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Temperature dependence of the resistance of three mesas in array 1. Lower inset: Optical micrograph of array of 400 × 60 μm mesas. Top inset: Numerical simulation of the c-axis component of THz-frequency electric field for an array of mesas with width and spacing 60 μm, showing the electromagnetic coupling of the mesas through leakage of radiation into the Bi-2212 base crystal (see Ref. 14 for details of simulation methodology).
Current-voltage characteristic and THz-emission power of three mesas in array 1 at 55 K.
(a) Radiation power versus bias voltage across mesa at optimized bath temperature for one, two, and three mesas. Curve for one mesa is same as in Figure 2 , albeit with intensity plotted against voltage instead of current. When multiple mesas are biased, the bath temperature must be reduced to offset the increased power dissipation and maintain the mesas at their optimal temperature. Inset shows scaling of maximum THz signal as approximate square of number of mesas. (b) Spectra at maximum THz power (for optimized bath temperature) for one, two, and three mesas. Spectrometer resolution is 0.075 cm−1 or 2.25 GHz. (c) Angular dependence of the emission from a single mesa and from three synchronized mesas. Regions “a” and “b” mark the acceptance angles for the spectrometer and bolometer, respectively. The data were taken with a slit 3 mm wide, corresponding to 14°.
(a) Bias dependence of the THz emission power of the second array for various activated mesas and I–V curves of mesa “g” and (b) emission spectrum of the second array for various activated mesas. A monochromatic emission line could not be achieved.
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