Trapped vortices in a superconducting microbridge

Author

Park, George S. ; Cunningham, Charles E. ; Cabrera, Blas ; Huber, Martin E.

Author_Institution

Dept. of Phys., Stanford Univ., CA, USA

Volume

27

Issue

2

fYear

1991

fDate

3/1/1991 12:00:00 AM

Firstpage

3021

Lastpage

3024

Abstract

Laser light pulsed onto a Nb microbridge drives it momentarily normal and changes the quantum flux state of a superconducting inductive loop. The flux state is measured by a SQUID coupled to the loop. With a Nd:YAG laser, vortices are never trapped in the microbridge; with a diode laser, vortices are sometimes trapped. The spatial distribution of the trapped flux was studied. The effect of the optical pulse fall time on the frequency of flux trapping was found to be unimportant from 200 ns to 8 ms. Noise spectrum analysis indicates that the laser diode is 5 to 25 times noisier than the Nd:YAG laser at the characteristic frequency of the loop. This noise is believed to be responsible for flux trapping in the microbridge

Keywords

SQUIDs; flux flow; laser beam effects; niobium; superconducting junction devices; type II superconductors; Nb microbridge; Nd:YAG laser; SQUID; YAG:Nd laser; YAl5O12:Nd; characteristic frequency; diode laser; optical pulse fall time; quantum flux state; spatial distribution; superconducting inductive loop; superconducting microbridge; trapped flux; trapped vortices; Charge carrier processes; Diode lasers; Frequency; Laser noise; Laser transitions; Niobium; Optical noise; Optical pulses; SQUIDs; Superconducting device noise;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/20.133846

Filename

133846