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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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how to find wavelength of emission where radiative recombination is occurring in a semiconductor?

how to find wavelength of emission where radiative recombination is occurring in a semiconductor?
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30 views

Why is no radiation emitted during the final transmission in He-Ne laser in Ne atom?

During the working of He-Ne laser, I have understood everything except for the fact that no radiation is emitted when the electrons go through their final transition and reach the ground state again. ...
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1answer
22 views

Single cycles in femtosecond pulses

I am studying for an exam next monday and out of nowhere a very fundamental question popped into my head and I can't stop thinking about it. So the generation of Attosecond-pulses works by Higher ...
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41 views

Can it be that apparent faster than light speed of shadow/laser dot is not actually faster than speed of light? [duplicate]

Many state that in fact laser dot or shadow can move faster than light but I beg to differ. My question, rather statement would be that nothing, not even apparent illusion of shadow or laser dot is ...
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18 views

Why some Lasers has a partial negative slope light current charateristics? [closed]

I think this it's due temperature effects on the operation of the device. Could this explain it? Ring semiconductor plot: SMSR is side-mode suppression ratio.
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1answer
23 views

How to maximize the modulation depth?

Suppose I am modulating a laser beam of a particular wavelength using AOMs. How do I ensure that I have achieved 100 % or the maximum possible modulation depth? My laser is 80 MHz rep rate laser and I ...
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2answers
39 views

High power laser with mode TEM00 [closed]

I wonder to get a help for me to imagine the collimated beam (I believe it's collimated) traveling though ND filter, chopper, beam splitter and then to a sample then reflected onto power sensor. I ...
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2answers
38 views

Working principle of an optical stretcher

I understand that while using an optical stretcher experimental apparatus we attach a small dielectric ball to the specimen of study which can either be a DNA molecule, a Biological cell or any ...
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1answer
30 views

Question about Optical tweezers working principle

Why do particles on the periphery of the laser beam in optical tweezers apparatus drift to the center of the beam? What force pattern causes this pull to the center?
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1answer
26 views

Collapse operators in multi-level atomic systems?

I'm trying to understand the case of multiple ground states and excited states. Due to selection rules, usually we say there should be 3 collapse operators, namely C_+1, C_-1, C_pi, corresponding to ...
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2answers
22 views

Polarization in Nd:YAG lasers

We were taught about He-Ne lasers in our Physics lecture and I took upon myself to self-study other type of Lasers. I was trying to make sense of the construction of Nd:YAG laser when I couldn't ...
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3answers
62 views

What happens to the $E$ and $B$ fields at the edge of a laser beam?

In an ideal plane wave, $E$ and $B$ fields run off to infinity in both directions along straight paths. I've always assumed the center of a laser beam looks like an ideal plane wave, with $E$ and $B$ ...
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Laser light radiation interactions with biological tissues?

I was wondering what are the interaction between light generated by a laser source and biological tissues (e.g. human skin) in terms of geometric optics. I suppose from my studies that a part of the ...
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Why is the image of a laser point both real and virtual when shone on a plane mirror? [duplicate]

I shined a laser pointer on a mirror to see how it reflects, quite interestingly, I saw the image of the laser point on the floor inside the mirror and an image on the floor right beneath me OUTSIDE ...
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93 views

Can photons oscillate?

If you fired a laser at the perfect angle at a mirror (for either mirror setup), and then quickly moved a mirror to replace the laser, will the light oscillate between the mirrors, as shown in the ...
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17 views

Link between a LED or laser efficiencies and carrier mobilities

Does anyone know if there is a simple formula/relationship between an LED or laser power conversion efficiencies (PCE) and the carrier mobility. So given everything the same, if I change the ...
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29 views

What does the time reversal of stimulated emission look like?

The lay-person level explanation that we give for stimulated emission goes something like this: because photons are Bosons, they "like" to be in the same state, therefore when a photon is passing by ...
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28 views

Optical deexcitation with energy higher than the excitation light?

Every line of the characteristic spectrum of an atom has not a perfectly defined energy (frequency), but a finite width (the higher the width, the shorter the lifetime of the excited state) right? ...
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1answer
21 views

How to find rayleigh range and beam waist if I took several measurements of beam radius at some fixed distance from the lens?

Figure 1. Figure 2. Set up is like in the figure 1. Collimated beam of 633 nm is passing through a biconvex (focusing) lens. Figure 2 shows Rayleigh range, it's same scenario as figure 1, light ...
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43 views

Equation of Laser Beam Divergence [closed]

I am doing experiment to calculate size of beam waist using diode laser. I have calculated beam spot size (x where $I=I_{max} /e^2$) at different distance from Laser source. I am thinking to fit the ...
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1answer
32 views

Looking for a cheap, easy to find laser gain media? [closed]

So I want to make my own home made laser, but I'm having trouble deciding on what gain media to use. I'm not an expert on lasers but I know the basics of how they work from reading online. I want to ...
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28 views

Too Low Visibility of Interferometric Autocorrelation data

I've done interferometric autocorrelation experiment by KMLabs femto-second laser. center peak of pulse laser is 777 nm & FWHM is 40 nm. I check it by spectrometer. and using BBO crystal(0.7 mm)...
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1answer
31 views

Best glass to reflect visible light (mainly Green)

i have a laser source which emits green light underwater (kept collimator under water) and planning to reflect the green laser back to free space(project is to establish air water interface). I want ...
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20 views

laser beam and their characteristics

Can a laser beam travel up to 5 kilometers and radiate a sample? Will the particles in nature decrease the intensity to a minimal that the laser will not be able to radiate?
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58 views

Lagrangian of a moving charge distribution under action of a eletromagnetic field

We all know that for a single charged particle, we can derive the Lagrangian starting from Lorentz law of force: $$ \mathbf{F}=q(\mathbf{E}+\mathbf{v}\times\mathbf{B}) $$ and by using the ...
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113 views

Can you burn invisible jelly balls with a laser?

Suppose you have some jelly balls with similar refractive index as that of water, like in this video. You put them in water, making it invisible. So, the optical behavior of the balls should be ...
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47 views

How does the billion RPS nano rotor not break?

News articles tell of a dumbbell shaped silica nanoparticle, suspended in a circular polarized laser, reaching 60 billion RPM. I plugged 160nm (half of the particle length) into a centrifugal ...
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1answer
23 views

Using beamsplitters for co-axial light paths

Good afternoon all, I have been racking my 'optics novice' brain on how to use the same optical path for both the transmit and receive optics for a simple laser range finder. For simplicity in the ...
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1answer
61 views

Laser induced damage in BBO crystal

Does the repetition rate [Hz] of a IR (1035 nm) pulsed laser play a role in the damage threshold of a BBO crystal?
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49 views

Measuring higher laser output behind single mode optical fiber than in front of it

I have a setup which includes a 637 nm toptica iBeamSmart laser which is reflected off two mirrors, passes through a line of dichroics (that should completely transmit it, they are used to couple ...
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1answer
16 views

For a laser that changes color discretely between each ultra fast pulse, what color would the laser appear to the naked eye?

Say you had a laser that pulsed faster than your eye could perceive it, so that it appeared to fire constantly. Imagine that in between each pulse the laser changed to every color of the rainbow for ...
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2answers
266 views

Why is making a laser that shines light over the full spectrum, i.e. a 'white laser', so difficult?

Why is it that, while there are red, green, and blue laser out there, I can't seem to find lasers that shine light over the full spectrum of colors"white lasers"? How hard is to make one? Is it ...
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Laser Powered Fusion Reactor

I've been doing research on Helium-3 fusion (2H + 3He -> 4He + 1p) and was thinking about how to overcome the Coulomb Barrier for this reaction, when an article from a science news website popped up ...
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Photon Flux Density of a 1 dimensional Top Hat by 1 dimensional Gaussian Profile

I am working with a laser right now that takes a 4 mm input beam and creates a 60 um Top Hat by 10 um Gaussian when viewed through a 60 mm lens. The laser beam carries 180 mW of power and the ...
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36 views

Is it possible for smaller laser beams to merge into one large beam - I.E, the Death Star?

In Star Wars, 8 laser beams fired by the death star merge into one large beam. Is this possible? It seems intuitive if you replace the laser beams with something like a bunch of baseballs (momentum in ...
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4answers
68 views

What is the electric field due to a coherent radiation? Is it polarized?

What is the time-structure (i.e., how does the magnitude and direction change with time) of the expectation value of the electric field $\langle\textbf{E}\rangle(t)$ of a radiation field described by ...
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1answer
27 views

Historic method to produce cophasal illumination before lasers?

In a bunch of old papers, written before lasers, the authors often refer to illumination with the same characteristics as a laser: single spatial mode and temporally lockstep. For example in: On the ...
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1answer
21 views

Diffusing a laser?

I haven't been able to find much information about this, maybe I'm searching the wrong thing but, how would you diffuse a laser beam from a thing collimated beam, into a "cone" of light? More ...
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35 views

Collimating light from a Powell lens

The background to the question is this: I have been trying to efficiently convert a Gaussian laser beam (TEM$_{00}$, $M^2\approx1.3$) to a uniform intensity distribution and found that the best way of ...
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1answer
186 views

How can I test if a ruby is real?

I purchased a $10\times12mm$ synthetic ruby online for 2\$. It looks similar to cubic zirconia (CZ). Are there any physical properties of a ruby I can test at home to determine whether it's real or ...
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How to calculate laser parameters for drilling 30um holes?

To drill such small holes around 30 micro-meter in Cu(used in Printed Circuit Boards), what type of laser should be selected? How to calculate the parameters of laser like its wavelength, pulse ...
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1answer
42 views

Need help understanding lasing threshold

I’m currently studying laser systems and doing some experimental work with a Nd:YAG laser that has a laser diode as the pump source. I think I understand the concept of lasing threshold, but there’s ...
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1answer
39 views

Is laserlight coupled into an optical cable visible at the other end of an st connector?

I am trying to focus some lasers into a single mode fiber optic cable which has a lens (ca. 0.7mm as far as I know) at the front on one end and a straight tip fiber optic connector on the other side (...
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2answers
36 views

Pockels Cell reverse propagation

Pockels Cells are called "voltage controlled waveplates", since the voltage changes the birefringence of the material, leading to the same birefringence induced change of total polarisation plane than ...
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28 views

Coherence requirements for laser as an optical oscillator

Lasers are popularly described as coherent light sources, but it seems to me that there are several different concepts or levels of coherence that need to be distinguished. (1) Same electronic or ...
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2answers
56 views

Propagation of a flat-top laser beam in free space

I have spent some time looking at how to design a field mapping system that turns a Gaussian beam profile into a top-hat beam. However, it would also be very useful to have a very sharp super-Gaussian ...
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39 views

How can I estimate the penetration depth of a laser in gallium oxide?

I am searching for a way to estimate the penetration depth of a laser with wavelength $\lambda$ in gallium oxide (Ga$_2$O$_3$) in a Raman setup, in order to know the depth at which I am probing. ...
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1answer
82 views

Polarize light after double slit experiment

Recently, me and a classmate did the double slit experiment in class with a laser, but since we had a polarizer (circular if it matters), we placed it after the double slit, and we observed an ...
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111 views

How do you measure small change in the angle of polarisation of a light beam? What is the smallest measurable angle?

Say you have a beam or pulse of light with known polarisation which then gets perturbed by something which causes that polarisation to rotate slightly, how could you measure this and what would be the ...
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3answers
57 views

Why electron/ion beams are not prefered over lasers as driver for inertial confinement fusion?

Most of hi-end ICF research facilities, and proposals for future powerplant or space-ship propulsion use lasers as driver. Problems with lasers intense lasers needed (e.g. NdYAG 3rd harmonic ...