Towards local oscillators based on arrays of niobium Josephson junctions

Abstract

Various applications in the field of terahertz technology are in urgent need of compact, widetunable solid-state continuous wave radiation sources with a moderate power. However, satisfactory solutions for the THz frequency range are scarce yet. Here we report on coherent radiation from a large planar array of Josephson junctions (JJs) in the frequency range between 0.1 and 0.3 THz. The external resonator providing the synchronization of JJ array is identified as a straight fragment of a single-strip-line containing the junctions themselves. We demonstrate a prototype of the quasioptical heterodyne receiver with the JJ array as a local oscillator and a hotelectron bolometer mixer.

Stochastic first passage time accelerated with CUDA

“…The resulting method requires to simulate the system in the low noise limits, when the relations (12,13) are strictly valid [18,19]. By the same token, in this limit simulations are extremely long, and hence the call for fast, parallel simulations.…”

“…In the Figure the error bar is not visible, for the speed of the algorithm has allowed to collect a large number of realizations (N r = 5120). This high accuracy allows to distinguish between the Arrhenius behavior τ ∝ exp ∆U ∆θ (12) and the detailed Kramers rate, obtained taking into account the prefactor corrections, for the special case of moderately underdamped systems. The model fits in this case with prefactor becomes [1]:…”

“…Kramers' rate theory [2,3]). From the experimental point of view, in Josephson Junctions (JJ) superconducting devices [4] the measurement of the threshold for the escapes is the only possibility (or the simplest way) to gain information on the internal dynamics of systems as quantum devices [5,6], threshold detectors [7][8][9] and arrays of JJ [10,11] of great interest for high frequency, up to the THz region, local oscillators [12]. The threshold for escapes is an essential physical information also in diverse systems .…”

Coherent amplification of radiation from two phase-locked Josephson junction arrays

“…The advantage of large JJ arrays working similar to lasers is discussed in more detail in [8]. The resonator can be a cavity of the JJs itself [2], an electrode with embedded JJs [9], or the dielectric substrate on which the JJ array is arranged [10].…”

“…For N oscillators, the supperradiant power increase is at most N 2 times the power from one oscillator and the superradiant gain factor is at most N. For large N, this could greatly enhance the emitted power. This is the main motivation for the development of Josephson oscillators based on arrays with many JJs [2,3,6,9,10,[12][13][14][15].…”