New answers tagged

2

In stimulated emission in a laser the emitted radiation has the same phase (and hence direction) as the incident radiation. The mirrors select some of those for regeneration back through the amplifier, where the process continues, and intense radiation builds up between the mirrors. Some of the atoms will decay by spontaneous emission, and that radiation ...


0

The photons generated in a laser optical cavity have frequencies imposed by the cavity resonances. Thus, when changing the refractive index in the cavity the cavity resonances change and the generated photons have different frequencies. Once generated the photons do not change frequency but the cavity refractive index change induces the change of the ...


3

The 'go to' partial differential equation here is surely the Heat equation (Fourier), here in one dimension: $$\frac{\partial T}{\partial t}=\kappa \frac{\partial^2T}{\partial x^2}+\frac{\dot{Q}(x,t)}{c_p\rho }$$ It can be easily expanded into three dimensions or expressed in polar, spherical or cylindrical coordinates. It's not clear from your question ...


1

Hints: The Jones matrix for e.g. right circular polarized light is: $$\frac{1}{2} \begin{pmatrix} 1 & i \\ -i & -1 \end{pmatrix}$$ To see this try applying this matrix to your linearly polarized Jones vector. It will give a right circularly polarized Jones vector. The Jones matrix for a quarter wave plate is:$$\begin{pmatrix} 1 & 0 \\ 0 & e^...


1

Optical properties of aluminum, and it's various surface treatments and coatings are readily available.; these are from Edmumd Optics: Bare aluminum will slowly oxidize, reducing the reflectance significantly for some wavelengths, and increasing surface scattering for others. This paper describes a number of anodization process parameters, and provides ...


2

The radius of curvature depends in detail on the beam profile and the aberration present in the beam. Indeed, in an aberrated beam, there is no simple definition of the radius of curvature. One of the problems with the $M$ parameter is that there is no simple relationship between it and the beam details; it is a very blunt characterization. If you want to ...


0

Yes, of course a gamma ray fel is a difficult goal, but work at Stanford several years ago, employing crystalline structure as a 'wiggler' seems to be an approach. I like to think that the crystal acts a little like a multicavity klystron, with each crystal unit acting as a resonator. Then as electrons traverse the crystal, interactions with these cavities ...


1

The dimensions and meaning of the B coefficients are not the same as the A coefficient. The probability of spontaneous emission does not depend on the radiation environment of the atom, whereas absorption and stimulated emission do. Given that, one has a choice of how one encodes that in terms of the B coefficients, which are only a property of the atom ...


1

I guess your question is: how the electrons "know" they should jump down when the photons come in? Well, stimulated emission is a theoretical discovery by Einstein. The strict explanation requires quantum mechanism. A simple explanation is the electron at the upper level is too lazy to think about where should it jump. So it just follow the incoming photon, ...


0

I think the original question is, why the white laser is electrical pump instead of optical pump? Because electrical pump is much easier for practical use. You just inject current then get light, especially you have multiple lasers with different colors integrated together. Why they made white laser? Because the light can propagate much longer and have ...


2

If by "transmission metals" you mean "transition metals", then there are transition metal doped fiber lasers, indeed I believe erbium doped fibers may have been the original gain medium for a fiber laser. As for a Ti:Sapphire fiber laser, I'll stick with the most salient physics reason hindering the building of such a device: there will of course be ...


2

As your question is really broad, I'm only going to cover a couple of fiber optical items, give the resources I used, and give a few more general resources you can use to look into other items. Concrete Fiber Optical Item Descriptions: A multiplexer is used for multiplexing (though it can be used in electronic switching). multiplexing (sometimes ...


3

"Burning" effect happens when you get a sufficiently high power per unit area. So what you need is a source of power, and a way to get all that power on a small area. In good sunlight, you can use a magnifying glass to get this kind of burning effect quite readily (wear sunglasses - you will be looking at a very tiny hot image of the sun if you do this ...


1

You can do the same, and you are right in your thinking. There are high intensity diode arrays available in the market. Several high energy lasers are also made in same fashion. If you look at world's largest laser NIF (National ignition facility) it is made from 192 laser beams. However there are several challenges with such lasers such as if the lasers ...


1

This is almost a duplicate then of Pauli exclusion principle in an electron beam. Almost because it asks about cathode ray beams. The answer there is yes; the Pauli exclusion principle plays a role similar to the neutron star role. For an accelerator beam, where the electrons and positrons are considered free particles, as were the LEP e+ e- beams, the ...


0

Yes, you can make an electron beam. And the Pauli exclusion principle doesn't prohibit it. According to the Pauli exclusion principle, two identical fermions (particles with half-integer spin) cannot occupy the same quantum state simultaneously. Here you may have missed the word simultaneously. An electron can have the same position in space (all quantum ...


2

As you know that the speckles in the laser comes from the low bandwidth of the laser. Hence to reduce the speckles one need to increase the bandwidth of the laser or to reduce the coherence properties of the laser. Similar to the reference given by you same authors also published another findings in nature photonics. The best solution would be to use a ...


0

A free-electron laser (FEL) is a parametric amplifier, which operates by transferring energy to the output signal (photon pulse) from an oscillator (electron bunch running down a long undulator magnet). An electron bunch is accelerated to relativistic energies and sent through a periodic magnetic structure (undulator) where transverse oscillations and ...



Top 50 recent answers are included