Continuous and reversible operation of Bi2212 based THz emitters just below Tc

Continuous and reversible operation of the THz-light emitters comprised of the intrinsic Josephson junction (iJJ) system of high-T-c superconductor Bi2Sr2CaCu2O8+delta (Bi2212) is reported. This reversible emission is observed in samples made of lightly underdoped crystals when a part of the mesa device is so overheated by Joule heating that the temperature reaches T-m near but still below T-c. while the irreversible type of emission occurs at less overheated condition. The large temperature gradient in the mesa due to overheating under high bias currents seems to be responsible for the new observed reversible emission. (C) 2010 Elsevier B.V. All rights reserved.