Spectrally-controlled, gain-switched operation of InGaN diode laser

Self-seeded, gain-switched operation of an InGaN multi-quantum-well diode laser is reported for the first time. Narrow-line, wavelength-tunable, picosecond pulses have been generated from a standard, uncoated diode laser with an external feedback.

Gain switching of an external cavity grating-coupled surface emitting laser with wide tunability

The gain-switched, single frequency operation of an external cavity grating-coupled surface emitting laser with a wavelength tuning range of 100 nm was presented. The light in the grating section was coupled out of the laser at a specific angle to the surface of the device. Analysis showed that within the driving current range, lasing in the device only occurred when the external cavity was properly aligned.

Is breast best? Perceptions of infant feeding

This study explored the reasons why young women from low income areas are among those least likely to breastfeed. Focus groups were conducted with 15 health professionals and 11 young, first time mothers were interviewed. Health professionals participating believed that white communities endorsed bottle feeding while Pakistani and Bangladeshi communities, although they accepted breastfeeding more readily, were likely to give prelacteal feeds of non-breast milk and to delay weaning. The interviews with mothers revealed a belief that 'breast is best' but factors intervened in a detrimental way resulting in the decision not to breastfeed or in early cessation. Participating mothers expected breastfeeding to be painful and were preoccupied with feeding and weight gain. The desire to have 'fat bonnie babies' demonstrated the mothers' moral attempts to be perceived as 'good mothers' although their actions went against the knowledge that 'breast is best'. Recommendations include educating health professionals about subcultures in their communities and reversing the misconception that breast milk is insufficient for a baby's healthy development. Promoting breastfeeding must include the crucial message that breast milk contains all the nourishment a baby needs.

Characteristics of Brillouin gain based distributed temperature sensors

A Brillouin-gain based distributed temperature sensor has been investigated experimentally and theoretically. The relation between Brillouin gain, input probe power and sensing length have been studied. The study shows that there is an optimum probe power providing a maximum Brillouin gain signal for a given sensing length.

22-km distributed temperature sensor using Brillouin gain in an optical fiber

We describe an experimental distributed temperature sensor that uses the temperature dependence of the Brillouin frequency shift. When a 22.2-km sensing length is used, we have observed a temperature resolution of 1°C and have obtained a spatial resolution of 10 m.

Multi-wavelength erbium/Raman gain based random distributed feedback fiber laser

A multiwavelength generation in a random distributed feedback fiber laser based on hybrid Raman and erbium gain and a Lyot all-fiber spectral filter is demonstrated for the first time. The use of erbium-doped fiber allows a multi-wavelength generation to be achieved at lower pump powers in comparison with random fiber lasers based on Raman gain only. The operating bandwidth and flatness of power distribution between different lines in generation are also improved in the hybrid gain configuration.

E-government strategy in Turkey:a case for m-government

Market orientation strategies are now expected to be integrated and enacted by firms and governments alike. While private services will surely continue to take the lead in mobile strategy orientation, others such as government and Non-Governmental Organizations (NGOs) are also becoming prominent Mobile Players (m-Players). Enhanced data services through smart phones are raising expectations that governments will finally deliver services that are in line with a consumer ICT lifestyle. To date, it is not certain which form of technological standards will take the lead, e.g. enhanced m-services or traditional Internet-based applications. Yet, with the introduction of interactive applications and fully transactional services via 3G smart phones, the currently untapped segment of the population (without computers) have the potential to gain access to government services at a low cost.

Phase shift keyed systems based on a gain switched laser transmitter

Return-to-Zero (RZ) and Non-Return-to-Zero (NRZ) Differential Phase Shift Keyed (DPSK) systems require cheap and optimal transmitters for widespread implementation. The authors report on a gain switched Discrete Mode (DM) laser that can be employed as a cost efficient transmitter in a 10.7 Gb/s RZ DPSK system and compare its performance to that of a gain switched Distributed Feed-Back (DFB) laser. Experimental results show that the gain switched DM laser readily provides error free performance and a receiver sensitivity of -33.1 dBm in the 10.7 Gbit/s RZ DPSK system. The standard DFB laser on the other hand displays an error floor at 10(-1) in the same RZ DPSK system. The difference in performance, between the two types of gain switched transmitters, is analysed by investigating their linewidths. We also demonstrate, for the first time, the generation of a highly coherent gain switched pulse train which displays a spectral comb of approximately 13 sidebands spaced by the 10.7 GHz modulation frequency. The filtered side-bands are then employed as narrow linewidth Continuous Wave (CW) sources in a 10.7 Gb/s NRZ DPSK system.

Experimental investigation of inter-modal cross-gain modulation and transient effects in a two mode group erbium doped fiber amplifier

We report what we believe to be the first experimental study of inter-modal cross-gain modulation and associated transient effects as different spatial modes and wavelength channels are added and dropped within a two-mode amplifier for SDM transmission.

Widely tunable gain-switched operation of external cavity grating-coupled surface emitting laser

Widely tunable gain switching of a grating-coupled surface-emitting laser (GCSEL) has been demonstrated in a simple external cavity configuration for the first time. Pulse duration in range of 40-100ps and wavelength tuning over 100nm have been achieved. High power, tail-free optical pulses have been observed at 980nm.

Self-seeded gain-switched operation of an InGaN MQW laser diode

Self-seeded, gain-switched operation of an InGaN multi-quantum-well laser diode has been demonstrated for the first time. An external cavity comprising Littrow geometry was implemented for spectral control of pulsed operation. The feedback was optimized by adjusting the external cavity length and the driving frequency of the laser. The generated pulses had a peak power in excess of 400mW, a pulse duration of 60ps, a spectral linewidth of 0.14nm and maximum side band suppression ratio of 20dB. It was tunable within the range of 3.6nm centered at a wavelength of 403nm.

Utilising fiction to promote english language acquisition

Towards the end of the university stage, students residing in the United Arab Emirates and specialising in subjects other than English are expected- amongst other university requirements- to have acquired adequate communicative competence as well as a repertoire of critical thinking skills. Despite the efforts made within the field of teaching English to EFL university students in the country, the output gained in terms of acquired skills and competencies is still below expectations. The main concerns of the current thesis are, therefore, a) to investigate the factors which inhibit EFL university students’ progress in the areas of acquiring adequate communicative competence as well as critical thinking skills, and b) to propose a course book and pedagogic methods to improve students’ progress in the areas of acquiring adequate communicative competence as well as critical thinking skills. Believing in the essential role literature plays in enhancing critical thinking and promoting communicative competence on the part of EFL learners, the current study introduces a course, designed and implemented by the researcher: LEARN AND GAIN. The proposed course is fiction-based language teaching, adopting the view that literature is a resource rather than an object, thus advocating the use of literature as one of the main resources in foreign/second language acquisition. Investigating whether or not the proposed course was effective in promoting EFL university students’ communicative competence as well as enhancing their critical thinking skills, a study sample taken from the study population was selected. Adopting an experimental design, the research project involved two groups: experimental and control. The experimental group students were exposed to the proposed course whilst the control group students were exposed to a general English language course. To examine treatment effectiveness, the researcher set and administered a pre-post test. Divided into two main parts, communicative critical reading competence and communicative critical writing competence, the pre-post test measured subjects’ communicative critical reading competence and subjects’ communicative critical writing competence. In addition, a pre-post questionnaire was administered and a semi-structured interview was conducted involving the experimental group students, to gain an awareness of students’ attitudes towards learning literary texts in general, and the proposed course in particular. To examine issues of interest and relevance, gender differences: male vs. female, and university major: science vs. non-science, were also examined for enrichment purposes. For the purpose of gathering sufficient data about subjects’ achievements on the pre-post, the following statistical tests were conducted: Mann-Whitney test, and paired data t-test. Based on the statistical findings, the experimental group students’ performance on the communicative critical reading competence pre-post test and the communicative critical writing competence pre-post test was significantly better than their counterparts of the control group students. Speaking of gender differences in relation to language performance on the communicative critical reading competence pre-post test and the communicative critical writing competence pre-post test, no significant differences were cited. Neither did the researcher cite any significant performance differences between science/non-science students on the communicative critical reading competence pre-post test and the communicative critical writing competence pre-post test. As far as the questionnaire’s findings are concerned, the experimental group students’ responses to the post-questionnaire’s items were more positive than those of their responses to the pre-questionnaire’s, thus indicating some positive attitudes towards literature, which students possibly gained throughout the course of implementation. Relating the discussion to the interview’s results, students conveyed their satisfaction with the proposed course, emphasising that promoting English language skills through the use of literary texts was rewarding. In the light of findings and conclusions, a number of recommendations as well as implications have been proposed. The current study aimed to arrive at some appropriate suggestions to a number of enquiries, yet concluding with some areas of enquiry to be explored for further research.

Q-switched induced gain switching of a twotransition cascade laser

A gain-switched laser transition, of a two-laser-transition cascade laser, that is driven by the adjacent laser transition which is Q-switched is demonstrated using a Ho3+ -doped fluoride fiber laser. Q-switching the 5|6 ? 5|7 transition at 3.002 µm produces stable gain-switched pulses from the 5|7 ? 5|8 transition at 2.074 µm; however, Q-switching the 5|7 ? 5|8 transition produced multiple gain switched pulses from the 5|6 ? 5|7 transition. The gain-switched pulses were measured to be of a similar duration to the Q-switched pulses suggesting that much shorter pulses of closer duration could be generated at pump power higher levels.

Experimental investigation of inter-modal cross-gain modulation and transient effects in a two mode group erbium doped fiber amplifier

We report what we believe to be the first experimental study of inter-modal cross-gain modulation and associated transient effects as different spatial modes and wavelength channels are added and dropped within a two-mode amplifier for SDM transmission.

22-km distributed temperature sensor using Brillouin gain in an optical fiber

We describe an experimental distributed temperature sensor that uses the temperature dependence of the Brillouin frequency shift. When a 22.2-km sensing length is used, we have observed a temperature resolution of 1°C and have obtained a spatial resolution of 10 m.