Classes and dangers of laser pointers

A laser pointer of less than 0.4 mW is considered eye-safe, even if you stare into it for an extended period. These lasers are class 1.

A laser pointer between 0.4 and 1 mW is considered class 2. It is considered safe from accidental exposure to eye damage. However, it can dazzle the person irradiated and cause that person to disrupt his activity of piloting a plane or driving a vehicle. Exposing drivers or pilots to this laser is subject to arrest and incarceration.

A laser pointer up to 4.99 mW is considered class 3A. It can burn the retina, but under normal conditions of accidental exposure, the person will look away or blink before permanent damage occurs.

A laser pointer between 5 mW and 500 mW is considered class 3B. This laser pointer is hazardous, and exposing anyone to the beam, even accidentally, is illegal and subject to arrest and incarceration. Although possessing or using such a laser is no longer prohibited, exposing another person to the beam, even accidentally, is a criminal offense. Class 3B laser pointers can set paper on fire, melt plastic, scorch wood, and even the diffuse reflection from a wall or piece of paper can cause eye damage. Laser goggles for this power laser and above are usually required by law. The legality of these lasers is a grey area. You can buy such laser pointers from China.

Shining a class 4 laser on a satellite or an airplane is severely frowned upon. It is treated about the same as being caught trying to smuggle a bomb on a plane. Although you can purchase such a laser pointer from China, they are illegal in most places unless you live in the middle of an enormous desert or Antarctica. Professionals in laser light shows, where the audience is protected from exposure at close range, use these lasers safely and are permitted by law when used according to safe practices.

Generally, laser pointers stop at about 20W. It becomes challenging to provide batteries for them, and they overheat because more power is dissipated in the device than is contained in the beam. Laser manufacturers sometimes claim 30% or more efficiencies, but 10% efficiency is typical.

Mid-power lasers are between 50 watts and about 1 kilowatt. They can cause severe skin burns at a distance, destroy a small drone, or destroy optical sensors at a distance.

Above 1 kilowatt and up to 50 kW is a modest laser weapon or an excellent laser cutting tool. It can damage planes, vehicles, and artillery shells, set buildings on fire from modest distances, or cut through an inch of steel right before the laser.

Above 50 kW is a serious laser weapon called a HEL (high energy laser) that could burn missiles, planes, or anything you can think of from great distances away. Possession of such lasers is generally limited to government agencies and their contractors.