What is a laser?
We are not new to ‘the laser’ word. The CD that we listen to is called the laserdisc. The VCD that we see is called the laserdisc. Their crafting is tied to lasers. Referring to lasers, people often think of “deadly light weapons” in science fiction novels. The laser can shine through a steel plate, even to solid material like a diamond; it will turn into blue smoke when it shines on it. So what is a laser?
Everyone knows that the atom makes up matter that is made up of the atomic nucleus and the electrons are moving around it. When the outside gives the atom a certain amount of energy, it is possible to send electrons to orbit a bit further. Then we say the atom goes from the low energy state to the high energy state. An atom in a high energy state is not as stable as in a low energy state. It tends to return to a state of low energy. When a spontaneous atom from a high energy state jumps to a low energy state, it will glow. That is spontaneous radiation. Also, if the atom is in a high energy state and using an external photon leads it back to the low energy state, the frequency of this outer photon is equal to the atoms’ natural frequency. The excited state then causes the exciting radiation of the atom. To put it simply: ordinary light is generated by atoms of radiant matter, while excited radiant matter atoms produce lasers.
In conventional light, in a state of spontaneous radiation, many atoms’ luminous action proceeds are independent of each other. They individually emit light of different frequencies. It’s like after the theater, everyone is in front of you and after, everyone is scattered in different directions. On the other hand, lasers are the luminous behavior of most atoms produced by exciting radiation. As a laser is produced, the frequency, phase, and direction are completely unified. It was like after the cinema was over, everyone was lined up in the same direction, taking their steps evenly, following the chants of “one, two, one” but neatly moving forward.