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4

The ${\rm sech}$ pulse is, in Kerr effect nonlinear optical mediums, an Optical Soliton. This means that it is the particular time variation such that the tendency of the pulse to spread out in time owing to linear dispersion is exactly counterbalanced by the nonlinear effect that tends to confine pulses in time. This balance is a stable one in a Kerr ...


3

I recently saw a video of a demonstration by a Japanese researcher who came up with a method that used a pair of high-powered (presumably) infrared laser beams that, where they intersected, heated the air enough to turn it into plasma, creating a pulse of white light. It works, but it's slow, low-resolution, & requires staggering amounts of power. If you ...


12

It is possible to hit spots in the air with laser pulses from multiple directions in such a way that air molecules in that spot become ionized and emit light, see the technology discussed in this article, along with this demonstration video. And if you just want a 2D screen rather than a 3D display, then of course you can also just use lasers to project it ...


6

Not really; you need to have the laser light pass through particles in a medium. Laser light is made of photons; in order to see the laser, photons must be reflected off of a something to your eyes. You cannot otherwise "see" a photon because photons don't interact via the electromagnetic force - in other words, photons don't emit photons. To see the laser ...


1

It sounds like you have a particular laser, and you don't know what spectrum it's emitting? The best way to answer this question would be to measure your emission with a spectrometer, but if you're asking here, that implies you don't have one. Let's pretend you got your laser from Coherent. You'll notice that different cavity designs can pick out different ...


2

You should stimulate emission from the entire ro-vibrational spectrum. There are a few modes in the P branch that will dominate, just because they have the largest oscillator strength. They're close enough in frequency that your output should be a homogeneously broadened peak centered around 10.6 $\mu$m. If you wanted to put an etalon or diffraction ...


0

Another relatively simple method: get an adjustable iris and measure the total transmitted energy (use a condensing lens behind the iris, perhaps) as a function of radius. Repeat at a few distances for better accuracy :-) Keep in mind this will be inexact for most laser diodes as their output is elliptical unless supplied by the manufacturer with a ...


1

If you have a powermeter and a translation stage available, you can do the following: Get a knife edge and put it onto the translation stage. Move the knife edge into the beam and measure the intensity for different positions. From this you can derive the beam width, however you may define it (1/e, FWHM, ...). Do this for different positions along the beam ...


2

I believe that the math covering condensed matter physics are very similar to that describing black holes and some high energy physics. So what was seen was an experimental result verifying the maths. Whether the maths really applies to a BH is unknown. In a way, it is more like solving equations experimentally using condensed matter as an analog computer. ...


2

I suppose you could say this is cheating, but you could surround the object emitting the sound with a perfect vacuum. Sound waves are vibrations in a medium; because a perfect vacuum has nothing in it, it cannot "conduct" (for lack of a better word) sound waves. You could attempt to levitate the object with magnets; because of Earnshaw's theorem, the setup ...


3

Assuming you're talking about propagation through free space, the beam will be diffracted by the aperture you pass it through (3cm in this case) and that will cause the beam to diverge. The far field angular divergence, $\theta$, is approximately given by the equation for the Airy disk: $$ \sin\theta \approx 1.22 \frac{\lambda}{d} \tag{1} $$ where $d$ is ...


2

Since single photon detectors exist, the answer is yes. Providing you have a few photons per second.


0

Lasers are emitters of synchronized photons. You can cut the intensity of the beam to only emit one photon at a time, experiments have shown lasers that could emit photons as low as 1 a second i believe. Your sensor would have to be able to detect and record the same for you to detect the weak laser. You would need to have every other possible light source ...


2

Perhaps you're looking for a beam expander? It takes a collimated beam and expands or reduces its size. I make no claim as to whether it reduces the intensity to a "safe" level, but it certainly reduces intensity.


2

You need a better lens. Seriously, which is to say that the LED is dumping its output power into a large solid angle, so re-collecting it all is rather difficult. Also, are you certain you're quoting the mean output power of both devices? If that's their peak power, the LED's mean power could be far less if (as with many LEDs) it's pulsed to reduce the ...



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