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Most of this thesis describes experiments conducted in order to generate soft x-rays of energy >67 eV from a laser-generated plasma, in order to pump the Xe III Auger laser at 109 nm. In attempts to obtain the optimal sub-nanosecond laser pulses for amplification in a very simple KrF (248 nm) laser a compact KrF oscillator was used to obtain 1 ml pulses of FWHM duration 2 ns, and plasma-truncated reflection of a focused KrF beam from metal targets gave 1.8 ns pulses. Longer pulses were obtained by truncated stimulated Brillouin scattering (TRUBS), and by plasma-truncated spatial-filtering. Experiments were conducted to pump the Xe III laser using the leading edge of a 20 ns KrF laser pulse. An off-axis spherical mirror produced a 3 cm line plasma on a tantalum target. A poor conversion efficiency to soft x-rays was observed. Unexpectedly poor KrF beam quality was shown to have been a potential cause, a fault in the detection system having been ruled out. A repeat experiment was started, employing tighter focusing and better KrF beam quality. A 7 ps KrF laser system was also investigated for the generation of the necessary plasmas. No 109 nm lasing was observed, and a low conversion efficiency into soft x-rays was measured. The short duration of the KrF pulse was suspected as the cause, and some attempts were made to compensate for this by means of preformed plasmas. Over the course of the work, several aspects of KrF laser technology were improved, including: the characterisation of a novel, safe, solid-state source of fluorine (F₂); the quantitative characterisation of nitrogen dioxide (NO₂) as a variable attenuator for KrF radiation; and the manufacture of uniform, transparent, electrodes led to the laser system having the highest single pulse energy (2.55 J) of any UV-preionised, discharge-excited, conventional-aperture KrF laser. Finally, separate work led to the development and absolute characterisation of a laser-plasma source of tunable VUV/EUV/XUV radiation (30 nm to 200 nm; 6 eV to 41 eV), as well as a sodium salicylate scintillator-based detection system. After optimisation of the target material, laser focusing, and micro-channel-plate (MCP) focusing of the plasma emission, an output of between 10⁶ and 10⁷ photons per shot in a 4 nm bandwidth could be delivered on target.

Vertical cavity surface emitting laser (VCSEL) structures have been grown by both metal-organic chemical vapour deposition (MOCVD) and molecular beam epitaxy (MBE). These incorporate 3 strained InGaAs / GaAs quantum wells placed resonantly in a two wavelength long optical cavity, formed between AlAs / GaAs quarter wave dielectric reflector stacks through which current is injected. The reflection spectra of these stacks is studied in detail; the effects on the laser threshold gain of absorption due to impurities and of errors in growth are investigated. Methods of disruption of the AlAs / GaAs heterointerfaces have been used to reduce the operating voltage. The completed designs use 200A intermediate layers containing 30 or 50% aluminium or a superlattice graded region simpler than that used in previous designs. The effectiveness acceptor dopants; Be in MBE, C and Zn in MOCVD; is studied also. Modulation doping was employed to reduce the effects of optical absorption. Devices were fabricated into mesas by SiC14 reactive ion etching or defined by proton implant isolation. MBE grown devices were resonant at wavelengths in the range 950 to 1059mn with essentially constant (at —1020nm) eihhi transition energies in the wells. A detailed study of the wavelength variation of threshold current density Jth (X)was made. A minimum of 366A.cnr2 was measured at 1018nm in mesa devices. A similar relation is found for ion-implanted devices but the minimum is increased to 535A.cm-2 by incomplete isolation. Gain calculations, including strain effects, are used to explain the Jth(X) variation. Implanted devices offer superior c.w. performance due to reduced thermal and ohmic resistances. The relative offset between the gain spectrum and cavity resonance was examined for c.w. operation. It was found that carrier thermal effects limit the output power rather than shifts in the offset. The bias voltage of MOCVD grown devices is as low as 1.7V and the threshold current is as low as 764A.cm-2. This is higher than for MBE grown devices because of growth thickness errors and non-optimal alignment of the gain spectrum and cavity mode. The uniformity in emission wavelength is ±1% over 80% of a 2 inch diameter wafer, offering suitability for very large uniform arrays.

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Typescript. / Bibliography: leaves [127]-130. / viii, 130 l illus., tables