A laser pointer below 0.4 milliwatts is considered eye-safe, even if you look directly at the high power laser pointer for a long time. These lasers are Class 1. Laser pointers between 0.4 and 0.99 mW are considered to be Class 2. It is believed to be safe to prevent accidental exposure from causing damage to the eyes. However, it dazzles the irradiated person and causes the person to interfere with his activities in flying an airplane or driving a vehicle. Exposing a driver or pilot to this laser will result in arrest and imprisonment.
A laser pointer up to 4.99 milliwatts is considered to be 3R category. It can burn the retina, but under normal conditions of accidental exposure, people will look away or blink before permanent damage occurs. Laser pointers between 5 mW and 499 mW are considered Class 3B. This type of laser pointer is very dangerous. Anyone exposed to Liang is unexpectedly illegal and subject to arrest and imprisonment.
Although it is no longer illegal to own or use this type of laser, if you expose others to the beam, even accidentally, it is a criminal offence. Class 3B laser pointers can ignite paper, melt plastic, burn wood, and even the diffuse reflection of walls or paper can cause eye damage. The law usually requires laser goggles with this power laser and above. The legality of these lasers is a bit of a gray area. You can buy such a laser pointer from China.
A laser pointer of 500 mW or greater is a class 4 green laser. It is extremely dangerous even at a distance. It may cause severe burns to the skin and cause accidental fires. Operation of Level 4 lasers outside of buildings or controlled airspace requires permission from the Laser Information Clearinghouse at Vandenberg Air Force Base. It is very unpleasant to accidentally irradiate a Class 4 laser onto a satellite or airplane. It was caught trying to smuggle bombs on the plane.
Although you can buy this laser pointer from China, they are absolutely illegal in most places, unless you live in a huge desert or in the middle of Antarctica. Used by professionals in laser shows. In this case, the audience can avoid close contact. If used in accordance with safety practices, these lasers are usually safe and permitted by law.
Usually the laser pointer stops at about 10 watt hours. It becomes very difficult to provide them with batteries and they can overheat because more power is dissipated in the device than contained in the beam. Laser manufacturers sometimes claim an efficiency of 30% or higher, but in reality, an efficiency of 10% is typical.
Medium power lasers are approximately between 50 watts and 1 kilowatt. They can cause severe skin burns at a distance, and even destroy a small drone or an optical sensor at a distance. More than 1 kilowatt and up to 50 kilowatts is a modest blue laser pointer weapon or an excellent laser cutting tool. It can damage airplanes, vehicles, shells and ignite buildings within a certain distance, or it can cut an inch of steel right in front of the laser.
More than 50 kW is a serious laser weapon called HEL (High Energy Laser), which can burn missiles, airplanes or anything you can think of at long distances. Owning such lasers is usually limited to government agencies and their contractors.