Temperature control of nematicon trajectories

Using modulation theory, we develop a simple [(2+1)-dimensional] model to describe the synergy between the thermo-optical and reorientational responses of nematic liquid crystals to light beams to describe the routing of spatial optical solitary waves (nematicons) in such a uniaxial environment. Introducing several approximations based on the nonlocal physics of the material, we are able to predict the trajectories of nematicons and their angular steering with temperature, accounting for the energy exchange between the input beam and the medium through one-photon absorption. The theoretical results are then compared to experimental data from previous studies, showing excellent agreement

Leadership Strategies to Influence Employee Engagement in Health Care

Hospitals are in a precarious financial position with declining reimbursement, eroding profit margins, and low patient satisfaction. The Patient Protection and Affordable Care Act of 2010 reform may decrease hospital reimbursement by $500 billion from 2010 to 2020, while low patient satisfaction may decrease profitability for hospitals by 27%. Employee disengagement may decrease patient satisfaction and consumer loyalty. The purpose of this phenomenological study was to explore the lived experiences of health care leaders as they worked to engage employees and provide better patient care. Improving patient care provides opportunities to capture new market shares, which increases sustainability of health care organizations. Expectancy theory shaped the conceptual framework of this study. Inquiry consisted of personal interviews with 23 mid-level hospital managers. Data analysis occurred with a modified Van Kamm data analysis process, which entailed descriptive coding and sequential review of the interview transcripts. Member checks and data saturation ensured trustworthiness of the findings. The findings from these personal interviews led to discovery of 4 themes of leader-employee engagement to include psychological commitment, expectation realization, trust actualization, and reduction in the leadership power distance. By applying employee engagement strategies aligned with these themes, leaders may influence patient care. This study contributes to social change by increasing health care quality for patients leading to a positive influence on medical care and societal health

Soliton-assisted random lasing in optically-pumped liquid crystals

We demonstrate a guided-wave random laser configuration by exploiting the coexistence of optical gain and light self-localization in a reorientational nonlinear medium. A spatial soliton launched by a near-infrared beam in dye-doped nematic liquid crystals enhances and confines stimulated emission of visible light in the optically-pumped gain-medium, yielding random lasing with enhanced features.See also erratum at:Appl. Phys. Lett. 110, 019902 (2017); https://doi.org/10.1063/1.4973864<br/

Nonlinear management of the angular momentum of soliton clusters

We demonstrate an original approach to acquire nonlinear control over the angular momentum of a cluster of solitary waves. Our model, derived from a general description of nonlinear energy propagation in dispersive media, shows that the cluster angular momentum can be adjusted by acting on the global energy input into the system. The phenomenon is experimentally verified in liquid crystals by observing power-dependent rotation of a two-soliton cluster.Comment: 4 pages, 3 figure

Highly Nonlocal Response benefit or drawback?

A highly nonlocal optical response in space has been shown to heal several shortcomings of beam self-action in nonlinear optics. At the same time, nonlocality is often connected to limits and constraints in both temporal and spatial domains. We provide a brief and rather subjective review of what we consider the main benefits and some drawbacks of a highly nonlocal response in light localization through nonlinear optics, with several examples related to reorientational soft matter, specifically nematic liquid crystals

Optical spatial solitons for all-optical signal processing

Nonlinear systems respond to an excitation in a non-proportional way and do not satisfy the superposition principle. Most of the linear models of physical systems (harmonic oscillator is probably the clearest example) are valid approximations only in a perturbative regime; beyond it their intrinsic nonlinear nature must be considered. The nonlinear world is a source of intriguing phenomena (both from theoretical and applicative points of view) and optics is one of the most accessible area where such effects can be studied. When light and matter interact, the former is able to change the medium properties, in particular the refractive index, so affecting its own propagation. Among the nonlinear processes we will consider self-confinement: the ability of a light beam to compensate its natural tendency to spread. When linear spreading is exactly compensated by non-linear self-focusing, a spatial soliton is formed. Spatial solitons preserve their profile during propagation, which makes them suitable candidates to carry and process other signals, just like waveguides. We will deal with spatial solitons in nematic liquid crystals, namely nematicons, in which nonlinearity is enabled by dipolar interactions between molecules and electric fields: the material is chosen on the basis of its high nonlinearity and versatility. This dissertation reports on the all-optical control of nematicons and some representative applications of signal processing. The work is mostly experimental, with some theoretical considerations wherever it is necessary for the comprehension of the observed phenomena. Chapter 1. Fundamentals of nonlinear optics and spatial solitons are firstly summarized. Then we examine Nematic Liquid Crystals and their physical properties, focusing the attention on their nonlinear optical response and introducing nematicons. Chapter 2. We report some experiments in standard samples. First, we examine the propagation of a nematicon in the presence of a tunable nonlinearity. Then we treat the nonlinear control of the interaction between two nematicons. Chapter 3. Here we present experiments in dye-doped liquid crystals. We describe the optical response of dye-doped nematics and two experiments. In the first, we discuss nonlinear self-steering of light, comparing undoped and doped liquid crystals; in the second we deal with the formation of optical interfaces in order to control the nematicon trajectory. Chapter 4. We introduce liquid crystal light valve as a novel environment for the propagation of nematicons. After a preliminary section where we explain the working principles of the valve, we illustrate the propagation of a nematicon in a fully controllable refractive index landscape. We review briefly the theorical approach, proposing and demonstrating the implementation of a reconfigurable set of all-optical signal processors. This activity was mostly carried out at NooEL - Nonlinear Optics and OptoElectronics Lab at the University ROMA TRE. The work on liquid crystal light valve was developed at the INLN (Institut NonLin´aire de Nice), University of Nice - Sophia Antipolis

Optical Detection of Dangerous Road Conditions

We demonstrated an optical method to evaluate the state of asphalt due to the presence of atmospheric agents using the measurement of the polarization/depolarization state of near infrared radiation. Different sensing geometries were studied to determine the most efficient ones in terms of performance, reliability and compactness. Our results showed that we could distinguish between a safe surface and three different dangerous surfaces, demonstrating the reliability and selectivity of the proposed approach and its suitability for implementing a sensor

Nematonics: from physics to photonics of reorientational solitons

Nematic Liquid Crystals are birefringent soft matter exhibiting unique nonlocal and nonlinear optical properties. Due to the interaction with finite-size light beams, self-focusing via molecular reorientation can balance out diffraction and result in self-confined beams, namely spatial solitons or nematicons, operating as waveguides for copolarized optical signals. Since nematicon propagation and confinement are determined by material properties that can be tailored by external fields, they allow implementing various photonic functionalities: from signal steering and addressing to bistability, from topological and optical symmetry breaking to beaming of random laser emission, to mention a few. Such proof-of-principle applications make nematic liquid crystals and nematicons a versatile platform for the study of complex light-matter interactions in nonlocal dielectrics and the demonstration of all-optical photonic devices for signal processing