Creation of Colloidal Periodic Structure

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2006 ????
Laser Optics (??? ??)
?? ?? ? ? ? ? ? P.W. Miloni, J.H. Eberly,
LASERS, John Wiley Sons, 1991 ??? W.
Demtroder, Laser Spectroscopy, Springer-Verlag,
1998 F. L. Pedrotti, S.J., L.S.
Pedrotti, Introduction to Optics, Prentice-Hall,
1993
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Chapter 1. Introduction to Laser Operation
1.1 Introduction LASER Light
Amplification by the Stimulated Emission of
Radiation 1916, A. Einstein predicted
stimulated emission 1954, C. H. Townes et al.
developed a MASER 1958, A. Schawlow, C.H. Townes
adapted the principle of MASER to light 1960,
T.H. Maiman Ruby laser _at_ 694.3 nm 1961, A.
Javan He-Ne laser _at_ 1.15 mm, 632.8 nm
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Einsteins quantum theory of radiation
N1, N2 No. of atoms at E1, E2 r photon
density A211/t21 spontaneous emission rate
B12, B21 stimulated absorption/emission
coefficients
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Four key elements of a LASER - Gain medium
(Active medium) - Pumping source - Cavity
(Resonator) - Output coupler
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Four key elements of a LASER
1) Pumping source - Optical Nd-YAG, Ruby,
Dye, Tisapphire, - Electrical He-Ne, Ar,
CO2, N2, LD, - Chemical HF, I2, 2)
Active medium - Gas He-Ne, Ar, CO2, N2,
- Liquid Dye - Solid Nd-YAG, Ruby,
Tisapphire, LD, 3) Cavity or Resonator -
Resonator with total reflector Maximizing the
light amplification - Output coupler
Extracting a laser light - Resonance condition
ml/2L (minteger)
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1.2 Lasers and Laser Light (Characteristics of
laser light)
Monochromaticity (???) - Linewidth(FWHM) 7.5
kHz (He-Ne laser)
ltlt 940 MHz (low
pressure Cd lamp) Coherence (???) - Definite
phase correlation in the radiation field at
different locations(spatial) and different
times(temporal) Directionality (???) -
Divergence angle f1.27l/D lt q2.44l/D
(diffraction limit angle)
Brightness (?? ??) - Radiance 106
W/cm2-sr (4mW, He-Ne laser)
ltlt 250
W/cm2-sr (super-high-pressure Hg
lamp) Focusability (???) - Focusing diameter
d f f
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1.5 Einstein theory of light-matter interaction
(Laser action)

• Number of photons,

• Number of atoms in level 2,

pumping
loss
spontaneous emission
stimulated emission

• In steady state

threshold number of atoms
Minimum(threshold) pumping condition
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Spatial distribution of laser beam (Gaussian beam)
Maxwells curl equations
Scalar wave equation
gt
Put,
(monochromatic wave)
gt Helmholtz equation
Assume,
gt
Put,
gt
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Gaussian beam
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Propagation of Gaussian beam - ABCD law
Matrix method (Ray optics)
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Ray-transfer matrices
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ABCD law for Gaussian beam
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example) Focusing a Gaussian beam
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Chapter 2. Classical Dispersion Theory
2.1 Introduction
Maxwells equations
(for nonmagnetic media)
Wave equations
(2.1.13)
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2.2 The Electron Oscillator Model
Equation of motion for the electron
Electric-dipole approximation
where,
relative coordinate of the e-n pair
center-of-mass coordinate of the e-n pair
reduced mass
Electron oscillator model (Lorentz model) ltrefer
p.30-31gt
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2.3 Refractive Index and Polarizability
Consider a monochromatic plane wave,
Dipole moment
where, polarizability
Polarization
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From (2.1.13),
dispersion relation in a medium
refractive index of medium
For a medium with the z electrons in an atom
(2.3.22a)
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Electric susceptibility (macroscopic parameter),

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2.4 The Cauchy Formula
From (2.3.22),
If we suppose further that
(as in like a gas medium)
Cauchy formula
where,