Questions tagged [interferometry]

Interferometry is the name for a class of measurement techniques based on the interference of coherent optical fields or other electromagnetic radiation. Generally, Interferometric measurements are extremely accurate, but can be difficult to perform. Common uses for interferometry are optical component metrology and stellar interferometry, although there are many applications.

Interferometry is a measurement method using the phenomenon of interference of waves (usually light, radio or sound waves). The measurements may include those of certain characteristics of the waves themselves and the materials that the waves interact with. In addition, interferometry is used to describe the techniques that use light waves for the study of changes in displacement. This displacement measuring interferometry is extensively used for calibration and mechanical stage motion control in precision machining.
Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy (and its applications to chemistry), quantum mechanics, nuclear and particle physics, plasma physics, remote sensing, biomolecular interactions, surface profiling, microfluidics, mechanical stress/strain measurement, velocimetry, optometry, and making holograms.

For more details see:
Handbook of Immunoassay Technologies: Approaches, Performances, and Applications by Sandeep K. Vashist and John H.T. Luong
Interferometry and its Applications in Surface Metrology By Dahi Ghareab Abdelsalam and Baoli Yao
Interferometry explained

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Could (old) LIGO have detected GW150914?

The merging black hole binary system GW150914 was detected in only 16 days of aLIGO data at a signal level that appears to be well above the detection threshold at around 5 sigma. There are no further events between 4 and 5 sigma in the same…
ProfRob
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Is LIGO flawed by the identical expansion of laser wavelength and arms in presence of a gravitational wave?

LIGO, Laser Interferometer Gravitational-Wave Observatory, is a large-scale physics experiment aiming to directly detect gravitational waves. The device measures the phase shift laser beams. If I understand this well, the measurement assumes that a…
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How does LIGO work?

LIGO is described as working as an interferometer, like a Michelson-Morley interferometer but with many reflections along the arms to increase the sensitivity. In MMs work it was assumed that the mirrors were held in a rigid relationship and so…
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Photons with half integer angular momentum - what's happening?

I have just read this article - what is happening? Analysing these beams within the theory of quantum mechanics they predicted that the angular momentum of the photon would be half-integer, and devised an experiment to test their prediction. Using…
user56903
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How are the 4 km arms of LIGO measured so accurately?

The arms of the LIGO interferometer are 4 km long. Now, LIGO functions by measuring the phase difference between two beams of light coming (as in a Michelson interferometer) to a sensitivity of $10^{-18}\: \mathrm m$. Now, we know that if the path…
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Phase added on reflection at a beam splitter?

If we have light of a particular phase that is incident on a beam splitter, I assume the transmitted beam undergoes no phase change. But I thought that the reflected beam would undergo a phase change of $\pi$. I have, however, read that it undergoes…
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Isn't LIGO basically measuring the luminiferous aether?

I am bit confused about this one. I am not very acknowledgeable about gravitational waves and LIGO. But if it is basically a Michelson interferometer and can detect shifts in vacuum, doesn't this means that we detected the luminiferous aether and if…
user102977
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Are human eyes interferometers?

It seems like 2 eyes is enough “wetware” to do interferometry inside brain. Can you definitely see some reason why this could not be happening, or some way to test if it does happen?
Euphorbium
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Michelson interferometry - is a compensator plate necessary?

I am studying the Michelson interferometer shown in figure 2 (similar design shown below) of the AMRITA vlabs tutorial. There it is stated that Since the reflecting surface of the beam splitter BS is the surface on the lower right, the light ray…
Idios
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Michelson interferometer circular fringes

Image source I have never done the experiment so as far as I understand, if the mirrors $M1$ and $M2$ are perpendicular to each other the observer at $O$ will see a circular fringe pattern. If additionally $M1$ and $M2$ are equidistant from the…
pseudomarvin
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How subjective laser speckle pattern is formed

I can not find a good explanation on how the subjective speckle pattern is formed (in terms of interference). Objective speckle. The image below explains well how the speckle is formed: the light from each point on the illuminated surface adds…
Nazar
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How does LIGO remove the effects of environmental noise?

Since LIGO is dealing with readings at nanometers, events such as vehicles driving nearby, and constant (but extremely minor) tremors of the earth can cause movement with the mirrors at nanometers. Such tiny movements are extremely difficult to…
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How can laser interferometry be used to measure path difference smaller than wavelength of laser light?

The currently proposed Gravitational wave detection apparatus consists of Michelson Interferometer which is supposed to measure distances of the order of $10^{-22}$m. But the wavelength of the light used is in the order of micrometers ($10^{-6}$m).…
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What prevents digital interferometry in an optical telescope array?

I understand it is common to combine an array of radio telescopes in to a single instrument using interferometry. This has the photon collecting area of the combined radio telescopes but an aperture (and hence resolving power) dependent on the…
Benjohn
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Why is the Pauli's exclusion principle not violated in the two neutron beams interference experiments?

It is my understanding so far that in this kind of experiments like the one measuring the 4π (i.e. 720° Dirac Belt trick) rotation characteristic of 1/2 spin fermions like neutrons, two neutron beams are polarized via S-G apparatus to the same…
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