The flow of a liquid film over a rapidly rotating horizontal disk has many applications inmedical, industrial, and engineering fields. A specific example is the heat and mass transfer processes between expanded liquid and surrounded dense gas. Diferent wave regimes of a liquid film depend on a flow conditions such as the properties of a liquid, its initial speed,parameters of environment, etc. Therefore, experimental investigation of the film flow over a spinning disk is needed to both validate theoretical predictions and establish methods for fluid flow monitoring.This thesis presents novel video-based algorithms for detection and tracking wave structural data of the liquid film flowing over a spinning disk reactor. The algorithms are based on the spiral model of wave and the quasi-optimal method for estimation of a wave velocity as ill-posed problem. Their performance is compared with results predicted by the fluid dynamics based on the Navier-Stokes equations in the case of thin film.Using experimental video data, the developed models and algorithms allow investigators to estimate the characteristics of wave regimes such as wavelengths, inclination angles, and the radial and azimuthal velocity components of the fluid. The accuracy of estimated characteristics was analyzed. It was shown that average distance between consecutive two waves,their spiral shapes, and the radial velocities of waves confirm the theoretical results and predictions. In particular, computed wavelength is within 1% and a change of the inclination angles is within 2% of the predicted values.

If small isoprenoids, the starting component of carotenoids, can be efficiently excreted from thermophilic cyanobacteria, they could help satisfy the demand for sustainably produced hydrocarbons. This is the driving force behind wanting to understand the response and regulation of isoprenoid pathways to environmental stimuli in the thermophilic cyanobacterium, Thermosynechococcus elongatus, BP-1. The portion of the isoprenoid pathway studied here is the carotenoid pathway since these products are critical to adaptation and they encompass the largest pool of isoprenoid compounds in cyanobacteria. Although synthetic biology in cyanboacteria has improved in recent years, there are many undiscovered metabolic complexities that make large-scale commercial production challenging. To address this need, I quantify and report for the first time metabolic shifts within the carotenoid pathway of BP-1 due to combined effects of temperature, pH and blue light. I show that metabolism shifts from the dicyclic into the monocyclic carotenoid pathway in response to pH, and that decreasing temperature drives flux into the end products of both pathways. Also, I report that the productivity of an uncommon carotenoid, 2-hydroxymyxol 2’-fucoside (HMF), approached 500 μg/L-day in cultures grown at 45 °C, high light intensity, and pH 8. In order to further elucidate these responses, I analyzed 42 RNAseq samples taken over time of BP-1 induced by cold and heat stress and compared these results to metabolomics data. I showed that crtR and crtG, two central carotenogenesis genes, are transcriptionally controlled and used weighted gene co-expression network analysis (WGCNA) to determine eight separate co-expressed modules of biological significance. Among the co-regulated heat response and cold response genes there were three and five non-coding RNA, respectively, providing targets for future investigation. Using subtractive genomics and transcriptional data I narrowed the potential missing steps of the myxol pathway in cyanobacteria to seven unknown BP-1 genes, two of which were confirmed not to be involved in the missing step(s). Finally, by generating a ΔcrtG mutant and testing it under different environmental parameters, I showed that HMF does not protect against high pH or low temperature (despite up-regulation at these conditions), and that CrtG has a higher affinity for monocyclic than dicyclic carotenoids. / text

Since their initial demonstration in 1994, quantum cascade lasers (QCLs) have become prominent sources of mid-infrared radiation. Over the years, a large scientific and engineering effort has led to a dramatic improvement in their efficiency and power output, with continuous wave operation at room temperature and Watt-level output power now standard. However, beyond this progress, new functionalities and capabilities need to be added to this compact source to enable its integration into consumer-ready systems. Two main areas of development are particularly relevant from an application standpoint and were pursued during the course of this thesis: wavelength control and wavefront engineering of QCLs. The first research direction, wavelength control, is mainly driven by spectroscopic applications of QCLs, such as trace gas sensing, process monitoring or explosive detection. We demonstrated three different capabilities, corresponding to different potential spectroscopic measurement techniques: widely tunable single longitudinal mode lasing, simultaneous lasing on multiple well-defined longitudinal modes, and simultaneous lasing over a broad and continuous range of the spectrum. The second research direction, wavefront engineering of QCLs, i.e. the improvement of their beam quality, is relevant for applications necessitating transmission of the QCL output over a large distance, for example for remote sensing or military countermeasures. To address this issue, we developed plasmonic lenses directly integrated on the facets of QCLs. The plasmonic structures designed are analogous to antenna arrays imparting directionality to the QCLs, as well as providing means for polarization control. Finally, a research interest in plasmonics led us to design passive flat optical elements using plasmonic antennas. All these projects are tied together by the involvement of Fourier analysis as an essential design tool to predict the interaction of light with various gratings and periodic arrays of grooves and scatterers. / Engineering and Applied Sciences

Στην συγκεκριμένη εργασία παρουσιάζεται ένα μοντέλο προσομοίωσης των Πολυμερών Οπτικών Ινών και συγκεκριμένα των GI-POF ικανό να υπολογίζει την κρουστική απόκριση και τη διασπορά των συγκεκριμένων ινών. Επίσης ακολουθούν προσομοιώσεις 2 απλών συστημάτων μετάδοσης μέσω POF με λέιζερ και φωτοδιόδους χιονοστοιβάδας και ένα πλήρες προσομοιωμένο σύστημα μετάδοσης 2 καναλιών με πολυπλεξία μήκους κύματος μέσω των POF. Σχολιάζονται τα αποτελέσματα και η δυνατότητα χρήσης των ινών στη δομή του δίκτυου Μετάδοσης Κινητής Τηλεφωνίας. Επίσης αναλύονται όλα τα πιθανά πρωτόκολλα για τοπικά οπτικά δίκτυα και όλες οι πληροφορίες για τις POF, τους κατάλληλους πομπούς και δέκτες που μπορούν να χρησιμοποιηθούν σε μελλοντικές εφαρμογές. / In the specific project it is presented a simulation model of Polymer Optical Fibers and especially of GI-POF capable of calculating the impulse response and the dispersion of the specific fibers. Also next, simulations were realised of 2 simple transmission systems via POF with laser and avalange photodiodes, and a complete simulated transmission system with 2 channels with Wavelegth Division Multiplexing via POF. Results are being discussed as also the possibility of POF use in structure of Transmission Network of Cellular Telephony. In addition, all available protocols for local optical networks are described and all necessary information about POF, suitable transmitters and receivers that can be used in future applications.

High-speed optical networks will require all-optical signalprocessing to avoid bottleneck due to optical-to-electrical (O/E)and electrical-to-optical (E/O) conversion. Enabling of opticalprocessing tasks such as optical buffering and data synchronizationwill require large tunable delay. Recently, slow-light physics gotwide attention to generate tunable delay. However, for a slow-lightsystem large delay comes at the expense of increased distortion.This dissertation presents a study of the slow-light systems andquantifies the limitations imposed on delay due to distortion andsystem resource constraints. Optimal designs for two- and three-lineBrillouin slow-light systems showed fractional pulse delay of up to1.7 compared to a single-line gain system. Optimal designs forbroadband Brillouin gain system showed upto 100\% delay improvementcompared to the Gaussian pump. Wavelength conversion and dispersionbased tunable delay systems showed bit delay of 15 bits. An opticalbuffer based on photorefractive medium for real-time data storagewas demonstrated by storing and retrieving a 7-bit data sequence.

Coarse Wavelength Division Multiplexing (CWDM) is becoming a popular way to increase the optical throughput of fibers for short to medium haul networks at a reduced cost. The International Telecommunications Union (ITU) has defned the CWDM network to consist of eighteen channels with channel spacings of 20 nm starting at 1270 nm and ending at 1610 nm.Four and eight channel AWGs on InP, suitable for CWDM, were fabricated using a novel and versatile S-shape design. The standard horseshoe layout will not work on semiconductor for AWGs with a free spectral range (FSR) larger than 30 nm. The AWG design provides operation insensitive to thermal and polarization fluctuations, which is key for low cost operation and packaging. It will be shown thatrefractive index changes over the large operating wavelength band produced negligible effects in the transmission spectrum.Standard AWG design assumes refractive index is a constant over the operating wavelength band. As a result, the output waveguide separations are held constant on the second star coupler. As the channel number increases, secondary focal dispersion causedfrom a changing refractive index can have detrimental effects on performance. A new design method will be introduced which includes refractive index dispersion by allowing the output waveguide separations to vary. The new design is consistent with standard design but is applicable in materials with a linear index dispersion over an arbitrarily large wavelength band.Lastly, a method for increasing the transmission using multimode waveguides is discussed. Traditionally, single mode waveguides are required in order to prevent higher order waveguide modes creating ghost images in the output spectrum. Using bend loss and waveguide junction offsets, higher order modes can be filtered from the output,thereby eliminating ghost images and at the same time, increase transmission.

With the manufacture of nano-scale features in the last ten years, it is possible to do optical experiments on features as small as a tenth/hundredth wavelength. It turns out that the experimental data cannot be explained by classical diffraction theories. Thus, it is necessary to develop new methods or use existing approaches which are effective in other fields, to solve problems in photonics. We use finite difference time domain (FDTD), to study transmission properties of sub-wavelength slits in a metallic film. By doing simulations on periodic and single slits, we confirm that the TE mode has a cutoff while a TM mode always has a propagating mode in the small apertures. Then we find that the transmittance is minimum when the array period is equal to the wavelength of surface plasmon polariton (SPP) at normal incidence. In fact, the SPP-like waves exist in both periodic and isolated slits, and they help the transmittance of small apertures. In order to establish the role of SPP in the transmission mechanism, it is necessary to single out each mode from the total fields. We developed Bloch mode method (BMM) to calculate the amplitudes of the lowest N orders, and the amplitudes tell us which one is dominant (not including the guided mode) at high and low transmission. BMM converges very fast and it is more accurate than FDTD since it does not suffer from numerical dispersion. Both methods can resolve the Wood anomaly and SPP anomaly; however, FDTD converges very slowly at the SPP resonance and oscillates around the value obtained through BMM at the Wood anomaly. BMM is not sensitive to material types, incident angles, and anomalies; it will be a useful tool to investigate similar problems.

Anisotropy in glass can lead to a transmitted double image due to birefringence. Stress-induced birefringence, the stress-optic effect, is undesirable for applications such as commercial imaging. The leading zero stress-optic glass exhibits dispersive effects near its absorbance edge and thus cannot be used in broadband applications. Finding zero stress-optic glasses with minimal dispersive effects over a broad band of the visible region requires a theory to predict which combinations of glass formers and modifiers could exhibit minimal dispersion. Two glass families known to have a zero stress-optic response using white light, tin phosphates and tin silicates, were studied as a function of composition and wavelength. Near the absorbance edge, dispersion varied considerably with composition for tin phosphate glasses, but remained constant for tin silicate glasses. The significant factor is the oxygen bonding influence near the band edge. This leads to composition rules for synthesis of broadband, zero stress-optic glasses.

No description available.

Surface plasmons are bound TM polarized electromagnetic waves that propagate along the interface of two materials with real dielectric constants of opposite signs. Surface plasmon resonance (SPR) sensors make use of the surface plasmon waves to detect refractive index changes occurring near this interface. For sensing purposes, this interface typically consists of a metal layer, usually gold or silver, and a liquid dielectric. SPR sensors usually measure the shift in resonance wavelength or resonance angle due to index changes adjacent to the metal layer. However this restricts the limit of detection (LOD), as the regions of low slope (intensity vs. wavelength or angle) in the SPR curve contain little information about the resonance. This work presents the technique of tunable laser interrogation of SPR sensors. A semiconductor laser with a typical lasing wavelength of 650nm was used. A 45nm gold layer sputtered on a BK7 glass substrate served as the sensor. The laser wavelength is tuned to always operate in the region of highest slope by using a custom-designed LabVIEW program. It is shown that the sensitivity is maximized and LOD is minimized by operating around the region of high slope on the SPR curve.