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 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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Matter wave coherence length

Coherence length is defined as (see here) The propagation distance over which a coherent wave (e.g. an electromagnetic wave) maintains a specified degree of coherence. Other questions see here, and ...
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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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Mach-Zehnder interferometer classical field [closed]

I knew that $$I \propto |E|^2$$ I wanted to calculate intensity on detector 1 and detector 2 in Mach-Zehnder interferometer. One path have electric field $E_{1}$ and the second $E_{2}$. Its splits in ...
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Bragg and Raman beam splitters

In atom interferometry, what is the difference between Bragg and Raman beam splitter operations? When reading articles on atom interferometry I am finding statements such as `using a Raman/Bragg beam ...
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Why is it harder to use a white light source in a Michelson Interferometer?

In a Michelson Interferometer, a light beam is split into 2 different beams that travel different optical paths, through the "arms" of the interferometer. Then, they are reflected and, ...
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Cause of phase shift in matterwave interferometers

I am studying matterwave interferometry and I have read that the phase shift accumulated between the two arms of the interferometer is due to a coupling of the atoms to non-inertial forces. What is ...
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How is the phase gain of a Fabry-Perot resonator for gravitational wave detection derived?

I am trying to understand the use of the Fabry-Perot (FP) resonator in the arms of a gravitational wave detector. A typical explanation is that the gain in power in the arms is equal to $\sqrt{F}$ (...
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Infinite sum of transmitted parallel light fields

I'm currently studying optics and came across the possibility of retrieving the original electric (light field) from a pair of partially reflecting mirrors, but I am confused by several ...
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Particles in an interferometer in a gravitational field

Let's assume one has a standard interferometer, consisting of an incoming beam which gets splitted in beam I and II and then culminated again. Now the interferometer is placed in a gravitational field,...
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Time difference evaluation in a Michelson-Morley apparatus with arbitrary orientation

Historically, by assuming the validity of the Lorentz-Fitzgerald contraction, the null result obtained in the Michelson-Morley experiment can be explained. In particular light travels along the two ...
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Fringe movement analysis to extract displacement

I am using a Michelson interferometer with the interferogram recorded on a CMOS sensor. I have taken a video of the fringes moving when a displacement of 50 $\mu m$ is imposed to one of the mirrors. ...
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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 ...
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Derivation of the probability of joint detection in Hong-Ou-Mandel interferometer

I read the Hong, Ou, Mandel. "Measurement of Subpicosecond Time Intervals between Two Photons by Interference", from PRL 59, 2044. Where the - now known as - Hong-Ou-Mandel interferometer ...
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Spatial intensity distribution of a LED source

I hardly find instruments for applications like wavefront sensing of large optics (more than 200 mm diameter) using a LED source or halogen lamp. Is the maximum width limited by the low spatial ...
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Setting up Twyman-Green interferometer

I am trying to reproduce some experiments for multiple degree of freedom homodyne interferometry, but I am struggling to understand the basics of the hardware I need. The literature I am referring to ...
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Obtain clear fringes from interferometer

I have just begun setting up an interferometer to take some measurements. I am trying to reproduce one paper I found in literature for 3 DoF homodyne interferometry. The detector is merly a CMOS ...
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Circular fringes in Michelson interferometer

The rays reflected by mirrors M1 and M2 meet at the glass G. For each ray(specifically 1 and 2 in the figure which may go on 1,2,3... for an extended object as is required for the experiment) as the ...
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Quantum interferometer with floating mirrors [duplicate]

I send photons one at a time through a Mach–Zehnder interferometer with two detectors. Quantum superposition ensures that photons only reach one of the detectors. The interferometer is initially ...
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Tidal effect on interferometry

Interferometry relies on the change in the phase of two orthogonal light beams reflected back to the source point. Assume there is an interferometer at the equator, one mirror is planted 1 mile due ...
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Why do we use sodium light in Michelson interferometer for doublets?

I have a question regarding Michelson interferometer. I would like to know why we use sodium lamp for observing doublets instead of He-Ne laser or a regular lamp. Any help and explanation is much ...
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Heterodyne interferometry, an alternative?

I am trying to setup an interferometer to monitor displacements and tilts between two surfaces. I am quite struggling because I never studied optics deeply. I have found in this paper (https://...
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Laser interferometry for relative movements between two mirrors

I have been struggling in the past weeks to understand how should I setup a laser interferometer for my experiment. I am not a physicist, and I am quite new to optics. I have a Cassegrain telescope ...
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What does it mean for a light to have low-coherence?

I've been searching about OCT imaging and understood that it is based on low-coherence light source. The problem is, I don't understand what is a low-coherence light source. Based on what points that ...
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3rd Dimension on LIGO

The LIGO interferometers are 2 dimensional, they have $4\rm\ km$ legs that are perpendicular to each other. Could a 3rd $4\rm\ km$ leg either with a straight up tower or deep into the earth, provide ...

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