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Optical Fibers
Published in Johan Meyer, Justice Sompo, Suné von Solms, Fiber Lasers, 2022
Johan Meyer, Justice Sompo, Sune von Solms
The guidance of a light beam in the optical fiber takes place because of the phenomenon of total internal reflection. Total internal reflection occurs when light passes from a higher refractive index material to a lower refractive index material. However, for total internal reflection to take place, specific conditions must be met. Let us consider Figure 2.1 where a ray of light is incident at the interface of two media of different refractive indices (i.e. air and glass), experiment shows that the ray will undergo partial reflection and partial refraction.
Waves
Published in Daniel H. Nichols, Physics for Technology, 2019
Refraction is the bending of a wave when it moves from one medium into another. Waves refract because the speed of the wave changes when the wave moves from one medium into another. For example, light travels slower through water than through air. A wave front, striking the surface of water from air, will bend because the speed of the wave changes when the wave enters the water. The wave front in the water will lag behind the incoming wave. As a result, the wave will bend (Figure 15.10).
Interlude of Physics II: Thermodynamics
Published in Franco Battaglia, Thomas F. George, Understanding Molecules, 2018
Franco Battaglia, Thomas F. George
It is not hard to formulate a general principle guaranteeing a unique outcome when constraints are removed in an isolated system: the path to follow for that is quite common in science. For instance, in optics, if a light beam goes from a point P inside a material to a point Q in another material, crossing at point R the interface separating them, the three points are not, in general aligned (the phenomenon is called refraction): the guiding principle specifying the light-beam trajectory states the existence of a quantity whose value, when computed along the real trajectory, is an extremum (maximum or minimum) when compared to the value computed along any other trajectory connecting P and Q. The principle at hand is called the Fermat principle, and the extremum quantity turns out to be the time taken by the beam to travel from P to Q: such a time—as required by the Fermat principle—must be a minimum.
Steering light in fiber-optic medical devices: a patent review
Published in Expert Review of Medical Devices, 2022
Merle S. Losch, Famke Kardux, Jenny Dankelman, Benno H. W. Hendriks
Refraction is defined as the change in direction of a transmitted light beam after it enters a second medium. Reflection is defined as the change in direction of a light beam at an interface that returns the light beam back to the original medium. The angle of incidence of the light beam on the surface and the material properties of the two media determine the intensity and direction of the refracted and reflected light beam. Another way to steer light is scattering: multiple changes in refractive index force the light beam to randomly change direction in a series of reflection events, resulting in diffuse light scattering. Lastly, a fundamentally different method to steer a light beam is diffraction. Diffraction is defined as the bending of light after encountering a small opening or obstacle. The light beam does not bend in one direction; instead, a diffraction pattern is generated by the interference of different wave fronts. Diffraction is predominant for apertures and obstacles with sizes in the range of the wavelength of the incident light.
Scattering of plane-wave through fluid medium of finite width between self-reinforced and triclinic half spaces
Published in Waves in Random and Complex Media, 2021
Shishir Gupta, Snehamoy Pramanik, Abhijit Pramanik
The angle is known as a critical angle where the refracted waves move horizontally. It happens because of When then where and denote the incident and reflected waves respectively. In this case, will be the critical angle. The characteristic of incidence angle is that it is equal to the critical angle in case the refracted angle is . At the position, where reflected and refracted beam becomes the total reflection, that is known as critical angle. When the angle of incidence reaches a certain critical value, the refracted ray lies along the boundary. This angle of incidence is known as a critical angle which is the largest angle of incidence for which refraction can still occur. For any angle of incidence greater than critical angle, wave will undergo total internal reflection. The actual value of critical angle is dependent upon the combination of materials present on each side of the boundary.
Reflection characteristics of superconductor-dielectric-superconductor junction at near-zero permittivity region
Published in Electromagnetics, 2019
Peng Chen, Luping Li, Kai Yang
Refractive index is defined as the ratio of the light speed in vacuum and the light speed in a medium. As the medium molecules always have thermal collisions when their ambient temperature are over absolute zero, the speed of light in the medium is often less than that in vacuum, which makes the refractive index greater than 1. Veselago (1968) proposed a hypothesis that conductance and permeability can be negative. Pendry has found that both the relative conductance and permeability could be negative when a split ring resonator is used to transform the electromagnetic wave. He named this new material as metamaterial (Pendry 2006). Soon more and more scientists began to use the metamaterial for various applications, such as filter and antenna (Kokkinos, Sarris, and Eleftheriades 2006; Studniberg and Eleftheriades 2009; Zhang, Fluegel, and Mascarenhas 2003). The metamaterial can greatly reduce the size of the radiofrequency (RF)/microwave circuits. Another application of the metamaterial is to design electromagnetic invisibility cloaks (Leonhardt 2006; Pendry 2006). As a tremendous potential application in the military, the electromagnetic invisibility cloaks soon became the research hot spot.