英语：
Since the laser is the 20th century,following the atomic energy,computers,semiconductors,after another great invention of human beings,known as "the fastest knife," "the most accurate of the foot," "the brightest light" and "exotic laser," .Its brightness of the sun's 10 billion times.Its principle as early as 1916,the famous physicist Albert Einstein has been found,but not until 1958 was only the first successful laser manufacturer.
What is a laser?What are the characteristics of it?
"Light by stimulated emission," is called the Laser
Laser Features:
(A) directional light-emitting
Ordinary light source is emitting in all directions.Let the light emitted in one direction communication,need to source a certain condenser fitted with devices such as car headlights and searchlights were installed condenser mirror effect,so that radiation is pooled together in one direction injection.