Добірка наукової літератури з теми "621.365.5"

Signal of PLC controller by PID operation after the output of numerical simulation between 0~1, and solid state relay can receive only signal, digital or switched on or off. Only connected the two, temperature control system can be realized. The experimental approach is to learn from PWM pulse width modulation technology, the numerical analog PID controller output into the heating time in a cycle, namely, solid state relay on time. By this method, the indirect control heating rod of equivalent power, the power output of the heating rod according to the control signal of controller output, so as to realize marine gear oil temperature PID regulation. This paper designs the control system used in the experiment. The temperature control experiment system; design of the electrical schematic diagram of the temperature control system, including two parts electrical schematic diagram of control circuit and main circuit of temperature control system design process. At the same time, the experimental scheme is designed. Analysis of the mechanism of temperature balance control object, and focus on the temperature within the experimental results are analyzed.

The rate at which new communications technologies are being developed has been immense and will continue to intensify for the foreseeable future. This evolution is fuelled by the desire to meet the wants and needs of the global community, by developing devices able to offer ever-increasing functionality, with greater complexity. To achieve this designers are forced to move to higher and higher frequencies. The antenna, as one of the fundamental building blocks of any radiated wave system, and as such, must develop along with the evolution of the communication system be it for, mobile, satellite or point to point systems. Antenna designers need to be able to test antenna, to ensure they exhibit the characteristics to which they were designed. Antenna test becomes progressively more difficult and costly as both, the operating frequency and the size of the antenna increase, especially for the measurement of the antenna Far-Field radiation pattern. Either the distance over which the measurement must be made becomes unfeasibly large or expensive measurement equipment is required to attain the phase component of the antenna field, where traditional methods for measuring close to the antenna are applied. Techniques have been developed to eliminate the need for the expensive phase measurement at reduced distances. Specifically of interest in this thesis, is the optical process of Off-Axis holography. The process allows phase information to be retained in a scalar measurement by use of a phase coherent known reference source. The reference desired reference source is a plane wave, which although possible at optical frequencies with the use of lasers is problematic at microwave frequencies. To date the plane wave characteristic required has been approximated using conventional radiating elements, which degrades the quality of the recorded holographic image. This thesis proposes a novel implementation of the Off-Axis hologram system, for application in the microwave frequency region. The novel system developed here addresses the problem of generating the desired plane wave characteristic. The conventional radiating element used to provide the near plane wave reference is replaced by a synthetic equivalent, which allows the magnitude and phase of the reference beam to be directly controlled at every measurement location required. Practical verification of the novel system proposed has been performed, with comparisons made between the results obtained from the novel technique and standard techniques used in industry. The comparisons show that the novel implementation is valid and able to provide good repeatable results.

The amalgamation of the technologies of Microfabrication and Rapid Prototyping and Manufacturing is a field that has witnessed a surge of research activity in recent years. This thesis demonstrates the development of a novel microfabrication system characterised by the use of Computer Generated Holograms (CGHs) as part of a StereoLithographic rapid prototyping system in cohesion with applied microfabrication techniques. CGHs are reconstructed using a laser diode operating at a visible wavelength (407nm) and subsequently implemented in the fabrication of a microstructure. The hologram encoding method utilized two-pixel macropixels implemented on a smectic, analogue ferroelectric liquid crystal (AFLC) spatial light modulator (SLM). This, in conjunction with the bipolar nature of the modulating device, allows for full complex optical modulation. A commercial photopolymer is chosen as the target material. The underlying chemical processes comprising its photochemical behaviour in its native state, as well as in the presence of sensitizers or visible light photoinitiators, are described and the suitability of each to the StereoLithographic processes evaluated. Experimental determination of the effect of such holograms on the target material is undertaken, which include nondegenerate four wave mixing to investigate optical characteristics and cure depth measurement techniques to evaluate photochemical response. The beneficial effects of using a visible light source with respect to the final physical properties of the component are determined. Final product microstructures displaying a variety of topologies are experimentally realised, accompanied by descriptions of their respective fabrication techniques and formulation requirements

Digital holography is a new technology emerged in 1994. Because of developments of Laser, personal computer, and CCD sensor, digital holography is finding a remarkably wide range for applications. The reconstruction algorithm is the corner stone of digital holography. It simulates and models the optical reconstruction process with numerical algorithms. A number of reconstruction algorithms have been developed for digital holography in recent years, for instance, the digital implementations of the Fresnel transform, the Fraunhofer transform, and Wavelet transform. We examined all above reconstruction algorithms and developed our own variants of Angular Spectrum and Wavelet/Chirplet reconstruction algorithms. Further to these reconstruction algorithms, we developed miscellaneous algorithms to make digital holography more sophisticated. To detect the focus of an individual hologram, auto-focusing algorithms are developed. To break the resolution limitation introduced by the CCD sensor we present digital in-line holography illuminated by divergent light and corresponding reconstruction algorithms. To expand digital holography in a wider range of common applications, digital video holography is exploited. The holographic video can be reconstructed in both z and time axes. We integrated all the algorithms into software for holographic recording and processing electronically. We also applied the digital holography in a real biological application, sediment erosion study.

Quantum optics has been a frontier of physics in the last few decades. Integrated quantum photonics which prompts the concept of realizing quantum optics operation on a chip is crucial for any potential applications beyond the optical bench. This thesis focuses on two important material systems (diamond and GaN) which both have the potential for integration of single photon sources and detectors with integrated quantum circuits and at the same time can minimize the footprint of the integrated quantum circuits due to their high refractive index. We have proposed and realized two new masking methods to fabricating higher aspect ratio diamond microlenses through plasma etching. We have also proposed and demonstrated a new approach to fabricating large cross-section edge-coupled rib waveguides on free-standing thin diamond substrates by combining inkjet printing of photoresist with photolithographic patterning technique. Single-mode GaN directional couplers with transmission varying between 0.1:0.9 and 0.55:0.49 have been studied and two-photon interference was demonstrated in a 0.55:0.45 GaN directional coupler. This is the first demonstration of two-photon interference realized on a compound semiconductor chip. Our work opens up a new way to achieve sophisticated integrated quantum photonic circuits based on GaN and other suitable compound semiconductors. Integrated quantum photonics is a widespread research topic, currently undergoing explosive developments. Future options including an all-diamond platform, III-V semiconductors or a hybrid system between diamond and III- V semiconductors are discussed as perspectives.

Photonics is revolutionising the way we live in a similar way to what electronics historically did. The main aim of this PhD project was to investigate and develop fabrication techniques leading to the realisation of mid-infrared photonic components based entirely on chalcogenide glass compositions which were prepared in-house, here at the University of Nottingham, Nottingham, UK. Chalcogenide glasses are based on the chalcogen elements of Group XVI of the Periodic Table and were chosen over conventional silica glass in the work described in this thesis for their significant advantages such as: a wide transmission window, for wavelengths of light from O .5 ~tm up to 25~tm depending on the glass composition, low phonon energies, high non-linearities and high refractive indices. The chalcogenide glass systems of As-Se, Ge-As-Se and Te-As-Se were synthesised and a new quenching technique was developed to prevent ampoule failures. In addition, the distillation of Te-As-Se system was optimised via the use of temperature monitoring. Two simulations were developed using commercial software; the first led to a large mode area, endlessly single mode microstructured optical fibre design and the second verified the photonic band gaps of a photonic band gap fibre from the literature. In particular, a methodology leading to the automation of chalcogenide glass cane drawing, a hot-collapse rig for investigating hot-collapsing of a tube onto a rod and a stacking mechanism for stacking chalcogenide glass canes have all been established as part of fabrication route that has been d~veloped towards the realisation of a chalcogenide glass all-solid core microstructured optical fibre (MOF) comprising 37 core/clad canes based on the design parameters simulated. Furthermore, a robust method for obtaining for the first time multimode optical couplers based on core-clad chalcogenide glass fibre using the method of fibre sidepolishing has been demonstrated experimentally. A key feature is a novel and reproducible procedure developed for obtaining controlled side (D) polishing of chalcogenide glass fibre using an innovative polishing apparatus. These achievements are particularly noteworthy because chalcogenide glass fibre is "more toxic (requiring the use of fume extractors), requires inert atmosphere to prevent oxidation and complicated preparation methods, is difficult to handle and, due to the higher refractive indices, exhibits a higher degree of reflection at glass-air (~20%) interfaces than conventional silica glass fibre. Over the last few years, infrared rnicroscopy (IR) has gained interest and has been used to study cells and tissues for cancer diagnosis. The fabrication of IR-transmitting chalcogenide glass optical fibre tips has been investigated and tips exhibiting reproducible and controlled taper geometries have been demonstrated experimentally. f --- Additionally, methods for metal-coating the tips in a thermal evaporation chamber and cleaving the tips using a focused ion beam (FIB) have been successfully developed. Small diameter tips have been used as an IR probe in scanning near-field infrared microscopy (SNIM) and larger diameter tips for transflection spectroscopy in an attempt to obtain optical and topographical cell tissue data for cell IR fingerprint recognition of Chinese Hamster Ovary cells using synchrotron radiation by employing B22 Beamline of the Diamond Light Source, Oxford, UK. IR spectra was successfully collected and showed good indication of the amide I and amide II bands related with cell DNA.

The subject of the thesis is the modelling, design, fabrication and characterisation of passive silicon photonic devices for near (NIR) and mid-infrared (MIR) applications. The NIR devices have been investigated with the aim to produce low temperature sensitive devices for optical interconnects, whilst the results obtained at AIR wavelengths promise great potential for a variety of applications such as sensing and biomedicine. Silicon photonics offers very promising prospects for meeting ever-increasing demands on data speed and bandwidth. Temperature sensitivity of resonant photonic devices is an important issue in the development of ultralow power optical interconnects. This research project reports on the design, fabrication, and characterisation of a low temperature sensitive strip silicon-an-insulator (SOI) racetrack resonators. A resonant wavelength shift of 0.2 pm/K at a 1550 mm wavelength is measured using polymer cladding. The influence of various parameters has been examined achieving a very good agreement with theoretical model. A significant reduction of waveguide propagation losses, improved racetrack resonator Q-value, and higher extinction ratio are obtained after overlaying the silicon waveguides with a polymer cladding. On the other side, MIR silicon photonics is gathering pace, driven mainly by the lure of possible applications such as sensing, free-space communications, thermal imaging and biomedicine. However, the field is still in its infancy and the first serious challenge is to find suitable material platforms for the MIR. The thesis reports experimental results for passive devices based on different material platforms such as SOl, silicon-an-sapphire and silicon-an-porous silicon. It is demonstrated that SOl is useful material for integrated group IV photonics in the 3-4 f.1,m wavelength range, where propagation losses of less than 1 dB/cm have been obtained. The design rules for single-mode and zero-birefringent SOl rib waveguides using stress engineering are also presented. Optical splitters and racetrack resonators based on SOl strip waveguides have been characterised in the 3.7-3.9 11m wavelength range.

The detection of single photons is now commonplace in labs across the world. This was initially due to the invention of photomultiplier tubes (PMTs) and multichannel plates (MCPs) but the explosion in adoption was undoubtedly due to the developments in Single Photon Avalanche Photodiodes (SPADs), and most notably in silicon. The cost, bulk, weight, and complexity all dropped, and thus significantly expanded the application space. Today SPADs are found in biophotonics, sensing, rangefinding, quantum key distribution (QKD), quantum computing, and more This thesis investigates a relatively new class of single photon detectors, commonly referred to as shallow junction SPADs, and their applicability to a range of applications. These offer a further step reduction in cost and additionally allow for the creation of individually addressable arrays as well as integrated circuitry along side the detection areas.