Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Nonlinear Optics( 비선형 광학 )
담당 교수 : 오 차 환
교 재 : A. Yariv, Optical Electronics in Modern Communications, 5th Ed.,
Oxford university Press, 1997
부교재 : R. W. Boyd, Nonlinear Optics, Academic Press, 1992
A. Yariv, P. Yeh, Optical waves in Crystals, John Wiley & Sons, 1984
2007 봄학기
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Chapter 1. Electromagnetic Theory
1.0 Introduction Propagation of plane, single-frequency electromagnetic waves in - Homogeneous isotropic media - Anisotropic crystal media
1.1 Complex-Function Formalism Expression for the sinusoidally varying time functions ;
],ARe[][2
|A|)cos(|A|)( )()( tititi
a eeetta aa
aie |A|Awhere
Typical expression ; tieta A)(
??
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Distinction between the real and complex forms
1) tieita
dt
d A)tsin(|A|)( a
2) )]cos()2[cos(2
|B||A|)()( babattbta
)2(|B||A| batie
* Time averaging of sinusoidal products
)cos(2
|B||A|)cos(|B|)cos(|A|
1)()(
0
bab
T
a dtttT
tbta *)ABRe(
2
1
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
1.2 Considerations of Energy and Power in Electromagnetic Field
Maxwell’s curl equations (in MKS units) ;
t
dih
t
be ped 0 m)(hb 0[ , ]
peeeiehett
)(20
mhhhehtt
00 )(
2
Vector identity ; BAABB)A (
ttt
mh
pehheeieh)e- 0
22
( 00
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Divergence theorem ;
sv
dadv nAA)( v s
n
dvttt
dadvs vv
mh
pehheeienh)eh)e 0
22
(( 00
: Poynting theoremTotal power flow into the volume bounded by s
Power expended by the field on the moving charges
Rate of increase of the vacuum
electromagnetic stored energy
Power per unit volume expended by the field on electric
and magnetic dipoles
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Dipolar dissipation in harmonic fields
The average power per unit volume expended by the field on the medium electric polarization ;
t
pe
volume
power
Assume, field and polarization are parallel to each other
]Re[)( tiEete EPPetp eti
0where],Re[)(
)Re(||2
*]Re[2
1
volume
power 200 ee
tiωtiω iEEEiiωωE ]e]Re[eRe[
Put, "' eee i
20 ||2
"
volume
powerEe
)*Re(2 ,
0 jiji
ij EEi
: Isotropic media
: Anisotropic media
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Ex) single localized electric dipole, )( exμ
power DF t
e
Let, position of electron :
electric field :
)cos(0 etxx tEex cos0
power DF )sin(cos)]cos([cos 0000 ee ttExetex
ttE
1) :2
e power DF tExe 2
00 cos
2) :2
e power DF tExe 2
00 cos
: The dipole(electron) continually loses power to the field
: The field continually gives power to the dipole
Power exchange between the field and medium via dipole interaction
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
1.3 Wave Propagation in Isotropic Media
Electromagnetic plane wave propagating along the z-axis in homogeneous, isotropic,
and lossless media constants)scalar :,(
Put, yx uhue yx he ,
t
eε
z
h
t
h
z
e xyyx
,2
2
2
22
2
2
,t
hε
z
h
t
e
z
e yyxx
General solutions : ,),( )()( kztix
kztixx eEeEtze )()(1
),( kztix
kztixy eEeEtzh
* Phase velocity :n
c
εkc 01
* wavelength : c
k2
2
* Relative amplitude :
where,xy
EH
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Power flow in harmonic fields
Intensity (average power per unit area carried in the propagation direction by a wave) :
*]Re[2
1|| yxyx HEheheI
(1.3-17) 2
||
2
||]*)(*)[(][Re
2
1 22 xxikz
xikz
xikz
xikz
x
EEeEeEeEeEI
Electromagnetic energy density :
*}Re{2
1
2*}Re{
2
1
22222
yyxxyx HHEEheV
E
(1.3-17) }|||{|2
1
222222 xxyx EEhe
V
E
For positive traveling wave : cEEV
Ixx
1
||2
/||2
1
/22
E
]W/m[||2
1 22 xEcI
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
1.4 Wave Propagation in Crystals-The Index Ellipsoid
In general, the induced polarization is related to the electric field as
zzzyzx
yzyyyx
xzxyxx
E,
where0P
: electric susceptibility tensor
)(
)(
)(
''3'3''2'3''1'30'
''3'2''2'2''1'20'
''3'1''2'1''1'10'
zyxz
zyxy
zyxx
EEEP
EEEP
EEEP
If we choose the principal axes, (Diagonalization)
zz
yy
xx
EP
EP
EP
330
220
110
zyx ,,
zz
yy
xx
ED
ED
ED
33
22
11
)1(
)1(
)1(
33033
22022
11011
where
0/n
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
)()( , rktirkti ee
00 HHEE
Secular equation
For a monochromatic plane wave ;
From Maxwell’s curl equations,2
2
t
E
E
0)( 2 EE kk
In principal coordinate,
z
y
x
ε
ε
ε
00
00
00
0222
222
222
z
y
x
yxzyzxz
zyzxyxy
zxyxzyx
E
E
E
kkεkkkk
kkkkεkk
kkkkkkε
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Simple example ( 0, zyx kkkk ) : wave propagating along the x-axis
0)(
0)(
0
22
22
2
zz
yy
xx
Ekε
Ekε
Eε
0xE : transverse wave !!
0,
0,
and
and
yz
zy
Eεk
Eεk
For nontrivial solution to exist, Det=0 ;
0222
222
222
yxzyzxz
zyzxyxy
zxyxzyx
kkεkkkk
kkkkεkk
kkkkkkε
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
zk
xk
yk
cnz /
cnz /cnx /
cnx /
cny /
cny /
Normal surface
Optic axis
Simple example ( 0zk
, determinant equation
02222
222
1222
3
yxxyyx kkkc
nk
c
nkk
c
n
)
2
322
c
nkk yx
: circle
11
2
2
2
cn
k
cnk yx
: ellipse
sc
nk ˆ
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Wave propagation in anisotropic media
Maxwell equations 2
2
t
D
E
Define the unit vector along the propagation direction as ,s sc
nk ˆ
( : wave vector)
DE )ˆˆ(2
2
ssc
n
Put, =1, and )()( BACCABCBA
)]ˆ(ˆ[2
2
E-ED ssc
n
)()( , rktirkti ee
00 HHEE
Taking scalar product, s on both sides :
0)]ˆ)(ˆˆˆ[ˆ2
2
E(-ED ssssc
ns
: propagation direction is perpendicular to the electric displacement vector not to the electric field vector E
kS
D
(poynting vector)
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Index ellipsoid
The surface of constant energy density in D space :
ez
z
y
y
x
x UDDD
2222
Energy density :
jiije EEU 2
1
reUD 2/
1/// 0
2
0
2
0
2
zyx
zyxor 1
2
2
2
2
2
2
zyx n
z
n
y
n
x: Index ellipsoid
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Classification of anisotropic media
1) Isotropic : zyx nnn ex) CdTe, NaCl, Diamond, GaAs, Glass, …
2) Uniaxial : zyx nnn (1) Positive uniaxial : xz nn
ex) Ice, Quartz, ZnS, …
(2) Negative uniaxial : xz nn ex) KDP, ADP, LiIO3, LiNbO3, BBO, …
):,:( ordinaryaryextraordin 0nnnn xez Fast/Slow axis
3) Biaxial : zyx nnn ex) LBO, Mica, NaNO2, …
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Example of index ellipsoid (positive uniaxial)
12
2
20
22
en
z
n
yx
)sin,cos,0( ee nn
s
x
y
z
)0,,0( 0n
)0,0,( 0n
),0,0( en
B
A
0
propagation direction
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Intersection of the index ellipsoid
s
y
z
A
0
)(en
0n
222 )( yzne
12
2
20
2
en
z
n
y
cos)(,sin)( ee nynz
)(
1sincos22
2
20
2
ee nnn
Birefringence : |)(| 0nne
000 |)90(|,0|)0(| nnnnnn eee
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Normal index surface
: The surface in which the distance of a given point from the origin is equal to
the index of refraction of a wave propagating along this direction.
1) Positive uniaxial (ne>no)
z
y
en0n
0n
2) negative uniaxial (ne<no)
z
y
0n
en
0n
3) biaxial ( )
z
y
yn
xn zn
zyx nnn
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
1.5 Jones Calculus and Its Application in Optical Systems with Birefringence Crystals
Jones Calculus (1940, R.C. Jones) : - The state of polarization is represented by a two-component vector - Each optical element is represented by a 2 x 2 matrix. - The overall transfer matrix for the whole system is obtained by multiplying all the individual element matrices. - The polarization state of the transmitted light is computed by multiplying the vector representing the input beam by the overall matrix.
Examples) - Polarization state :
- Linear polarizer (horizontal) :
- Relative phase changer :
y
x
V
VV
00
01
y
x
i
i
e
e
0
0
Report) matrix expressions - Linear polarizers (horizontal, vertical) - Phase retarder - Quarter wave plate (fast horizontel, vertical) - Half wave plate
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Retardation plate (wave plate)
: Polarization-state converter (transformer)
Polarization state of incident beam :
y
x
V
VV where,
yx VV , : complex field amplitudes along x and y
s, f axes components :
y
x
y
x
V
VR
V
V
V
V)(
cossin
sincos
f
s
Polarization state of the emerging beam :
f
s
f
s
f
s
exp0
0exp
V
V
lc
in
lc
in
V
V
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Define, - Difference of the phase delays :
c
lnn
)( fs
- Mean absolute phase change : c
lnn )(
2
1fs
f
s
2
2
f
s
0
0V
V
e
eeV
Vi
ii
Polarization state of the emerging beam in the xy coordinate system :
f
s
cossin
sincos
V
V
V
V
y
x
y
x
y
x
V
VRWR
V
V)()( 0
,cossin
sincos)(
R
2/
2/
00
0i
ii
e
eeW where,
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Transfer matrix for a retardation plate (wave plate)
2)2/(2)2/(
2)2/(2)2/(
0
cossin)2sin(2
sin
)2sin(2
sinsincos
)()(),(
ii
ii
eei
iee
RWRWW
1WWTransfer matrix is a unitary ( ): Physical properties are invariant under unitary transformation
=> If the polarization states of two beams are mutually orthogonal, they will remain orthogonal after passing through an arbitrary wave plate.
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Ex) Half wave plate
1
0 : beamincident ,4/, V
4/cos4/sin)2/sin(2
sin
)2/sin(2
sin4/sin4/cos
2)2/(2)2/(
2)2/(2)2/(
ii
ii
eei
ieeW
)115.1(
0
0
i
i
0
1
01
0
0
0' i
i
i
iV : x-polarized beam
Report : Problem 1.7
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Ex) Quarter wave plate
1
0 : beamincident ,4/,2/ V
)115.1(1
1
2
1
i
iW
i
ii
i
iV
1
212
1
1
0
1
1
2
1'
: left circularly polarized beam
: y-pol.
0
1 : beamincident ,4/,2/ V
ii
iV
1
2
1
0
1
1
1
2
1'
: right circularly polarized beam
: x-pol.
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Intensity transmission
In many cases, we need to determine the transmitted intensity, since the combination of retardation plates and polarizers is often used to control or modulate the transmitted optical intensity.
Incident beam intensity :
y
x
V
VV
22
yx VVI VV
Output beam intensity :
y
x
V
VV
2'2'' yx VVI
Transmissivity :22
22
yx
yx
VV
VV
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Ex) A birefringent plate sandwiched between parallel polarizers
,)(2 oe d
nn 4/
2cos
0
1
0
2cos
2sin
2sin
2cos
10
00'
i
iV
dnnI oe )(
cos2
cos' 22
: fn. of d and
Ex) A birefringent plate sandwiched between a pair of crossed polarizers
02
sin1
0
2cos
2sin
2sin
2cos
00
01' i
i
iV
dnnI oe )(
sin' 2
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Circular polarization representation
It is often more convenient to express the field in terms of “basis” vectors that are circularly polarized ;
1
0:CW
0
1:CCW and : constitute a complete set that can be used
to describe a field of arbitrary polarization.
Right circularly polarized Left circularly polarized
Rectangular representation : Circular representation :
y
xyx V
VVV
1
0
0
1V
V
VVV
1
0
0
1V
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Transformation
y
x
y
x
V
VT
V
V
i
i
V
V
1
1
2
1
V
VS
V
V
iiV
V
y
x 11
examples)
1
1
0
1
1
1
i
i
V
V
iiiV
V
y
x 1
1
011
Report :
?
?
0
1
?
?
1
0
?
?
1
1
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Faraday rotation
In certain optical materials containing magnetic atoms or ions, the two counter-rotating, circularly-polarized modes have different indices of refraction when an external magnetic field is applied along the beam propagation direction.
This difference is due to the fact that the individual atomic magnetic moments process in a unique sense about the z-axis (magnetic field direction) and thus interact differently with the two counter-rotating modes.
EBiED 0
)0(
)0(
0
0
)0(
0
0
)0(
)(
)(
))(2/(
))(2/())(2/(
)/()/(
V
V
e
ee
eV
eV
zV
zV
i
ii
znciznci
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Ignoring the prefactor, exp[-(i/2)(++-],
)0(
)0(
0
0)(
)()(
)(
V
V
e
ezV
zVzF
zF
i
i
anglerotationFaraday
)(2
)(2
1)(
F
znnc
zwhere,
Why (Faraday) rotation angle ?
)0(
)0(
cossin
sincos
)0(
)0(
0
0)(
)(
FF
FF
1
)(
)(
y
x
y
x
i
i
y
x
V
V
V
VT
e
eT
zV
zVzF
zF
In rectangular representation,
)0(
)0()( F
y
x
V
VR
Nonlinear Optics LabNonlinear Optics Lab. . Hanyang Hanyang Univ.Univ.
Basic difference between propagation in a magnetic medium and in a dielectric birefringent medium :
<dielectric birefringent medium> <magnetic medium>
CW for +z
CW for -z
CW for +z
CCW for -z
B
Report : proof by calculating Jones matrix.