Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

1
vote
0answers
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 ...
0
votes
0answers
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?
2
votes
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 ...
0
votes
0answers
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 ...
1
vote
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
0
votes
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
2
votes
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 ...
2
votes
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 ...
3
votes
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 ...
0
votes
0answers
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 ...
0
votes
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 ...
0
votes
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 ...
1
vote
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. ...
2
votes
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 ...
0
votes
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) ...
1
vote
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 ...
0
votes
0answers
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 ...
1
vote
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 ...
0
votes
0answers
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, ...
0
votes
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 ...
0
votes
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 $|1\rangle$ ...
0
votes
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 ...
2
votes
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 ...
2
votes
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}+...
0
votes
0answers
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/...
0
votes
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 ...
1
vote
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?
0
votes
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 ...
1
vote
0answers
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 ...
0
votes
0answers
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 ...
1
vote
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 ...
0
votes
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 ...
0
votes
0answers
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 ...
0
votes
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{...
0
votes
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.
1
vote
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 ...
0
votes
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 ...
1
vote
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 ...
1
vote
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 =...
0
votes
0answers
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 ...
0
votes
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 ...
0
votes
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?
1
vote
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 ...
0
votes
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 '...
0
votes
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 ...
0
votes
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 ...
0
votes
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 ...
0
votes
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 ...
1
vote
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-...
0
votes
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\...