta}$ Transition Edge Bolometer Arrays

“…However, based on previously reported single pixel studies [11], [12], as the thickness of the substrate decreases, the thermal diffusion length becomes comparable to the thickness of the substrate at higher frequencies as shown in (2), and the Kapitza boundary resistance affects the response for a higher ranges of frequencies. For example, in Fig.…”

“…This is especially true at the low and mid ranges of the modulation frequencies, , where the thermal diffusion length is in the same range as the substrate thickness. In this range, the substrate thermal conductance and thermal capacitance become the dominant parameters that affect the response of the bolometers [11]. Fig.…”

“…5, is 1 mm at 4 Hz modulation frequency. At frequencies below 4 Hz, the heat wave is expected to face the boundary resistance that reduces the phase of the response [11], [12]. However, since there is no such boundary in the back-etched bolometers, the phase of the response ends up being higher compared to the normal substrate based bolometers.…”

Superconductivity transition dependence of the thermal crosstalk in YBa/sub 2/Cu/sub 3/O/sub 7-x/ edge-transition bolometer arrays

“…The phase and magnitude of the optical response of the devices were measured with SR 850 DSP lock-in amplifier, the input of which was amplified with an ultralow noise preamplifier (Stanford SR 570). As a radiation source, electrically modulated, fiber coupled IR laser diode with wavelength of 850 nm, and 12 mW power was used [4]. The system is capable of measuring all four devices in one cooling cycle without altering the electrical or thermal contacts, or the optical setup.…”

“…This is interpreted to be caused by the fact that the thermal diffusion length in this range is comparable to the substrate thickness leading to an almost similar temperature variation for all the neighbor devices. In this range of frequency, the Kapitza boundary resistance is the dominant thermal parameter affecting the response [3], [4], and all the devices behave as if they are perfectly coupled to each other. As the thermal diffusion length starts to be comparable to the distance between the devices, the response curves start to diverge from each other.…”