Editing Michelson interferometer (section)

== Technical topics ==
===Step-phase interferometer===
This is a Michelson interferometer in which the mirror in one arm is replaced with a [[Gires–Tournois etalon]].<ref>{{cite journal|author=F. Gires |author2=P. Tournois |name-list-style=amp |date=1964|title=Interféromètre utilisable pour la compression d'impulsions lumineuses modulées en fréquence|journal=[[Comptes Rendus de l'Académie des Sciences de Paris]]|volume=258|pages=6112–6115}}</ref> The highly dispersed wave reflected by the Gires–Tournois etalon interferes with the original wave as reflected by the other mirror. Because the phase change from the Gires–Tournois etalon is an almost step-like function of wavelength, the resulting interferometer has special characteristics.  It  has an application in [[fiber-optic]] [[Telecommunication|communications]] as an [[optical interleaver]].

Both mirrors in a Michelson interferometer can be replaced with Gires–Tournois etalons. The step-like relation of phase to wavelength is thereby more pronounced, and this can be used to construct an asymmetric optical interleaver.{{Citation needed|date=June 2014}}

===Phase-conjugating interferometry ===
The reflection from phase-conjugating mirror of two light beams inverses their phase difference 
<math>\Delta \varphi</math> to the opposite one <math>-\Delta \varphi</math>. For this reason the interference pattern in twin-beam interferometer changes drastically. Compared to conventional Michelson interference curve with period of half-wavelength <math>\lambda/2</math>:
<math display="block">I(\Delta L) \sim [1+ \gamma(\Delta L) \cos (2k\Delta L)],</math>
where <math>\gamma(\Delta L)</math> is second-order correlation function, the interference curve in phase-conjugating  interferometer <ref name="Okulov, A YU 1980">{{cite journal |title=Laser interferometer with wavefront reversing mirrors
|journal=Sov. Phys. JETP|volume=52 |issue=5 |pages=847 |year=1980 
|last1= Basov |first1=N G
|last2= Zubarev |first2=I G
|last3= Mironov |first3=A B
|last4= Michailov |first4= S I
|last5= Okulov |first5= A Yu
|bibcode=1980ZhETF..79.1678B}}</ref>
has much longer period defined by frequency shift <math>\delta \omega = \Delta k c</math> of reflected beams:
<math display="block">I(\Delta L) \sim [1+ [\gamma(\Delta L)+0.25] \cos (\Delta k\Delta L)],</math>
where visibility curve is nonzero when optical path difference <math>\Delta L > \ell_\text{coh}</math> exceeds coherence length of light beams. 
The nontrivial features of phase fluctuations in optical phase-conjugating mirror had been studied via  Michelson interferometer with two independent PC-mirrors 
.<ref name="Okulov, A YU 1980J">{{cite journal |title=Phase fluctuations of the Stockes wave produced as a result of stimulated scattering of light
|journal=Sov. Phys. JETP Lett.|volume=31 |issue=11 |pages=645 |year=1980 
|last1= Basov |first1=N G
|last2= Zubarev |first2=I G
|last3= Mironov |first3=A B
|last4= Michailov |first4= S I
|last5= Okulov |first5= A Yu
|bibcode=1980JETPL..31..645B}}</ref> The phase-conjugating Michelson interferometry is a promising technology  for coherent summation of laser amplifiers.<ref name="Boyd, R W 1997">{{cite journal |title=Brillouin-enhanced four-wave-mixing vector phase-conjugate mirror with beam-combining capability
|journal=Optics Letters|volume=22 |issue=6 |pages=360–362  |year=1997 
|last1= Bowers |first1=M W
|last2= Boyd |first2=R W
|last3= Hankla |first3=A K
|doi=10.1364/OL.22.000360|pmid=18183201|bibcode=1997OptL...22..360B|s2cid=25530526 }}</ref>
Constructive interference in an array containing  <math>N/2</math> beamsplitters of <math>N</math> laser beams synchronized by 
[[phase conjugation]]
may increase the brightness of amplified beams as <math>N^2</math>.<ref name="Okulov, A Yu 2014">{{cite journal | title=Coherent chirped pulse laser network with Mickelson phase conjugator | journal=Applied Optics | volume=53 | issue=11 | pages=2302–2311 | year=2014 | last1= Okulov |first1=A Yu|doi=10.1364/AO.53.002302 | pmid = 24787398 | arxiv = 1311.6703 | bibcode=2014ApOpt..53.2302O | s2cid = 118343729 }}</ref>