Within one microsecond of the laser pulse passing, the air ionizes and the beam cannot continue. Since the formation of plasma takes one microsecond, an interesting application is to form a short-lived ionization path in the air to conduct lightning. Now this is living on the edge. This is something I have never done with a laser pointer, but my colleagues have written about it. Talk about taser using steroids.
The most ambitious application of high-energy lasers. It has been proposed to use lasers to propel spacecraft. This application requires a laser that is one million times more powerful than today. I think this is science fiction. It's like comparing the speed of the ant (the laser today) with the speed of the F16 fighter (the laser needed for spacecraft propulsion). Also consider that such a laser consumes all the electricity generated by the North American power grid.
So far, laser pulses have propelled potential spacecraft (toys) from the ground to an altitude of about one hundred meters. The main force comes from rapidly expanding ionized air, not photon momentum. The efficiency of photon momentum at non-relativistic spacecraft speeds is incredibly low. Supporters of laser propulsion are passionate about this topic.
They believe that all power, orientation, focus, and diffraction problems are only engineering challenges that can be solved. But by contrast, it makes the Apollo project look more like an Eagle Scout project. Due to the tremendous effort, I don't believe that such a project is sustainable. Support for Apollo declined within 8 years after the start. Since the goal is to reach a star system a few light years away, the project’s lifespan will take at least 20 years, and the return will be very small.
I own a 5mW laser (such as a laser pointer) and a 120 W laser (ie 120,000 mW), which are in my green laser pointer cutting machine. The 5mW laser is quite safe-as long as you don't look directly at it, it won't hurt you. The 120W laser can easily cut half-inch solid wood. You can blind yourself without even looking at it-its light reflection can do this.
The 50W laser is still a very important device-it can cut 1/4 inch wood (maybe more if you have patience)... it can ignite paper or cloth from the entire room without any problem. You might think this is unlikely. My 120W laser is only 20% stronger than a 100W incandescent bulb. But think so. The surface area of a 100W light bulb may be 100 square centimeters-if you touch it, it will become hot enough to burn you.
The beam from the laser carries about the same energy-but the beam is only the diameter of a pencil-say 1 square centimeter. So the light it produces (in my case, it’s infrared) is 100 times hotter than a 100W incandescent bulb—enough to ignite anything that burns 20 feet away. However, if you focus the beam (as I did in my Lasersaur), you can reduce it to approximately 1/10 mm. This is 1/10,000 of a square centimeter-if you do this, the generated light is a million times brighter/hotter than the surface of a 100-watt bulb... This is a huge amount of energy!