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 ...

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Why do LIGO use a quarter wavelength for detecting gravitational waves?

I have already researched into this and I am left slightly confused still. I have gathered that the use of a quarter wavelength is to turn a linearly polarised wave into a circularly polarised wave. ...
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Measuring tides in a swimming pool

The tidal range of a perfectly fluid inertialess ocean on the Earth (taking into account lunar tides only) is approximately half a metre: this is the range between "high" and "low" points of an ...
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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 ...
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Mach-Zehnder interferometer and the Fresnel-Arago laws

I have been reading this paper on a mathematical treatment of the Fresnel-Argo laws. In the paper they essentially they take the electric field: $$E_i=E_i(t)$$ and introduce a phase factor, ...
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Interference experiment and entanglement with apparatus

Consider a single photon in a Mach-Zehnder interferometer. Considering the photon only, the output state is the sum over both paths $$\vert 1 \rangle + \vert 2 \rangle=\vert \psi \rangle + ...
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Mach-Zehnder probabilities

Where can I find the computations of probabilities for Mach-Zehnder experiments, say at the undergraduate level? For example I'm thinking of the type of experiments described at the beginning of David ...
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66 views

Why are they building eLISA and what implications would it have?

I understand that the next step after LIGO is to plan and build eLISA, I understand that out in space there are a lot less interferences compared to Earth which makes it a good way to detect things we ...
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1answer
36 views

Difference between Amplitude and Intensity Interferometer?

A lot of books explain the first order and second order coherence correlations for light. They explain the difference between these using interferometers (Michelson and Hanbury-Brown and Twiss (HBT) ...
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Michelson Fringes

When using a Michelson Interferometer to view circular fringes (i.e with mirrors in exact perpendicular alignment and a relatively large difference in arm length) would fringes be observed using a ...
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110 views

Michelson interferometer finding $\frac{\Delta \nu}{\bar \nu}$?

Let us say we send light with wavenumber $\bar \nu \pm \frac{\Delta \bar \nu}{2}$ through a Michelson Interferometer. Using the intensity at the center of the interference pattern $I(x)$ (where $x$ is ...
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How to measure an image's contrast?

I'm studying Fourier optics and Interferometry and I intend to determine the contrast of an image using computer software. My teacher of Experimental Physics didn't tell me how to do it, and so, I'm ...
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34 views

Circular array of (4, 6 or 12) interferometers with circumferential end points for GW analysis?

If both or, at least, one of the two current LIGO installations instead of the single interferometer would have the circular array of (4, 6 or 12) interferometers (with circumferential locations of ...
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How can LIGO's measures be unequivocaly tied to gravitational waves? [duplicate]

I understand that there are 2 devices so that the signal cannot have a local stimulation as a source. But why couldn't it be seismic activity for instance? Given the accuracy of the devices couldn't ...
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22 views

Gravitational Ripples [duplicate]

Recently the observance of Gravitational Ripples was reported using the LIGO detector. LIGO consists of two arms perpendicular to each other through which a split laser beam is passed and then ...
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70 views

LIGO: Importance of photons

In LIGO, a photon beam travels in two perpendicular direction and time taken by each beam is noted. Non zero time difference is a signature of GWs here. What if I use electron beam travelling at ...
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1answer
87 views

Gravitational waves veracity? [closed]

W/r to the recent announcement of gravitational wave detection, since the signal to noise ration appears to be about 3 to 1 (not really very good) and there is no collaborating evidence from neutrino ...
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47 views

Have gravitational waves any effect on the electromagnetic waves in interferometers?

I am not into general relativity, but the explanation of how an interferometric gravitational antenna works is generally pretty basic. In the recently published paper announcing the detection of ...
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234 views

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. ...
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Multi-directional ether

In the Michelson-Morley experiment,the two beams of light should be directed at right angles in order to test the existence of ether, but that postulate is based on the prediction that ether has only ...
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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 ...
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165 views

What are the wave characteristics for the detected gravitational wave?

I'm curious to know what the amplitude and wavelength of the detected gravitational waves are? The paper mentions some characteristics of the detection event, but not what that means for the wave ...
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142 views

How well can we localize gravitational wave sources?

A recent question cited a story about the recent gravitational wave detection saying that we can use the gravitational wave sensing to find supernova earlier in their process of collapse: [with ...
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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 phase difference between two beams of light comming (as in Michaelson's Interferometer) to a sensitivity of ...
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169 views

How thermal noise is avoided in LIGO?

I think I have understood properly the principle of LIGO, however the sensitivity is around $10^{-18}~\rm m$ of accuracy of distortion. That looks pretty small... just starting with simpler phenomena, ...
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How does LIGO reduce noise below what it is detecting? [duplicate]

LIGO is designed to detect changes in length on the order of 10,000ths the scale of a proton. I know they are extremely well isolated from their surroundings, but how could we even approach isolation ...
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Why are the arms of the LIGO interferometer so long? [duplicate]

The LIGO experiment consists of two interferometers, where each one of them has two 4 km long arms. Within these, light is further trapped via Fabry-Pérot cavities to achieve a total path length of ...
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How much time distortion was caused by GW150914?

I understand (at least I think I understand) that LIGO used distortion of space to detect GW150914 (one arm grew longer, the other arm grew shorter, causing interference in the returning laser-pulse ...
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Orientation of the LIGO Arms

The orientation of the interferometer arms at both sites are approximately Northeast-Southwest and Nortwest-Southeast, though I assume that, on account of the Earth's curvature, no pair of arms is ...
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1answer
178 views

LIGO discovery: if the space “time” metric is changed, how is it measured? [duplicate]

Regarding the wonderful 2016 news about gravitational waves. Travel time in one arm of the LIGO is ~ 30μs. A gravitational wave affects the arm for some few hundred of these laps. Then for example ...
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2answers
252 views

Could discovered gravitational waves in fact be an aether wind? [duplicate]

Proving the existence of gravitational waves might revolutionise cosmology, but the method used by LIGO is quite similar to the famous Michelson-Morely interferometer built more than a hundred years ...
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How does light behave after experiencing fully destructive interference, as in an interferometer?

I'm thinking about a laser interferometer like the one used in LIGO. Here's the basic layout (from Wikipedia - Interferometry): My understanding is that the half of the light that is reflected by ...
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1answer
27 views

How do large interferometers work?

In very large Michelson interferometer a such as LIGO, how can we keep the two light paths at the exact same distance in order to avoid any unwanted and noisy fringes shift? When I used to make ...
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1answer
165 views

How did LIGO detect the source location of the black holes mentioned to be the cause of today's announcement?

Today LIGO announced discovery of Gravitational waves. What method was used to determine the source location of the waves?
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Einstein's original papers predicting gravitational waves? [closed]

I came across the original handwritten papers in which Einstein predicted gravitational waves1: and since LIGO announced they've detected a signal confirming the predictions I was wondering if ...
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242 views

How is LIGO so sensitive? [duplicate]

My understanding is that interferometers can detect distance changes on the order of the wavelength of light being used. LIGO uses 808 nm light but has a sensitivity of 10^-18 m. Where do those 11 ...
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Loss of interference in single-photon Mach–Zehnder interferometer with detector in only one arm

I have read that if you have a Mach–Zehnder interferometer (doing a single-photon experiment) and put a non-destructive detector in only one of the two arms (connected to the first beam splitter), you ...
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3answers
631 views

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 ...
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How to sketch transmission of ht eMZI in frequency domain?

I enrolled in to Optics&Electronics class and this is my homework: There are 5 questions and they were understandable and familiar(Teached in class) but question 3 is something else! I am not ...
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1answer
94 views

What is an Unbalanced Interferometer

I have read in some papers about a so-called unbalanced interferometer. This appears particularly in the context of Experimentally verifying the Englert-Greenberger-Yasin Duality Relation. However, I ...
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1answer
34 views

Help to find a simple setup for optical surface topography

I'm looking for some help from someone expert in optics to create an inteferometry based setup to map the surface of a small object. This is for a small lab project so I'm not looking for a really ...
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Interferometer based on atoms and gravitational field detection

I know that ultra cold atoms can be used to measure a gravitational field, but how does this work exactly. More specifically, I know that an interferometer based on atoms can be used to make very ...
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Michelson–Morley experiment's aether; Why is the time gained from travelling downwind less than that lost travelling upwind?

From the Wikipedia article on the Michelson–Morley experiment, explaining one of the concepts behind the landmark experiment: "If the Earth is traveling through an aether medium, a beam reflecting ...
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How could you match the phase of two waves?

Imagine the Mach-Zehnder interferometer with split beams of a laser guided in a way that would result in constructive interference in one direction and destructive interference in the remaining ...
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1answer
49 views

How does localization affect interferometry?

A classic setup (I suppose it's classic) in introductory quantum mechanics has a single photon passing through a double slitted grating. Directly across each slit of the grating is a device that can ...
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3answers
111 views

How to measure thickness of an ultra-thin metal layer?

I have a sample of a metal (aluminum/oxide) layer with a gradual thickness ranging from monolayer to 100nm. This layer is deposited on a transparent substrate, like glass. How can I measure this ...
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3answers
192 views

Mach-Zehnder Interferometer: two output interference pattern question

I have drawn diagram so not to confuse. So far, I've heard that in Mach-Zehnder interferometer, two output should have one constructive interference, and one destructive interference for other. ...
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1answer
24 views

Literature on interferometry

I am looking for a good book/notes etc. about interferometry. I need detailed information about optical as well as atom interferometers with strong emphasize on quantum version for high precision ...
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57 views

A ray matrix of tilted beam splitter in a Mach-Zehnder interferometer

What does a ray matrix ABCD correspond to a plane tilted beam splitter (BS) in the Mach-Zehnder interferometer? Thank You!
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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 ...