# Tag Info

12

Given that most green pointers are frequency doubled from a 281.8 THz infrared laser ($c$/1064 nm), it's possible that you have a two frequencies $f_1$ and $f_2$ in the original infrared laser (i.e., it is multimode). After passing through the "frequency doubling" nonlinear crystal you see three frequencies: $2 f_1$, $2f_2$, and $f_1 + f_2$. It looks like ...

6

What the others have already told you is that the pattern forming is a speckle pattern: each bump in the surface acts as a source for a spherical wave, these waves then interfere to produce this pattern. (The black dots and circles in the image below.) In the wikipedia-article there is also mentioned the concept of "objective speckle pattern": when the ...

4

When you first apply current to a laser diode, it does behave as an LED. Light is output across a (relatively) broad spectrum by spontaneous emission. But once the current reaches the threshold current, then positive feedback causes one (or a few) modes to oscillate. Further increases in input power will increase the ouput in those particular modes, but the ...

4

I suspect you are referring to the speckle pattern of a laser which is a diffraction effect associated with the (microscopic) roughness of a surface. Image from the above linked article;

3

The phenomenon you are describing is an intensity pattern know as speckle pattern. Speckle patterns are very prominent in patterns produced by coherent (single frequency) light such as laser beams. The speckle effect is a result of the many photons in a beam having different phases and amplitudes, which add together to give a resultant amplitude ...

3

I will explain the basic idea. The ink that is in the skin is just metallic particles that on average have bigger size than the one the white cells can "fight" and remove from the system. Although the body recognizes the "alien" particles living in the skin and constantly fights them (and this is the reason the tattoo wears out) it is unable to remove big ...

2

Theoretically yes, the laser principle does not consume any material. There is a light source that excites the electrons in the material to higher levels, they deexcite to some intermediate one, here the avalanche of photons appears producing the laser light and leaving the electrons in the ground state. And you can repeat the process without a loss.

1

In my experience (PhD student working on laser plasma interaction experiments) these PIC codes are pretty closely guarded by their creators. There are a few out there, for example OSIRIS, VORPAL, and TurboWave in addition to VLPL. Of these I think only VORPAL is commercially available (through Tech-X) and the others you would need to contact the groups ...

1

In order to generate entanglement you need an interaction, by which I mean that the dynamics have a term that is a function of two different degrees of freedom that you intend to entangle$^1$. The type of nonlinearity in this case is what is known as spontaneous parametric downconversion or SPD, which is a nonlinear optical process. 1) How does this ...

1

theoretically if its components never wore out then yes. however in practice things do wear out eventually and so no it could not be done in the same way that a perpetual motion machine can work in theory but not in practice.

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