# Many waves at one point

1. Jul 2, 2014

### enquirealways

If an extremely large no. ( may be infinite) waves are concentrated at one point, what effects can happen?

2. Jul 2, 2014

### Staff: Mentor

Waves of what?

Classically, multiple waves simply superpose ("add up") without affecting each other, if their differential wave equation is linear.

With very high energy densities, the linear assumption may no longer be true. With light waves, there's a whole field of "nonlinear optics" in which quantum effects come into play at high energy densities.

3. Jul 2, 2014

### enquirealways

I mean if infinitely large no. of EM waves concentrate at one point, can it lead to formation of some kind of particles?

4. Jul 2, 2014

### A.T.

You can decompose any waveform into an infinite number of components. As for formation of particles:
http://en.wikipedia.org/wiki/Matter_creation

5. Jul 2, 2014

### enquirealways

I visited the webpage. Nothing much was there regarding concentration of waves/energy.

So, extremely large assemblage of energy leads to what, particles or a black hole.

6. Jul 2, 2014

### UltrafastPED

Laser physicists do this all the time: concentrate light into small regions of space and time.

The spatial part is done through deformable mirrors; this is done in order to correct phase errors. Modern telescopes also use this principle. See http://spie.org/x87035.xml

The temporal part is done via laser pulse compression; this is the realm of the "ultrafast" lasers, lasers with pulse duration less than one picosecond (10^-12 seconds). This type of laser does not yield a narrow wavelength; it requires greater and greater bandwidth (=range of wavelengths/frequencies) in order to generate shorter pulses. Few femtosecond (10^-15 seconds) are regularly generated today.

The trick is to get a short pulse duration along with more energy in the pulse; power = energy/time, so the power density can be increased by increasing the pulse energy, or decreasing the pulse duration. Both can be done together with a chirped pulsed amplification (CPA) laser.

The irradiance is a measure of power delivered per unit of area; with a well focused laser the "spot size" is limited by the wavelengths of the light; the best that can be done is a spot about one wavelength in diameter. So for a typical CPA laser running in the near infrared (NIR) at 800 nm, the minimum spot size is about one micron in diameter.

As the power delivered increases, so the number of effects which can be measured. At 10^13 watts/cm^2 very fine holes can be "drilled" through thin sheets of metal - without any debris or signs of melting being left behind. This effect is exploited in modern laser eye surgery, and in micro-machining.

At 10^19 watts/cm^2 when delivered upon a metal or ceramic target, electron-positron pairs can be created.

At 10^22 watts/cm^2 electron, neutron, and proton beams can be generated, along with x-rays.

All of these experiments have been conducted in multiple laser labs. It is generally known as non-linear optics, or high field optical science. There are many threads of research using the same tools.

I did my dissertation at CUOS, creating far from equilibrium states in materials, and measuring the material response at sub-picosecond time steps.

7. Jul 3, 2014

### enquirealways

So, at the present moment, creation of a blackhole doesn't seem a possibility via this method.

8. Jul 3, 2014

### UltrafastPED

I doubt that a black hole could be created this way, but you could try the calculations! You can look up the energy density required for black hole formation, then calculate the laser power required if it could be compressed into a package one wavelength^3.

More powerful lasers are being designed; at the next level the lasers should be able to "break the vacuum", which means that particle-antiparticle pairs can be created directly from the vacuum, and not require a material medium.

See https://en.wikipedia.org/wiki/Extreme_Light_Infrastructure
and http://www.telegraph.co.uk/science/science-news/8857154/Worlds-most-powerful-laser-to-tear-apart-the-vacuum-of-space.html [Broken]

Here is the ELI site: http://www.eli-laser.eu/

Last edited by a moderator: May 6, 2017