Search

Gain has been observed at 10.6 micrometers due to stimulated emission of radiation by relativistic electrons in a spatially periodic transverse magnetic field. The magnitude of the measured gain is close to the theoretical value for the stimulated emission process. The dependence of the gain on electron energy and current and on the polarization of the stimulating radiation are also consistent with the stimulated emission hypothesis. The results raise the possibility that this mechanism can be used in the development of a new class of tuneable high power lasers.

The possibility of using very high Q superconducting microwave cavities to obtain a strong coupling between the electromagnetic field and a Josephson junction has prompted a study of such systems. Expressions have been obtained describing the dc I-V characteristic of a junction biased so that the Josephson radiation frequency is near a resonance of the cavity in which it is located. The rf power coupled into an X-band (10 GHZ) TE(011) mode cavity from a weakly coupled junction is approximately 3 x 10 to the-13th power (I sub 0) squared Q watts, where I sub 0 is the critical current of the junction and Q is the cavity Q. When the coupling between the junction and cavity is large enough, the I-V characteristic becomes multiple valued and the power coupled to the cavity depends on the state of the system. The maximum power which can be coupled to the cavity is approximately 0.58 I sub 0 V(dc), where V(dc) is the voltage required to bias the junction to the resonant frequency of the cavity. (Author)

The document is the final report on work intended to study the properties of evaporated Josephson junctions coupled to high Q superconducting microwave cavities. The report discusses areas in which experimental and theoretical advances have been made, as well as areas in which problems remain. (Author)