An LED light that puts out a few watts of light can maybe illuminate a room.
So a laser that puts out a continuous beam with just 1 Watt of power (1 Joule of energy per second) does not sound that impressive… but that light is coherent and collimated, allowing it to be precisely aimed, and focused onto a very small area. This is why a 10mW (10 milli-Watt) laser pointer is ‘dangerous’, it can be focused by your eye to such a small point that even that little power, concentrated that much, can do damage to your retina.
10 mW concentrated on a 200 micron diameter spot is a power density of 32Watts/cm2 (sunlight is ~0.1 W/cm2), if that happens on your retina, it could create permanent damage. (which is why most cheap laser pointers are less than 1mW and not extremely collimated)
So what can you do with a 1Watt laser other than possibly blind yourself?
You can make it a 1 Watt pulsed laser- you could divide that 1 Joule of energy per second among 1000 pulses every second, each with 1 milli-Joule of energy-500microseconds on, 500 microseconds off- 1 pulse per millisecond. The AVERAGE power would still be 1 Watt, but the PEAK power within each pulse now 2Watts (power is just energy/time – .001J/.0005seconds= 2 Watts).
If you have the technology you can keep making the pulses shorter and keep pushing the peak power higher, even though the average power stays the same.
Using a Nobel Prize winning (2018) technique called Chirped Pulse Amplification, you can make pulses extremely short- easily reaching pulse durations of 0.0000000000001 seconds (or, alternately 10^-13 seconds, 1/10,000 of a nanosecond, or 100 femtoseconds) in a table-top system. Pulses so short that you are firing pancakes of light just a few 10s of microns thick.
A 1 milli-Joule pulse with a duration of 10^-13 seconds has a peak power of 10 billion watts. If you then focus that pulse onto a tiny spot, you can reach intensities that simply do not otherwise exist in our universe. 10^16 Watts/cm2… 100 million billion times the intensity of sunlight on your face… this can be created in the lab- albeit for a very short time, in a very small area.
Light is a wave of oscillating electric and magnetic fields- when intensities are as absurdly high as 10^16 W/cm2 the oscillating electric field of the light actually dwarfs the electric field binding electrons to atoms. There is no material made of normal matter that can survive exposure to this intensity.
Atoms exposed to such a field will have electrons suddenly torn away at relativistic speeds – in an instant you are left with a bunch of positively charged ions sitting next to eachother- the positively charged ions repel each other and accelerate away from each other -also reaching relativistic speeds… This is called a Coulomb explosion.
This process has been used to create tabletop fusion- focusing short light pulses into Deuterium clusters, leading them to undergo Coulomb explosions and the ionized Deuterium fragments collide at extremely high speeds and undergo fusion- it will never lead to fusion power, but allows a compact way to study fusion in the lab.
But putting aside cutting edge research, there are many practical applications for these short laser pulses….
To Be Continued…