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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Why distance between source images in Michelson interferometer experiment is twice the distance between two mirrors

In the Michelson interferometer experiment, there are two mirrors which are perpendicular to each other. When we see in telescope, we see one mirror, let's name it (a), directly and one mirror as ...
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Orienting birefringent crystal the right way in an interferometer

I'm working in a lab that involves transforming the polarization state of one beam of light in an interferometer via a Barium Borate (BBO) birefringent crystal. As the polarization state is altered ...
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Calculating Coherence Length and spectral width given an interferogram

I'm currently doing a lab in which we use a Michelson-Morley interferometer to analyse different light source. One of the mirrors in the interferometer is moved by a stepper motor. One of the light ...
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How does two-wavelength interferometry mitigate vibrations in density measurements?

I am currently using interferometry to measure the density of a plasma. The interferograms are suffering from vibrations, and I know that two-wavelength interferometry may mitigate this. I am however ...
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Why does constructive interference occur at zero path difference in a Michelson interferometer?

I was reading Introductory Fourier Transform Spectroscopy by Robert Bell. In chapter 9 "Beamsplitters" he states for self-supporting dielectric beamsplitters: "There are $\pi$ phase ...
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How to simulate a Mach-Zehnder Unbalanced Interferometer with Single Photons?

I'm currently working on a project using a Mach-Zehnder Interferometer (MZI) with weak coherent pulses (single photons). In order to simulate the results I would like to use the Qutip library of ...
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How can two beams in the Michelson interferometer come back at the same time?

I am trying to understand this concept from my textbook. According to the figure below, the time difference between the two paths $\Delta t=0$. But why is this the case? Looking at the picture, the ...
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Michelson-Morley interferometer in free fall

We suppose that we have a Michelson-Morley interferometer in free fall, will there be no interference: the round trip time in both arms of the interferometer is the same?
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LIGO's upper-bound on the Michelson-Morley null result?

LIGO is essentially a Michelson-Morley experiment. What is its measured upper-bound on the fringe shift? The most recent Michel-Morley experiment "Michelson–Morley experiment#Subsequent ...
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Why is a Small Coherence Length Desired for Fiber Optic Gyroscopes?

For interferometric measurements based on the Sagnac effect, typically a light source is injected into counter-propagating paths of a fiber optic coil. The rotation of this coil of fiber optic cable ...
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Small crack in bottom corner of a beam splitter

I'm working with a Sagnac interferometer. To split a laser beam (He-Ne), we are using a cubical, non-polarizing beam splitter from Thor Labs (BS031). The beam splitter is fastened to a stand that is ...
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Phase shifts in different beam splitter designs

I am trying to understand how a Mach-Zehnder interferometer works. It seems that it will work whether we use two beam splitters that consist of either glass prisms glued together a sheet of glass ...
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Extreme sensitivity to the input scale of a Continuous Fourier Transform approximation from Discrete Fourier Transform

Is there a way to 'bypass' the condition $\Delta k=\frac{1}{x_{max}-x_{min}}$, which requires the range of $x$ to be very large when approximating the CFT encountered in Michealson Interometery as a ...
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Why is wavefront quality important, and what is the relationship between the coherence length of a laser and its wavefront quality (if any)?

I am currently studying laser interferometry. I understand that the coherence length of a laser, $L_\text{coherence} = c T_\text{coh}$, where $c$ is the speed of light and $T_\text{coh}$ is the ...
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Contraction in SR vs GR

I've always had a bit of fuzziness concerning relativistic contraction which I will try to put into words. Iiuc in SR, moving objects contract in the direction of their travel, as measured by rulers ...
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Why is the sample interferogram given by the following integral of the intensity pattern?

I am trying to understand equation (2) in the paper by J. E. Greivenkamp with the title Generalized data reduction for heterodyne interferometry from year 1984. If you dont have acces to the article, ...
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Reduction Ratio in Michaelson Interferometer

I am trying to work out the relation between a $\mu$step and the distance moved by the moveable mirror in the Michaelson Interferometer: The mirror on the stage is moved by a stepper motor. Inside ...
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Is $I(\lambda)=I(\tilde{\nu})$ true in general in Fourier Optics?

Say the spectrum of a light bulb is given by $$I(\lambda)=I_0exp\left(-\frac{(\lambda-\lambda_0)^2}{2(\delta \lambda)^2}\right)$$ (i.e. a gaussian) if I want the intensity in terms of the wavenumber $\...
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Misconception with Fourier Transforms in a Gaussian Light source?

So for a Michaelson Interferometer , we know that the (complex) interferogram ($I=I(\Delta)$, $\Delta$=path difference between two mirrors) is related to the intensity profile of the light source $(...
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What is the difference between this "spectral width" and the laser linewidth (FWHM)?

I am currently looking at the 1550nm fibre-coupled DFB laser diodes on Alibaba for use in interferometry experiments. These are commonly used in optical communications applications, but it seems to me ...
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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 ...
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How can I simulate michelson's interferometer circular fringes?

I wanto to simulate the circular fringes on a screen for the michelson interferometer. I know how to identify if there will be a destructive or constructive interference, but what about the radius of ...
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Mach-Zender Interferometer with an external Phase shifter

On passing a input beam of form $\begin{pmatrix} { \alpha\\ \beta} \end{pmatrix}$ through a Mach-Zender interferometer with a phase-shifter of phase $\delta$ on either lower leg or upper leg of the ...
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Why do two-beam interferometers have a relatively broad "fringe width" compared to single-beam interferometers?

I recently overheard someone discussing the basics of interferometry setups. They said that two-beam interferometers have a relatively broad "fringe width" compared to single-beam ...
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Is it possible to use a distributed camera array to fake an interferometric sensor without phase data?

Astronomical interferometry is a technique which uses multiple small telescopes to mimic one giant telescope. It requires the phase of the light to be captured for it to work. It is widely used in ...
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Fabry-Pérot-Interferometer: What Reflectivity

Apologizing for that narrow question, but considering such interferometer with mirrors characterized by Reflectivity $R$ and reflection coefficients $r = \sqrt{R}$, where $R$ describes the amount of ...
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Why do the Fringes in Michelson Interferometer move inward/outward?

We did this experiment using Michelson Interferometer of monochromatic source $\lambda$ to find the refractive index $n$ of dry air in a chamber of length $L$ by counting the number of fringes moved ...
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Optical path difference between the first and p-th transmitted wave for a plane wave incident on a Fizeau interferential wedge

In this paper: Ayerden, N. P., Graaf, G. D., & Wolffenbuttel, R. F. (2016). Compact gas cell integrated with a linear variable optical filter. Optics Express, 24(3), 2981-3002. https://doi.org/10....
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Add coherence length factor in source term for light source

I am trying to model the behavior of a Michelson-interferometer driven by a light source with a short coherence length (i.e. some centimeters at max.). By placing transmittive material in one of the ...
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I polarize the slits (one H, the other V) of a Young's double-slit. If my source is H or V, do I see fringes? What about if my source is D or AD?

In my journey to understand light better, I build a "polarized Young's interferometer". Imagine the following polarizations: horizontal, vertical, diagonal, and anti-diagonal (H, V, D, and ...
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Is spatial coherence more important for interferometry, or is temporal coherence more important for interferometry?

I am currently going back through my textbook Laser Systems Engineering by Keith Kasunic. Chapter 1.2 Laser Engineering says the following: One of the primary goals of laser engineering is to meet ...
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Resolution of a Michelson Interferometer using a Webcam

I've built a Michelson interferometer which uses a webcam as screen. This setup shall measure and correct drifts in optical path difference of the two interferometer arms. I have problems determining ...
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Since a collimated beam is always in focus, can't I simply just emit a collimated beam over the varying distances as the target object moves?

I am designing an interferometer for an experiment. The setup consists of (1) the laser source, (2) the interferometer itself (consisting of optical components and photodetector(s)), and (3) the ...
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How does the quality of the reflected light compare to the emitted light? And how do I manage this (reflected) light quality well?

I am designing an interferometer for an experiment. The setup consists of (1) the laser source, (2) the interferometer itself (consisting of optical components and photodetector(s)), and (3) the ...
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What photodetector parameters should I be focusing on, and in what priority, to maximise the performance of such an interferometer?

I'm trying to select a photodetector for an interferometry experiment. The interferometer will be trying to measure subtle vibrations occurring at a relatively high frequency (high kHz to low MHz). It ...
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Do interferometers require equal-powered (or as equal as possible) beams being emitted at the target and the photodetector(s)?

I am designing an interferometer for an experiment. The setup consists of (1) the laser source, (2) the interferometer itself (consisting of optical components and photodetector(s), and (3) the target ...
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How does beam shape (elliptical vs circular/Gaussian) affect interferometry?

I want to understand the importance of beam quality to interferometer systems. This article says the following: A very high (close to diffraction-limited) beam quality, associated with a high spatial ...
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How does the effective focal length work for aspheric lenses? How should I select an aspheric lens?

I am currently looking at aspheric lenses on Thorlabs. I want to use them as a collimation optic for my interferometry experiment. Note that the lenses have a listed EFL (effective focal length). But ...
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Do interferometers require polarizing beam splitters, or do they require non-polarizing beam splitters?

I want to build an interferometer. In order to do so, I need to buy some optical components, such as beam splitter cubes. These beam splitter cubes, and other optical components, come in a polarizing ...
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Interferometry experiment using laser beam reflection from object: does being closer to the object produce a better signal/measurement?

Let's say we're conducting an interferometry experiment. The experiment is such that we're reflecting collimated laser light off some object and then using the information contained in the reflected ...
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Interferometry: effect of aspheric lens on self-mixing effect

I want to perform self-mixing interferometry experiments using a laser diode, as was done here. I'm going to use a low-power laser diode. However, I want to improve the performance of the device, ...
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Is there measurable heat at the point of contact with a material subject to light that is deliberately set up to interfere with itself?

When a laser is spaced to produce two beams separated by exactly 1/2 the applicable wavelength, interference occurs, and there's no visible light, at least to the human eye. But is there heat ...
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Michelson interferometers and earth's rotation

Has anyone ever deliberately/specifically tried to detect earth's rotation on its axis using a Michelson interferometer?
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What is 'optical phaseshift'?

In interferometry, it is said that lasers can be used to measure the 'optical phaseshift' of something. I am familiar with the concept of phase in the context of waves, but I don't understand exactly ...
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Is interferometry with variable wavelength/baseline/resolution possible?

The angular resolution $R$ of a telescope array with baseline $B$ at wavelength $\lambda$ is $$ R=\frac{\lambda}{B} \;.$$ As far as I understand, interferometers like VLBI operate at a single ...
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Which path information vs fringe visibility can be explained by Heisenberg principle?

the fact that in interferrometry, the which path information deletes the fringe visibility reminds me the Heisenberg principle, but how to derive this relation?
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Could the Michelson-Morley experiment have detected gravitational waves?

If everything went perfectly and they had no outside noise while conducting the experiment, could they have detected gravitational waves? What would it have looked like to them?
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Claims of detection of gravitational waves with an accelerometer

Is this claim: https://earthscience.stackexchange.com/q/21236/ of detection of gravitational waves with accelerometers legitimate? I do not know much about this, but given how gravitational waves form ...
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Mach Zehnder classical output [closed]

$E_{0}$ is input to the first beam splitter and the output from the first beam splitter: $|E_{0}|^2=|E_{1}|^2+|E_{2}|^2$ $E_{1} = \frac{E_{0}}{\sqrt{2}}\;sin( \omega t - kx)$ $E_{2} = \frac{E_{0}}{\...
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How to know the true value of the measured quantity from an interferometer phase?

For an interferometer, the measured signal will oscillate as a function of the accumulated phase $\phi(x)$ as a sinusoid or cosine, where $x$ is a quantity we are trying to measure from the ...
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