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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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Laser beam diameter with Interferometer [on hold]

Is it possible to measure laser beam diameter used as a source in an interferometer? If so, then how to go about designing such an interferometer?
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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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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 ...
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$U(2)$ or $SU(2)$? Interferometers and Jones matrices

Recently I've been trying to understand why the scattering matrices that describe an interferometer should be $SU(2)$ matrices rather than $U(2)$. The condition of unitarity is undiscussed as it ...
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Alignment of Michelson interferometer using IR LED

I am trying to align the Michelson interferometer using 780 nm LED. But I am not getting any interference pattern in the CCD. Initially I align the interferometer using Laser to get the equal path ...
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Average number of fringes

Context: Trying to comprehend the Frequency ratio method(fringe counting method) which employs a Michelson interferometer, used for calibrating accelerometers. Problem: A Michelson interferometer is ...
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Confusion in the Michelson-Morley experiment about beam-splitter vs compensator

From what I know of the original experiment, the beam-splitter was a half-silvered mirror, and one of the paths had a compensator in the form of a glass plate. My questions are: (1) Since the glass ...
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Separation distance of Michelson Interferometer

Suppose I would like to use Michelson Interferometer to observe fringes of equal thickness by creating an angle between the mirrors. Why is it vital for the path difference between the mirrors to be ...
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Why do we use superposition instead of tensor product in interferometer?

In the description of a neutron interferometer here, it says: In an interferometer the incident beam is split into two (or more) separate beams. The beams travel along different paths where they ...
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How can the Mach-Zehnder interferometer results be consistent with an epistemic view on the wavefunction (WF)?

If the epistemic view on WF is that something is happening in the mind of the observer (e.g. he observed something and then the WF changed for him) then how is this view consistent with the results ...
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Where does the energy of the destructively interfering light waves go in this interferometer setup?

In one type of Mach-Zander interferometer two parallel light guides are diffused into a $\text{LiNbO}_3$ wafer. There are electrical contacts deposited along each light guide. At the end of the light ...
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Source for Interferometer experiments with single photons

The Phys.SE question Single Photon Single Slit Interferometry is about the results of such experiments. What I’m interested is to read about interferometer experiments with single shooted photons. Who ...
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Why do interferometers only split a wave into two beams?

I was recently reading about interferometers and was wondering why it isn't common practice to split a wave into three orthogonal beams? I know very little about the topic and this may seem daft, but ...
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Why is there blindspot for LIGO interferometer?

I am thinking maybe when the gravitational wave hits the 2 mirrors at the same time but the two mirrors are very far apart, so what could be the cause for the blindspot?
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Michelson interferometer with and without Gaussian beam

In this video from MIT OpenCourseWare for a Michelson interferometer are demonstrated circular fringes. I’m curious, how the mode of the laser influences the shape of the fringes. Can one conclude ...
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Accurate way to determine the distance between lines in a spectrum

I will be doing an experiment where we superimpose Edser-Butler fringes with the spectrum from a mercury lamp. We will be using exact fractions method to determine the distance between de plates in ...
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Modified double slit with interferometer

Imagine I do a setup as seen in the picture below: burrowed concept from LIGO, the idea here is to use the gravitational force exerts by the heavy particle to bend the laser beams when passing through ...
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Path difference between rays in Michelson interferometer with inclined mirrors

If mirrors of Michelson interferometer are inclined the resulting configuration is the one in picture (tha analogy is with the thin wedge) where ray appear to come from $O$. If the distance between ...
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Why do the Michelson-Morley (1887) & Michelson-Gale (1925) experiments both measure a ~0.02 fringe shift?

As I mentioned here, the 1887 Michelson-Morley experiment placed an upper bound on the fringe displacement of about 0.01 or 0.02. Why did the 1925 Michelson-Gale experiment also find a fringe shift of ...