We investigated the emission of subterahertz frequency electromagnetic radiation from high-TC superconducting c-axis NdBa2Cu3O7−δ∕PrBa2Cu3O7−δ∕NdBa2Cu3O7−δ trilayer thin film tunneling junctions when external electric and magnetic fields are applied. The current-voltage characteristics under applied ab-plane magnetic fields H (up 8T) exhibit well defined steps, Vn, such that eVn≈hωp∕(2nπ), where the plasma frequency ωp≈0.4 THz and n=1,2,3,….. These steps may be interpreted using Josephson plasma dynamics. The applied voltage creates oscillating currents via the Josephson coupling energy EJ (EJ=hIJ∕4πe, where IJ is the Josephson current and h is Planck’s constant) and the charge energy EC (EC=e2∕2C, where C is the junction capacitance). Thus the Josephson plasma becomes excited by the tunneling current, with some of the energy being emitted as subterahertz frequency radiation. Our results provide a new insight into a solid-state quantum system with considerable potential for new solid-state terahertz emission sources.

Shallow impurity states of donors and acceptors in Ge have been investigated by far-infrared laser magnetospectroscopy. The Zeeman splitting of the impurity states produces resonant absorption of the laser radiation at certain magnetic fields. The data are compared to measurements made using a conventional spectrometer and good agreement is found.

A doublet observed for the G line of Zn-(0) without applied perturbation is attributed to relative shifts of the two Gamma(4)(-) states which are part of the compound excited state of this transition. This effect also increases the energy spacing between the G doublet and the rest of the lines of the Lyman series. The energies and widths of all the lines are temperature dependent at temperatures where group III lines no longer show these effects. Zeeman measurements have demonstrated conclusively that the low temperature Lyman series of Zn-(0) in Ge arises from the 1 Gamma(1)(+) ground state. These studies also establish that the Zeeman excited states of Zn-(0) are compounded from wave functions identical to those of the ground state of Zn- and the excited states of group III accepters in Ge.

A brief review is given of the Zeeman and piezo-Zeeman results for the spectra of shallow acceptors in germanium. Also included are new data for the Zeeman spectra of thallium with B ∥〈100〉 and boron, gallium and thallium under B ∥〈111〉. The observations are for field strengths up to 7T and the results compared with recent calculations of these effects. New data for neutral zinc in germanium with B ∥〈100〉 is also indicated.

A simple enhancement technique which was found to increase Raman scattered signals from local modes of hydride and deuteride ions in CaF2 and SrF2 by a factor of up to five is described. It enabled the fundamental and all three second harmonic transitions of both hydride and deuteride ions located in the tetrahedral Td sites to be observed. Anharmonic potential well constants for these sites are reported.

Experimental results are presented on the behaviour of the C line of gallium impurity in germanium under uniaxial compression along a 〈100〉 direction. The C line stress spectrum is found to have ten components arising from the splitting of a complex final state consisting of the closely spaced combination: 1Γ-7+3Γ-8+3Γ+8. The participation of the even parity state in the C transition has not been previously reported. Recent theoretical calculations are shown to give splitting values in good agreement with these results.

A novel cryostat which permits the simultaneous application of a uniaxial compressive force and a uniform magnetic field to a crystalline solid has been used to study impurity spectra in semiconductors. The application of such a force along a <100 > crystallographic direction, for example, converts germanium from cubic to tetragonal symmetry. The stress-modified line spectrum can then be studied using Zeeman spectroscopy.

Experimental results are presented of the Zeeman spectrum of the stress components of the D and G lines of gallium impurity in germanium. The interpretation of the results based on symmetry unambiguously demonstrate that the g-factors of the ground state are essentially zero. From this and theoretical expressions for g-factors of Γ8 states of T̄d symmetry, experimental values have been determined for the g-factors of the excited states of the D and G transitions. These values compare well with those obtained by Zeeman observations on the unstressed material.

The deformation potential constants and intensity parameters of some of the states and optically induced transitions of gallium impurity in germanium have been determined both experimentally and theoretically. The latter are based on the effective mass wavefunctions of Kohn and Schechter and of Mendelson and James. Reasonably good agreement is found between the experimental and theoretical results.

A detailed study has been made of the optical transverse Zeeman effect for trivalent erbium ions at sites of tetragonal C4v symmetry in crystals of calcium fluoride with magnetic fields of up to 6T. Interpretation of the optical absorption spectrum is complicated by the presence of magnetically non-equivalent C4v sites and Er3+ sites of other point symmetries, but selective excitation of fluorescence with a tunable dye laser has been used to isolate the spectrum of ions in the required transverse C4v sites. Selective laser excitation spectroscopy has also been used to locate several previously undetected Er3+ crystal-field energy levels for the C4v site. A crystal-field analysis has successfully accounted for the observed transverse Zeeman patterns, including the variation in these patterns as a function of orientation of the magnetic field in the (100) crystal plane and as a function of magnetic field strength.

Infrared and Zeeman infrared measurements of the tetragonal symmetry cerium fluoride ion and neodymium fluoride ion charge compensation sites in calcium and strontium fluoride are reported. The neodymium results are supplemented by optical absorption and fluorescence measurements. Crystal field analyses successfully account for the observed2F72/(4f1) and4I92/,4I112/(4f3) multiplet crystal field splittings and for the measured Zeeman splitting values.

Infrared measurements of hydrogenated strontium-fluoride crystals containing trivalent rare-earth ions, and EPR measurements of hydrogenated strontium-fluoride crystals containing gadolinium are reported. The infrared results show that the hydride ions associated with the rare-earth ions occur in several different sites whose relative occurrence changes abruptly in the vicinity of holmium. For the rare-earth ions before holmium in the rare-earth series, there are two principal sites. One of these has tetragonal symmetry and the other rhombic symmetry. These two sites, and two additional sites of rhombic symmetry, are also observed in the case of the gadolinium-doped crystal by EPR. For the heavier rare-earth ions beyond holmium in the rare-earth series, the tetragonal and rhombic symmetry sites are replaced by a low-symmetry site. Additional sites produced by ultraviolet irradiation of the crystals and the sites observed in the hydrogenated barium-fluoride crystals containing trivalent rare-earth ions are also described. Possible models for the various sites are proposed.