The majority of the matter in the known universe is believed to be in the form of Dark Matter, and its widely accepted description is done by Cold Dark Matter (CDM). Nevertheless, its exact properties and composition are still unknown, and it is one of the most active areas of research in Cosmology. The use of Cold Dark Matter has been successful to describe the general behaviour of Dark Matter at large scales. However, it has encountered problems explaining phenomena at other regimes as on the scale of galaxy halos. Therefore, other models have been proposed over time which are able to retain the reasonable success of CDM on large scales and extent it to other regimes where CDM has problems to explain the observed data. One of such models is Scalar field Dark Matter (SFDM). Its properties allow it to produce similar results at large scales and solve the problems encountered at galactic scales. Nevertheless, the difficulty to obtain direct observations of Dark Matter makes it difficult to give a definitive comparison between the models. Therefore, it is important to study dark matter through different methods of analysis that would allow to increase the validity of its scope, and these methods are constantly being researched. In this work, a particular density profile known as Wave Dark Matter is implemented as a gravitational lens to study its behaviour in the cases where it produces strong lensing of light and of gravitational waves. Analytical functions for the description of a soliton core and a soliton core + NFW tail are applied to a sub-sample of 6 galaxies from The Sloan Lens ACS Survey to constrain the lensing parameters and their relation with the profile. Furthermore, by considering the soliton core to be the main contributor to the mass profile, this is implemented as a lens for the case of the wave approximation and further to describe the major effects of the lens on gravitational waves. It was found that the soliton core is too compact and dense in order to reproduce the observed values of the data for the lensed galaxies. However, adding a NFW tail alleviates the problem and reaches radii and masses within the range reported in the literature, although the size of the NFW tail cannot be properly constrained. Meanwhile for gravitational waves, it was found that the lensing parameters of the soliton core, if they are expected to describe a galaxy, will be such that they are more likely to be observed spaceborne gravitational wave detectors. In summary, therefore, a wave dark matter soliton in combination with a NFW tail is able to represent a galaxy, and the combination of ligh and gravitational waves should give new insight on the validity of the profile as a description of Dark Matter galactic haloes.

Minute-long gravitational-wave (GW) transients are currently a little-explored regime, mainly due to a lack of robust models. As searches for long-duration GW transients must rely on minimal assumptions about the signal properties, they are also sensitive to GWs emitted from unpredicted sources. The detection of such sources offers exciting and strong potential for new science. Because of the large parameter space covered, all-sky long-duration transient searches require model-independant processing and fast analysis techniques. For my PhD thesis, I integrated a set of fast cross-correlation routines in the spherical harmonic domain (SphRad) [50] into X-pipeline [95], a targeted GW search pipeline commonly used to search for GW counterparts of short and long duration GRBs & core-collapse supernovae. Spherical harmonic decomposition allows for the sky position dependancy of the coherent analysis to be isolated from the data [40] and cached for re-use, saving both time and processing units. Moreover, the spherical harmonic approach offers a fundamentally different view of the data, allowing for new possibilities for rejecting non-Gaussian background noise that could be mistaken for a GW signal. The combined search pipeline, X-SphRad, underwent a thorough internal review within the LIGO collaboration, which I led. The pipeline good functioning was assessed by rigorous tests including comparing a test data set with a standard sky grid-based analysis. I have developed a novel pixel clustering method that does not depend on the amplitude of potential signals. By using an edge detection algorithm, I quantify each pixel in the spectrogram by its similarity with its neighbours then extract features of sharply changing intensity (or ‘edge’). The method has shown promising results in preliminary tests. A simplified version of the algorithm was implemented in X-SphRad and large-scale testings are currently being processed.

The advent of gravitational wave (GW) astronomy has provided a new window through which to view and understand the Universe. To fully exploit the potential of GW astronomy, an understanding of all the potential electromagnetic counterparts to a gravitational wave detected source will help maximise the science returns. Here I present a study of the electromagnetic emission from relativistic jets that accompany the merger of binary neutron stars or black hole-neutron star systems. These counterparts provide a probe for the structure and dynamics of these relativistic outflows. Binary neutron star, or neutron star-black hole, mergers are thought to be the dominant progenitor of short gamma-ray bursts (GRBs). Here we investigate the possibility that there is a hidden population of low-Lorentz factor jets resulting in failed GRBs, on-axis orphan afterglows, and what kind of counterparts can be expected given a merger-jet population dominated by these failed-GRB jets. I find that for GW detected mergers, ∼ 80% of the population of on-axis events may result in a failed GRB afterglow. The afterglow of a failed GRB is characterised by the lack of any prompt emission; where the γ-rays are emitted within an optically thick region of the low-Lorentz factor (Γ) outflow and significant suppression via pair production and a high opacity results in the photons coupled to the pair plasma. This plasma will undergo adiabatic expansion, and the photons will decouple at the photospheric radius. The energy in the prompt photons, for a sufficiently low-Γ outflow, will have been significantly suppressed. GW detected mergers have a Malmquist bias towards on-axis events (i.e. the rotational axis of the system), where the peak of the probability distribution is an inclination ∼ 300. If the jets from these mergers have an intrinsic structure out to wider angles, then the majority of mergers will be accompanied by electromagnetic counterparts from these various jet structures. By making some simple assumptions about the energetic structure of a jet outside of a bright core region, the various temporal features that result from a given jet structure can be predicted. Where the population of merger jets is dominated by a single structure model, I show the expected fractions of optical counterparts brighter than m_AB = 21. On 17 August 2017, the Light Interferometer Gravitational Wave Observatory (LIGO) in collaboration with Virgo detected the merger of a binary neutron star system. Various electromagnetic counterparts were detected: the GRB 170817A by Fermi/GBM and INTEGRAL; an optical, blue to red, macro/kilo-nova from ∼ 1/2 day post merger to ∼ 5 − 10 days; and a brightening radio, and X-ray counterpart from ∼ 10 days. Optical detection of this counterpart at a magnitude ∼ 26 was made at ∼ 100 days post-merger. Analysis of this counterpart is consistent with the afterglow of a Gaussian structured jet viewed at the system inclination, ∼ 18 ± 80. If all short GRB jets have a similar jet structure, then the rates of orphan afterglows in deep drilling blind surveys e.g. the Large Synoptic Survey Telescope (LSST), will be higher than those expected from a homogeneous, or ‘top-hat’ jet, population. The rates for the various jet structures for orphan afterglows from mergers are discussed, showing that for a population of failed GRBs, or an intrinsic Gaussian structure, an excess in the orphan rate may be apparent. Understanding the dynamics and structure for the jets from black-hole systems born at the merger of a compact binary can help give clues as to the nature of jets from black holes on all scales. As an aside, I show empirically that regardless of black hole mass or system phenomenology, the relativistic jets from such systems share a universal scaling for the jet power and emitted γ-ray luminosity. This scaling could be due to the similar efficiencies of various processes, or alternatively, the scaling may be able to give insights into the emission and physical processes that are responsible for high-energy photons from these outflows. GW astronomy offers a probe of the most extreme relativistic outflows in the Universe, GRBs. The predicted electromagnetic counterparts from these outflows, in association with GW detections, provides a way to probe the Lorentz-factor distribution for merger-jets. Additionally, the phenomenological shape of the afterglows, at various inclinations, gives an indication of the intrinsic structure of these jets. An understanding of these dynamical and structural qualities can be used to constrain the parent population, merger rates, and binary evolution models for compact binary systems.

Stars are of fundamental importance to the entire field of astronomy. The conversion of elements and the distribution of energy throughout the lifetime of stars drives the evolution of the Universe. Despite this, we do not have a unified understanding of the formation process for all stars. This thesis attempts to move forward this understanding, by focussing on the question: How do the initial conditions of star-forming regions vary across environments, and do these influence the process of star formation? To investigate the initial conditions of star formation, regions on the verge of forming stars have to be first identified and analysed. These regions have to be untouched by the disruptive effects of stellar feedback, such that the natal conditions of the gas – e.g. kinematics and chemistry – are not destroyed. Quiescent regions that are expected to form low-mass stars have been well studied over the past few decades, and the general process of low-mass star formation is well understood. Only relatively recently, however, has a group of objects being identified as being potential hosts of these initial stages of high-mass star formation: Infrared Dark Clouds (IRDCs). The study of these objects is difficult, due to both their rarity and complexity. An end-to-end understanding of high-mass star formation is, therefore, much less developed compared to their lower mass counterparts. This thesis presents the study of a sample of IRDCs within the Disc and Centre of the Milky Way; two very different environments. Several key aspects of the star formation process within IRDCs from these environments are investigated. Firstly, a chemical signpost – the deuterium fraction of N2H+ – is used to identify the regions of dense and cold gas on the verge of forming high-mass stars within a quiescent Disc IRDC, which can be used to study the initial conditions for star formation. Omitting potential beam dilution effects, chemical modelling suggests that the cloud could have reached a global chemical equilibrium, and, if so, would also be dynamically old (survived for several free-fall times). This timescale, with estimates of the embedded stellar mass, is used to determine star formation rates and efficiencies. Secondly, the kinematic structures within two apparently similar Disc IRDCs are identified using dense gas tracers – C18O and N2H+. The properties of these structures appear to be very similar, hinting at a similar formation scenario for both clouds, or, potentially, that these may be inherent to the larger Disc IRDC population. The dynamics of these filaments also show that they may be merging, which would suggest a compressive mode of turbulence driving. These structures are then linked to the larger kinematic structures – identified using a lower density tracing molecule, 13CO – and found to show good coherence with the brightest, most extended structures. These are then placed in the context of the previously identified Galactic scale structures, and in doing so show that IRDCs could be the densest parts of the much larger arm or inter-arm filamentary structures. Thirdly, the level of star formation within the Galactic Centre is investigated on both global (∼ 100 pc) and local (∼ 1 pc) scales. On a global scale, the star formation rate has been determined from all the available observational star formation diagnostics – i.e. direct counting of young stellar objects and integrated light measurements – and found to be in agreement with previous studies; i.e. around one-to-two orders of magnitude lower than predicted by the star formation models. On individual cloud scales, the star formation efficiency per free-fall time is in better agreement with the model predictions. However, uncertainties on the properties of these regions, such as the mode of turbulence driving, limit the further verification or falsification of the star formation theories. Lastly, the investigation of the local scale star formation within the Galactic Centre highlighted a particular part of the parameter space as the most promising to further test the star formation theories. In light of this, high-spatial resolution ALMA observations have been taken of two Galactic Centre clouds within this regime. Early results show that they have a complex structure, similar to that seen within Disc IRDCs, containing both filamentary and core-like features. Investigation of the brightest, most compact core region shows that it contains a very rich chemistry, and, of particular interest, is the rigorous detection of the pre-biotic molecule formamide (NH2CHO). When placing the results of this thesis in the bigger context of star formation theory, they appear to show interesting implications for the initially posed question – what is the influence of environment on the process of star formation? It is found here that despite the very different cloud scale properties of these regions, the star formation efficiency per free-fall time is surprisingly similar. To investigate this, the properties of the individual sites of high-mass star formation, the high-mass star-forming cores, are compared. Interestingly, despite the different environmental conditions, several key properties of the cores, such as their size and mass distribution, are also found to be very similar. The similarity of high-mass core properties and star formation rate per free fall time implies that once a region has produced high-mass cores, the evolution of these cores towards star formation must be similar. The difference in the global/environmental properties of the gas must then be setting the total star formation rate within these regions, by limiting the number of cores that can form. In particular, the mode of turbulence driving may play a major role in governing the fraction of gas that can be converted into stars per free-fall time within these two environments.

Understanding the formation and evolution of our galaxy, the Milky Way, has been an ongoing process, which with the development of large-scale surveys has picked up considerable pace. Together with these new surveys, pipelines have been constructed which allow for the rapid and automatic processing of this wealth of new data. These codes are able to turn raw data files into tables of stellar parameters and chemical abundances in far less time than if they were analysed by hand. The results from these surveys open new windows on to the history of our galaxy and other disk galaxies. In this thesis, we present the development of a new pipeline, the STellAR Parameter AND Abundances pipeline (STARPANDA), which is able to rapidly derive stellar parameters, CNO abundances and other elemental abundances by utilising measurements of spectral features in both observed and synthetic spectra. We take the observed spectra, synthetic spectra and line lists employed by the APOGEE survey and produce new values for the stellar parameters, CNO abundances and Al abundances of the APOGEE stars. We then compare our results with those achieved by the APOGEE pipeline.

Stripped-envelope supernovae (SE-SNe) are a subset of core-collapse supernovae; the explosive death of a massive star. Their defining characteristic is the lack of promi- nent He and/or H envelope suggesting significant mass loss prior to explosion. Their progenitors may be high mass single stars (> 30 M⊙) or lower mass stars that are stripped via binary interaction. Since their discovery as a separate population in 1983, and until recently, the data on these objects steadily increased. SN discoveries have increased year on year since the early 2000s with the advent of targeted and untargeted surveys looking at the skies for transient objects. As a result, some of these surveys have amassed photometric and spectroscopic data on a large number of SE-SNe. The last few years has seen this data made available, dramatically increasing the number of objects with data. I present an investigation into the bulk properties of SE-SNe, using a large database accumulated from public sources, the Palomar Transient Factory, the Public ESO Spectroscopic Survey of Transient Objects, and my own observations. I begin the investigation by constructing and analysing the largest set of bolometric light curves of SE-SNe to date – 85 objects. The light curves are analysed to derive temporal characteristics and peak luminosity Lp, enabling the construction of a lumi- nosity function. Subsequently, the mass of 56Ni synthesized in the explosion, along with the ratio of ejecta mass to ejecta kinetic energy, are calculated. It is found that broad-lined SNe Ic (SNe Ic-BL) and gamma-ray burst SNe are the most luminous sub- types with a combined median Lp, in erg/s, of log10 (Lp)= 43.00 compared to 42.51 for SNe Ic, 42.50 for SNe Ib, and 42.36 for SNe IIb. It is also found that SNe Ic-BL synthesize approximately twice the amount of 56Ni compared with SNe Ic, Ib, and IIb, with median MNi = 0.34, 0.16, 0.14, and 0.11 M⊙, respectively. SNe Ic-BL, and to a lesser extent SNe Ic, typically rise quicker than SNe Ib/IIb; consequently, their light curves are not as broad. Next I examine the spectroscopic properties of these SNe using analytical methods. For He-rich SNe, the presence of H becomes the focus. The strength, velocity, and ratio between absorption and emission of H are measured, along with additional analysis of He I lines, in order to categorize the SNe. The He-poor SNe are ordered according to the number of absorption features N present in the spectra, which is a measure of the degree of line blending. The kinetic energy per unit mass Ek/Mej is strongly affected by mass at high velocity, and such situations principally occur when the outer density profile of the ejecta is shallow, leading to the blending of lines. Using the results, the existing SE-SN taxonomic scheme is adapted I then present the data and analysis of 19 SE-SNe observed since 2012. These SNe are analysed within the context of the earlier findings in this work, as well as exam- ining the ejecta mass distributions as derived from an analytical light curve model. The results support the assertion that SE-SNe reside in a parameter space which is still under-sampled as approximately 20 – 25 percent of these objects have properties that deviate significantly from that of the bulk population. The statistics of the ejecta mass distributions also provide evidence that these SNe arise from relatively low mass progenitors (< 25 M⊙) as the mean ejecta mass for all SN types is 2 – 4 M⊙. Furthermore, distribution of ejecta mass appears unimodal, which suggests that SE-SNe are preferentially arising from one channel; stars that undergo binary interaction. Understanding SE-SNe is important as their stripped pre-explosion progenitor stars are hot, making them sources of ionizing radiation. Their explosions influence their local environment by injecting energy, both radiative and kinetic, and seeding the ISM with the ashes of nucleosynthesis. Finally, they are a source of neutron stars and stellar mass black holes in the universe, which gives rise to other astrophysical events such as X-ray binaries, pulsars, and strong gravitational wave events.

No description available.

There are a host of open questions in the study of massive clusters relating to cluster formation and evolution. Understanding these processes can be useful in studying their host galaxies and how they have evolved. The formation of globular clusters is also a well debated topic, which is yet undecided and requires many more observations to constrain the theories. Here I present the work carried out during my PhD, with the goal of furthering our understanding of cluster formation and evolution using observations of massive clusters of various ages. Firstly, HST WFC3 data of the well studied face-on spiral galaxy M 83, combined with an existing cluster catalogue, was used to investigate the timescale by which young massive clusters become free of gas. This has implications for globular cluster formation theories, in addition to the survival of clusters at young ages. The presence of Wolf-Rayet stars was also investigated within the clusters and the unreliability of Hα photometry in young cluster age and mass fitting was explored. Secondly, the cluster population of NGC 1566 was used to investigate the cluster mass function and disruption in the galaxy. Whether the mass function has a truncation in the form of a Schechter function and whether disruption is environmentally and mass dependent are two questions that still persist in this area. For NGC 1566 I find that the mass function does show a truncation and using the observed luminosity function in conjunction with models, that an underlying Schechter mass function fits the observations well. Additionally the galaxy shows evidence for environmentally dependent disruption as the average timescale for the disruption of a 10⁴ msun cluster varies with galactocentric radius. A difference in age in radial bins is also indicated in a colour change found with U-B between consecutive bins, that shows more young clusters towards the centre of the galaxy and fewer at the edge. Finally, low resolution FORS2 spectra of two intermediate age massive clusters in the SMC (Lindsay 1 and Kron 3, 6-8 Gyr old) were used to look for the signatures of multiple populations (MPs), as observed in ancient GCs. The main driver behind this project was to investigate the possibility that YMCs can be considered young GCs and used to constrain their formation, and also to explore the role cluster age has in determining the presence of MPs. A subpopulation of N-enriched stars was found in each cluster, consistent with the presence of MPs. This indicates that MPs are not limited to ancient GCs and their formation mechanism must be operating until a redshift of at least 0.65, much later than the peak of GC formation at ≈ 3. It hints at a common formation mechanism between massive clusters of varying ages, including GCs, and suggests that YMCs can be used to constrain GC formation. The publications from these projects have contributed mainly to constraining GC formation theories and provides evidence for commonality in the formation mechanism used to produce GCs and YMCs alike.

Gravitational waves are an important prediction of Einstein's General theory of Relativity. Derived as a solution to the Einstein field equations, they are predicted to be produced in systems where there is an asymmetric acceleration of matter, and exist as a time varying quadrupolar distortion in spacetime. Due to the rich variety of scientifically interesting astrophysical sources predicted to be producing gravitational radiation, there is significant international effort directed towards their detection. A large network of ground based interferometric detectors is in operation, with upgrades to increase sensitivity already in progress. They operate on the principle of measuring the time varying displacement in the interferometer path length an incident gravitational wave will induce. However, the predicted amplitude of gravitational waves requires the measurement to be made over several kilometres with a displacement sensitivity of less than 10^-18m/sqrt(Hz). Ground based detectors operate in the ~10-10000 Hz region, and are fundamentally limited at the low frequency end by the noisy gravitational environment of the Earth. To enable detection of low frequency sources, LISA - the Laser Interferometer Space Antenna - is a planned mission to place an interferometric gravitational wave detector in space, sensitive to gravitational waves in the 0.1-1000 mHz region. Consisting of a triangular constellation of three spacecraft, LISA will aim to detect gravitational waves by monitoring the fluctuation in the separation between free-falling test masses over a baseline of 5 million kilometres with an accuracy of around 10pm/sqrt(Hz). To demonstrate that LISA technology, such as the ability to place test masses into a suitably quiet gravitational free-fall, is viable, a precursor mission - LISA Pathfinder - will launch in the next few years. LISA Pathfinder will monitor the relative displacement between two free-falling inertial test masses using an interferometer, with the goal of verifying that the required quality of free-fall is achievable in LISA. This work presented in this thesis relates to the development of interferometry for LISA Pathfinder and LISA, the construction of the LISA Pathfinder flight model interferometer, and initial work on developing the interferometer for LISA. The interferometers required for LISA and LISA Pathfinder must be constructed to be durable enough to survive launch and stable enough to measure displacements of a few picometres at frequencies down to a few mHz. Further, to help minimise noise from sources such as residual jitter of the test masses, the beams which probe the test masses must be aligned to within ±25 micrometers of the nominal reflection point. Using ultra low expansion substrates like Zerodur, and attaching optical components with hydroxide catalysis bonding offers one solution which can provide the durability and stability required. To achieve the accuracy of beam positioning, a system which allows measurement of absolute propagation direction of a laser beam was developed. Combined with a coordinate measuring machine, this allows the absolute position of a mm-scale laser beam to be measured with an accuracy of around ±5 micrometers and ±20 microradians. This system can operate in two modes: first as a measurement system allowing measurement of an existing beam; and secondly as a target, where it can be positioned to a desired theoretical (such as the nominal reflection point of a test mass) and a beam can be aligned onto it. Combined with a method of precision adjusting optical components at the sub-micron and microradian level prior to hydroxide catalysis bonding, it enables absolute alignment of ultra-stable interferometers to micron level. Using these techniques, the flight model interferometer for LISA Pathfinder was successfully constructed to meet the alignment and performance requirements. The control system that will maintain the test masses in near free-fall requires a very accurate measure of the attitude of the test masses. This measurement will be provided by the interferometer using differential wavefront sensing (DWS). The flight model interferometer was calibrated to establish the coupling factors between the DWS read-out and the attitude of the test mass to ensure maximum performance of the control system. Building upon the experience gained in developing and building the LISA Pathfinder interferometer, a prototype of the LISA optical bench is in development. The LISA interferometer is significantly more complicated than that of LISA Pathfinder. Some of its features include: imaging systems to minimise coupling of beam tilt to displacement noise; a precision beam expander to generate a beam appropriate for the telescope; a redundant fibre injector system, creating two beams collinear to within a few microns and 10-20 microradians; and polarisation optics for beam steering. The development and current state of the design for the prototype optical bench is presented, along with an overview of its features.

In 1916 Einstein published his General Theory of Relativity, from which the existence of gravitational waves was predicted. Gravitational waves are considered to be ripples or fluctuations in the curvature of space-time, propagating isotropically from their source at the speed of light. However, due to the weak nature of gravity, observing this phenomenon presents a great challenge to the scientific community. Small deviations in the apparent positions of stellar objects were measured by Eddington during a solar eclipse in 1919, which confirmed the curvature of space-time and its effect on light, and there have since been many astronomical observations of gravitational lenses. In 1993 Hulse and Taylor were awarded the Nobel Prize in Physics for their observations of a pulsar in a binary system, providing strong evidence for energy loss by emission of gravitational waves. However, the quest for a direct detection of gravitational waves is ongoing through the development of ever more sensitive technology. The development of laser interferometry, based on Michelson topologies, pro- vides the most encouraging route to observing gravitational radiation. There is currently a global network of first generation interferometric gravitational wave detectors in operation, including GEO600 (UK/Germany), Virgo (Italy/France) and TAMA (Japan) as well as several second generation detectors under construction such as Advanced LIGO (USA) and LIGO-Australia (Australia). In the coming years GEO600 will also undergo a series of small sequential upgrades to GEO-HF, while Virgo aims to become an order of magnitude more sensitive across the entire frequency band, as Advanced Virgo. The Institute for Gravitational Research (IGR) at the University of Glasgow has for many years been in strong collaboration with the Albert Einstein Institute in Hanover and Golm, the University of Hanover, the University of Cardiff and the University of Birmingham. The Glasgow group have been involved with developments on GEO600 since its initial construction in 1995, from which a lot of technology has been subsequently adopted for use in other large baseline detectors. There is a 10m prototype interferometer housed in the JIF laboratory at Glasgow, which is utilised for testing new technology and optical configurations of interest to this and the wider collaboration. The research contained in this thesis has been carried out on the Glasgow prototype to investigate novel technology of potential importance to future generations of gravitational wave detectors. In Chapter 1 the history of gravitational radiation is discussed, along with a summary of Einstein’s General Theory of Relativity to reveal the nature of gravitational radiation production. From this analysis several potential sources of astronomical origin are detailed for which the design of ground based detectors are optimised. Various interferometric solutions for detecting gravitational waves are described in Chapter 2, beginning with the most fundamental Michelson topology and thereupon key enhancements, such as Fabry-Perot cavities, power recycling and signal recycling are outlined. The Pound-Drever-Hall scheme used to sense and control the relative distances between each optical component is detailed, including modifications to this technique for controlling significantly more complex systems with many optical elements. The most important attribute in the overall design of an interferometric gravitational wave detector is the total noise limit to the sensitivity, which is comprised of both technical noise and fundamental noise. A summary is provided of the seismic, thermal, and laser noise contributing to technical noise as well as the fundamental quantum noise, consisting of photon shot noise and radiation pressure noise. From this discussion, the author introduces the current global network, and proposed future generations of ground-based detectors intended to open a new field of gravitational wave astronomy. In all proposed upgrades and future detectors the input power must be increased to improve detector sensitivity. Two experiments were designed, con- structed and completed at the Glasgow prototype interferometer related to separate issues of concern for high power regimes. In the first experiment, one of the arms of the Glasgow prototype was commissioned as an all-reflective optical cavity, whereby the partially transmissive input mirror was replaced with a three-port diffraction grating mounted on the bottom stage of a triple pendulum. This investigation was designed to characterise the performance of the grating compared to the conventional input mirror of a Fabry-Perot cavity, whilst revealing issues related to the dynamics of suspended grating input couplers on the control signals. The realisation of grating devices for use in interferometric systems would open a pathway to mitigating the otherwise limiting thermal noise associated to the mirror coatings. The other arm of the Glasgow prototype was chosen to investigate the modified dynamic behaviour of suspended cavity mirrors when signifiant radiation pressure forces are incident. The experiment involved replacing one of the suspended cavity mirrors with a light-weight counterpart designed specifically to increase the overall sensitivity to radiation pressure. By probing the system response for different cavity detunings, it was possible to observe and char- acterise the opto-mechanical resonance, commonly termed an optical spring, which induces optical rigidity at lower frequencies and enhanced sensitivity around the resonant feature. Although optical rigidity suppresses the system response, which is otherwise undesired within gravitational wave detectors, it does however enable systems, which under the right conditions can be self-locking, i.e. the mirror control turned off. Furthermore, the enhanced detector sensitivity at the optical spring frequency can be optimised for different frequencies of interest, and could potentially be used to beat the limit imposed by the Heisenberg Uncertainty Principle for independent cavity mirrors. Together, these experiments may provide information useful to the design of future interferometric gravitational wave detectors.