ABSTRACT
Josephson effects were predicted theoretically by B. D. Josephson in 1962. Josephson effects occur in weak links, structures which link two bulk superconductors 1 and 2, capable of carrying a supercurrent but not as strongly superconducting as the bulk materials. This chapter applies a specified voltage to the weak link, but many weak links have impedances at the relevant microwave frequencies of a few ohms or less. The surprising appearance of the oscillatory current is the d.c. Josephson effect. The ability of weak links to provide tunable oscillator power at very high frequencies can be very useful, but the power available from a single junction is of order RIJ2 typically less than 1 μW, and from a low-impedance source which is difficult to match; practical applications usually therefore make use of a suitable array of weak links.
