Faraday effect ) Passive polarizing elements 2) Faraday rotation rotators, isolators, compensators 4) Magnetic field measurements
Dec 31, 2015
Faraday effect
1) Passive polarizing elements
2) Faraday rotation
3) rotators, isolators, compensators
4) Magnetic field measurements
1) Passive polarizing elements
Anisotropic absorption: polarizers
Anisotropic index (crystals) birefringence, waveplates
Optical activity
= difference in index for the two different circular components
Principle of reciprocity applies
n of the order of 10-4
Birefringence: n of the order of 10-2
2) Faraday rotation
Rotation of the plane of polarization proportional to a magnetic field
Resonant effect:
n
+-
J=1
J=0
m=-1
m=+1
Difference between sublevels proportional to magnetic field.
2) Faraday rotation
The dispersion of any line extends very far (Lorentzian)ANY transparent medium has a Faraday effect.
Rotation is
At 790 nm, for TGG:V = 4.5×103oT−1 m−1
BK7 glass: 150
3) rotators, isolators, compensators
saturableabsorberdye jet
GTGG
Magnetic material of length l:
lTGG = Terbium Gallium Garnet
9 mm TGG 30 nT/Hz
Resolution: 10 nT or Faraday rotation of 8x10-9radSlope sensitivity inversely proportional to size
Femtosecond temporal resolutionExtracavity pumpIntracavity probe
Actual measurement
IPI
saturableabsorberdye jet
TGG l
Resolution:
8x10-9rad
Faraday rotation
0.3 Hz, for 9 mm TGG
IMPOSSIBLE TO MEASURE!
B = 10 nT
vs
80 MHz
temporal resolution
G
Intensity and time dependence of magnetic material:
Measure beat note as a function of position
l
Pump Probe experiment: External pump, internal probe