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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.

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Michelson interferometer phase difference when both mirrors are equidistant?

Using the following image as a reference. Source Why is there a phase difference added in the following equation? $2d \cos \theta =m \lambda + \frac{1}{2} \lambda$ I read it is because the beam ...
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What does it mean to extract phase from interferograms?

I hear a lot extract the phase from the interferograms, I need to know what does it mean? and what is the significance of that?
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How does a single satellite like the upcoming BIOMASS use interferometry?

The future satellite BIOMASS, from the ESA, will supposedly use p-band frequency interferometry to detect changes in forests. By itself? How?
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Does the spectrum of two-beam interference also show an interference pattern?

I know when you interfere two beams you get an interference pattern with a fringe pattern of λ/(2*sin(θ/2)) in physical space. It seems that there must also be modulation of the spectrum. Is this ...
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Are interference patterns the basis for all other measurements of light frequencies and wavelengths?

The wavelength or frequency of monochromatic electromagnetic radiation is determined indirectly by calculations on the interference or diffraction pattern. These patterns are generated by gratings, ...
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Why does an interferometer with mirrors even work? [duplicate]

My understanding is being thwarted by something basic I am missing. One starts with a light beam that is split into two perpendicular paths. There are two light paths that travel some distance. The ...
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How do I obtain coherence length of a monochromatic laser with data about the visibility?

I am using a Michelson interferometer and have obtained data about the visibility. However, I am now having trouble knowing what to plot in order to find the coherence lenghth of the laser. I thought ...
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95 views

A common misunderstanding regarding which path information in a double slit and Mach-Zehnder interferometer?

I just can't get my head around this. What does he mean when he says that a hit at one of the detectors doesn't imply that the particle went though a certain path? He calls this the "separation ...
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Why don't (can't) astronomers take advantage of interferometry to the extreme?

Reading and watching from various sources (e.g: APOD, ESO videos, or Wiki), whenever interferometry is mentioned, it is also usually explained like this: An astronomical interferometer consists of ...
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Cause of difference of coherence distance between different light source

I was doing my first interferometry experiment today, and we had to calculate a certain beam's coherence length (the distance in which it behaves regularly). I was explained that different beams have ...
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Does frequency of light change in the LIGO interferometer arms?

There are a number of questions on the internet and on this site asking about how the LIGO interferometer measurement works given that the gravitation wave stretches both the length of the ...
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How is it possible to build such large interferometers?

How is it possible to build interferometers of virtually any width when the tiny photon wave packets entering each side of them, which are then made to interfere with themselves, would seem to need to ...
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Is Sentinel able to obtain wave spectrum by interferometric Data?

I have recently read many articles on recovering wave spectrum from the AT-INSAR image spectrum (through interferometric images). However, it is not clear to me whether Sentinel is a viable option, ...
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What do fringe patterns have to do with VLBI?

I think I have fundamental confusions with how VLBI works. I don't know why: Resolution increases when incident rays meeting to a focal point from a farther separation along an axis perpendicular to ...
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Maintaining phase relationships and other general principles of interferometry

I have a few confusions with some basic principles of interferometry. Bob Campbell's So you want to do VLBI writes: Phase relationships among all points on the wavefront will be preserved ...
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How can I define the phase out of a Mach–Zehnder interferometer?

currently I am trying to learn more about integrated photonics, more specifically about optical processing (Matrix multiplication, for instance). I have read different books regarding classical ...
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LIGO test masses in free fall

I know that the LIGO test masses are considered to be in free fall. However, they are supported by pendula. I thought that free fall means the only acting force is gravity - doesn't the tension in the ...
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How would measuring the number of photons on a finite number of pulses break coherence of a weak coherent laser source in COW QKD protocol

I' m trying to understand attacks on Quantum key distribution protocols. In the COW QKD protocol, pulses from Alice are passed through an asymmetric coupler and a fraction 'T' of the photons are sent ...
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Air wedge interferometer (Fringe separation)

From Hecht optics, From the setup, $ \alpha = \frac {d}{x}$ $--> d = x \alpha$ $d$ is the varying thickness of the air wedge The condition for constructive interference, $ ( m + \frac {1}{2} ) \...
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Fringes of equal inclination (Haidinger fringes) Why is the interference pattern circular?

From Hecht optics 5th edition: It says 'With an extended source, the symmetry of the setup requires that the interference pattern consists of a series of concentric circular bands centered on the ...
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Could the black hole photo be a gravastar?

Mazur-Mottola gravastars would in many ways appear identical to black holes. Does the new radio-photograph of M87* taken by the Event Horizon Telescope eliminate M87* as a gravastar candidate, and ...
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Unexpected wavelength jumps in a laser observed: a fundamental noise source in VCSELs?

I observed an unexpected signal while developing an interferometric sensor using a VCSEL laser. In order to debug this noise I designed the following device that converts minute changes in the laser's ...
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If two observers look at the same quantum object, will they see the same thing?

Let's say two observers, one at the North pole and one at the South pole, both observe the Moon. Will they see the same Moon, or a subtly different Moon? Intuitively it feels like they should see a ...
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Precise Event Horizon Telescope locations?

Presumably, in order to perform their interferometry, the Event Horizon Telescope correlator needs to know (i) exactly the time of an observation, which I understand is accomplished by timestamping ...
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Direct observation of Gravitational Waves via increased resolution

First, congrats to the event horizon team for the first photograph of a black hole. Not to downplay the significance of the photo, but it is a bit blurry. Still, it got me thinking. One might expect ...
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Why is the Standard Quantum Limit (SQL) in Interferometers added as that of mass $m$ and not $2m$?

We write $$(\Delta z)^2 = (\Delta z)_{PC}^2 + (\Delta z)_{RP}^2 + (\Delta z)_{SQL}^2$$ to indicate the contributions to the total error from photon counting error, radiation pressure error and the ...
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How much more precise would LIGO have to be?

The planets and a spinning black hole both drag their local frames and thus generate gravitational waves The amplitude should be proportional to the size of the celestial body, while the frequency of ...
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What is the meaning of this operator?

In interferometry with coherent light, the final output is differenced detectors. That is, $\left<N\right> = \left<N_1\right> - \left<N_2\right>$ where $N_i$ is the number operator ...
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Why gravitational wave stretches on $x$-axis would necessarily compress on the $y$-axis?

I read gravitational wave is a traverse wave, usually produced by inspiraling neutron stars or black holes, and laser interferometer such as LIGO is commonly used to detect them, since the setup of ...
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Unable to get interference from milk using Time domain OCT (Michelson Morley interferometer) approach

I was able to construct time domain Optical coherence tomography based on Michelson Morley interferometer using a LED. While testing the interferometer, I used glass slide, layers of scotch tape. I ...
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Is the refractive index neglected in the standard Michelson interferometer equation: $\lambda=2d/N$

Hoping someone can help with this. It's a simple question, but I can't seem to find the answer anywhere: I'm looking at the basic Michelson interferometer experiment, where you measure the wavelength ...
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Radiation Pressure Noise in Gravitational Wave Detection

I am trying to work out where equation 9 comes from in Martynov et al. (2016), who discuss the radiation pressure noise in the LIGO detector. $$L(f) = \frac{2}{cM\pi^2 f^2} \left(h \nu G_{-} P_{\rm ...
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What does the interferogram in Michelson interferometer mean about the topology of the specimen?

I'm want to know how can I evaluate the surface of a fibre by using the interferometer of Michelson. The object beam in this method is reflected from the object and combined with the reference beam to ...
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How do quantized photons interact in an interferometer?

Since light is quantized into photons, how can a single rare photon entering one side of a large, [say, 100 meter wide], interferometer from a very dim star, a phton which is only in the ...
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How interferometric techniques can be used to investigate the topology of polymers?

I need to study the topography of a specific polymer, knowing that my lab is an optics lab with many interferometric techniques, how can I use these techniques to investigate the topology?
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plane vs diverging waves michelson itnerferometer

I'm wondering if there's a difference in the interference pattern achieved in the michelson interferometer if the source of light is sending plane waves vs sending diverging waves (for example by ...
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What is the power received by a CW Laser telemeter photodetector?

I have a CW Laser telemeter emitting 2 mW power at 660 nm. The target has diffusivity equal to 0.6. The receiving optics has a diameter of 8 cm. I could not understand how to evaluate the power ...
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What are the differences between a Michelson and Self-Mixing interferometer?

I'm approaching to interferometric devices. I would say that Michelson interferometer uses a laser source and a "discrete" system of mirrors and other optical components such lenses and screens. On ...
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142 views

Evolution of the operators in Mach-Zehnder interferometer

I have trouble understanding how the operators that change the initial state, change when adding extra splitters. As an example, I will use an idealized Mach-Zehnder interferometer where the splitters ...
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White Light Interferometry [closed]

I have arrived at a way to produce Arago’s spot with a quality white led flashlight. How would I go about writing a small educational paper on this? And, most of what I have seen on the web uses ...
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Why sample is placed after the interferometer in FTIR?

In all image of schematics of FTIR I found (Wikipedia for example), the sample is placed after the interferometer: Wouldn't this miss some emergent effects, such photo-induced absorption, since the ...
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De Broglie Wavelength of a particle at the turning point of a fountain

If you think about an atom which is launched in some kind of straight fountain, upward in the gravitational field. At the turning point the velocity and therefore the momentum of the particle seems to ...
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Can traps measure which path in an interferometer?

it is possible in an interferometer to block the paths with screens so that the particle is well located in one of the paths. I wonder if it is the same when instead of screen we use traps in which a ...
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Delayed choice experiment for misaligned Mach-Zender interferometer

In quantum Mach-Zender interference, a single photon can be prepared to have a 100 percent probability of traveling through a particular path (that classically would be a 50 percent chance). This can ...
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How does electronic speckle holography produce fringes?

For the out-of-plane set-up shown below, the system is only sensitive to displacements of the object along the z-axis. To create an ESPI image, an image before an after displacing the test object are ...
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Does LIGO accounts for Sagnac effect?

After reading Sagnac effect one thing immediately come to my mind is LIGO, I only read that the team building LIGO have already considered the curvation of Earth surface but what about Earth's ...
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Derivation of the index of refraction of glass as a function of rotation angle and number of fringe transitions

Recently, I've looked at how the index of refraction of a piece of glass can be related to the angle of rotation from normal incidence and the associated number of fringe transitions through a ...
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How fast a quantum state updates in a quantum experiment when the experimental setup itself changes. Are there known experiments on this?

Consider the following Sagnac interferometer setup: where $B$ is a beam splitter which can be raised and lowered with an adjustable frequency $f$, $D$ is a detector which does not click when $B$ is ...
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Mach-Zehnder interferometer reaction to input light with polarization state ±45˚?

We have a Mach-Zehnder interferometer with two non-polarizing beam splitters. The polarisation state of the input beam is a superposition of +45˚ and -45˚ polarizations. In the upper arm of the ...
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Fabry-Perot cavity modelling

I'm trying to understand the modelling used for Fabry-Perot cavities, such as it is done in e.g. this paper: http://aip.scitation.org/doi/10.1063/1.1729109 The model given is based on the following ...