This work is focused on exploring a unique integration of techniques, Raman micro-spectroscopy and atomic force microscopy (AFM), which when combined offer more than the sum of their respective parts. The non-invasive chemical specificity afforded by Raman spectroscopy, combined with the nanoscale-resolution topographic imaging of AFM offer much individually. The physics underlying the practical application of each technique is very general; Raman spectroscopy detects molecular vibrational shifts using light, and AFM uses a physical probe to interact with a surface to provide topographic (and mechanical) information. As a result, there are few restrictions to the possible samples that can be studied with these techniques, from semiconductors and geological crystals, through to simple organic chemical structures all the way to complex biological molecules and systems such as cells and tissue. In this work, a synthetic biomaterial composed of diphenylalanine (FF) peptide units which self-assemble into strong tubular structures is used as a sample of interest when exploring the different possibilities available from a combined Raman-AFM instrument. First, the combined system was set up in order to perform tip-enhanced Raman spectroscopy (TERS), a technique promising Raman spectroscopic imaging at the resolution of AFM imaging. A relatively young technique, TERS has huge potential in extending the reach of Raman spectroscopic imaging to the nanoscale, at a regime where a great deal of structure exists, but is usually blurred by conventional diffraction-limited Raman microspectroscopy. A major focus in this work is addressing a current problem with TERS: the fabrication of suitable probes. TERS typically utilizes AFM tips modified to have a silver nanoparticle, capable of locally enhancing the Raman signal, attached at the probe apex. A new method is presented here that promises several improvements over existing approaches, as the entire fabrication can be performed in-situ on the instrument. Tips produced in this way are then characterized by electron microscopy and tested on FF nanotubes. Following this, several techniques for the synthesis of silver nanoparticles are explored for use in TERS. Here, the focus is particularly on decahedral nanoparticles, which can be grown into rod shaped particles with well- defined shapes and sizes. These are important considerations for obtaining the desired enhancing properties for TERS probes. Finally, the AFM-Raman instrument is used to investigate the mechanical properties of FF tubes using several methods. AFM force spectroscopy of tubes suspended across a gap can be used in conjunction with a bending beam theory to measure the Young's modulus of individual tubes. A new type of co-localized experiment using polarized Raman spectroscopy on a suspended tube under various forces from the AFM is tested, and subsequently information relating to the hydrogen bonding network is used, in conjunction with existing X-ray data, to determine the molecular contributions to the modulus using a simple model for amyloid fibrils. Each experiment operates at the single fibril level, with the same fibrils being used, such that different methods can be compared for a single FF tube.

Optical tomography is considered to be a non-invasive and non-ionising technique that can create a digital volumetric model of an object by reconstructing 3D images made from light transmitted and scattered through the object. It is becoming of increasing importance in the area of tissue engineering and biomedical diagnostics. The main limit of pure optical techniques is the heavy scattering of tissue, which causes a poor imaging resolution. Ultrasound modulated optical tomography (USMOT) combines optical and ultrasonic techniques to produce optical contrast at ultrasound resolution. The modulation mechanism for incoherent USMOT is considered to be a secondary effect when coherent light is used. However, it is still valuable as it offers a chance to simulate the modulation of fluorescent light. In this thesis, several models of fluorescence imaging systems are presented including incoherent USMOT, Fluorescence lifetime extraction system, full field illumination (FI) system and scanning input (SI) system. A simple incoherent USMOT model is presented which allows varying of acoustic and optical parameters to provide an optimum setup to measure the incoherent USMOT effect. Afterwards, the combination of incoherent USMOT and fluorescence imaging is applied to provide an optimized SNR of modulated fluorescent light by changing the modulation frequency. With the presence of ultrasound, a novel lifetime extraction technique is presented which provides more accurate lifetime measurements and further makes it possible to extract fluorescence lifetimes in a heavily scattering medium. A broad range of excitation and emission optical parameters of NIR fluorescence imaging system have been investigated which aims to find out the optimized imaging pairs based on the SNR and spatial resolution detected. The scanning input system turns out to be better than the full field illumination system based on the spatial resolution detected, and longer wavelengths may lead to a higher SNR but degraded spatial resolution. The spatial resolution has been taken into account in fluorophore and imaging system selection over a broad range of excitation and emission wavelength. Experimental results are shown as well as a supplement to the simulations.

The growing demand for wireless communication capacity and the overutilisation of the conventional radio frequency (RF) spectrum have inspired research into using alternative spectrum regions for communication. Using optical wireless communications (OWC), for example, offers significant advantages over RF communication in terms of higher bandwidth, lower implementation costs and energy savings. In OWC systems, the information signal has to be real and non-negative. Therefore, modifications to the conventional communication algorithms are required. Multicarrier modulation schemes like orthogonal frequency division multiplexing (OFDM) promise to deliver a more efficient use of the communication capacity through adaptive bit and energy loading techniques. Three OFDM-based schemes – direct-current-biased OFDM (DCO-OFDM), asymmetrically clipped optical OFDM(ACO-OFDM), and pulse-amplitude modulated discrete multitone (PAM-DMT) – have been introduced in the literature. The current work investigates the recently introduced scheme subcarrier-index modulation OFDM as a potential energy-efficient modulation technique with reduced peak-to-average power ratio (PAPR) suitable for applications in OWC. A theoretical model for the analysis of SIM-OFDMin a linear additive white Gaussian noise (AWGN) channel is provided. A closed-form solution for the PAPR in SIM-OFDM is also proposed. Following the work on SIM-OFDM, a novel inherently unipolar modulation scheme, unipolar orthogonal frequency division multiplexing (U-OFDM), is proposed as an alternative to the existing similar schemes: ACO-OFDMand PAM-DMT. Furthermore, an enhanced U-OFDMsignal generation algorithm is introduced which allows the spectral efficiency gap between the inherently unipolar modulation schemes – U-OFDM, ACO-OFDM, PAM-DMT – and the conventionally used DCO-OFDM to be closed. This results in an OFDM-based modulation approach which is electrically and optically more efficient than any other OFDM-based technique proposed so far for intensity modulation and direct detection (IM/DD) communication systems. Non-linear distortion in the optical front-end elements is one of the major limitations for high-speed communication in OWC. This work presents a generalised approach for analysing nonlinear distortion in OFDM-based modulation schemes. The presented technique leads to a closed-form analytical solution for an arbitrary memoryless distortion of the information signal and has been proven to work for the majority of the known unipolar OFDM-based modulation techniques - DCO-OFDM, ACO-OFDM, PAM-DMT and U-OFDM. The high-speed communication capabilities of novel Gallium Nitride based μm-sized light emitting diodes (μLEDs) are investigated, and a record-setting result of 3.5Gb/s using a single 50-μm device is demonstrated. The capabilities of using such devices at practical transmission distances are also investigated, and a 1 Gb/s link using a single device is demonstrated at a distance of up to 10m. Furthermore, a proof-of-concept experiment is realised where a 50-μm LED is successfully modulated using U-OFDM and enhanced U-OFDM to achieve notable energy savings in comparison to DCO-OFDM.

Call number: LD2668 .T4 1986 G36 / Master of Science / Agronomy

Master of Science / Department of Animal Sciences and Industry / R. Scott Beyer / Over the decades much has been discovered about the appropriate lighting management strategies for raising commercial meat-type poultry. Our knowledge of light preference, wavelength, intensity, intermittent lighting, and avian spectral sensitivity continues to improve our management strategies. In this work, a total of 5 experiments were conducted. The first 2 experiments investigated the effects of Light emitting diodes (LED) lights on growth performance of broiler chicks. Broiler chicks were raised under LED lights at different intensities: 5, 10, 15, 20, and 25 lux. A significant linear relationship (P < 0.05) was found in experiment 1 between body weight gain and light intensity. In experiment 2, a linear trend was noticed between body weight gain and light intensity. As the light intensity increased, chick weight increased. Feed: gain ratios were not affected by light intensity. The third experiment also examined growth performance using LED lighting as well as the effects of feed form and different lighting intensities upon behavior. The broilers fed a pelleted diet had significantly better performance than those fed crumbles. Under more intense light it was discovered that broilers spend significantly more time (P< .05) consuming feed compared to dim light. The fourth experiment focused on broiler preference for light color, and feed form during feeding. The broilers were offered either pelleted or crumbled feed and served under 4 different light colors: red, white, blue, and green. It was found that broilers statistically preferred pelleted feed, and white lighting, with red being the 2nd color choice of preference while green and blue were statistically not chosen. The fifth experiment focused on chick preference for feed color, when under different light color. One day old chicks were offered dyed feed: red, yellow, blue, green or light brown iv (control) under 5 different colors of light: red, yellow, blue, green, and white. It was found that chicks significantly preferred red dyed feed, especially under blue light. In conclusion, it was found that LED lights can have positive effects on broiler performance. Broilers show a preference for white lighting and pelleted feed. Young chicks show a preference for red dyed feed.

Master of Science / Department of Architectural Engineering and Construction Science / Fred Hasler / Over 26.6 million people suffer from Alzheimer's Disease in the United States, and while no cure exists, how their built environment is illuminated - lamp type, color selection, wavelengths emitted, luminaire specifications, and luminaire layout - may enhance the lives of Alzheimer's patients (APs), their relatives, and caretakers. Research has found mixed results when it comes to selecting the correct lamp, but most researchers agree illumination levels benefit APs quality of life. Achieving higher illumination levels can be achieved by adding more luminaires to the ambient lighting layout, placing additional task lighting in specific locations, or using light therapy. Exposing APs to higher illumination levels can have positive behavioral benefits and help shift the circadian rhythm. Common problems such as aggression, sleepiness, and agitation can be reduced if proper lighting layouts or light therapy is used on a consistent basis. Adding to research, several Alzheimer’s facilities in Kansas and Colorado were contacted to complete questionnaires about their lighting and resident’s behaviors. Upon analysis, these facilities concurred with research about lamp types, daylight, and luminaire layouts showing higher levels of illumination were preferred by APs and also where they displayed their best behaviors. Ninety percent of facilities agreed that APs enjoyed sitting by the windows, and over half agreed APs exhibited better behavior while seated here. Homes with CLFs documented APs were typically more calm and happy than those with tubular fluorescents, but the conclusions made need additional research to support the findings.

Doctor of Philosophy / Department of Industrial & Manufacturing Systems Engineering / Shuting Lei / Lasers have been widely used as a manufacturing tool for material processing, such as drilling, cutting, welding and surface texturing. Compared to traditional manufacturing methods, laser-based material processing is high precision, can treat a wide range of materials, and has no tool wear. However, demanding manufacturing processes emerging from the needs of nano and 3D fabrication require the development of laser processing strategies that can address critical issues such as machining resolution, processing speed and product quality. This dissertation concerns the development of novel laser processing strategies based on spatial, temporal and spectral control of light-matter interaction. In the spatial domain, beam shaping is employed in ultrafast laser micro-processing. Zero-order Bessel beam, generated by an axicon, is used for selective removal of the back contact layer of thin film solar cells. Bessel beam’s propagation-invariance property gives rise to an extension of focal range by orders of magnitude compared to Gaussian beam, greatly increasing process tolerance to surface unevenness and positioning error. Together with the axicon, a spatial light modulator is subsequently used to modify the phase of laser beam and generate superpositions of high-order Bessel beam with high energy efficiency. With the superposed beam, processing speed can be increased significantly, and collateral damage resulting from the ring structures in the zero-order Bessel beam can be greatly suppressed. In the temporal domain, it is demonstrated that ionization in dielectric materials can be controlled with a pair of ultraviolet and infrared pulses. With the assistance of the long-wavelength infrared pulse, nano-scale features are achieved using only a small fraction of threshold energy for the short-wavelength pulse. Computer simulation based on the rate equation model is conducted and found to be in good agreement with experimental results. This study paves the way for future adoption of short-wavelength laser sources, for example in the extreme ultraviolet range, for direct laser nano-fabrication with below-threshold pulse energy. In the spectral domain, a short-wavelength infrared laser is used to generate modification in the bulk of silicon wafers, in an attempt to develop 3D fabrication capabilities in semiconductors. Issues such as spherical aberration correction and examination procedure are addressed. Permanent modification is generated inside silicon by tightly focusing and continuously scanning the laser beam inside the samples, without introducing surface damage. The effect of laser pulse energy and polarization is also investigated. These results demonstrate the potential of controlling laser processing in multiple dimensions for manufacturing purposes, and point to a future when laser can be used as naturally and efficiently as mechanical tools used today, but is targeted at more challenging problems.

No description available.

The first part of this paper analyses basic principles of light aircraft industry and an export strategy of the company Aerospool with the aim to identify key aspects of this industry. The second part covers specifically the market of the USA. It contains competition analysis and PEST analysis which identifies key specifics of this market. SWOT analysis discover strengths and weaknesses of the company in the context of US market and threats and opportunities, which company can meet at this market. In the end there is a proposition of possible way of bigger penetration of the company Aerospool.

An important aspect of third-order optical nonlinearity is the intensity-dependent refractive index, where the intensity of the light itself affects the refractive index. This nonlinear effect is known as Kerr nonlinearity. In this work, a theory of amplification based on Kerr nonlinearity is developed. Kerr nonlinearity is well known to exhibit instability. Our amplification theory is based on seeding this instability. The full theory is developed to obtain the vectorial wave equations of the instability. It is shown that for materials of interest, vectorial effects are negligible across the instability regime and the scalar theory gives an accurate account of Kerr instability amplification. It is also shown that this instability analysis is a spatiotemporal generalization to four-wave mixing, modulation instability, and filamentation instability. It fact, it can be considered a seeded conical emission process. Subsequently, the theory of plane wave Kerr instability is explored. Quantitatively, the importance of pump wavelength, linear dispersive properties, and non-collinear angles for optimal amplification are demonstrated. Next, the seed beam is generalized to a finite Gaussian pulse in both time and space; the effect of a finite seed beam is quantitatively analyzed. Our analysis of Kerr instability in bulk dielectric crystals demonstrates the potential to amplify pulses in the wavelength range of ~1-14 μm. Whereas plane wave amplification is shown to extend to 40 μm in the example materials shown, material damage limits finite pulse Kerr instability amplification to about 14μm. There, seed pulse output energies in the 50 μJ range appear feasible with a ratio of pump to seed pulse energy in the range 400-500. Three key aspects of Kerr amplification are the capacity for single cycle pulse amplification, that it is intrinsically phase-matched, and its simplicity and versatility. As the Kerr instability gain profile is of Bessel-Gaussian nature in the transverse space domain, it lends itself naturally to the amplification of Bessel-Gauss beams. It is shown that pump-to-seed energy amplification that is more effcient than the Gaussian case by a factor of about 5-7. Whereas in the Gaussian case, the efficiency is on the order of about 0.15-0.2%, in the Bessel-Gaussian case it is on the order of about 1%. It is also demonstrated that Bessel-Gaussian seed beams centered at longer wavelengths than ordinary Gaussian beams may be amplified. Lastly, Bessel-Gauss beams are known to have favourable properties, such as being diffraction-free over a certain propagation range. Finally, a quantum optical theory of Kerr instability is developed. In particular, we explore a theory of the generation of ultrashort photon pairs (biphotons) from vacuum with Kerr instability.