The work in this thesis is in the fields of profilometry and Fourier transform spectrometry. Deformation measurement of diffuse objects by phase stepping was achieved by thermal frequency drift in a HeNe laser. The system was easy to construct, required no specialised components, was immune to the effects of piezo-actuator hysteresis, and was capable of producing phase maps in which noise was less than 1/20λ. A method was proposed for measuring absolute surface profile by scanning frequency over the range of a white light source. The coincidence technique of coherence radar was used to measure surface profiles in three dimensions to micron accuracy. Spatial techniques were developed to process the large data set quickly and efficiently. A novel Fourier transform spectrometer was developed to measure the spectrum of narrowband light sources. Heterodyning techniques gave a resolution of 0.01nm with a free spectral range of =2.5nm. The Sagnac common path design afforded immunity to vibration. The mode structure and mode hopping characteristics of a typical laser diode were measured as a function of diode injection current. An improved Fourier transform spectrometer was developed. Based on a Michelson interferometer. The instrument could resolve to 0.013nm over a =3nm free spectral range. Instrument operation was simplified and functionality was extended to non point sources.

Experimental techniques for measuring fluorescence lifetimes were evaluated for the purpose of studying the fluorescence quenching of the biologically important dye ethidium. A synchronously pumped cavity dumped dye laser was used to produce stable high repetition rate picosecond pulses for sample excitation. A system was established for recording nanosecond decay profiles by time correlated single photon counting. A careful investigation of the factors which contribute to the instrumental time jitter enabled an overall impulse response of 600 ps to be achieved. Software was developed for analysing fluorescence decay profiles by the method of convolution and curve fitting and its capability for accurately resolving multiple exponential components was evaluated using simulated data. Some improvement in accuracy was obtained by modifying the Poisson weights used in the curve fitting routine to allow for non-statistical errors, caused primarily by the wavelength dependence of the time response of the single photon counting photomultiplier. Fluorescence polarization effects are discussed. The rotational lifetime of Rhodamine 6G in ethylene glycol was determined by measuring the fluorescence polarization anisotropy decay and the Debye-Stokes-Einstein theory reaffirmed for small molecules at moderate viscosities. The torsional rigidity of DNA can be determined by measuring the depolarization of fluorescence of tightly bound (intercalated) ethidium, and this was not observed to change appreciably when the antitumour drug amsacrine also binds to the DNA. The fluorescence quenching of DNA intercalated ethidium by anticancer drugs was studied by accurately resolving the fluorescence decay profiles into exponential components. The lifetimes and proportions are interpreted in terms of current theories for drug binding and fluorescence quenching mechanisms. The fluorescence quenching behaviour by the antitumour drug amsacrine is consistent with a previously proposed electron transfer mechanism.

Light and atoms couple together via the electromagnetic interaction. The simplest form of this interaction is the electric dipole interaction, and in its quantised form it provides a useful starting point for the investigation of quantum effects in optics. Two examples of quantum noise manipulation of the light field due to interaction with atoms will be presented, as well as an analysis of a simple model for laser cooling of trapped atoms. The first example of quantum noise manipulation is the investigation of a quantum non-demolition measurement scheme based on a three-level atomic system in the ladder configuration. An effective two-level model of the atomic system is used, which enables the inclusion of spontaneous emission noise from the upper atomic level. The system is found to perform well, when detuned far from resonance. The second example is the treatment of squeezing in the intensity difference between two modes coupled by a three-level atomic system in the ladder configuration. The noise correlations are similar to those occurring in the optical parametric oscillator, and give rise to good squeezing when the system is well detuned from the intermediate level. The simple model of laser cooling consists of a single two-level atom with quantised centre-of-mass motion constrained to move in a one-dimensional harmonic potential while interacting with a single-mode classical travelling light field. It is shown that there is an analogy between this model and the Jaynes-Cummings model. This gives rise to interesting coherent effects including quantum collapses and revivals in the atomic inversion. Sideband cooling occurs for this model when the light field is tuned to the atom's first lower vibrational sideband. The strong sideband and Lamb-Dicke perturbation regimes are defined. Analytic results have previously been obtained for the latter regime, but we carry out a numerical investigation of the steady state and time evolution behaviour in the former regime. Differences in the behaviour in the two regimes are discussed. Finally the possibility of observing quantum jumps between trap levels is discussed.

This thesis is concerned with the generation of picosecond pulses and their propagation through both resonant and non-resonant media. This was achieved by constructing a passively modelocked Erbium doped fibre laser (EDFL) which was used to study pulse propagation through sections of standard communications grade optical fibre, dispersion shifted optical fibre, and also through an Erbium doped fibre amplifier (EDFA) module. The EDFL produced a train of ˜2 psec pulses at 4 MHz, tunable over the erbium gain band ( 1520 - 1570 nm). The laser was constructed from commercially available components and had the property of stability combined with low pump power requirements to produce ˜50 Watt peak power pulses. The laser cavity geometry included a nonlinear optical loop mirror, which has the property of efficiently switching high peak power pulses, and allowed pulsed operation without the aid of any high-speed electronics. An EDFA module of identical geometry to that used in the laser was also constructed, and this was probed using the pulses from the EDFL. The traditional temporal and spectral measurements were found to be inadequate to allow a complete description of the pulse amplification process to be developed. To overcome this problem the technique of frequency resolved optical gating (FROG) was applied for the first time to optical fibre research, and allowed an indirect measurement of the electric field of the pulse. This complete description of the pulse was used in a numerical model to describe pulse propagation in an optical fibre. Fundamental propagation terms in the model were treated as free parameters in a minimisation scheme, which could be determined for a fibre under examination. This technique was shown to be accurate when used to examine pulse propagation through both standard and dispersion shifted optical fibre. A comprehensive numerical model was developed for the EDFA, and it was apparent from this model that a pulse propagating through an optimised EDFA encounters an atomic inversion distribution which is a strong function of distance along the amplifying fibre. It was also shown from the experimental results that the EDFA exhibited resonant dispersion, which is characteristic for propagation through an atomic medium on resonance.

An investigation has been carried out into the operation of a mode-locked argon laser at a wavelength of 514.5 nm and a repetition rate of 76.8 MHz. The characteristics of the pulses from the laser have been found to depend on the intra-cavity power level in the laser, and at average intra-cavity power levels exceeding 4 W, the pulses from the laser have a duration of typically 35 psec accompanied by a characteristic double-peaked spectrum with a spectral width of 13 GHz These pulse durations are approximately three times shorter than expected based on the inhomogeneously broadened transition bandwidth of 4 GHz. The dependence of the pulse characteristics on the intra-cavity power level has been explained by a model of pulse propagation where the coherent coupling between the pulse and the atomic polarisation in the laser gain medium is included. Detailed examination of the pulse structure reveals the presence of afterpulses that have a typical intensity two orders of magnitude lower than the main pulse. These afterpulses are interpreted as ringing arising from coherent Rabi-type oscillation of the atomic polarisation associated with the circulating pulse in the laser. Numerical simulations of the mode-locked laser have also been developed based on the fully coherent Maxwell-Bloch equations, and the results from the simulations reproduce well the experimentally observed variation in pulse characteristics. Based on results from the simulations, the short pulses observed at high intra-cavity powers are interpreted as the superfluorescent π –pulse solutions predicted in the long distant limit of pulse propagation in a swept-gain amplifying medium. The laser operation has also been studied in a mode-locked cavity dumped configuration. In this case the combination of the coherent mode-locking processes described above with the cavity dumped operation at a repetition rate of 3.8 MHz results in the observation of stable pulses with peak power of 1.6 kW.

The development of a mobility spectrometer which yields a complete spectrum every 25 seconds is described. The spectrometer uses a Differential Gerdien Chamber of the First Order with 8 collecting electrodes, giving a set of 8 "electrode charges" corresponding to each observed spectrum. A Least Squares iteration is used to fit the parameters of a function which describes the complete mobility spectrum. The spectrum function's parameters can be fitted reliably with standard deviations of 3% or better. The spectrometer was used for observations of temporal variations in the atmospheric ion mobility spectrum at Auckland. These show a clear diurnal variation, and demonstrate that the spectrum can change significantly in an interval of 100 seconds. Atmospheric polar conductivities calculated from the mobility spectrum (which agreed well with independently measured conductivities) indicate that large ions can contribute as much as 40% of the total conductivity.

The technique of quantum trajectories (stochastic Schrödinger equations or Monte Carlo wave functions) for open systems is generalized to the non-Markovian regime. I consider a microscopic model of an open system consisting of a boson field coupled linearly (with an excitation preserving coupling) to a localized system. The model allows for a field with an arbitrary dispersion relation and an arbitrary mode-dependent coupling to the system. The trajectories are formulated as continuous measurements of the output field from the system. For a general dispersive field these measurements must be distributed in space for this formulation to be possible. The result of this formulation is a non-Markovian equation for the system conditioned on the measurements. A method of numerically simulating this equation has been determined and implemented in some test cases. Numerical simulation is possible if one can introduce a finite memory time for the evolution of the reduced system. As an illustration, the method is applied to the spectral detection of the emission from a driven two-level atom and also to an atom radiating into an electromagnetic field where the free space modes of the electromagnetic field are altered by the presence of a cavity. In both cases the non-Markovian behaviour arises from the uncertainty in the time of emission of a photon that is later detected (or reabsorbed), although, in the second case, the non-Markovian behaviour is intrinsic to the system environment coupling whereas, in the spectral detection case, it is a consequence of the choice of measurement process. The generalization of the techniques of quantum trajectories to the non-Markovian regime promises to make a range of open system problems where the Born-Markov approximation is invalid tractable to numerical simulation. / Whole document restricted, but available by request, use the feedback form to request access.

This thesis deals with the electromagnetic radiation that is reflected from and emitted by a clear or cloudy terrestrial atmosphere. Calculations are performed in order to estimate the radiation exitant to space in the visible, the near visible, and the two infrared windows at approximately 4 μm and 11 μm. The NOAA-9 satellite Advanced Very High Resolution Radiometer (AVHRR/2) is used as the data acquisition system. The satellite AVHRR system is described, as well as future TIROSN satellites. The pre-launch calibration of the radiometer is described in some detail. Post-launch calibration is examined using a reflectance difference method. The radiometer gains are shown to have changed by more than 20% from their pre-launch values. A LOWTRAN based atmospheric model suitable for New Zealand is developed to provide cloud free transmission values. Atmospheric scattering is shown to contribute negligibly to visible cloud measurements (for 8-bit radiometer resolution). The Channels 1 to 3 terrestrial reflectance is averaged from more than two years of satellite data. Sea-surface state is examined as a function of windspeed. A method of extracting surface temperature in rugged terrain is developed. Dual temperature measurements at 10.8 and 11.8 μm are used to estimate surface air temperature. The transfer of radiation in a single layer cloud is calculated as a function of cloud thickness, observation/illumination geometry and the effective radius of the cloud drop-distribution. The variation in drop-size is contained in an ensemble of modified-Gamma distributions whose effective radius varies from 1 to 30 μm with a fixed dispersion of 0.25. A technique is established which allows effective cloud radius to be estimated from 3.7 μm AVHRR/2 imagery. The radiation values at 0.65 μm and 11.8 μm are used to correct the 3.7 μm reflectance for variation in cloud thickness and temperature respectively. The procedure is limited to warm clouds of moderate optical depth. In addition, the inversion process generates values of cloud top height and temperature, cloud depth and column liquid water content. The method is used to observe the development of orographic cloud formed over the southern half of the North Island of New Zealand. The inversion results for this type of cloud are in agreement with aircraft measurements carried out by the New Zealand Meteorological Service and are well fitted by a simple drop-growth model.

The results of observational studies of very high energy (VHE) and ultra high energy (UHE) gamma ray emission, by various astrophysical objects, made from 1988 to 1990 with the JANZOS Cerenkov facility are presented. The active galaxy Cen A and the Galactic X-ray binary systems Vela X-1, Cen X-3, and Cir X-1 were monitored for VHE gamma ray emission above 1 TeV. No evidence was found for persistent or episodic emission from any of these objects. Upper limits on the VHE fluxes above 1 TeV of 2.1×10-11, 2.7×10-11, 3.6×10-11 and 3.5×10-11 cm-2 s-1 respectively were obtained for these objects. These limits are consistent with previous observations made by other groups. Various objects in the Magellanic Clouds were monitored for UHE gamma ray emission using the Cerenkov technique at large zenith angles. This technique has been found to be more sensitive at UHE energies -100 TeV than the conventional air shower technique. During 1990 the equipment was modified to allow a sky coverage of 7°×23° at large zenith angles. This enabled most of the extent of the Large Magellanic Cloud to be surveyed at UHE energies. An examination of the UHE database yielded no evidence for persistent emission from SN1987A and selected X-ray pulsars in the Magellanic Clouds. Upper limits on the UHE fluxes (in cm-2s-1) above the given threshold energies were obtained as follows: SMC X-1, 2.4×10-13 (>30 TeV); SN1987A, 2.3×10-13 (>65 TeV); PSR0540-693, 2.3×10-13(>65 TeV); LMC Trans, 1.5×10-13(>130 TeV); LMC X-4, 1.3×l0-l3 (>140 TeV). Evidence was found for two episodes of pulsed gamma ray emission above 65 TeV from SN1987A. On the nights of May 28 and June 23, 1990, a periodicity search using the Rayleigh test showed significant power at 18.356 ms. This is near a periodicity reported at optical wavelengths in September, 1990. The chance probability for the individual period was about 10-6 on each of the two nights. Excess events of the order of 1σ were also seen on these nights. The overall chance probability, allowing for all degrees of freedom, was found to be 0.1%. Evidence was also found for a single episode of gamma ray emission above 140 TeV from LMC X-4 on May 27, 1990. Excess events were seen with a statistical significance of 2.4 σ. A periodicity test showed maximum Rayleigh power at 13.488 s on this night. The chance probability for the individual period was 8×10-3 and the overall chance probability was found to be 0.5%. Adopting a recent estimate of the pulsar population in the Large Magellanic Cloud, an upper bound of 3×1034 erg s-1 on the luminosity of an average pulsar, at energies >65 TeV, was obtained.

Building on Kibblewhite's long term investigations of the nonlinear wave-wave interactions and the infrasonic ocean noise and the microseisms these induce, this thesis further explores the physical nature of these processes. The classical description of this interaction, which takes into account only the homogeneous component of the induced field, has been extended to include the inhomogeneous component. A complete expression for the wave induced noise spectrum is established following a geometrical analysis of the dispersion relations among interacting waves. The relative importance of these two components and their directivity properties are also calculated and discussed. It is shown that while at observation points deeper than 500 meters the effects of the inhomogeneous component can be regarded as negligible, it can cause an increase of noise level of up to 40 dB in the region near the surface of the sea. Furthermore, in contrast to the nearly omni-directional distribution of the homogeneous component of the induced acoustic field, there is a tendency for the energy associated with the inhomogeneous component to focus in the wind direction. Based upon a multilayer analysis of a visco-elastic geoacoustic model, Green's functions and the spectral transfer functions relating the surface source pressure field to the underwater noise and microseism fields are derived for both near and far field cases. A 3-dimensional presentation defined on the dispersion plane (frequency and horizontal wave number) is introduced to describe the sea bottom reflection-loss and, Green's functions, and is extended to include the inhomogeneous region for the first time. The characteristics of this 3-D presentation are explained in terms of the geoacoustic parameters. The influence of the interaction of multiple seas (and swell) on the induced acoustic field are also discussed in this thesis. All these effects are considered in the calculation of the synthetic spectra of both the noise and microseism field. When compared with measured data excellent agreement is found between the theoretical and experimental results, which provides further confirmation that the nonlinear interaction is the most important source of the infrasonic ocean noise, as well as confirming the basic validity of the procedure introduced by Kibblewhite and Ewans to derive the ocean noise spectra from microseism records.