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. B

    Michelson Interferometer IR Lab Question

    I've been reading up on Fourier Transform Infrared Spectroscopy and the Michelson Interferometer. My main sources are "Principles of Instrumental Analysis" by Skoog etc and Fourier - Transform Infrared Spectrometry by Griffiths and Haseth. I believe I understand the theoretical principles...
  2. H

    B Whatever Happened to the Bell V Interferometer for Gravitational Waves?

    Decades ago a massive neodymium bar was going to be used for measuring GW's. I know noise was a problem. Anyone know what happened to this technology? Sounded cool, a big bell at the resonance frequency of a GW.
  3. R

    A ALIGO interferometer sensitivity

    Hi everyone! One thing that's been bothering me about all the hype and comments related the detection of GWs by the aLIGO team is that given the amazing sensitivity(strains~1.0E-22) achieved by the interferometers nobody has mentioned the possibility that they have become sensitive to not only...
  4. J

    I Vertical Interferometer Experiments: Michelson-Morley, Miller, etc.

    The original interferometer experiments -- Michelson-Morley, Miller, etc. -- were all done parallel to the Earth's surface. Have any been done vertically?
  5. W

    How Does a Michelson Interferometer Measure the Thickness of a Piece of Plastic?

    I'm reading about an experiment done with a Michelson interferometer. The aim is to measure the thickness of a piece of plastic. They use white light, so the central fringe in the interference pattern, corresponding to equal path lengths in the two beams can be used as a reference. Why does that...
  6. L

    Optics: Center of Fizeau Fringe? Michelson Interferometer

    Hello everyone, i am simulating a Michelson interferometer, where one mirror is slightly tilted, see picture.. This results in circular arcs / hyperbolic cross-section fringes. The center of these fringes depends on the focal length i am using, see picture. Is there an analytical expression for...
  7. E

    Michelson Interferometer ring contraction

    I have been trying for hours to understand what is physically causing the interferometric rings to contract when the separation of the mirrors is reduced. From the equation: m\lambda = 2Lcos\theta, where m is the number of fringes, if we consider just one fringe at a fixed wavelength...
  8. E

    Question about Michelson-Morley interferometer

    Must the two arms of a MM interferometer be equal for fringes to appear? What is the tolerance on that? Would that give the length of the wave packets?
  9. H

    Are the two paths in an interferometer indistinguishable?

    For the case of an electron passing through a double slit, there will be an interference pattern if it is indistinguishable which slit the electron passes through. If we put a light source behind the slits to measure which slit the electron passes through, the interference pattern is destroyed...
  10. Alex299792458

    B How Does Michelson-Morley Interferometer Measure Space-Time?

    I was watching a video about space travel and one of the methods of going into space is using warp drive and to test if warp drive was possible they had to created a device to test if their ideas for warp drive was possible they had to measure space-time it's self and they said a...
  11. Thomasphysicist

    Odd delayed choice interferometer interpretations

    This thread is about my not understanding the conclusion that scientists came to that the photon makes a 'decision' on how to travel. In a simple interferometer experiment, a photon displays interference fringes only when a second beam splitter is present. According to Wiki, this led scientists...
  12. M

    Fabry Perot Free Spectral Range

    Hi all, the question which I'd like to share is the following: if you look at the formal theory of any random optics book for FP interferometer you will get to the formula of the FSR (Free Spectral Range), defined as "The wavelength separation between adjacent transmission peaks" (Wikipedia)...
  13. Robsta

    Interferometer to measure refractive index of a gas

    Homework Statement I've uploaded a diagram showing a two beam interferometer that can be used to monitor changes of refractive index in a gas cell. it is illuminated with monochromatic light of wavelength λ. The light is linearly horizontally polarised. The two polarizing beam splitters (PBS)...
  14. S

    Michelson Interferometer (Zero Path Difference)

    Homework Statement A Michelson interferometer is illuminated with a laser with a wavelength of 514.5nm. A Haidinger fringe pattern is photographed with a lens of focal length 55mm. The diameter of the two adjacent circular fringes in the image are 1.53mm and 2.62mm. How far would the mirror...
  15. B

    Infrared spectroscopy to find water absorption lines

    Hi I am currently trying to find the water absorption lines by using a Michelson interferometer, as a detector I am using an ocean spectrometer. The data obtained is thus the spectrum's "received" by the spectrometer. Am I right to assume that in order to find the absorption peak/peaks I should...
  16. N

    Measurement of Momentum in Neutron Interferometer

    Homework Statement https://dl.dropboxusercontent.com/u/62834965/neutron_interferometer.png Consider a neutron interferometer (NI), such as the Mach-Zehnder interferometer in the figure. We send in a beam of neutrons. We assume that the flux of neutrons is so low (neutrons can be very slow)...
  17. Spinnor

    Casimir effect excludes photon modes*, same for two slit interferometer?

    Can we say that a point light source (turned off) together with a two slit interferometer and say a photographic plate detector exclude certain photon modes? Light does not go to certain parts of the photographic plate so can we say that the source (turned off), the interferometer, and the...
  18. zrek

    The Quantum Computer and beamsplitter

    Dear fellows, please help me to imagine the physical working of a quantum computer (QC). I have read here ( http://www.cs.rice.edu/~taha/teaching/05F/210/news/2005_09_16.htm ) that the basic idea behind it is the phenomenon that you can find in the Mach–Zehnder interferometer But how come this...
  19. R

    How Does a Michelson Interferometer Measure Distances?

    Homework Statement My personal question: What does a Michelson interferometer tell us? The actual problem: A Michelson interferometer is used to precisely measure distances of the order of 1 mm using a laser of wavelength 632.8 nm. a) If the motion of one mirror is 1 mm, what is the...
  20. StevieTNZ

    PBS Interferometer: Testing Polarization of Photons

    Hi there In "Dance of the Photons" by Anton Zeilinger (pgs. 82-84), Zeilinger has a polarising beam splitter interferometer as such- http://img.photobucket.com/albums/v608/steviet/IMG_20140905_0001_zpsc8add996.jpg (assume the length of paths are the same) The input photon is polarised 45...
  21. E

    Gravitational Interferometer and Kalman

    Hello everybody! Extreme interferometers like Ligo, Virgo, Leo600, Tama300 try to detect gravitational waves http://en.wikipedia.org/wiki/Gravitational-wave_detector and ground movements are one difficulty for them. The mirrors are suspended in several stages to insulate them, sometimes...
  22. A

    Mirau White Light Interferometer. Light Source?

    Hi everyone, I'm building a white light interferometer and need help choosing and finding a white light source. I'm using this mirau objective: http://www.edmundoptics.com/microscopy/infinity-corrected-objectives/nikon-interferometry-objectives/59312 Here is the setup: I know...
  23. A

    Do I understand the Fizeau interferometer? How to read interferogram?

    Hi, I'm just wondering if someone could help me better understand how the Fizeau interferometer works...http://upload.wikimedia.org/wikipedia/commons/2/2f/Fizeau_interferometer_testing_optical_flat.svg From my understanding, the source shines light through a collimating lens and the light goes...
  24. U

    Michelson Interferometer - calculating errors

    Homework Statement Part (a): Find an expression for intensity, interference phase and total change of interference phase. Part (b): Find an expression for <L1>/L0 and its error. Part (c): Find an expression for Δø1 and proportionality constant. Part (d): Find an expression for n(0) and α...
  25. G

    Michelson interferometer fringes

    Since 2 splitted beams meet at ONE spot later on, we have just one beam which flows to the detector, therefore I expect to see just one light spot, where the BRIGHTNESS is changing depending on at which phase 2 beams meet. Pattern with fringes happens when we have multiple sources, like Young's...
  26. U

    Michelson Interferometer: Optics

    Homework Statement A Michelson Interferometer has incident light in range 780-920 nm from a source. Intensity as a function of x (distance from central maxima) is given by: I_{(x)} = 3I_0 + 3I_0 cos(K_1x) cos (K_2x) - I_0 sin (K_1x) sin (K_2x) where ##K_1 = 1.3 x 10^7 m^{-1}## and ##K_2 =...
  27. A

    Fabry Perot Interferometer

    Design a Fabry perot interferometer, that provides a transmission of T =1 for light with λ1 = 499nm under orthogonal incidence and a transmission for λ2 = 500nm of T≤0.01 (without any further maxima in between). How big has to be the finesse? Draw the transmission curve of several Fabry -...
  28. S

    A paper about Planar Interferometer Arrays

    Hello, I have attached a paper about Planar Interferometer Arrays. Now I’m trying to understand this paper but something confuses me. I am very thankful if somebody can help me with it. 1: It seems to me that direction cosines and phase differences are 1:1 correspondent, that is, a phase...
  29. S

    Geolocation of emitters using an interferometer array

    Hello, in a paper about geolocation of emitters using an interferometer array I read such a description about a kind of array: Such arrays support locating emitters using some form of triangulation or bearings-only geolocation over several dwells as the satellite moves in its orbit. I...
  30. S

    Some basic questions about radio interferometer (Direction Finding)

    Hello, I’m a beginner to interferometer technology. While reading the attached article about this technology I find two formulas are missing. Please help me with them. 1. On page 5-8.8: rms angular accuracy. 2. In Table 3 on page 5-8.9: DF Accuracy. As far as I understand the space...
  31. S

    Resolution limit of delay line interferometer

    Hello All I am using a very basic delay line interferometer to measure the linewidth of a laser source. Basically there is a 1550nm laser that emits light which is split, and one half of the light travels down a 700m delay line before being recombined and the interference is observed. This...
  32. A

    Need some help trying to understand the Michelson interferometer

    Refer to the second diagram on this website http://electron6.phys.utk.edu/optics421/modules/m5/Interferometers.htm Using monochromatic light at first, you produce an interference pattern using the Michelson interferometer. If you set the relative tilt of the mirrors so that they are...
  33. L

    Michelson interferometer average power derivation

    Homework Statement Using the trig product identity, cosαcosβ=\frac{1}{2}[cos(α+β)+cos(α-β)], show that the time-average power at the detector can be written as Pavg = 1+cos(δ) That = is supposed to be a proportional symbol. Homework Equations Other than the ones given in the problem...
  34. K

    Question about Interferometer Outcomes

    Hey I got a quick question that I figure you guys could answer quite easily and would be easiest to understand if I just show a picture of the diagram: OK if we refer to figure (c) in the diagram above, how would the outcome(s) change if we replaced the mirror M with another beam...
  35. Artlav

    Failure to make a Mach–Zehnder interferometer?

    Hello. I'm trying to make a "Mach–Zehnder interferometer", that would show a same-named paradox. In plain words: Two half-silvered mirrors, two full mirrors, the beam is split, then merged together. At the merge point one way the photon is canceled out, while the other way it is combined...
  36. I

    Why can't I see fringes with eyepiece in my Michelson Interferometer?

    Hello Forum I have constructing a Michelson Interferometer using sodium light. For viewing the fringes, I have used spectrometer telescope with objective lens of 178mm focal length, 35mm dia and eyepiece 15X. I can see the localized fringes when I view through the objective glass but without...
  37. R

    Solving for Mirror Displacement in a Michelson Interferometer

    Homework Statement The distance between the movable mirror and the beam splitter in a Michelson interferometer is increased a small amount. When this happens, you see 200 dark fringes move across the field of view. If the incident light was 600nm, by how much was the mirror moved (in...
  38. H

    Neutron Spin Time Evolution in Interferometer

    Hey Everyone, I'm working on a question and can't quite get the answer out. QUESTION: Part (a) "\left|\alpha\right\rangle and \left|\beta\right\rangle are the eigenfunctions for neutrons polarized respectively along positive and negative z directions. If the neutron, initially in...
  39. F

    An interferometer with two arms is constructed above

    I have attached the problem as the image is needed for the question. a) Basically, from what I understand the wave is being split, thus each chamber receives the total number of wavelengths/2. The chambers, however are vacuums, so the number of wavelengths passing in doesn't change right...
  40. B

    Why is the equation for delta t in a Michelson interferometer 2(L/v - L/c)?

    Homework Statement In one arm of a Michelson interferometer the light passes through a glass tube of length L which contains air. The air is pumped slowly out of the tube and during this process it is found that the intensity of light reaching the eye has increased and decreased n times...
  41. J

    Why do Michelson interferometer usually needs 2 mirrors?

    I've been wondering this for quite some time. Why do a typical set-up of Michelson interferometer usually requires 2 mirrors? Why not one for adjustment? Why not just shine the laser through the beam splitter? Thanks.
  42. binbagsss

    Interferometer and Interference.

    I have some questions regarding a fabry perot interferometer. (they aren’t problems as such however I have had a good look around the internet and am struggling to find what I’m looking for). 1) Why is it that a circular fringe pattern is observed. How does a single source interfere with...
  43. StevieTNZ

    Mach-Zehnder interferometer Application

    Hi there, Is there an application available on the web, or an .exe for Windows, that enables me to run an experiment involving a Mach-Zehnder interferometer -and will display the relevant result - allowing me also to add wave plates and rotate them appropriately, and define the inputs (i.e...
  44. S

    How to use interferometer for surface roughness calculations?

    Dear all I am working on a project and I need to measure the surface roughness of a specific type of wood. I don't want to make things complicated because I have to make the instrument myself. I think an interferometer can help me to measure surface roughness but I really don't know how to...
  45. S

    White-Juday Warp Field Interferometer Experiment

    White-Juday "Warp Field Interferometer" Experiment Here is a presentation by Harold White on what he's calling the White-Juday Warp Interferometer Experiment, which is part of their investigation into the theoretical Alcubierre Warp concept...
  46. S

    Exploring Interference Patterns: Building and Testing a Michelson Interferometer

    I would like an outside opinion on something I've been thinking about lately. If one of the outer mirrors on a Michelson interferometer was to be misaligned by a small angle of theta, what would be the shape of the interference pattern in the detector plane? What would happen to this pattern as...
  47. I

    Understanding Wave Direction in Michelson-Morley Interferometer

    Hello, I would like to understand the Michelson–Morley interferometer, but with the laser being an omnidirectional photon source and a pipe. http://img822.imageshack.us/img822/6520/interferometer.png There are two pipes, but only one transmits light. The other absorbs the light, because...
  48. X

    Building a Mach–Zehnder interferometer

    Hello, I was interested in building a Mach-Zender interferometer at home, and I was wondering if that is possible within reason and if anyone on here would happen to have some useful advice on how to accomplish this. What kind of (affordable) components would be recommended to use? How...
  49. I

    Self-Mixing Interferometer vs Capacitive Sensor

    I'm trying to build a non-contact displacement sensor, sensitive to motion in the micrometer to millimeter range, for a research project. My two best choices are a self-mixing laser interferometer and a capacitive displacement sensor. Has anyone had enough experience with these types of sensors...
  50. M

    Mach–Zehnder interferometer question, path detection

    In a Mach–Zehnder interferometer experiment, can you measure which path the beam took by measuring the change in momentum of the (fully silvered) mirrors (i.e. if path A was taken then the mirror on path A was "pushed" a bit, if path B was taken then the mirror on path B was "pushed" a bit)?
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