Theoretical Study of the Optical Manipulation of Semiconductor Nanoparticles under an Excitonic...
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Transcript of Theoretical Study of the Optical Manipulation of Semiconductor Nanoparticles under an Excitonic...
Theoretical Study of the Optical Manipulationof Semiconductor Nanoparticles
under an Excitonic Resonance Condition
+ Reference +
T.Iida and H.Ishihara, Phys.Rev.Lett. 90, 057403(2003)
ITOH Lab. Kei IMAIZUMI ( M1 )
Abstract
“Manipulation” means “skillful handling”.
Optical manipulation is the technique of handling small objectsusing mechanical interaction between light and matter.
Force
・ Manipulating the semiconductor nanoparticle・ Size selective manipulation
Contents
• IntroductionApplication, History
• Maxwell stress tensor method• Calculation Result
The merit of using electronic resonanceHeat problemSize selective manipulation
• Summary
Application
Handling of DNAT. T. Perkins,
D. E. Smith, S. Chu(1994)
Biology, Chemistry, Material engineering…
Kansai Advanced Research Centerhttp://www-karc.nict.go.jp/
Polystyrene bead with a diameter
of 1 μm captured by laser
History of optical manipulation
19c
196019701985
1986
1995
Lorentz derived the equationof motion of a charged particle.Laser was invented.A.Ashkin accelerated micro-size particles by laser.Laser cooling of atoms
A.Ashkin demonstrated the trapping of dielectric particlewith single focused laser beam.Bose Einstein condensation of atoms
1997 Nobel PrizeS.Chu, C.Cohen-Tannoudi, W.D.Phillips
2001 Nobel PrizeE.A.Cornell, W.Ketterle, C.E.Wieman
Difficulty of manipulating nano-particles
Electronic Resonance• Manipulating the nano-particles• Size selective manipulation
Atomic scaler λ≪
μmr λ≫
nm
difficultex.)atom trapping
ex.)optical tweezer
Forces
Scattering force, Absorbing force Gradient force
Resonance
The interaction between light and matter increases.
Maxwell stress tensor methodLorentz Force
Maxwell Equations
< > : time average
T : Maxwell’s stress tensor
n : normal vector
S : Surface of the matter
volume integral
surface integral
resonance
susceptibilityEob , Δob
constant depending on the object
object Incident electric field
About the resonance
P
Escat
resonantnonresonant
P Escat
ε : Resonance P : large Escat : large
drEP
14
1
laserob
bbb EE
The merit of using electronic resonance
Greater advantage of resonance about smaller object!
ObjectCuCl particle
hwt = 3.2022 [eV]
R=100nm
R=50nm
The size dependence of its maximum value in the energy range 0 ~ 4 eV.
100nm → No difference 10nm → 104 times lager
Handling smaller object Resonance light
Heat problemAbsorption Heat problem
R=50nm
〈 I 〉
〈 II〉
〈 III 〉
<I>,<III> ・・・ Scattering Prevent the heat problem<II> ・・・ Absorption
Size selective manipulation
• Quantum size effect-Discrete energy levels-Energy shift depends on the size
Energy level
Future
Application to nanotechnology.
Particular particles
Propagating plane wave
Image
Summary
• When the size is less than 100nm, the use of electronic resonance has the merit.
• The exerted acceleration increases as the size decreases.
• The peak position of the force sensitively varies with the size change.
Nanoscale size selectionnanotechnology
Optical tweezer
Glass sphere (dielectric particle)
21 nn 2n
1n
lens
Force
p
laser
Force~ pN
R>>λ
μm
Gradient ForceUniform electric field
+
+
+
sloping electric field
-
-
-
cancel each other
+
+
+
-
-
-
E E
total force
In the sloping electric field, the power works.
Quantum size effectDiscrete energy levels
Energy shift depends on the size
2
22
2MRE
E dot size
Size change Energy gap change
Atom Semiconductor nanoparticle (quantum dot)
Quantum dot laser
Quantum dot laser・ Laser wavelength depends on the dot size.
・ Low threshold.
・ Stable property at high temperature.
threshold :しきい値
Useful property↑
The same size dots are needed.
Maxwell stress tensor method
Lorentz Force (of N charges)
G(t) is the summation of momenta