Physicists discovered lasers while studying the structure of the atom. Since the introduction of the laser, the laser has been used in industry, agriculture, scientific research, national defense in various fields, laser science and technology has become one of the fastest growing areas of science and technology.
In 1913, the Danish physicist Bohr proposed that atoms can exist in a series of different energy levels, and can only jump from one energy level to another. An atom at a lower energy level can become a higher energy level after absorbing energy; when an atom at a higher energy level becomes a lower energy level, it puts out excess energy in the form of radiation (spontaneous radiation).
In 1917, Albert Einstein proposed that an atom jumping from a higher energy level to a lower energy level can be realized in two different ways, through spontaneous radiation or excited radiation. Ordinary light source of light is mainly spontaneous radiation; in the excited state of the atom in some other role, such as light, caused by the atomic jump, the atom is forced to light, the atom of this type of light is called excited radiation.
After the theory of stimulated radiation was put forward, it was not taken seriously, 30 years later, until 1951, the American physicist Towns interest in this. One day after his walk, sitting on a bench silently thinking about this issue, suddenly he produced a new idea: under normal circumstances, most of the molecules of matter are in the low-energy state, can change this situation, the number of molecules in the high-energy state, and then irradiate these molecules with microwaves, so that it is excited to emit energy, which produces an amplification effect. This process of making most of the atoms or molecules in a container turn to high energy is called particle number inversion, which is necessary for quantum amplifiers and lasers. He immediately sketched out some basic design requirements on the back of an envelope, and after three years of many experiments, the microwave excited amplifier (quantum amplifier) was finally successfully developed. The early microwave excited amplifier was a small metal box filled with ammonia molecules in an excited state. When the microwave into the box filled with excited state of ammonia molecules, it sends a beam of pure and strong high-frequency microwave beam.
The Soviet scientists Basov and Prokharov independently carried out similar work and succeeded, and in 1964, Towns, Basov, and Zenokharov were awarded the Nobel Prize in Physics.
With the development of quantum amplifiers, the possibility of extending these principles from the microwave band to the light wave band began to be considered.
The first theoretical scheme for a laser was proposed by Towns and Shollo in 1958. They proposed that a slender column be made from a substance with amplifying properties, and that it have mirrors equal to each other at each end. One of the mirrors for the total reflector, the other side of the partial reflector, light is reflected back and forth along the column, forming an optical frequency **** vibration cavity.
The world's first laser was successfully developed in 1960 by Dr. Mayman of the United States. He used a ruby monobloc as the working substance, with the two end faces smoothed and silver-plated. Ruby's main component is alumina, its lattice has a small part of the aluminum atoms replaced by chromium atoms, when the xenon lamp as an excitation source sends out a strong light irradiation of ruby, ruby chromium atoms in the absorption of green and blue light, from the ground state jump to the excited state, resulting in the number of particles reversed. The first laser, with an output power of 10 000 watts, had very pure crystal rods, produced by artificial means, and emitted a laser intensity of 10 million times that of sunlight.