What is Interferometer: Definition and 177 Discussions

Interferometry is a technique in which waves are superimposed to cause the phenomenon of interference, which is used to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy (and its applications to chemistry), quantum mechanics, nuclear and particle physics, plasma physics, remote sensing, biomolecular interactions, surface profiling, microfluidics, mechanical stress/strain measurement, velocimetry, optometry, and making holograms.Interferometers are devices that extract information from interference. They are widely used in science and industry for the measurement of microscopic displacements, refractive index changes and surface irregularities. In the case with most interferometers, light from a single source is split into two beams that travel in different optical paths, which are then combined again to produce interference; two incoherent sources can also be made to interfere under some circumstances though. The resulting interference fringes give information about the difference in optical path lengths. In analytical science, interferometers are used to measure lengths and the shape of optical components with nanometer precision; they are the highest precision length measuring instruments in existence. In Fourier transform spectroscopy they are used to analyze light containing features of absorption or emission associated with a substance or mixture. An astronomical interferometer consists of two or more separate telescopes that combine their signals, offering a resolution equivalent to that of a telescope of diameter equal to the largest separation between its individual elements.

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  1. A

    I Exploring Co-Phasal Wave Fronts in Fizeau Interferometry

    I am studying Fizeau analysis for wedge problem. I reached to this part and I cant follow. I have two questions and any help will be appreciated 1) what is meant by co-phasal wave fronts? does it mean that they have the same phase? ( how can I Think about the wave fronts in this case) 2) why...
  2. P

    I Is this a valid quantum Cheshire cat?

    I just watched Sabine's Hossenfelder very recent new video on the Quantum Cheshire effect. From experience, everything Sabine's says on either entanglement/quantum interpretations or not-physics, is heavily biased to her worldview. However I thought it was fun to see what she was going to say...
  3. Precious Adegbite

    I What Is the Smallest Change Detected by a Multiport Interferometer?

    Good morning all... please I'd like to know what's the smallest ever recorded change in phase or wavelength any multiport interferometer has ever been able to detect. And which multiport interferometer detected it.
  4. dykuma

    I Fabry-Perot Interferometer mirrors

    I am trying to build a Fabry-Perot interferometer to make some narrow band filters, and I was wondering if anyone can go into the specifics of whether there's anything special about the types of mirrors used in construction. I started by trying to see how hard it really is to make one on my...
  5. Marilyn67

    I Mach-Zehnder interferometer, but with an entangled beam?

    Hello, The Mach-Zehnder interferometer makes it possible to highlight the corpuscular and undulatory aspect of light, (in particular using single photons). By using the "continuous" beam from a coherent source, one is able to visualize directly on two screens E1 and E2, an interference pattern...
  6. H

    I Looking For Explanation of New Interferometer Article

    https://physics.aps.org/articles/v15/162 Looking for a layman's summary of this article. If I spent a couple of hours maybe I could do it. Then again, maybe not.
  7. B

    I Are there inherent limits to Interferometer size?

    The recent high angular resolution images of M87's inner black hole taken by radio telescopes around the globe all linked together in a computer to simulate a giant interferometer, suggest that to achieve still better angular resolution we would need to supplement the terrestrial receiving...
  8. Salmone

    I Why do we always see interference pattern in Michelson interferometer?

    In a Michelson interferometer with a monochromatic laser, why do we always see an interference pattern even if we move one of the mirrors? Shouldn't it be a certain distance for which the movable mirror reflects the wave to be in opposite phase with the other wave so that they interfere...
  9. A

    I Counterfactual quantum computation on interferometer

    I watched a video on the topic by Sabine Hossenfelder. Now it is said by many that this proves the photon "knows" something in advance because a certain state of a certain beam splitter can be probed in theory without the photon ever encountering that beam splitter because it took another path...
  10. B

    Correct Angle for FSW in Fabry-Perot Interferometer

    Sorry for the lack of formatting, I'm in a rush to write this before I go pick someone up from work. My question is what is theta1? Is it 45 degrees because that's the angle the light hits the boundary of the plate to the n1 medium? Or is it 0? It seems like it should be 45 but there's an...
  11. Z

    Michelson Interferometer with a lens

    Hello everyone, i have a homework but I'm so confused how to solved it , can someone make a solution manual for this homework?, Thankyou.
  12. warhammer

    I Correct Formula for "No Fringe Condition" (Michelson Interferometer)

    In two different textbooks, there are two different formulas with different derivation styles for the "No Fringe Formation" Condition. In approach (a), they use an amalgamation of bright and dark for 2 wavelengths having very minute difference in the following manner: 2dcostheta=n*λ(1)...
  13. GhostLoveScore

    Interferometer delay & line light spreading

    In every article that I've read about optical interferometers they explain that collimated light from farther the telescope is sent down the delay line, and then into a beam combiner with other beam. Like in the photo below But they all only show light that enters the telescope along the axis...
  14. M

    I Gaussian beam in a Fabry-Perot interferometer

    Hello I am reading some introductory laser cavity stuff and I am a bit confused about the existence of gaussian beams in the Fabry-Perot interferometer. If you solve the stability condition for a cavity (i.e. asking for the q parameter to reproduce itself after one round trip) you get that in...
  15. Aurora_b

    Circular fringes in a Fabry-Perot Interferometer

    Fabry-Perot Interferometer contains an etalon(an optical cavity created by 2 partially reflective mirrors placed parallel to each other separated by a small distance). When light enters the etalon it gets reflected back and forth between both the mirrors, being partially reflective, every time...
  16. zeronem

    I Photon states and interference in an Interferometer

    Hello. I have a question. In the book I am reading, They derive the Ubs operator applied on a photon state with the beam splitter at a ratio of 50/50. A beam splitter that is used in the Mach-Zehnder interferometer. I'm having a hard time deciphering whether the formula for beam splitter...
  17. S

    B Phase shift in Mach-Zehnder interferometer

    I'm confused by the phase shifts in a Mach-Zehnder interferometer because I keep finding two different explanations. One explanation (for example, given on Wikipedia, but also elsewhere) states that on each reflection, the phase shift is 180 degrees, but only, if light is reflected from the...
  18. Marilyn67

    A Influence of strong measurements in a Two Slit Interferometer

    Hello, I am interested in weak measures since I discovered this paper: https://arxiv.org/ftp/arxiv/papers/1206/1206.6224.pdf I understood that retro-causality is only an interpretation and that's not more exploitable than the famous experiments of quantum gum delayed choice. In fact, we...
  19. J

    B Beamsplitter in a Michelson interferometer

    For a science fair experiment at high school I built a Michelson interferometer that could achieve a single interference state. Now there are two beams exit from such an interferometer, if a dielectric beamsplitter/combiner is used, one beam exits in a constructive state, and the other in a...
  20. P

    Finding the unitary matrix for a beam splitter

    Hello, I have some trouble understanding how to construct the matrix for the beam splitter (in a Mach-Zehnder interferometer). I started with deciding my input and output states for the photon. I then use Borns rule, which I have attached below: To get the following for the state space...
  21. G

    I Franson interferometer: Entanglement?

    Hi. As far as I understand the Franson interferometer, the photons are in an entangled state like $$\left|\Psi\right\rangle=\frac{1}{\sqrt{2}}\left(\left|\text{short}\right\rangle\left|\text{short}\right\rangle+\left|\text{long}\right\rangle\left|\text{long}\right\rangle\right)$$ if the setup...
  22. HotFurnace

    B Rayleigh Interferometer: Impact of Slip Placement on Interference Pattern

    What will change if we place the slips in front of the converging lens instead of behind the collimating lens? My teacher say nothing will change in the interference pattern but I doubt his answer.
  23. Marisa5

    Coherence pattern of HeNe laser in interferometer

    Hello, i hope i posted this in the correct forum! When measuring coherence of a HeNe laser using a Michelson interferometer, there are key points along the moving interferometer arm where coherence is highest. The distance between each of these peaks corresponds with the length of the laser...
  24. malak

    I Michelson interferometer dimensions

    hi i want to design michelson interferometer device for measuring small distance movement i am using laser diode with a wavelength 635 nm and power 3 mw can anyone tell me how can i decide the dimensions (from source to beam splitter , for beam splitter to fixed mirror , from beam splitter to...
  25. N

    I have problem with a mirror on Michelson interferometer

    My students and I tried to create a Michelson inerferometer like yours (08557.00). The problem is with a mirror that moves. How did you solve this precise translatory movement? Professor of Physics Nikola Gledić - Technical school Šabac, Serbia Thanks in advantage!
  26. P

    Interferometer- 2 spectral lines

    Homework Statement An interferometer is illuminated by light from a sodium lamp, which emits two narrow spectral lines at wavelengths of 589.0nm and 589.6nm, with the intensity of the 589.0nm line being twice that of the 589.6nm line. Show that there are values of d at which the visibility of...
  27. Clara Chung

    Question about Fabry interferometer

    Homework Statement Homework EquationsThe Attempt at a Solution I need help on part b and c. Here is my attempt: Ai=Ai,0 exp(ikz-wt) (1 + √R1√R2 exp(iδ) + [√R1√R2 exp(iδ)]^2 +......) =Ai,0 exp(ikz-wt) / (1- √R1√R2 exp(iδ)) => |Ai| = |Ai,0| |(1 + √R1√R2 exp(iδ))| / ( (1 - √R1√R2 cos(δ))2 +...
  28. B

    Relationship between interference and arm length in MZI

    A question about the Mach-Zehnder interferometer. My understanding is: If its two arms are equally long, there is destructive interference in one output and constructive interference in the other output. So, the intensity of light detected at the first output should be 0% and at the second...
  29. W

    Mach-Zehnder Interferometer interpretation

    Hi all, I have a problem trying to interpret the mathematics of this experiment and would like some help. I think it's best I write out all my ideas (and misconceptions) so that I can be corrected. An illustration of the setup is below. Thanks in advance for any assistance! Let the following...
  30. Decimal

    I Amplitudes in a Michelson interferometer

    Hello, I am having a hard time understanding a result relating to a michelson interferometer. I always assumed that when the beam hits the wave splitter both resulting waves will have half the amplitude of the original wave. However using this assumption does not give the correct irradiance for...
  31. B

    I All-fiber Mach-Zehnder interferometer

    Experimentalists, would you mind sharing your experience building a fiber-based Mach-Zehnder interferometer? What equipment did you use? How hard is it to achieve the same length of both arms with the fiber and couplers that you can buy online? And how sensitive is the resulting interferometer...
  32. Marcus95

    Fringe Visibility of Sodium Doublet in Michelson interferometer

    Homework Statement The sodium D-lines are a pair of narrow, closely spaced, approximately equal intensity spectral lines with a mean wavelength of approximately 589 nm. A Michelson interferometer is set up to study the D-lines from a sodium lamp. High contrast fringes are seen for zero...
  33. VSayantan

    Fringe-Shift in Michelson Interferometer with a Moving Source

    Homework Statement The Michelson interferometer in the figure below can be used to study properties of light emitted by distant sources A source ##S_1##, when at rest, is known to emit light at wavelength ##632.8~ \rm nm##. In this case, if the movable mirror is translated through a...
  34. T

    Transmission and reflectivity in a Michelson interferometer.

    Homework Statement Sketch and explain the operation of the Michelson interferometer. How is the transmission of the interferometer modified if the amplitude transmission t and reflectivity r of the partially-reflecting beamsplitter are not equal? What happens to the fraction of light that is...
  35. E

    I Confusion about Dirac Notation (interferometer)

    Hello everybody, Dirac notation uses "bras"( <a| ) and "kets"( |b> ), which are row vectors and column vectors respectively, but what would something like |a, b> mean? It makes no notational sense to me Context: A couple of photons going through beam splitters in an interferometer. One is...
  36. R

    Interference of Two Waves (Interferometer)

    Homework Statement The input signal to the interferometer shown in the picture below is given by: $$E_{\text{in}}=\sqrt{P}\exp\left(j\omega_{0}t+\frac{jD(t)\pi}{2}+j\varphi_{p}(t)\right). \tag{1}$$ ##P## is the power that is received. The delay present in one arm of the interferometer is...
  37. rkatcosmos

    Using multiple mirrors in Michelson Interferometer

    The number of mirrors typically used in Michelson Interferometer is 2. I am looking up the respective Wikipedia article and MIT's youtube video. I am wondering, for the sake of one of my experiment, whether more than 2 mirrors can be used in the interferometer? I require the traversing mirror...
  38. weezy

    I Interference of a single photon in an interferometer

    I think we can all agree that when we are shooting many photons one by one, through an interferometer, we can eventually land up with the interference pattern. This can be explained by saying that two photons combining in some areas to give four photons and in some places annihilating each...
  39. E

    How Does LIGO Detect Gravitational Waves Using Laser Interferometry?

    Homework Statement In-phase light from a laser with an effective power of 2x105J and a wavelength of 1064nm is sent down perpendicular 4km arms of the LIGO detector. (i) Determine the number of photons traveling in the interferometer arms. (ii) Assuming the detector is sensitive enough to...
  40. G

    I Why doesn't momentum transfer on mirrors reveal which path?

    Hi. In a Mach-Zehnder interferometer, there are mirrors in both paths. When a photon gets reflected on a mirror, it transfers momentum. Also, mirrors are classical objects that are usually not assumed to exist in superposition states. Shouldn't it (at least in principle) be possible to measure...
  41. M

    I Built an HBT Interferometer but don't get the physics

    Hi Guys, I was tasked with building a cheap Hanbury-Brown Twiss Interferometer >$50-100. Below is an image of my design requirements which i managed to implement within a 32bit micrcotronoller and i am able to measure time differences down to 100ps over a range of up to 1us-1ms at around...
  42. R

    Special Relativity: Rotated Michelson Interferometer

    Homework Statement The aether-wind theory of the Michelson-Morley experiment was discussed in class for the special case where the arms of the interferometer (each of equal length L) are parallel and perpendicular to the wind. In this problem we consider the general case for an angular setting...
  43. Charles Link

    Insights Fabry-Perot and Michelson Interferometry: A Fundamental Approach - Comments

    Charles Link submitted a new PF Insights post Fabry-Perot and Michelson Interferometry: A Fundamental Approach Continue reading the Original PF Insights Post.
  44. C

    B Delayed choice experiment and FTL communication

    I've been thinking about a communication system that could allow faster than light communication. The basic principle that would make this system work come from the double-slit experiment and Wheleer's delayed choice experiment, taking advantage of the different patterns that would appear on a...
  45. Cocoleia

    Michelson interferometer moves and bright fringes disappear

    Homework Statement In a Michelson interferometer, as one of the mirrors is moved, 250 bright fringes disappear into the centre. If the light wavelength was 800nm, how far was the mirror moved? Homework EquationsThe Attempt at a Solution My logic is: If we were to count how many passing bright...
  46. S

    A Solve Gravitational Interferometer & Geodesics

    I was trying to solve this excercise: Now I was able to find the eq. of geodetics (or directly by Christoffel formulas calculation or by the Lagrangian for a point particle). And I verified that such space constant coordinate point is a geodetic. Now, for the second point I...
  47. G

    I How can gravitational waves be detected if spacetime itself warps?

    Hi, First: I'm pretty sure my question has been asked numerous times, so I'm absolutely happy with links to other threads. I've used search but it didn't come up with satisfying responses, probably mainly because I don't really know what search terms to use. So the question is: How can a...
  48. F

    B Question about Michelson-Morley experiment

    Hi, I think I have a good grasp of the principles underlying the Michelson-Morley experiment, but I am not sure about a detail. In basic textbooks a simplified situation is presented whereby the ether wind is along one of the two arms of the interferometer. Simple classical physics calculations...
  49. henil

    Lateral shearing interferometer

    what will happen to fringes if the shearing plate thickness is changed ?