Why does the laser have high monochromaticity?
In the visible spectrum, the color of light waves is related to "frequency." The narrower the wavelength range of the light emitted by the source, the simpler its color, that is, the more monochromatic the light source. Monochromaticity is usually measured by δλ/λ(or δν/ν), where λ and v are the central wavelength and frequency of the radiated wave, respectively, and δλ and δν are the widths of the spectral line. Since its invention, laser has been widely used in industrial processing, medical cosmetology, scientific research and other fields with its own excellent characteristics. Laser has four main characteristics, namely, high brightness, good directivity, good monochromaticity and high coherence. These characteristics are interrelated, so the laser can be applied to different scenarios.
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The general rule is that the power emitted by the light source in a certain direction with unit solid Angle and unit area is called the brightness of the light source in this direction. The increase in laser brightness is mainly due to the high concentration of light in the direction of emission. The Laser pointer has a very small Angle of emission (usually expressed in e radians) and is almost a highly collimated beam, allowing directional and concentrated emission. Therefore, the laser has a very high brightness. The brightness of the solid-state laser can be as high as 1011W/cn2Sr. Moreover, the laser beam after focusing, because of its high brightness characteristics, can produce strong thermal effect. The temperature in the focus range can reach thousands or even tens of thousands of degrees, and can be melted or even vaporized to absorb the laser. The ability of living tissue or non-living material. For example, industrial precision equipment welding welding, lamp hole, cutting and other new technology; Medical tissue cutting (light knife), surface tumor gasification, microspectroscopic analysis are all using the high temperature effect of laser high brightness. The laser power density is measured in mw/cm2 or W/cm2 and the energy density is joule /cm2. In common light sources, the spectral lines with wavelength λ=605 have the best monochromaticity. The krypton isotope 86 (KR86) lamp emits at 7nm wavelength. At low temperature, the half-width of the spectral line is δλ=0.47×10-6 m, and the monochromaticity is δλ/λ= 10-6. Emission wavelength λ=632 of a single-mode frequency stabilized He-Ne laser. The monochromaticity of the output laser reaches δλ -10-10 ~ 10-13 when the half-width of the laser is less than 10-12μm. Class. Lasers are arguably the simplest light source in the world. Generally speaking, the monochromaticity of single mode frequency stabilized gas laser is the best. The monochromaticity of solid state laser marking machine is poor, mainly because the gain curve of working material is very wide, it is difficult to ensure the operation of single longitudinal mode; Semiconductor lasers have the worst monochromaticity.
2021-09-27 12:20:37
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