Physics
Rectilinear Propagation
Rectilinear propagation refers to the straight-line path that light takes when traveling through a uniform medium. This principle is a fundamental concept in optics and is used to explain how light travels in a vacuum or through a transparent medium. It is a key aspect of understanding the behavior of light in various optical systems.
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5 Key excerpts on "Rectilinear Propagation"
eBook - PDF- Shun Lien Chuang(Author)
- 2012(Publication Date)
- Wiley(Publisher)
Phys. Chem. B 108, 17740-17747(2004). 18. L. A. Coldren and E. R. Hegblom, Fundamental issues in VCSEL design, Chapter 2 in Vertical-Cavity Surface-Emitting Lasers, C. W. Wilmsen, H. Temkin, and L. A. Coldren, eds., Cambridge University Press, Cambridge, UK, 1999. Light Propagation in Anisotropie Media and Radiation The propagation of light is an extremely interesting topic because many common phenomena such as refraction of light, polarization properties of light, and scattering of light can be observed every day. The Rayleigh scattering of light by water mole-cules has been used to explain why the sky is blue in the daytime and red in the evening. In Section 6.1, we discuss some basic properties of the propagation of elec-tromagnetic waves in uniaxial media [1, 2]. We then present light propagation in gyrotropic media and the magnetooptic effects [3,4] in Section 6.2. The phenomenon of Faraday rotation and its application to optical isolators are discussed. In Section 6.3, we present the general solutions to Maxwell's equations for a given current density J and a charge density p, which satisfy the continuity equation. We discuss the gauge transformation including the Lorentz gauge and the Coulomb gauge; the latter will be used in the Hamiltonian to account for the interaction between the elec-trons and the photon field in semiconductors in Chapter 9. The radiation of the electromagnetic field is presented in Section 6.4 with the aim that the far-field pattern from a diode laser and laser arrays [5] will be derived once we know the laser mode on the facet of the laser cavity. 6.1 LIGHT PROPAGATION IN UNIAXIAL MEDIA Consider the case of a uniaxial medium [1,2] described by D = e-E ~ε 0 0 = 0 ε 0 0 0 ε ζ = (6.1.1a) (6.1.1b) (6.1.2) Physics of Photonic Devices, Second Edition. By Shun Lien Chuang Copyright (c) 2009 John Wiley & Sons, Inc. 227
- Vladimir Troyan, Yurii Kiselev(Authors)
- 2010(Publication Date)
- World Scientific(Publisher)
Chapter 5 Ray theory of wave field propagation The exact solutions of problems of sounding signals propagation are constructed only for limited number of media models. As a rule, this set of media includes uniform medium, layered homogeneous medium, uniform medium with the inclu-sions of high symmetry. For the interpretation of real geophysical fields (seismic, acoustic, electromagnetic) it is necessary to construct the approximate solutions for the wave propagation in non-uniform media. So, it exists in the Earth not only the interfaces, on which one the elastic properties vary by jump, but also areas, inside which there is a smoothly varying variation of elastic properties. From the physical point of view the ray theory is interpreted as follows: the waves propagate with local velocities along ray pathways and arrive in the observation point with ampli-tudes described by a geometrical spreading of rays from a source to the receiver point. At an enunciating of this chapter we shall follow the description introduced in (Ryzhikov and Troyan, 1994). 5.1 Basis of the Ray Theory One of the most common method of the solution of the equations of wave propa-gation is the method of geometrical optics (Babic and Buldyrev, 1991; Babic et al. , 1999; Kravtsov, 2005; Bleistein et al. , 2000). This method is a shortwave asymp-totic of a field in weak non-uniform, slow non-stationary and weak-conservative media: the sizes of the inhomogeneity are much greater than the wavelength and time intervals of the non-stationarity much more than the period of oscillation. The shortwave asymptotic allows to consider the medium locally as homogeneous and stationary and is based on the assumption of a wave field in a form ( ϕ ) a “quick” phase and a “slow” amplitude multiplier factors. Let us consider a formal scheme of the space-time ray method.
eBook - PDF- Slawomir Sujecki(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
11 2 Light Propagation in Homogenous Media In this chapter, we discuss the numerical analysis of light propagation in homogenous media. It is assumed that the reader is familiar with wave optics, electromagnetic optics, and Fourier optics (see [1,2]). In particular, we discuss the application of the Fourier method. In the first section, we discuss the application of the Fourier method to study optical beam propagation in homogenous media. In the second section, we extend the Fourier method and study optical beam reflection and refraction. In the third section, we discuss the application of paraxial and wide angle approximations. Finally, in the last section, we discuss the modelling of optical systems that include thin bulk optical elements. In this chapter, we also introduce several basic concepts that are further explored in the remaining chapters of this book. A description of the application of ray optics methods can be found in Poon and Kim [2]. FOURIER METHOD The Fourier method provides a simple and an efficient way of calculating the evo-lution of an optical beam envelope function when propagating in a homogenous medium. To explain how the Fourier method works, we introduce the Cartesian coordinate system ( x,y,z ) and consider the simplest case, namely an optical wave that propagates with the propagating vector in the plane ( x,z ).
eBook - PDF- Md Nazoor Khan, Simanchala Panigrahi(Authors)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
i. Fresnel’s diffraction In this class of diffraction, the light source and the obstacle are separated by finite distance. Therefore, the wavefront incident on the obstacle is either cylindrical or spherical. Diffraction 187 Figure 3.1 (a) The shadow of a straight edge formed by a parallel beam of sunlight. The shadow is not very sharp. The encroachment of shadow by light is called diffraction. (b) A rough sketch of intensity distribution on the screen ii. Fraunhofer’s diffraction In this class of diffraction, the light source and the obstacle are separated by infinite distance. Therefore, the wavefront incident on the obstacle is plane. In the laboratory, infinite distance is created by placing a lens in between the light source and the obstacle so that the light source is at the focus of the lens. 3.3 Fresnel’s Explanation of Rectilinear Propagation of Light The greatest difficulty encountered by the supporters of the wave theory of light was how to explain the observed fact that light propagates in a straight line. In the year 1815 French physicist Augustin-Jean Fresnel gave the correct interpretation of the Rectilinear Propagation of light on the basis of wave theory of light by combining Huygens’ principle of secondary wavelets with the principle of interference. In addition to this, he concluded that Rectilinear Propagation of light is only approximate. 3.3.1 Fresnel’s assumptions i. Observable diffraction pattern is produced only when the wavefront is incident on a sharp obstacle or passes through slits. ii. The principle of interference holds good also for secondary wavelets originating from all the points of the unobstructed wavefront. 188 Principles of Engineering Physics 1 iii. By applying the interference principle to the secondary wavelets originating from all the points of the unobstructed wavefront the resultant intensity at a forward point can be calculated taking into account their relative amplitudes and phase differences.
eBook - PDF- Jerry D. Gibson(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
Reflection coefficient: Ratio of strength of reflected light to that of the incident light. Refraction: Process of bending a ray of light away from its original direction. Repeater: Electronic circuitry that takes in a degraded signal and restores or reconstitutes it for further transmission. Scattering: Process by which portions of light energy are redirected (by encounters with microscopic obstacles or inhomogeneities) to undesired directions and thereby lost from the propagating wave. Single-mode operation: Operation of an optical fiber under conditions that allow only one mode to propagate along it. Snell’s law: Law governing reflection (reflection angle equals incidence angle) and refraction (compo-nent of propagation vector tangential to the interface is preserved) of a ray of light encountering the interface between media of different optical density. Spatial Fourier spectrum: Description of some quantity that varies in space in terms of its decompo-sition into constituent sinusoidal components of different spatial frequencies or periodicities. Spatial frequency: The number of cycles per unit length of a quantity that varies periodically in space. 45 -10 The Communications Handbook Spatial wavenumber: Reciprocal of a quantity’s interval of periodicity in space. Standing wave: Resultant of counterpropagating waves, with a spatial distribution that does not move. Step-index fiber: The type of optical fiber whose core and cladding each have a uniform index of refraction. Total internal reflection: Process of reflecting light incident from a denser medium toward a less dense one, at an angle sufficiently grazing to avert transmission into the less dense medium. All of the incident light power is reflected, although optical fields do appear beyond the interface. Transverse electric: Descriptive of a mode of propagation whose electric field vector is entirely trans-verse to the direction of propagation.
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