Gamma-ray vortex beams carrying orbital angular momentum

42 Pages·2017·5.11 MB·English

JLab Student Seminar 3/22/2017
Gamma-ray vortex beams carrying
orbital angular momentum
Yoshitaka Taira
National Institute of Advanced Industrial Science and Technology (AIST), Japan
Visiting scientist: Mississippi State University and Jefferson Lab.
In this seminar...
I will talk about
so called
vortex beam,
orbital angular momentum beam,
twisted beam.
Does someone know that?
Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 1
Outline
Polairzation and wave fronts of light
Optical vortex
Electric field and Poynting vector
Generation, Measurement, Application
Electron vortex, X-ray vortex
Gamma-ray vortex
Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 2
Light
Sun LED
Synchrotron light
Wikipedia
YY.. TTaaiirraa,, GGaammmmaa--rraayy vvoorrtteexx bbeeaammss ccaarrrryyiinngg oorrbbiittaall aanngguullaarr mmoommeennttuumm 3
Electromagnetic wave spectrum
Frequency (Hz)
1 1 1 1 1 1 1 1 1 1 1
1 1 1 0 0 0 0 0 0 0 0 0 0 0
0 0 0 1 1 1 1 1 1 1 1 1 1 2
7 8 9 0 1 2 3 4 5 6 7 8 9 0
V
Radio, TV Microwaves Infra-red is Ultraviolet X-rays Gamma-rays
ib
le
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0 0
m c m µ n p
0 m c m 0 µ m 0 n m 0 p m
m m m µ m n m p m
m m m
Wavelength
7 6 5 4
0 0 0 0
0 0 0 0

n n n n
m m m m
λ λ
Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 4
Linear polarization
λ
z
y Incoming electric field
( )
E = e E exp ikz − iωt
x 0
x
Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 5
Circular polarization
λ
z
y Incoming electric field
e + iσe
( )
x y
E = E exp ikz − iωt
0
2
Spin angular momentum (SAM)
x = σħ (σ = ±1)
Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 6
Wave front -position of the same phase-
Wave front
Electromagnetic
wave
Phase
0 2π 4π
Wave fronts of
plane wave
Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 7
Outline
Polairzation and wave fronts of light
Optical vortex
Electric field and Poynting vector
Generation, Measurement, Application
Electron vortex, X-ray vortex
Gamma-ray vortex
Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 8
Vortex beams -Helical wave front creation-
Wave front Phase
Forming a helical
wave front.
( )
E ∝ exp iφ
Carrying orbital angular
momentum (OAM)
ℓħ
Total AM
= OAM + SAM
= ℓħ + ħ
M. Padgett et al., Phys. Today 57 (2004) 35.
Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 9