Solid-State Theory
0260031
Dr. Hongwei Chu
Room 139, Building N5
hongwei.chu@sdu.edu.cn
15165199229
Scores
Final Examination (50%) + Presentation (50%)
Introduction
This lecture is mainly about the way light interacts with
solids, specially designed for the first year graduate
students in Physics, Optical Engineering. At the same
time, I hope some of the topics will be of particular interest
to students and researchers of other disciplines in
chemical, environmental, or material engineering in the
campus.
Introduction
Contents
01
Introduction
02
Classical propagation
03
Interband absorption
04
Excitons
05
Luminescence
06
Nonlinear optics
Introduction
Overview of optical
properties and models
Linear
optics
Nonlinear
optics
Electronic Physics
Vibronic Systems
Vibrational Physics
Intraband absorption
Luminescent defects and
impurites
Phonons
Excitons
Intraband emissions
…
…
…
Introduction
Refraction
•
Reflection
Light waves propagate with a smaller velocity < c.
•
Some of the light is reflected from the front surfaces
Interface refraction: Snell’s Law
•
If any of the propagation light reaches the back surfaces,
the reflection occurs again
•
•
•
•
Light-mater
interactions
Absorption in the propagation resonant with ΔE
•
•
Absorption/Luminescence
Luminescence: spontaneous emission of light from
the excited states to the ground state in solids
•
•
Scattering
Light waves change the propagation directions, possibly
its frequency after interacting with the medium
•
•
Nonlinear optics
Other phenomena when the light propagates through the medium
•
SHG, SFG, FWM, etc
•
Propagation
•
The light enters the medium and propagates
through it
•
Transmission
•
The amount of light transmitted related to the reflectivity at
both faces, along the way the light propagates through the
medium
Introduction
• Reflectivity, R
•
R=reflected power/ the incident power
Optical
coefficients
• Transmissivity, T
•
T=transmitted power / the incident power
Introduction
Excited State
Ωs
Absorption
hv
Relaxation
Emission
hvs
Ground State
Introduction
Scattering
Mie Scattering
Rayleigh Scattering
Raman Scattering
 elastic scattering of light
 elastic scattering of light
 Inelastic scattering of light
 d~/> λ
 d<<λ
 Raman active molecules
 Mie signal is proportional to d2
 is proportional to 1/λ4
 Raman shift ~ vibrational mode
 stronger
 Normal
 Weaker (6 order smaller than Mie)
 strong angular dependency
 Species non-selective
 λRa on λl
 Mie imaging
 λRL~ λin
 Raman spectrometer/imaging
spontaneous
Introduction
Example
The reflectivity of silicon at 633 nm is 35% and the absorption coefficient
is 3.8×105 m-1. There is a silicon wafer with a thickness of 10 µm. Try to
calculate the transmission and optical density of this wafer.
Introduction
Complex refractive index
Introduction
Complex refractive index
Introduction
Complex dielectric constant
Introduction
Example
Introduction
Optical materials
Crystalline
Glasses
Metals
Molecular materials
Doped
Introduction
Characteristic optical physics
Crystal symmetry
Electronic bands
Crystals: long range translational order
32 classes: point group symmetry
230 classes: space group symmetry
Vibronic bands
Density of stats
7 Crystal systems
14 Bravais Lattices
Cubic
Primitive I(Body-) Facecentered
Tetragonal
PI
Orthorhombic
P I F C(side-centered)
Hexagonal
P
Monoclinic
P
Triclinic
PC
Trigonal
P
Delocalized states and
collective excitations
Introduction
Crystal symmetry
Note: the point group symmetry of a crystal is lower than that of an individual atom (highest possible symmetry
owing to the spherical invariance).
the point group symmetry 
Optical anisotropy: crystal is anisotropic if the properties are
not the same in all direction.
Lifting of degeneracies: Free atoms: spherical symmetric, no
preferable directions. Zeeman effect can describe the
splitting of degenerate magnetic levels when the atom is put
in a magnetic field. The same atom in a crystal, owing to the
crystal
field
determined
degeneracies can be lifted.
by
the
lattice,
some
level
Introduction
Electronic bands
Introduction
Density of States
l
Thanks for attention