(1) direction light
Ordinary light sources emit light in all directions. In the propagation direction, it is necessary to install a certain number of condensing devices, such as car headlights and searchlights, and install mirrors to condense the emitted light onto the light source, so that the radiation emitted by the light can be concentrated in one direction. The laser emitted by the laser is basically in one direction, and the divergence angle of the beam is very small, only about 0.00 1 radian, which is almost parallel. 1962, man irradiated the moon with laser for the first time. The distance between the earth and the moon is about 380,000 kilometers, but the laser spot on the surface of the moon is less than two kilometers. The spotlight effect of this clause is very good. The light of the seemingly parallel searchlight beam is directed at the bright moon, and its spot diameter will cover the whole moon.
(2) Very bright.
Before the invention of laser, the brightness of high-voltage pulsed xenon lamp in artificial light source was equivalent to the brightness of the sun, while the brightness of ruby laser was tens of billions of times that of xenon lamp. Very high, because the brightness of the laser lights up distant objects. The illumination of ruby laser beam on the moon is about 0.02 lux (unit), the color is bright red, and the laser spot is clearly visible. The strongest searchlight illuminates the moon, and the illumination is only about one trillion lux, which is imperceptible to human eyes. The main reason is very high laser directional brightness. Lots of photons? Natural high energy density is concentrated in a very small space.
(3) Very pure color
The color of light is determined by the wavelength (or frequency) of light. Wavelengths correspond to specific colors. The range of sunlight is about 0.76 micron to 0.4 micron, and the corresponding colors are seven colors from red to purple, so the sunlight is far from the monochromatic wavelength distribution. The light emitted from a light source emitting a single color is called a monochromatic light source, which emits light with a single wavelength. Such as neon lamp, helium lamp, krypton lamp, hydrogen lamp, etc. All are monochromatic light sources, which only emit light of a specific color. Although monochromatic light source has a single wavelength, it still has a certain distribution range. For example, the red light emitted by krypton lamp has good monochromaticity, and the wavelength distribution range with the highest monochromaticity is still 0.0000 1 nm. If carefully identified, including dozens of red people. Therefore, the narrower the radiation distribution range of light wavelength, the more monochromatic it should be.
The wavelength distribution range of laser output light is very narrow, so the color is pure. For example, in order to output red He-Ne laser, the wavelength distribution range of light can be reduced to 2× 10-9 nm, which is one ten thousandth of the wavelength range of red light emitted by krypton lamp. Therefore, monochromatic laser is far more than any monochromatic light source.
In addition, laser has other characteristics: coherence. The frequency, phase and vibration direction of laser are highly consistent, which makes the overlapping areas of laser light intensity distribution overlap spatially and presents a stable intensity alternation phenomenon. This phenomenon is called interference of light, and laser is coherent light. The light emitted by a common light source is called incoherent light because its frequency, vibration direction and phase are inconsistent.
The flash time may be short. Due to technical reasons, the flash of ordinary light source cannot be very short, and the camera, flash and flash are all about one thousandth of a second. The pulse laser with short flash time can reach 6 femtoseconds (1 femtosecond = 10- 15 seconds). The production, scientific research and military use of light sources have a brief flash.
Stimulate emissions]
What is "stimulated radiation"? Albert Einstein, a great scientist, put forward a new theory in 19 16. This theory is that there are different numbers of particles (electrons) distributed in different energy levels in the material composition of atoms. They excite particles with high energy levels according to certain photons, and particles with a little (from high conversion energy level) to low energy level. When they appear, they will radiate light with the same properties as the light that excites them. Under certain conditions, weak light will excite strong light. This is the so-called "stimulated emission amplified radiation (laser) laser with four main characteristics: high brightness, high directivity, high color rendering and high coherence.
Laser has been widely used in laser welding, laser cutting, laser drilling (including oblique holes, different holes, gypsum drilling, steel punching, punching and packaging printing), laser quenching, laser heat treatment, laser marking, glass carving, laser fine-tuning, laser lithography, laser film processing, laser packaging, laser repairing circuits, laser wiring technology, laser cleaning and so on.
After more than 30 years of development, lasers are almost everywhere now. It has been applied to all aspects of life research: laser acupuncture, laser cutting, laser cutting, laser welding, laser quenching, CD, laser rangefinder, laser gyroscope, laser vertical instrument, laser scalpel, laser bomb, laser radar, laser gun, laser gun ... In the near future, laser will definitely be more widely used.
Laser weapons can't directly harm targets or direct energy weapons that emit laser beams. According to the attack mode, the weapon system mainly depends on lasers and tracking, aiming and launching devices, usually laser chemical lasers and solid-state lasers. The laser weapons used can be divided into tactical laser weapons and strategic laser weapons. The laser weapon of CO2 laser has the advantages of fast attack speed, flexible and accurate turning, electromagnetic interference and so on. However, it also has the weakness of being susceptible to weather and environment. With the development history of laser weapons for more than 30 years and the breakthrough of key technologies, the United States, Russia, France, Israel and other countries have successfully carried out various laser targeting experiments. Low-energy laser weapons have been put into use, mainly used to interfere with and blind photoelectric sensors, as well as attack human eyes and some enhanced observation equipment. According to the current level, high-energy laser weapon chemical laser is expected to be deployed on ground and air platforms in the next 5- 10 years.
Application of laser in medicine
Lase system for dentistry
According to the different functions of laser in dental application, it can be divided into several different laser systems. The difference between lasers: the wavelength of light, an important feature of lasers with different wavelengths is their function in different tissues. Light has low absorbance and low penetration in visible light and near infrared spectrum, and can penetrate deeper into tooth tissues, such as argon ion laser, diode laser or Nd: YAG laser (Figure 1). Er: YAG laser and CO2 laser have poor light penetration, and only 0.0 1mm penetrates the tooth structure. The important characteristics of the two kinds of differential lasers are: the intensity of laser (that is, power supply), such as diode laser in diagnostic application, its intensity is only a few milliwatts, and sometimes it is displayed by laser.
Laser is used for treatment, usually a few watts of moderate intensity laser. The effect of laser on tissue depends on the laser pulse of the transmission device. Typical continuous pulse laser transmission devices: argon ion laser, diode laser, CO2 and Er: YAG laser are emitted by short pulse laser or several short pulse Nd: YAG lasers, and the intensity (i.e. power) can be as high as1000W or higher. The absorbed laser is only suitable for cutting hard tissues.
Application of laser dental caries diagnosis
1。 Demineralization, superficial dental caries
& gt2。 Recessive dental caries
Application of laser therapy
1。 incision
2。 Processing of filling polymer cavity