n - Fachhochschule Jena
n - Fachhochschule Jena
n - Fachhochschule Jena
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Laser<br />
Principle of Michelson Interferometer<br />
Linearly<br />
polarised<br />
laser mode<br />
Beam<br />
combining<br />
∆φ = (4π/λ0)·(n∆L+L∆n) ·2<br />
Photo<br />
detector<br />
Reflector<br />
Beam<br />
splitting<br />
L 0<br />
Beam splitter Reflector<br />
When does interference<br />
take place?<br />
• Coherence, i.e., defined<br />
phase relations: Path<br />
difference ∆L < coherence<br />
length<br />
L c ~ λ 0 2 /δλ (δλ spectral width)<br />
• Equal states of polarisation<br />
(superposition of electric field<br />
vectors !)<br />
• Almost equal wavelengths<br />
(frequency difference occurs<br />
as intensity modulation<br />
frequency !)<br />
FOS - 39
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