PP-Ch9-3rdEd-Sample

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*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
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Fig 9.1
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Light is an electromagnetic wave
An electromagnetic wave is a traveling wave that has time-varying electric and magnetic 
Fields that are perpendicular to each other and the direction of propagation z.
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Ex = Eo cos(tkz + )	
Ex = electric field along x at position z at time t, 
k = propagation constant, or wavenumber = 2/
 = wavelength
 = angular frequency
Eo = amplitude of the wave
 is a phase constant which accounts for the fact that at t = 0 and z = 0 Ex may or may not necessarily be zero depending on the choice of origin. 
(tkz + ) =  = phase of the wave . 
This equation describes a monochromatic plane wave of infinite extent traveling in the positive z direction.z
Fig 9.2
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
A plane EM wave traveling along z, has the same Ex (or By) at any point in a given xy plane.
All electric field vectors in a given xy plane are therefore in phase. The xy planes are of 
Infinite extent in the x and y directions.
Fig 9.3
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Wavevector
A traveling plane EM wave along a direction k.
Fig 9.6
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Refractive index n and the group index Ng of pure SiO2 (silica) glass as a function of 
wavelength.
Fig 9.8
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
A light wave traveling in a medium with a greater refractive index (n1 > n2) suffers 
reflection and refraction at the boundary.
Fig 9.9
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Light wave traveling in a more dense medium strikes a less dense medium. Depending on
The incidence angle with respect to qc, which is determined by the ratio of the refractive 
Indices, the wave may be transmitted (refracted) or reflected. 
(a) i < c
(b) i = c
(c) i > c and total internal reflection (TIR).
Fig 9.12
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Internal reflection:
(a) Magnitude of the reflection coefficients r// and r vs. angle of incidence i for n1 = 1.44 and
n2 = 1.00. The critical angle is 44. 
(b) The corresponding changes // and  vs. incidence angle.
Fig 9.13
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
The reflection coefficients r// and r versus angle of incidence i for n1 = 1.00 and n2 = 1.44.
Fig 9.14
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
When i > c, for a plane wave that is reflected, there is an evanescent wave at the boundary
propagating along z.
Fig 9.20
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Complex Refractive Index and Reflectance
Refractive index and extinction coefficient vs. normalized frequency, /0.
(b)	Reflectance vs. normalized frequency
Fig 9.23
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Absorption coefficient  versus wavelength  for various semiconductors. 
SOURCE: Data selectively collected and combined from various sources.
Fig 9.24
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Electron energy (E) vs. crystal momentum hk and photon absorption. (a) Photon absorption in a direct bandgap semiconductor. (b) Photon absorption in an indirect bandgap semiconductor (VB, valence band; CB, conduction band)
Fig 9.26
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Attenuation in optical fibers
Illustration of typical attenuation versus wavelength characteristics of a silica-based optical
fiber.
There are two communications channels at 1310 and 1550 nm.
Fig 9.28
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Photoluminescence
Photoluminescence: light absorption, excitation, nonradiative decay and light emission, and
Return to the ground state E1.
The energy levels have been displaced horizontally for clarity.
Fig 9.31
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Polarization
(a) A linearly polarized wave has its electric field oscillations defined along a line perpendicular
to the direction of propagation z. The field vector E and z define a plane of polarization.
(b) The E-field oscillations are contained in the plane of polarization.
(c) A linearly polarized light at any instant can be represented by the superposition of two fields
Ex and Ey with the right magnitude and phase.
Fig 9.35
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Fig 9.38
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Birefringent Retarding Plates
A retarder plate.
The optic axis is parallel to the plate face. The o- and e-waves travel in the same direction but
at different speeds.
Fig 9.43
*From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
Transverse Pockels cell phase modulator. A linearly polarized input light into an electro-optic
Crystal emerges as a circularly polarized light.