Abstract

Electrical pulses 0.6 ps in duration have been generated on a transmission line structure by use of a fast-recombination-time photoconductive switch driven by a subpicosecond optical pulse. [1] These wide bandwidth electrical pulses are ideal for measuring the absorption and dispersion of a transmission-line-substrate combination by observing their propagation along the structure. [2] This technique has been applied here to the study of superconducting transmission lines. Briefly, by Fourier transform techniques the complex frequency content of the pulse can be found, and by comparing the pulse before and after propagation, the absorption and dispersion are calculated. The niobium lines become superconducting at 9 degees Kelvin. The transmission lines are He vapor cooled and temperature regulated in an optical dewar. The opto-electronic sampling technique used is well suited to operation inside a dewar since all fast electrical signals (0-1 THz) are confined to the sample and only slow signals (0-1 KHz) must leave the dewar.

© 1986 Optical Society of America