The basic physical principle of the material's stimulated radiation to emit strong light was proposed by Einstein as early as 1917. However, it was not until 1960 that the first real laser generator was made in the United States, and human beings saw the true meaning of lasers for the first time. Atoms are stimulated to emit light, so they are called 'lasers'. The principle is that after the electrons in the atom absorb energy, they will transition from the low energy level to the high energy level, and then fall back from the high energy level to the low energy level. The excited photon beams have highly consistent photon optical properties. Therefore, the laser has better monochromaticity, directivity and higher brightness than ordinary light sources. In 1958, Americans Schawlow and Tony Townes discovered a special phenomenon: when they shine the light emitted by a neon bulb on a rare earth crystal, the molecules of the crystal will emit bright, always converging together. glare. According to this phenomenon, they proposed a set of principles that when a substance is excited by the same energy as its molecular natural oscillation frequency,
Will produce strong light that does not diverge. But this strong light at this time can not be regarded as a strict laser. However, because the two jointly published a paper of great value, they won the 1964 Nobel Prize in Physics. This is only one step away from the real laser. In May 1960, Mayman of the Hughes Laboratory in California announced that he had obtained a laser with a wavelength of 0.6943 microns. This was the first real laser ever. Mayman became the first inventor to realize the laser. By July 1960, Mayman disclosed the world's first practical laser. The solution is to use a high-intensity flash tube to excite the ruby. The material basis of ruby ??is actually corundum containing chromium atoms. When ruby ??is excited by strong light, it emits red light. A hole is drilled on the surface of a ruby ??plate coated with a reflective layer, and the light overflows from this hole, which is a very concentrated thin beam of red light. This most primitive laser showed its amazing potential as a weapon from the beginning.
When the light beam is focused on a point, it can make the material irradiate the surface quickly exceed 30,000 degrees Celsius, which is several times higher than the temperature of the solar photosphere. There is hardly anything on earth that can withstand such intense heat. If multiple laser beams are superimposed or focused, the material at the focus will instantly disappear. In the year when Americans announced the invention of the ruby ??laser. The Soviets Basov invented the semiconductor laser again. It is characterized by small size, high coupling efficiency, fast response speed, wavelength and size matching with fiber size, direct modulation, and good coherence. Therefore, most of the later low-power laser practical devices and laser communication mostly used semiconductor lasers. Later, people conducted a more in-depth exploration and summary of the laser excitation method, and found that there are several excitation methods. 1. Optical pump laser. Including most solid-state lasers and liquid lasers, and a few gas lasers and semiconductor lasers. That is to say, a real light is used to excite a real laser. 2. Electrically excited laser. Most gas lasers are excited by the gas discharge method, and the common common semiconductor lasers are usually excited by the junction current injection method, and can also be excited by the high energy electron beam injection method.