Power enhancement of the high-Tc superconducting terahertz emitter with a modified device structure

Abstract

Continuous and monochromatic terahertz electromagnetic waves can be generated with sizable power (∼30 μW) by the mesa-shaped device made of the high-Tc superconductor Bi2Sr2CaCu2O8+δ, by synchronizing the phase of the Josephson currents between multi-stacked intrinsic Josephson junctions. From the previous experimental results on the line width, spatial distribution of the emission, etc., we think that the relatively weaker power may originate from the partial failure of the phase synchronization of the Josephson currents in the mesa device. This may be improved by modifying the device structure to enhance the Josephson current density inside the mesa. In the present study, an array of four rectangle-shaped mesas with the dimensions of 80±5 μm×350 μm×3.2 μm was fabricated on a thin Bi2Sr2CaCu2O8+δ single crystal, where several slots were made around the mesas by photolithography and chemical etching techniques in order to weaken electrical connection between mesa and superconductor base. The best result of the emission power for the array so far obtained is ~80 μW at 0.42 THz, which is about 2.7 times bigger than the previous champion data in our group.