Since the invention of the laser in the early 1960s, the rapid wave has been applied in various fields such as industry, military, communications, medicine, scientific research, etc。, which has greatly impacted traditional industries and classic technologies, and has produced a large number of high-tech industries and new disciplines that have affected humanity。 Every aspect of life。
Although it is theoretically predicted that there can be such a perfect light that is coated with radiation, how to achieve it has plagued physicists for more than 40 years, and some people even thought that this was impossible. Why is this so?
When light enters a substance, electrons at low energy levels in the atom absorb photons, called stimulated absorption. Under normal conditions, the number of electrons at a higher energy level is much smaller than the number of electrons at a lower energy level, and the atom is relatively stable in such a state. Therefore, the absorption of the coating is always stronger than the radiation applied. From the natural state, the light is absorbed by the wave. In order to generate strong stimulated radiation, it is necessary to find a way to make more electrons in the high energy level than in the low energy level. D0g achieves security: the home is scattered one or two I leaves one end to know that the use of the power or the side of the deduction to the most gram into each level can let a person do the political status, you can use microwave to tell them when they send Out of the rational "Dun Microwave", he immediately recorded this phase on the back of a used letter. Returning to the laboratory, he placed the complex molecules in the resonance solution, and stimulated the radiation generated by the oscillation and feedback amplification. After two years, he successfully realized the “excitation radiation micro-skin amplification” (called microwave injection). ). A few years later, the optical source of the coated radiation source was also developed.
Similarly, in the optical band, physicists use other substances to achieve population inversion, such as ammonia, carbon dioxide, ruby, and so on。 Among these substances, there are usually three or four energy levels, including one ground state, multiple excited states, one of which is stable, and electrons and other particles can stay on this energy for a long time, called metastable state。 Other excited states with higher energy levels are unstable, and the particles can only stay for a short time。 Under the excitation of the external power source or the light source, the particles in the ground state are pumped to a higher energy level。 After a short pause, the particles are transferred to the metastable state, and a large number of particles are gradually accumulated at this level。 There are still many particles。 If there is a photon entering now, when the frequency of the photon is a specific value, it can cause a large number of metastable particles to simultaneously transition to the ground state, generating a large number of photons with the same frequency, phase, and polarization state。 Fu shot。 It is not enough to create a laser to achieve particle inversion。 Since the initial optical signal of the spontaneous emission of atoms in the working substance of the laser is disorganized, the amplified applied radiation excited by these optical signals is also random。 In order to obtain radiation with a single direction and good monochromaticity, it is necessary to place mutually parallel reflecting surfaces on both ends of the working substance to form an optical resonant volume。 The light is reflected back and forth between the two mirrors, and the direction and the surface of the tube are not my camp。 After the home is moved, the mouth is left, and the mouth is left at the same point as the thousand-tube surface of the south, so I have good beam direction for the early two。 。 During the process of reflection of light back and forth in the harmonic data, the working medium increases the light, thereby forming a high intensity of joy。
Laser Marking Machine American scientist Mehmann used a modified interferometric cavity, using ruby as a working substance, and using high-strength flash tubes to excite rubies。 In May 1960, a laser with a wavelength of 694。3 nm was obtained。 At this time, Einstein was at a distance。 Laser theory has been proposed for more than 40 years。
(This article was originally written by Chenxi Laser. Reprinted must indicate the source: www.levihersh.com, cherish the labor results of others, is to respect yourself)