All Questions
30
questions
1
vote
1
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66
views
Why laser output power fluctuates after passing through two 1x2 fiber optic couplers?
When laser source is launched into two 1x2 50/50 fiber optic couplers connected as below the output power constantly fluctuates in range of 70 uW.
The fluctuation happen roughly one to two times per ...
- 240
1
vote
0
answers
36
views
Which method of laser diode operation is less likely to cause mode hopping: constant current or constant power?
If a laser diode is uncolled and operates in a CW mode then which method of operation is less likely to cause mode hopping: constant current or constant power?
- 240
1
vote
1
answer
56
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Why fiber optic Sagnac interferometers don't produce multiple interference fringes
I have seen a few Sagnac fiber optic interferometers however, those that I've seen don't produce multiple fringes but rather just one luminant dot with varying intensity. Even if a beam expander is ...
- 240
1
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0
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30
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What are the causes for $g2$ ( intensity) value changes in a Mach-Zehnder setup at a fixed reference path and fixed sample?
I'm using a Multimode laser passing it through a Mach-Zehnder interferometer. I am able to get almost constant $g2$ (intensity) from the sample. However, the reference arm intensity keeps fluctuating ...
- 11
0
votes
1
answer
83
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The purpose of acoustic optical modulator (AOM) in Heterodyne Interferometry for Plasmas
I do not understand the purpose of an acoustic optical modulator (AOM) in a heterodyne interferometry system. Take the system below as an example (taken from a UW Dissertation)
My understanding for a ...
0
votes
0
answers
22
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Explain laser stability and interferograms relationship
I am using a Twyman-Green interferometer to record phase-stepped interferograms. The interferometer uses a monochromatic diode laser (visible light). As you observe the interferogram on the screen, ...
- 31
1
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0
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41
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What Is The Easiest Way to Measure a Short Distance With Laser Light?
I'm an EE, so please forgive if this question is dumb.
The word "easiest" means, "What requires the least amount of optics experience?"
"Short distances" means 0.01 to 1 ...
- 175
1
vote
3
answers
781
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Measuring coherence length with the Michelson Interferometer
In lab, I've been asked to measure the coherence length of a green-light laser source using a Michelson Interferometer. To do so, I configure the interferometer such that a circular fringe pattern ...
8
votes
2
answers
578
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Magically reappearing fringes in Michelson interferometer for large path length differences?
I've built a simple Michelson interferometer from two mirrors and a beam splitter according to the following schematic:
Image source
My setup differs from the one in the publication in that mirror M1 ...
- 181
0
votes
2
answers
160
views
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 $(...
- 1,047
1
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0
answers
47
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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 ...
- 889
2
votes
1
answer
515
views
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 ...
- 889
3
votes
0
answers
121
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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 ...
- 889
0
votes
1
answer
78
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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 ...
- 889
0
votes
2
answers
575
views
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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