Disordered photonics is the study of light in random media. In a disordered photonic medium, multiple scattering of light and coherence, together with the fundamental principle of reciprocity, produce a wide range of interesting phenomena, such as enhanced backscattering and Anderson localization of light. They are also responsible for the existence of modes in these random systems. It is known that analogous processes to Bose-Einstein condensation can occur in classical wave systems, too. Classical condensation has been studied in several contexts in photonics: pulse formation in lasers, mode-locking theory and coherent emission of disordered lasers. All these systems have the common theme of possessing a large ensemble of waves or modes, together with nonlinearity, dispersion or gain. In this work, we study light condensation and its connection with light localization in a disordered, passive dielectric medium. We develop a theory for the modes inside the disordered resonator, which combines the Feshbach projection technique with spin-glass theory and statistical physics. In particular, starting from the Maxwell’s equations, we map the system to a spherical p-spin model with p = 2. The spins are replaced by modes and the temperature is related to the fluctuations in the environment. We study the equilibrium thermodynamics of the system in a general framework and show that two distinct phases exist: a paramagnetic phase, where all the modes are randomly oscillating and a condensed phase, where the energy condensates on a single mode. The thermodynamic quantities can be explicitly interpreted and can also be computed from the disorder-averaged time domain correlation function. We launch an ab initio simulation campaign using our own code and the Shaheen supercomputer to test the theoretical predictions. We construct photonic samples of varying disorder and find computationally relevant ways to obtain the thermodynamic quantities. We observe the phase transition and also link the condensation process to the localization. Our research could be a step towards the ultimate goal: to build a ”photonic mode condenser”, which transforms a broadband spectrum to a narrow one - ideally, to a single mode - with minimal energy loss, aided solely by disorder.

Visible blue light wavelengths in the 400-470-nm range have been observed to have antimicrobial properties. The purpose of this review article is to delineate the mechanism of action, optimizing conditions, and public health and clinical applications of antimicrobial blue light (aBL) as characterized by the current literature. A widely accepted hypothesis for the mechanism of bacterial inactivation by aBL is that the light causes photoexcitation of endogenous photosensitizers, porphyrins and flavins, which leads to the release of reactive oxygen species that subsequently lead to cell toxicity. Factors that have been observed to be associated with enhanced antimicrobial action include increased duration of exposure, pre-treatment with quinine hydrochloride, and exposure of target bacteria to sub-lethal stress conditions. Studies examining the effect of repetitive exposure to sub-lethal levels of aBL on bacteria show no significant evidence of development of resistance. Additionally, aBL has exhibited the ability to inactivate multidrug-resistant (MDR) bacteria. While studies have also observed aBL to have efficacy in inactivating fungal and viral pathogens, there is a need for further research to elucidate the mechanisms of photoinactivation of fungi and viruses by aBL. Multiple studies have shown that aBL is effective in causing significant CFU reduction in biofilms, an observation that supports the application of aBL for decontamination of surfaces and treatment of localized infections. aBL has demonstrated efficacy in eliminating foodborne pathogens found on food surfaces and exposed surfaces in the food processing environment. Studies applying aBL to decontamination of surfaces in the clinical environment have concluded that it is a viable decontamination practice that shows promise for helping to minimize the spread of healthcare-associated infections (HAIs). Existing literature provides evidence in favor of the application of aBL in clinical contexts such as the treatment of gonococcal infections, eye infections, and otitis media, and in the decontamination of stored platelets and plasma. Studies investigating these clinical applications have demonstrated the efficacy of aBL for inactivating the clinically relevant pathogens, as well as the preservation of normal human cells upon exposure to the doses of light that are lethal to the pathogens. / 2022-11-18T00:00:00Z

This thesis investigates the constancy of light speed with respect to the light age using an active fiber-based Mach-Zehnder interferometer (MZI) illuminated by sunlight. The original sunlight in one arm, which has the age of 8.3 minutes since it was emitted from the sun, interferes with the young light generated by stimulated emission from an optical amplifier in the other arm, which is coherent to the sunlight. The speed difference between the sunlight and the newly regenerated light is obtained by measuring the phase variations as the interference signal travels along a span of single-mode fiber. System error is eliminated by the self-calibration which is achieved by alternatively switching other two local amplified spontaneous emission light sources and the sunlight as the input to the MZI, and then comparing the measured phase differences of these three sources. The relative accuracy of light speed measurement is . Consider the 8.3 minutes age of the sunlight, for a possible variation of light speed of c with light age in optical fiber, we obtainĢc/c is less than 1.7 / Master of Science

This thesis focuses on creating an interactive installation as immersive experience for hearing-impaired user. To date, little research has been conducted especially on interactive (sound) installation for impaired visitors, particularly these visitors with hearing impairments or who are hard-of hearing. Based on literature research and a case study, a new lighting design proposal was developed for Soundforest, an interactive musical installation at Scenkonstmuseet in Stockholm, Sweden. The audio-experience is enhanced ambient lighting, which alters in brightness depending on the interaction of visitors. For evaluation, a prototype was set up in the installation space and tested by one participant. The first testing leads to the assumption that the additional layer of ambient lighting can enhance the emotional experience of the visitors. The results show that the test person had great pleasure in interacting with the prototype. Still, to develop a full picture of the consequences and emotional effects, additional research is required.

No description available.

Player response in the horror video game genre is primary to its success allowing players to experience emotional arousal through elaborate game design. This thesis aims to investigate how, specifically light mechanics, can help elicit responses in Amnesia: The DarkDescent to bring attention to the light techniques that can be used by game designers to elicit such emotional reactions. Observations, interviews, and emotional facial recognition software were used to investigate the various patterns of behavior that players had while playing Amnesia: The Dark Descent. Results showed that most participants used light attributes to benefit their emotional state and all participants used them to enhance their gameplay environment. The tools that derive from light mechanics were noticed both consciously and subconsciously. Further, each participant displayed shifts of emotion, such as surprise, fear, anger, and happiness. As well as players’ physical and in-game behavior patterns were found to be related to fear responses, in terms of events where they interacted with light attributes and were in the presence of danger. The results suggest that the usage and portrayal of light attributes are dependent on the players' perception of the valued use of light and the potential of danger. It was revealed that emotional value has a significant impact on how players perceive light mechanics. Nonetheless, the individuals were able to modulate their own emotional arousal through the attributes of light mechanics.

The lethal effect of ultraviolet (UV) light on microorganisms is well known and many studies have been undertaken into the effects of UV induced damage. Most of this work has been experimental; by comparison relatively little theoretical work has been undertaken to analyse the kinetics of the UV inactivation process, or to develop quantitative methodologies to support the experimental work. This paper presents a new and simple model for quantifying the photolysis rate. A theoretical study is also presented in this paper which quantifies photolysis rates for E. coli O26 and E. coli O157:H7. This study uses experimental data collected by Tosa and Hirata, and reveals the photolysis rate for E. coil O26 during the UV irradiation process to be 4.69 x 10(-3) m2 J(-1). By comparison, E. coli O157:H7 is much more susceptible to UV induced damage than E. coli O26, having a photolysis constant of only 2.09 x 10(-3) m2 J(-1).

Materials with resonant features can have a rapidly changing refractive index spectrally or temporally that gives rise to a changing group index. Depending on the wavelength of the input light, this light can see regimes of normal or anomalous dispersion. Within these regions, the group index can become large, depending on the optical effect used, and give rise to slow or fast light effects. This thesis covers two platforms that exhibit the use of slow and fast light. Slow and fast light are used to manipulate and enhance other optical effects in question. As the focus of this thesis, we examine a rotating ruby rod and spaceplates based on multilayer stacks, both considered as slow- and fast-light media. Light propagation through each platform is modelled and simulated to compare to the experiment. The simulation results for both platforms match well with the measured experimental effects and show the feasibility and utility of slow or fast light to manipulate or enhance optical effects. We simulate light propagation in a rotating ruby rod as a rotating, anisotropic medium with thermal nonlinearity using generalized nonlinear Schrodinger equations, modelling the interplay of many optical effects, including nonlinear refraction, birefringence, and a nonlinear group index. The results are fit to experimentally measured results, revealing two key relationships: The photon drag effect can have a nonlinear component that is dependent on the motion of the medium, and the temporal dynamics of the moving birefringent nonlinear medium create distorted figure-eight-like transverse trajectories at the output. We observe light propagation through a rotating ruby rod where the light is subject to drag. Light drag is often negligible due to the linear refractive index but can be enhanced by slow or fast light, i.e., a large group index. We find that the nonlinear refractive index can also play a crucial role in the propagation of light in moving media and results in a beam deflection. An experiment is performed on the crystal that exhibits a very large negative group index and a positive nonlinear refractive index. The negative group index drags the light opposite to the motion of the medium. However, the positive nonlinear refractive index deflects the beam along with the motion of the medium and hinders the observation of the negative drag effect. Therefore, it is deemed necessary to measure not only the transverse shift of the beam but also its output angle to discriminate the light-drag effect from beam deflection. This work could be applied to dynamic control of light trajectories, for example, beam steering and velocimetry. For the following two chapters, we will focus on a different slow-light platform. This platform focuses on optics that we developed and tested that compress the amount of free-space propagation using multilayered stacks of thin films known as spaceplates. We design and characterize four multilayer stack-based spaceplates based on two design philosophies: coupled resonators and gradient descent. Using the transfer-matrix method, we simulate and extract the angular and wavelength dependence of the transmission phase and transmittance to extract and predict compression factors for each device. A brief theoretical investigation is developed to predict resonance positions, spacing, and bandwidth. We measure the transverse walk-off to extract the compression factor of four multilayer stack-based spaceplates as a function of angle and wavelength. One of the devices was found to have a compression factor of $R=176\pm14$, more than ten times larger than previous experimental records. We increased the numerical aperture of one of the devices by ten times, and we still observed a compression factor of $R=30\pm3$, two times larger than the most recent experimental measurements. We also measured focal shifts up to 800 microns, more than 40 times the device size, typically 10-12 microns thick. The multilayer stack-based spaceplates we studied here show great promise for ultrathin flat optical systems that can easily be integrated into a modern-day imaging system.

No description available.

Visible Light Positioning (VLP) uses modulated LED luminaries to help locate a receiver inside a building. Indoor positioning is becoming an increasingly important service, and visible light has many advantages over other technologies used in indoor positioning systems (IPS). However existing VLP approaches have major drawbacks in robustness that have hindered their ability to be commercially deployed. This work proposes and demonstrates a new way of using light signals in an indoor localization system, titled Angular Diversity Visible Light Positioning (AD-VLP). AD-VLP uses optics at the transmitter to create a structured overlapping light pattern that can be used for positioning. This method is shown to have several advantages over existing VLP approaches, including increased robustness over intensity based techniques while still using a single element receiver. This work also includes an experimental implementation of the proposed AD-VLP system using existing mobile device technology. The experiments prove that sub-meter accuracy is obtainable, even when the receiver is oriented away from the transmitter. / Thesis / Master of Applied Science (MASc)