Monolithically integrated polarisation mode convertor with a semiconductor laser

In this thesis, the design, optimisation, fabrication and operation of waveguide based semiconductor lasers, integrated with polarisation mode convertors (PMCs), is described. Devices are fabricated in the GaAs/AlGaAs and InP/AlGaInAs material systems, using two types of structures; single PMC and back-to-back PMCs. The convertor designs are based upon air trenches, of sub-wavelength dimensions, being introduced into waveguide structures in order to achieve an asymmetric cross-sectional profile, resulting in wave-pate functionality. The GaAs/AlGaAs PMCs are fabricated using reactive ion etching (RIE), and the phenomena of RIE lag technique is also exploited for obtaining the required asymmetric waveguide profile in a single etch step. These are then integrated with semiconductor lasers. The InP/AlGaInAs PMCs are fabricated using a combination of RIE and inductively coupled plasma (ICP) etching and are integrated with semiconductor lasers and also differential phase shifter (DPS) sections to realise devices with active polarisation control. Integrated devices fabricated on InP/AlGaInAs material system with a semiconductor laser, a PMC followed by a DPS section yields ~40 % polarisation mode conversion whilst the DPS section is held at the transparency condition. Greater than 85 % polarisation mode conversion was also obtained with back to back PMCs, which was complement to the devices fabricated with a single PMC. Furthermore, a first active polarisation controller, monolithically integrated with a semiconductor laser is reported. High speed modulation of the integrated device with 300 Mbps is also demonstrated via current injection to the phase shifter section of the device

Generation of high speed polarization modulated data using a monolithically integrated device

We report on the generation of high speed polarization modulated data via direct electrical binary data injection to the phase shifter section of a monolithically integrated laser diode integrated with a polarization controller. The device is fabricated on standard InP/AlGaInAs multiple quantum-well material and consists of a semiconductor laser, a passive polarization mode convertor and an active differential phase-shifter section. We demonstrate the generation of 300 Mbit/s Polarization Shift Keyed data

AlGaInAs/InP Based Five & Three Quantum Wells Mode Locked Laser Diodes: A Comparative Study

Comparison of performance of semiconductor mode-locked laser diodes fabricated using AlGaInAs/InP material containing 5 and 3 quantum wells (QWs) inside the active region is reported. The simulations and experimental results show that lasers containing five QWs materials produce larger beam divergence and temporally broader optical pulses. For improvement in the mode-locking of lasers and reducing the far-field pattern, the number of QWs inside the active region was decreased from five to three and a far-field decreasing layer along with a thick spacer layer were introduced in the n-cladding region of epitaxial material. Before growing the material, simulations were carried out to optimise the design. The lower optical confinement factor and higher gain saturation energy of three QWs based mode-locked lasers provide higher average and peak output power, reduced and symmetric far-field pattern, better radio frequency (RF) spectra, shorter optical pulses, and stable optimal mode-locking for a wide range of gain current and saturable absorber reverse voltage

Bifunctional Heterogeneous Catalysts for Biodiesel Production using Low Cost Feedstocks: A Future Perspective

Currently, the fossil fuel sources are the major contributors to the world\u27s energy mix. However, these conventional energy sources are depleting very fast due to their finite nature and extensive uses. An addition to their finite nature, environmental problems related to their uses are getting progressively worse and worse, initiating challenging debates for scientific communities. Biodiesel, a renewable fuel, has shown promising prospects due to its strong socioeconomic benefits and motivations in most of the countries of the world. Bifunctional heterogeneous catalysts are strongly recommended for biodiesel production from different feedstocks to simplify the process. This review highlights the challenges and opportunities associated with the heterogeneous catalysts and some recommendations to design an efficient bifunctional heterogeneous catalyst for economical biodiesel production from waste cooking oil

Seasonal influence, heat unit accumulation and heat use efficiency in relation to maize grain yield in Pakistan

Variations in ambient temperature affect crop yield by modifying the duration of phenological phases and physiologicalprocesses. An experimental study was carried out at the Maize and Millets Research Institute (MMRI),Yusafwala, Sahiwal, Pakistan, to determine the seasonal effects of temperature on indigenous and exotic maize(Zea mays L.) hybrids based on morphological, phenological, physiological and grain quality traits in four differentgrowing seasons: kharif 2016 and 2017, and spring 2017 and 2018. Seven indigenous and three exotic hybridswere sown in a randomized complete block design with a split plot arrangement, in three replications. Significantdifferences between hybrids and growing seasons were found for grain yield, related traits and temperature indices(cumulative heat units, photothermal index and heat use efficiency). Correlation analysis disclosed a significantpositive relationship between grain yield and net photosynthetic rate (0.854, P≤0.01), number of grains per ear(0.624, P≤0.01) and heat use efficiency (0.980, P≤0.01) in spring seasons. During kharif, net photosynthetic rate(0.675, P≤0.01) and heat use efficiency (0.996, P≤0.01) contributed significantly to grain yield, whereas number ofgrains per ear (−0.146, not significant) had no significant impact on grain yield. Cumulative heat units and heat useefficiency resulted the temperature indices with the greatest influence on grain yield, and should be consideredduring the selection of parents to develop high-yielding, climate-smart maize hybrids. Indigenous maize hybridsshowed higher yields and were more heat tolerant than exotic hybrids, and the spring sowing season appearedto be the most suitable for the cultivation of maize crops

Sports Culture in South Asia: Effects of Modern Bowling Action Rules on Cricket, an Information Technology Perspective

Cricket, a famous game played and watched at its peak in Asia. The game is governed by International Cricket Council (ICC). It is a team sport of eleven players in each side with different roles, of which one is bowler. The bowlers have followed different styles of bowling sinces game has started, of which some declared illegal initially. In our study, we have focused on the cases of illegality reported form South Asian region in post 1990 period a new era of biomechanics based bowling laws started. We have also investigated the updated ICC process for bowlers review and remedy along with biomechanics based labs established worldwide. Finally, we have proposed a new information technology based bowling action evaluation solution, lower in cost and affordable at domestic level. Such study will help bowlers, their coaches and viewers to understand the biomechanics based bowling laws, standings of South Asian bowling after these laws and alternative solutions to rescue it

Consequences of diverse use of nitrogen sources on grain yield, grain quality and growth attributes of hybrid maize (Zea mays L.)

A two year field experiment was conducted to check the consequences of diverse use of nitrogen sources on grain yield, grain quality and growth attributes of hybrid maize (Zea mays L.) at the Agronomic Research Area, University of Agriculture, Faisalabad during Autumn 2008 and 2009. Experiments were laid out in a randomized complete block design with factorial arrangement comprising 3 replications with a net plot size of 3 × 5 m. Treatment comprised two hybrids: that is, H1 (Pioneer-30Y87) and H2 (Pioneer-31R88) with combination of six nitrogen sources S0 : Control (0) kg N ha-1, S1: Urea (50%) + Poultry manure (50%), S2: Urea (50%) + Farm Yard Manure (50%) , S3: Urea (50%) + Pressmud of sugarcane manure (50%), S4: Urea (50%) + Compost (50%), S5: Urea (50%) + (PM+FYM+PMS+ Compost) 50% . Results of grain yield (t ha-1), grain protein content (%) grain oil content (%), leaf area index, leaf area duration, dry matter accumulation, crop growth rate and net assimilation rate was found to be significant during 2008 and 2009. It was concluded that hybrid maize H1 (Pioneer - 30Y87) produced better grain yield (6.14 t ha-1) during 2008 when nitrogen sources S1: Urea (50%) + Poultry manure (50%) was applied in combination as compared to grain yield (6.0 t ha-1) in hybrid H2 (Pioneer -31R88) during 2009. Growth and quality attributes also performed better in 2008 as compared to 2009 at nitrogen sources S1: Urea (50%) + Poultry manure (50%).Key words: Nitrogen sources, hybrid maize, yield, growth, quality

A Roadmap to Elevate Pakistan Sign Language among Regional Sign Languages

Several nations have worked hard to make their societies truly inclusive by developing gadgets, tools, services, and applications. A lot of work has been done for bringing the deaf community to the mainstream. Tools and applications exist for several sign languages including American Sign Language (ASL), Chinese Sign Language (CSL), Indian Sign Language (ISL) and Arabic Sign Language (ArSL). These tools help translating natural language text into respective sign language and vice versa. Similarly, standard corpora exist for all afore-mentioned sign languages and for many other languages. Unfortunately, no such noticeable development exists in the case of Pakistan Sign Language (PSL). This research aims to define a roadmap for the development of Pakistan Sign Language so as to bring it at par with other sign languages of the world.&nbsp

Detection of Paracetamol as substrate of the gut microbiome

Gut microbiome, a new organ; represent targets to alter pharmacokinetics of orally administered drugs. Recently, in vitro trials endorsed the idea that orally administered drugs interact and some of their quantity may be taken up by normal microbiome during transit through gut. Such transport mechanisms in microbiome may compete for drug with the host itself. Currently, no data confirms specific transport system for paracetamol uptake by gut microbiome. In vivo trial was conducted in normal healthy male rats (n=36). Paracetamol was administered orally in a single dose of 75mg/kg to isolate microbial mass after transit of 2, 3, 4, 5 and 6 hours post drug administration. Paracetamol absorbance by microbiome was pursued by injecting extracted microbial lysate in RP-HPLC-UV with C18 column under isocratic conditions at 207nm using acetonitrile and water (25:75 v/v) pH 2.50 as mobile phase. Paracetamol absorbance (14.10±0.75μg/mg of microbial mass) and percent dose recovery (13.16±0.55%) seen at transit of 4 hours was significantly higher (P<0.05) compared to other groups. Study confirms the hypothesis of homology between membrane transporters of the gut microbiome and intestinal epithelium. Orally administered drugs can be absorbed by gut microbes competitively during transit in small intestine and it varies at various transit times