The reason why the laser is known as magical light is that it has two characteristics that ordinary light does not have.
1. Directivity is good - ordinary light source (the sun, incandescent or fluorescent lamp) to emit light in all directions, but the direction of the laser light can be limited to less than a few milliradians solid angle, which makes the illumination in the irradiation direction of 10 million times.
The laser diffuses every 200 kilometres diameter less than 1 meter, if shoots to the moon which is 3.8 × 105km from the Earth, the beam diffuses less than 2 kilometres, but the ordinary searchlight diffuses several kilometres to dozens of meters.
Laser collimation, guidance and ranging make use of good directivity.
2. High brightness - Lasers are the brightest light source of our time, comparable only to the intense flash of a hydrogen bomb explosion. The brightness of sunlight is about 1.865 × 109 cd / m2, and the output brightness of a high-power laser can be 7 to 14 orders of magnitude higher than that of sunlight.
Although the total energy of the laser is not necessarily large, because of the high concentration of energy, it is easy to produce high pressure and tens of thousands of degrees Celsius or even millions of Celsius in a tiny spot. Practical applications such as laser drilling, cutting, welding and laser marking take advantage of this characteristic.