Laser (a laser) means light amplification by stimulated emission, is a high quality light source.
The characteristics of the laser: 1. Directional monochromatic. Energy concentration. Coherence
Laser biological tissue effects:
Photothermal effect. Photochemical effect. Electromagnetic effects 4. Pressure effect
Laser biological tissue: a high-power laser coagulation, burning in addition to two low-power laser irradiation of vaporization
Three. "Knife" finely divided
Laser is a nature originally does not exist, due to the shock issue has good directionality and high brightness, good color and good coherence properties of light. Physicists to generate the laser mechanism traceable to the 1917 hypothesis of Einstein to explain the blackbody radiation law, the light absorption and emission via stimulated absorption, stimulated emission and spontaneous emission are three basic processes. As we all know, any kind of light emission is related to its state of motion of material particles within. When the particles (atoms, molecules or ions) in the low-en ergy level of absorption of external energy (light) of the appropriate frequency to be excited (stimulated absorption) transition to the corresponding energy level is always trying to transition to a lower level go, the excess energy released form of a photon. Without external photon effect alone released spontaneously (spontaneous emission), then release the light is the ordinary light (such as lights, neon signs, etc.), which is characterized by the size of the frequency of light, the direction and pace of very inconsistent. But if it is under the direct role of foreign photon transition to low energy levels by the high energy level, the excess energy released form of a photon (stimulated emission), the photon is released outside the incident photon frequency, phase, direction of propagation exactly the same, which means that the external light has been strengthened, which we call optical amplification. Obviously, if adopted by the shock absorption, so that the number of p articles in a high energy level more than at the low levels of (inversion), the magnification of this optical phenomenon is more obvious, then there is likely to form the laser.
The laser is labeled the magic of light, because it is the ordinary light do not have any of the four features.
Good direction - ordinary light source (sun, incandescent or fluorescent) light-emitting in all directions, the direction of the laser light can be restricted within the solid angle of less than a few milliradians, which makes the illumination in the irradiation direction to improve ten million times. Laser collimation, orientation and distance measurement is to use a good direction this feature.
(2) high brightness - the laser is of the brightest light only flash can be comparable to the hydrogen bomb explosion instantly strong. The brightness of the sunlight is about 103 W / (cm 2 steradian), a high-power laser output brightness of the sunlight of 7 to 14 orders of magnitude higher. Thus, although the total energy of the laser are not necessarily great, but since the energy is highly concentrated, it is easy to generate high pressure and tens of thousands of degrees Celsius or even millions of degrees Celsius in a tiny point. Laser drilling, cutting, welding and laser surgery is to use this feature.
3 monochromatic - the light is an electromagnetic wave. The color of light depends on its wavelength. Ordinary light source light emitted typically contain a variety of wavelengths, the mixing of the various colors of light. Sunlight contains red, Tang, yellow, green, green, blue, purple seven colors of visible light and infrared light, UV and visible light. The wavelength of a laser, only concentrated in a very narrow spectral band or frequency range. Such as helium-neon laser wavelength of 632.8 nm, the wavelength range of less than one ten thousandth of nano. Monochromaticity of the laser, for precision instruments to measure and motivate some chemical reactions and other scientific experiments provide a very favorable means.
Coherence - interference is a property of the wave phenomena. Laser-based, highly directional and monochromatic features, it is bound to the excellent coherence. This feature of laser holography to become a reality. - The so-called laser technology, is to explore these features to develop a variety of laser and explore the application of laser technology general benefit of mankind. Since 1960 successfully developed the world s first ruby ??laser, China has also successfully developed in 1961 made the first ruby ??laser, laser technology is considered the 20th century, following the quantum physics, radio technology, nuclear technology, semiconductor technology, electronic another new major scientific and technological achievements in computer technology. 30 years, laser technology, the rapid development of not only the development of the various characteristics of a variety of lasers, laser applications, expanding the field, and formed a compact disc juk ebox, laser medical treatment, laser processing, laser holography, laser photo-typesetting printing , laser printing, and laser weapons and other emerging industries. The rapid development of laser technology, making it one of today s new technological revolution, "leading technology".
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