Control of gigahertz antenna radiation using optically triggered Y–Ba–Cu–O superconducting microbridges

Abstract

Ultrafast voltage transients from optically thick YBa 2 Cu 3 O 7−x (YBCO) microbridges, dc-biased and triggered with femtosecond optical pulses at temperatures below the YBCO critical temperature were used to excite radiation of a transmitting gigahertz-frequency antenna. The shape of the power spectrum of the antenna radiation depended on the time evolution and amplitude of the YBCO photoresponse transient, which was controlled by the incident laser fluence and the microbridge temperature and bias current. The main contribution to the above 10 GHz radiation was attributed to the photoresponse rising edge, generated due to the initial supercurrent redistribution and the kinetic-inductive effect. Low-frequency antenna radiation was excited by the photoresponse component associated with heating and cooling effects generated in the superconducting microbridge. Our antenna radiation approach can be used for time-resolved investigation of electric current distributions in photoactivated YBCO thin films.

Tunable Broadband Radiation Generated Via Ultrafast Laser Illumination of an Inductively Charged Superconducting Ring

“…Superconducting photo-switches integrated into standard transmission systems have been shown to generate ultrawide band (UWB) microwave radiation7. Integrating a superconducting photo-switch together with a superconducting antenna (typically millimeters in dimension or less) has been shown to generate THz UWB radiation689.…”

Investigation and Application of Ultrafast Photoresponse of YBa2Cu3O7-δMicrobridges, Excited by High Fluence Optical Pulses

“…2) in the same range of laser fluences, showing no evidence of saturation at I bias = 0.29I c . Assuming that the radiation power increases with an increase in PR amplitude and decreases in risetime [5], we conclude that the antenna radiation was excited by superposed photokinetic and bolometric PR components [2,4].…”

“…Suppression of superconductivity in the hot spot affected the amplitude and risetime of the photokinetic PR component, which appeared with no delay in respect to the FOP. The bolometric PR component, exhibited a few nanoseconds initial delay with respect to the FOP [2,4], the nanosecond risetime, and amplitude, after a linear rise saturated at 16 mJ cm −2 when the laser fluence increased (see the inset to Fig. 2).…”

“…Light absorption by the YBCO film at T < T c , created highly energetic quasiparticles, whose ultrafast thermalization developed a hot spot in the superconductor and, depending on laser fluence and biasing conditions, a transition of the superconductor into resistive/normal state [1][2][3][4]. Suppression of superconductivity in the hot spot affected the amplitude and risetime of the photokinetic PR component, which appeared with no delay in respect to the FOP.…”

“…The approach of PR driven transmitting-antenna radiation [4] and ultrafast oscilloscope for measurements of PR waveforms were used in our experiments.…”