1. ### A Laser Ablation of a fused silica surface

I read in couple of articles, like this one: https://link.springer.com/content/pdf/10.1007/BF00324203.pdf that regions of fused silica surface can be ablated by laser... I have two questions: 1- Why does the ablation occur? 2- does the ablation happens when the laser waist point is under the...
2. ### B What is the meaning of polarization ratio?

I was trying to research about polarizing lasers for an experiment, and there were some things that were confusing? A website said, I was wondering if the polarization ratio was the same as the extinction ratio? Also, I was curious because I thought 100:1 would be a lot, and not much light...
3. ### I Photon induced magnetic effects

Hello all: Reading about HB-11 start up and they mentioned laser induced magnetic field : How is that created and the size of the magnetic field is in kilo Tesla range any one heard of that Best Hagop
4. ### Optical Laser to refract/reflect water vapor and smoke... angles?

Building visibiity sensor.... What is best angle to detect water vapor reflection from laser, and refraction? I plan to have two open cylindrical containers painted flat black and put inside eachother so the overlap is about 0.5-1" (adj to limit ambient light vs airflow). Laser is cheap red...
5. ### I Surface temperature-laser radiation

Hello, I'm looking for the governing equations for the laser radiation on a surface. I understand there are several types and methods. I was wondering if there is an equation to show all the parameters in calculating a surface temperature after laser radiation for a specific time. Some of the...
6. ### Misc. How can I enlarge the light produced by a laser?

I need to enlarge the light produced by a small laser beam that I have for a science project. I can't buy a larger laser because they're too expensive and not in the right color. Any suggestions? Thanks!
7. ### Measuring the Distance between the Fringes of a Diffraction Grating

I have been preparing for a physics practical on diffraction. More specifically, we will use a CD as a transmission grating (by peeling off the reflective layer), and measure the distance between the fringes for a specific distance between the CD and the viewing wall. However, it is unclear...
8. ### B Why is milk smoother and flatter than water?

I have conducted an experiment involving projecting a laser beam onto a surface and observing speckles that move relative to us. Those speckles become less visible (maybe smaller?) when the surface is smooth and that is especially the case with milk. I have dyed milk and water to see whether in...
9. ### I Trying to Generate Entangled Photons

I've been trying to generate entangled photons using KTP laser pointer that normally produces green light at 532 nm. I was hoping that after removing the IR filter, I could add a reflective coating (right now the coating I have is a glittery metallic green nail polish) to reflect the green light...
10. ### I Minimum number of cycles in a short pulse laser

Hello to all, In a short pulse laser emission setup, can a pulse be emmited with beam lenght shorter than one wavelenght? (can a pulse have a duration shorter than its period?) Lets say a laser emmiter shoots a quarter cycle pulse, what would happen to this short beam? (lets supose the...
11. ### Laser cavity

I guess the resonator will be stable when both focal lengths of lens and curved mirror meet. The curved mirror is fixed and it's focal length: $$f_{curved} = \frac{R_{2}}{2} = 50 \, mm.$$ Then the d should be: $$d=f_{lens}+f_{curved} = 100 \, mm.$$ I think that's also the distance for which the...
12. ### B Poisson spot madness

Recently, I started to experiment with a laser and a coin used as a lens, being inspired by an old Cody's Lab video. My initial assumption was that through diffraction, the laser will be focused onto a spot on when the coin is a certain distance away from the wall. In a way, I imagined it as an...
13. ### I Laser Linewidth Calculation

Hi guys, It's one of the questions I'm asking myself needlessly but I really wonder about this ;) Say I have a laser at a wavelength λ. I can calculate the frequency by ν=c/λ. Then the linewidth Δν=cΔλ/λ2 that can be found through differentiation of two sides of the equation. The question is...
14. ### I Laser gain and the saturation effects

Hello, I study laser physics, using "Laser Physics" by Eberly and Milloni. I am confused regarding the notion of gain and the saturation effect. According to the book, the gain is defined as ## g(v) = \dfrac{g_o(v)}{1+I_v/I^{sat}_{v}} ## where ## I^{sat}_{v}## is the saturation intensity and...
15. ### A What is the difference between 1/2 wavelength and 2 overlapped wavelength? (pulsed laser autocorrelation)

So, I was working on autocorrelation for my pulse laser system and I started to wonder what is the difference between single wave with 400nm of wavelength and two 800nm waves overlapped. In the knowledge, I know of, is that wavelength is the length between two picks. And when it is pulse laser...
16. ### A Modes and Q-factor(s) of a random laser

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 unique random lasing mode, or is it just a single mode? Similarly what is the right way to...
17. ### I Controlling light diffraction angle with a holographic "lens"

I'm a physics student, and working on a class project that requires coming up with a method to control the exit angle (diffraction angle) of a monochromatic light source. For example, taking a laser (monochromatic, coherent light source), spreading the beam, and directing the light at a piece...
18. ### I What is the effect of a Laser on gravity

Hi everyone, I have this topic ,and I searched all over the internet without any results what is the affect of Laser Beam on cancelling the Gravity or reducing it if anyone can refer to a reference that can help me I will appreciate it
19. ### I Single-mode vs multi-mode fiber coupling

Hi, Is coupling light from a laser into a single-mode fiber (transverse electric) more difficult than coupling to a multi-mode fiber? If so, is it due to the geometry? Does the laser light have multiple modes to begin with or it can be designed to have just one mode? Thanks
20. ### I What exactly is the thermal lens effect?

Hello, i just wanted to ask if you can explain to me what thermal lens effect is? I am supposed to answer why laser beam passing through ink or soy sauce creates this effect and i can't find any information on what actually this thermal lens is. I know of course that it is a lens, but why does...
21. ### I What is meant by Spectral and Spatial Shaping of a laser

Hi, I am new to the forum so apologies if I placed this in the wrong subforum though I think the subject is classical enough to be here. I was hoping to get a concise answer to what is meant by spectral and spatial shaping of a laser. My intuition says that we are modifying the amplitude of the...
22. ### A Relation of laser pulse length and the Output Coupler trasmissivity

Dear all, I'm within my Ph.D. studies in laser engineering and most of the details are rather new to me. Working on short pulse systems, my advisor told me some times about the relation of the output coupler transmissivity and the outcoupled pulse length, but more as a rule of thumb. According...
23. ### I Reflected Light Beam

Hello, I have a question or perhaps a few questions regarding light and mirrors. When we point light at a mirror, it gets reflected back. But we can see the point light (assuming that it is a laser for the sake of simplicity) at a surface opposite to the reflective surface of the mirror. What...
24. ### B Gravitational Redshift of a laser

If we run two identical lasers and put one at sea level and one on top of a high mountain, will they operate at different frequencies?
25. ### Laser pumping: further increasing injection above threshold?

Above the threshold, the stimulation emission becomes dominant for lasing. If increasing the pumping, what will be the change of spontaneous emission and its contribution to the output power and FWHM of the signal, based on the threshold carrier density clamping and the threshold gain clamping...
26. ### Mirror: refractive index and thickness

Homework Statement Hello everyone ! I hope this is the correct place to ask. Here is my probem: I have to measure the refractive index and the thickness of the glass part of a mirror. The idea that I have, and that has been approved by my teachers, is the following: In order to measure the...
27. ### I Why can't there be a 2-level laser with Non-Optical Pumping

Hi everyone, I would like to understand the answer to the question in the title. I got that when we use optical pumping of a laser, the probability, given an incoming photon of adequate energy, for an atom to absorb it and for an other to produce some stimulated emission out of it are equal...
28. ### A 3D subsurface laser engraving for translucent minerals?

3D Subsurface Laser Engraving works for clear glasses like Schott BK7 and B9 Borosilicate Glass. How does one do the same for relatively translucent minerals? I have read research papers on using lasers for tattoo removal and cancer radiation therapy. However, I want to know how the laser's...
29. ### B Why parts of the laser ray seem brighter than other parts

Hi. When we see a laser ray, it seems that part of the ray are brighter than the other parts and they seem like they’re vibrating and moving. It also seems there are fractures in its path. I want to know why do we see like this? For example see this picture (it is from wikipedia). I circled...
30. ### Number of Photons inside a Laser Cavity

<< Mentor Note -- thread moved from the technical forums, so no Homework Help Template is shown >> Let's say you have a laser cavity with two mirrors at either end, one is considered 100% reflective, the other 99.9%, so that a wave beam is emitted through this lower reflectivity mirror. I know...