Questions tagged [laser]
Light Amplification by Stimulated Emission of Radiation. A means of creating coherent light by either driving an atomic or molecular transition in an optical cavity or firing a beam of electrons through an undulator.
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29 views
Calculate beam radius for gaussian laser beam with lenses
So I know that the beam radius is
$$w_R(z) = w_{0R}\left[1+\left(\frac{z\lambda M^2}{\pi w_{0R}^2}\right)^2\right]^{1/2}$$
for a Gaussian beam at a distance $z$.
Now, I need the equation for the ...
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10 views
Question regarding demonstration of Poisson's spot
https://youtu.be/y9c8oZ49pFc
At around 5 minutes into the video, to show Poisson's spot, the laser beam is made to go through a diverging lens. Is it necessary to use a diverging and why?
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1answer
50 views
Identify reasons for laser intensity fluctuation
I got a Mitsubishi LPC-826 laser diode (single mode) with laser driver iC-HG. There is no cooling device, but data was captured after 30 mins switching on (which should be temporally stable). The beam ...
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12 views
Regarding the demonstration of Poisson's Spot
This video is one by Veritasium on Poisson's Spot.
https://youtu.be/y9c8oZ49pFc
In the later half of the video where he does the experiment by using a laser, why does the laser beam have to pass ...
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1answer
19 views
What are the losses in a laser cavity?
I studied that to get the lasing conditions gain must overcome the losses. But what are the losses? Thanks a lot
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1answer
14 views
Why can't cavity length be minimized to spread the spacing between allowed frequencies in a laser cavity?
I came to conclusion that it is because by doing so the threshold gain for lasing increases but I'm not completely sure of that. Thanks
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1answer
16 views
Random laser modes its Q-factor(s)
Many papers about random lasers mention the Q-factor of random lasers. Since a random laser has multiple peaks close to each other like shown in the figure. Does each of these peaks correspond to a ...
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3answers
64 views
Why do lasers need mirrors at the edge of the cavity?
If the avalanche stimulated emissions start from the first absorbtion that occurs in the cavity then why are mirrors needed? I imagine a photon that even without mirrors stimulates extra coherent ...
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1answer
39 views
Why does the intensity of the scattered light vary when a monochromatic laser is shined into a transparent object?
When a laser is shined into a glass ball such as this video (link) or a bottle of water (link) the light is refracted through the whole transparent body. However, the intensity of the light scattered ...
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16 views
Why do beam-expanders change the amount of diffraction of laser beams?
I recently learned that a perfectly collimated laser beam will still diverge due to diffraction. I was also told that using a beam-expander changes the amount of divergence caused by diffraction the ...
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0answers
9 views
Ionization of a Column of Air Using Laser
First, I know there is a question similar to this already, but I am asking it in much more detail and I have done much more research than the original asker. Say I wanted to ionize a 3 metre long path ...
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2answers
10 views
Optics - Polarization's Effect in a Blazed Reflective Diffraction Grating
I'm doing an undergraduate research project, part of which requires me to build an extended cavity diode laser (ECDL). The new diode mounts take receive the diode in a 90 degree rotation of the old ...
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1answer
21 views
Why does wavelength coherence affect diffusion?
Not to be confused with the relationship between wavelength and photon localization.
But, laser light is is able to stay concentrated over a vast distance, much more so than every-day lamp light. ...
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1answer
68 views
How can I create a laser beam as thin as possible?
Given a cheap laser pointer diode module with a lens that creates a beam which is about 3-4mm wide when it leaves the laser, i would like to create a beam significantly thinner (in one dimension at ...
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1answer
41 views
Constant width laser beam possible? [duplicate]
This https://www.gentec-eo.com/blog/spot-size-of-laser-beam article states that laser beam width changes along the length of the ray (the function stated doesn’t look like it could be a constant 1)
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1answer
42 views
Laser speckles relative to laser?
I know there are subjective laser speckles forming in the eye as well as objective laser speckles forming on the illuminated surface. What I wonder is, are there any speckles that are constrained to ...
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18 views
Simulation of QW gain
For a student project, I need to compute and plot the gain of a semiconductor quantum-well.
In my case, I am interested to reproduce the results from Schwartz et al. (Investigation and comparison of ...
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2answers
34 views
Do the results of this laser experiment demonstrate nonlinear optical phenomenon?
In my photonics class, we conducted an experiment to observe the Beer-Lambert law and the effects of filters(absorption, transmittance, and reflection). We shined a red(632nm) 5mW Helium-Neon laser ...
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15 views
DNA diffraction/ with spring, high school experiment
Whilst conducting a high school experiment with a laser and a spring I noticed something peculiar as I extended the spring the x pattern angle widened and as the spaces between the spring shortened, ...
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1answer
55 views
What happens if I replace an IR laser diode with CD burner laser diode in green laser pointer [closed]
I was wondering what happens if CD burner photons hit the crystal NdYO4 and KTP 780 nm wave length where original 808 nm IR pumper diode. I am confused with NdYO4 crystal I know that KTP is a ...
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0answers
48 views
Rotating Frame Transformation for three level system
I am trying to solve a task from an exercise sheet:
We consider a three-level system ($\Lambda$-configuration) with three eigenstates $|1\rangle$, $|2\rangle$ and
$|3\rangle$. The levels $|1\rangle$ ...
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1answer
40 views
Difference between amplitude modulation and intensity modulation
If a few kHz modulation is imposed on the 80MHz pulse train of a laser by the means of either a Mch-Zehnder interferometer or a single acousto optical modulator triggered by an external function ...
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2answers
234 views
Are there any types of lasers that emit orange and yellow light?
That is, without the introduction of nonlinear optics for frequency multiplication. In the case of orange light, I've often wondered in orange minerals like Lead Molybdate (PbMoO4) fluoresce the way ...
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1answer
43 views
Question about Homodyne detection
In this Review of modern physics, section "II. A.", optical homodyne detection is briefly reviewed. In equation (9), it is stated that the fields after the beam splitter are
$$E_{1}=\frac{E_\text{L}+...
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18 views
Can line lasers create double-slit like interference patterns?
I don‘t have the tools to test this experimentally and I did not find any experiments online.
Line lasers are laser pointers that shine through a cylindrical lens (https://en.m.wikipedia.org/wiki/...
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0answers
30 views
What is the power required for ground-to-ground laser communication?
I have read that laser technology is being researched for ground-to-space communication but what about ground-to-ground? How much power would a laser require to communicate over short distances like ...
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1answer
47 views
What is 'Spectral Domain'?
In a paper which deals with optical coherence tomography they say they are dealing in the spectral domain. What exactly does that mean?
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1answer
37 views
Possible to change optical properties of tissue?
I am looking at an optical coherence tomography scheme which is based on a michelson interferometer. The basic idea is that a laser beam is split by a beamsplitter, half of which goes into some tissue ...
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37 views
Would a radio frequency (RF) laser have any advantage over ordinary radios?
In the radio part of the electromagnetic spectrum it is really easy to make very clean and powerful RF waves using modern electronics, and it really isn't that hard to make arbitrary RF waves.
But ...
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10 views
Average power and power density in microscopy
In a microscopy experiment, usually the power density at sample is reported like XX MW/cm^2 . Is this the power at the objective focal spot. Can it be calculated if we have the info like objective ...
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1answer
61 views
Unexpected wavelength jumps in a laser observed: a fundamental noise source in VCSELs?
I observed an unexpected signal while developing an interferometric sensor using a VCSEL laser. In order to debug this noise I designed the following device that converts minute changes in the laser's ...
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0answers
33 views
Lasers: why when a photon kicks a excited electron, the two released photons have the same polarization?
When a photon kicks a excited electron, why do the two released photons have the same polarization?
I was playing with some lasers and am trying to understand the principles at play. I just read ...
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16 views
Simplest model of laser coupling
I am not familiar with classical/quantum optics. I have a possibly very basic question about physics of laser interaction. I think my question can be broken into two parts:
(1) What is the simplest ...
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0answers
17 views
Gain Coefficient of lasers and intensity paradox?
It can easily be shown that the intensity of a laser is
$$I = I_0e^{z\gamma} \,, \tag{1}$$
where $\gamma$ is the gain coefficient.
It can also be shown that
$$\gamma = \frac{\gamma_0}{1+I/I_{\text{...
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2answers
68 views
Spaceship A and Spaceship B move in opposite directions at half the speed of light, and A fires a laser at B, does the laser light reach Spaceship B? [closed]
This question has been bugging me for a week now!
I believe it would, but logically, I feel like I'm missing something.
Please give a full explanation.
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0answers
18 views
How can I focus a laser in the gap between two slits?
I’m trying to focus a green laser in between two slits. The slit width is 0.2mm and gap between the slits is also 0.2mm. I measured the laser’s minimum spot size. It’s elliptical with major and minor ...
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0answers
13 views
Wavelength vs change in angle of polarization?
My project is on polarimetry. I am searching for a base idea. What is the relationship between Wavelength vs change in angle of polarization? Note- Please do not lin this to optical activity(even ...
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4answers
79 views
Does putting an aperture in a laser beam make the smallest point it can be focused to larger or smaller?
If you put an aperture in a laser beam to block some of it, I would imagine that the spot it can be focused to becomes larger due to diffraction. The numerical aperture of the system is limited by ...
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1answer
45 views
Confused about intensity of a laser beam
For normal natural light coming from the sun, the electromagnetic waves emanate from the sun with a spherical wavefront, then we can calculate the intensity of these waves reaching us on Earth by $ I =...
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21 views
spot size in a microscopy experiment
How does a laser spot looks like under a high Numerical Aperture objective. I am attaching the profile I am getting in my case. Just wondering how can I calculate my spot diameter or point spread ...
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1answer
16 views
Finding intensity of laser after round trip in cavity with single mirror [closed]
I came across a question in a text book today, and was wondering if someone could maybe check to see if my physics and workings are correct, as I am getting a intensity value greater the what going ...
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1answer
54 views
Poor man's laser? [closed]
Would it be possible to use a non-laser light source to etch a flat surface? Using lenses or parabolic mirrors to focus the light to a point?
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2answers
49 views
Can lasers cause glare or reflections?
When going to the movie theater I sometimes notice reflections from the projector on my glasses and I find it very annoying. What happens is that the light hits the back of my glasses and i can see a ...
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1answer
34 views
What does 'coupling' mean? (Laser)
I assume this question is so basic that no YT-video or paper I found answers it. But in order to understand I have to know what it refers to.
I'm talking about laser coupling to be exact. I have a '...
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0answers
10 views
What can be done to a laser' setup to increase its slope efficiency?
Having a fibre laser, whose setup consists of a pump diode, a YDF and of a fully reflecting mirror parallel to the fibre, what can I do in order to improve the slope's efficiency without adding any ...
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0answers
6 views
DIfference between pump diode power and fibre's input end power?
I am reading some measurements done on a fibre laser, and the first data shown is the Current v Power table of the pump diode used in the experiment.
After that, a fibre is added to the system and a ...
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0answers
11 views
What characteristics of a fiber laser can I get from the input, output and unabsorbed pump data?
I aligned a pump diode with a fiber laser and added a dichroic mirror in front of the laser to separate the pump light from the light radiated from the fiber.
This way I was able to analyse the power ...
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2answers
29 views
Lasers to direct waste heat?
I've been thinking about ways to cloak ships in space, since they all are warmer than their background they can be seen in the IR spectrum (given a large enough telescope).
So I was thinking, could ...
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1answer
35 views
How to decrease the Q-factor of a resonator?
I was trying to create a mode-locked laser in order to create high-intensity light pulses, this experiment was done a while ago and with someone else, and in our notes says that the laser cavity's q-...
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1answer
23 views
Why do the Einstein rate equations require broadband radiation?
The Einstein rate equations govern the absorption and emission of photons from a two-level system of energy levels.
It states that the rate of absorption of photons is given by $\textrm{N}_{1}\rho\...
