Diagram of microscope, illumination, and cryostat arrangement employed in this experiment.
Calibration curves of the temperature dependence of the fluorescence intensity over a Au and BSCCO surface measured with respect to a base temperature of 61 K.
(a) Temperature dependence of the c-axis resistance, Rc , of the BSCCO mesa. The blue symbols are estimates of the c-axis resistance obtained from the sub-gap resistance as deduced from the IV-curves (inset of Fig. 3(a) ). The blue dashed line is an interpolation between these data and the resistance data above Tc . (b) Current-voltage characteristic for a mesa at 61 K (blue curve, bottom axis) plotted together with the current dependence of the THz output power (red curve, top axis). Arrows indicate current values for which thermal images are shown in Figure 5 . The inset shows a schematic of the BSCCO mesa fabricated onto a BSCCO base crystal using photolithography and Ar-ion milling. The wavy red lines symbolize the THz-radiation emitted from the sides of the mesa.
(a) Optical micrograph of the THz source mesa used in this experiment. An identical adjacent mesa (not energized in this experiment) is also shown near the top of the image. The Au contacts continue to the right; they are however not visible in this image since they follow an inclined sample surface (see inset in Fig. 3(b) ). (b) Thermal fluorescent image of same area at 61 K and 20 mA, under which conditions the radiated THz power is maximized (at approximately 58 μW). The difference between the mesas with and without applied power is clearly visible.
(a) and (b) Temperature profiles measured along the dotted lines in Fig. 4(a) at a bath temperature of 61 K, and increasing bias current. (c) Thermal fluorescent image of the mesa at increasing bias current. Images in (c) are calibrated for Au surfaces, but the temperature profiles in (a) and (b) are obtained using a position-dependent calibration function. Note the difference in color-scale in Figs. 5(c) and 4(b) .
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