Fabrication of a single mode laser by UV-writing in neodymium doped silica-on-silicon

We describe the fabrication of a waveguide laser by UV-writing in neodymium doped silica-on-silicon. The substrate is fabricated by Flame Hydrolysis Deposition and solution doping techniques. Lasing at 1048-1056nm was observed with a slope efficiency of 33% and threshold of 4mW for the transition. Lasing was also observed at 1356nm

The design and evaluation of Link: a CAL system designed to address psychology students' misconceptions about correlation

This thesis describes the design, development and evaluation of Link, a computerassisted learning program for correlation, which is targeted at psychology students in higher education. Computer technology is being increasingly used on statistics courses, suggesting that computer-assisted learning programs on statistical concepts will be increasingly used by students in higher education. To inform the design of Link, an empirical study was conducted to investigate students’ difficulties with correlation. It was found that psychology students held misconceptions relating to negative correlations, the strength of correlations and that they infer causality. The design of Link was also informed by research-based principles of learning, research and developments in computer-assisted learning and a review of computer-assisted learning programs that cover correlation. A formative evaluation study involving eighteen psychology students found that having used the program, students’ general understanding of correlation was significantly improved. Unlike previously existing computer-assisted learning programs that were reviewed, Link makes use of data from two authentic studies in psychology. In addition. Link provides learner activities specifically designed to address students’ misconceptions about correlation. A summative evaluation study of Link involving fifty psychology students was undertaken to assess the effect on students’ understanding of correlation. The findings of this evaluation provided further qualitative data on students’ misconceptions. Moreover, it was found that the use of Link significantly contributed to students’ general understanding of correlation

Coupling ratio tuning of direct UV-written X-couplers for cascaded power splitters in WDM networks

We present a study of low polarisation sensitivity 2 degrees X-couplers with 20% coupling ratio tuning via refractive index asymmetry, attaining 50:50 power splitting at 1550nm. The device has less than 5% coupling ratio variation over 30nm in the C-band and <0.7dB polarisation dependent loss

Direct optical observation of walls and disclination effects in active photonic devices

Liquid crystal tunable Bragg Gratings defined in planar substrates via a laser patterning technique exhibit complex wavelength tuning. This tuning displays threshold points and hysteresis. These tuning features are shown to be a manifestation of physical processes occurring in the confined geometry of our tunable devices. Such physical processes include the formation and removal of line disclinations and an associated wall. We discuss the effect of walls in the liquid crystal with regards to voltage tuning characteristics and whether they may allow faster wavelength tuning

Are we teaching our students what they need to know about ageing? Results from the National Survey of Undergraduate Teaching in Ageing and Geriatric Medicine

Introduction - Learning about ageing and the appropriate management of older patients is important for all doctors. This survey set out to evaluate what medical undergraduates in the UK are taught about ageing and geriatric medicine and how this teaching is delivered. Methods – An electronic questionnaire was developed and sent to the 28/31 UK medical schools which agreed to participate. Results – Full responses were received from 17 schools. 8/21 learning objectives were recorded as taught, and none were examined, across every school surveyed. Elder abuse and terminology and classification of health were taught in only 8/17 and 2/17 schools respectively. Pressure ulcers were taught about in 14/17 schools but taught formally in only 7 of these and examined in only 9. With regard to bio- and socio- gerontology, only 9/17 schools reported teaching in social ageing, 7/17 in cellular ageing and 9/17 in the physiology of ageing. Discussion – Even allowing for the suboptimal response rate, this study presents significant cause for concern with UK undergraduate education related to ageing. The failure to teach comprehensively on elder abuse and pressure sores, in particular, may be significantly to the detriment of older patients

Second-harmonic generation in a direct-bonded periodically-poled-LiNbO₃ buried waveguide

We report the fabrication of a 12µm-thick periodically poled LiNbO3 planar waveguide buried in LiTaO3 by direct bonding of precision-polished surfaces. Frequency doubling of the 1064nm output of a cw diode-pumped Nd:YAG laser was performed in a 5.5mm-long device with a 6.50µm-period grating at an elevated temperature of 174°C. The resultant green second-harmonic output exhibited fundamental-spatial-mode characteristics at a 4.3% /W conversion efficiency

A picosecond optical parametric oscillator synchronously pumped by an amplified gain-switched laser diode

We demonstrate a picosecond optical parametric oscillator synchronously pumped by a fiber-amplified gain-switched laser diode. Up to 7.3W at 1.54µm and 3.1W at 3.4µm is obtained at pulse repetition rates between 114.8 and 918.4MHz

Ultra-wide planar Bragg grating detuning and 2D channel waveguide integration through direct grating writing

We present a technique for defining 20 channel waveguide structures with internal Bragg gratings in photosensitive germanosilica-on-silicon using two interfering focussed UV beams. Grating detuning across the S, C, and L bands is demonstrated

First demonstration of direct UV written Bragg gratings in collapsed fibre planar samples

First demonstration of planar Bragg gratings UV written into collapsed fibre planar samples with >200µm cladding thickness is presented. Multiple gratings were written across the sample profile to accurately determine core layer flatness and uniformity

Novel active waveguide devices in direct-bonded structures

This thesis describes a series of experimental studies on the use of direct bonding for optical waveguide fabrication. The direct bonding technique involves contacting two ultra-clean polished surfaces to form an adhesive-free vacuum-tight bond. Optical materials bonded in this way can be formed into waveguide devices, and this work extends direct bonding to include periodically poled materials and a new solid-state ion-exchange process.  The first result of this work describes the fabrication of a 5.5-mm-long, 12-µm-thick periodically poled LiNbO3 planar waveguide buried in LiTaO3. Frequency doubling experiments performed with this device demonstrate a conversion efficiency of 4.3 %W-1, a value 40% greater than that calculated for an optimised bulk device of similar length.Also demonstrated is a photorefractive iron-doped LiNbO3 waveguide buried in non-photorefractive magnesium-doped LiNbO3. In optical limiting experiments this device demonstrates a change in optical density of 2 and photorefractive response time of 5 milliseconds, representing 20 times greater optical limiting and 60 times faster operational speed than the bulk material.  K+-Na+ ion-exchange between direct-bonded glass layers is studied and used as a novel solid-state technique for waveguide fabrication. This process is also developed to incorporate direct-UV-written channel waveguides in an ion-exchanged buried photosensitive glass layer. Finally, operation of a single-mode channel waveguide laser in neodymium-doped photosensitive SGBN glass (based on a composition of silica, germania, boron, and sodium) is demonstrated, with propagation losses of &lt; 0.3 dB cm-1 and milliwatt-order lasing thresholds. <br/