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Fig 9.1
Light is an electromagnetic wave
An electromagnetic wave is a traveling wave that has time-varying electric and magneticFields that are perpendicular to each other and the direction of propagation z .
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From Principles of Electronic Materials and Devices, Third Edition , S.O. Kasap ( McGraw-Hill, 2005)
E x = E o cos( t kz + )
E x = electric field along x at position z at time t,k = propagation constant , or wavenumber = 2 / = wavelength = angular frequency
E o
= amplitude of the wave
is a phase constant which accounts for the fact that at t = 0and z = 0 E x may or may not necessarily be zero depending onthe 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
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Fig 9.2From Principles of Electronic Materials and Devices, Third Edition , S.O. Kasap ( McGraw-Hill, 2005)
A plane EM wave traveling along z , has the same E x (or B y) 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.
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Fig 9.3From Principles of Electronic Materials and Devices, Third Edition , S.O. Kasap ( McGraw-Hill, 2005)
Wavevector
A traveling plane EM wave along a direction k .
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Fig 9.6From Principles of Electronic Materials and Devices, Third Edition , S.O. Kasap ( McGraw-Hill, 2005)
Refractive index n and the group index N g of pure SiO 2 (silica) glass as a function of wavelength.
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Fig 9.8From 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) suffersreflection and refraction at the boundary.
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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 onThe incidence angle with respect to qc, which is determined by the ratio of the refractiveIndices, the wave may be transmitted (refracted) or reflected.(a) i < c(b) i = c(c) i > c and total internal reflection (TIR).
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Fig 9.12
From Principles of Electronic Materials and Devices, Third Edition , S.O. Kasap ( McGraw-Hill, 2005)
ernal reflection:Magnitude of the reflection coefficients r // and r vs. angle of incidence i for n1 = 1.44 and
= 1.00. The critical angle is 44 .The corresponding changes // and vs. incidence angle.
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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.
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Fig 9.14
From Principles of Electronic Materials and Devices, Third Edition , S.O. Kasap ( McGraw-Hill, 2005)
E v a n e s c e n t
w a v e
W a v e f r o n t
I n c i d e n t
w a v e
E r ,
y
E r , n2
n1
> n2
E r , E r ,
E v a n e s c e n t
w a v e
R e f l e c t e d
w a v e
k r
When i > c, for a plane wave that is reflected, there is an evanescent wave at the boundary propagating along z .
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Fig 9.20
From Principles of Electronic Materials and Devices, Third Edition , S.O. Kasap ( McGraw-Hill, 2005)
Complex Refractive Index and Reflectance
(a) Refractive index and extinction coefficient vs. normalized frequency, / 0.(b) Reflectance vs. normalized frequency
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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.
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Fig 9.24
From Principles of Electronic Materials and Devices, Third Edition , S.O. Kasap ( McGraw-Hill, 2005)
Electron energy ( E ) vs. crystal momentum k and photon absorption. (a) Photon absorption in adirect bandgap semiconductor. (b) Photon absorption in an indirect bandgap semiconductor (VB,valence band; CB, conduction band)
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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 opticalfiber.There are two communications channels at 1310 and 1550 nm.
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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, andReturn to the ground state E 1.The energy levels have been displaced horizontally for clarity.
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Fig 9.31
From Principles of Electronic Materials and Devices, Third Edition , S.O. Kasap ( McGraw-Hill, 2005)
Polarization
A linearly polarized wave has its electric field oscillations defined along a line perpendicular he direction of propagation z . The field vector E and z define a plane of polarization.The E -field oscillations are contained in the plane of polarization.A linearly polarized light at any instant can be represented by the superposition of two fields
and E y with the right magnitude and phase.
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Fig 9.35
From Principles of Electronic Materials and Devices, Third Edition , S.O. Kasap ( McGraw-Hill, 2005)
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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 butat different speeds.
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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.