Nội dung bài viết / Table of Contents
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The birth of the Laser comes from quantum theory, invented by scientist A. Einstein in 1916. In 1954, British and American scientists simultaneously invented a Laser generator for practical application. Laser testing in humans began in the 1960s. The Laser represents “Light Amplification by Stimulated Emission of Radiation”.
The Laser is a source of artificial light obtained by amplifying the light by the radiation emitted when the highly activated elements of a corresponding physical environment are strongly activated.
The Laser is a light with many special properties as natural or artificial light and has very useful uses, can be applied in many fields of science and technology and life, creating a whole scientific and technological revolution after his birth.
Principle of creating the Laser
The principle of Laser emission is based on forced emission. When projecting a beam of light onto a physical environment, three fundamental optical phenomena occur: absorption, free emission, and forced emission.
When we launch into the physical environment a monochromatic beam of light containing the energy of each photon, it will interact with optoelectronics and force them to emit secondary photons with the same energy, the same direction. transmission, polarization, phase … with photons caused coercion.
The phenomenon of forced emission is amplified according to the chain reaction: 1 born 2, 2 born 4…Thus, forced radiation increases the number of photons, that is, the ability to amplify light through the environment.
For a machine to emit Laser radiation, it must have three main components: the active environment in which the forced emission must be greater than the absorption; excitation source for activating the active substance of the Laser; the function of the resonator chamber is to increase the amplification of the light by reflecting it several times through the active substance. The first Lasers born in the active environment are reflected in the environment, stimulating the environment to emit other rays. Laser beams passing through the reflector partially exit to form the Laser beam output. The Laser beam can transmit continuously or pulsed.
Basic structure and mechanism of operation of the Laser
High orientation: the laser emits an almost parallel beam, which makes it possible to project thousands of kilometers without dispersing.
The monochromatic properties are very high: the beam has only one color (or wavelength). This is the most special property that no light source have.
Uniformity of photons in the Laser beam.
Ability to generate extremely short pulses: milliseconds (ms), nanoseconds, picoseconds, to focus extremely high laser energy in extremely short time.
Laser solids: about 200 solids can be used as Laser active medium. Some common solid Lasers: YAG-Neodym (yttrium aluminum garnet, abbreviated YAG plus 2-5% neodymium), λ = 1.060 nm (near-infrared spectrum), can transmit continuously up to 100W or transmit pulse with frequency 1.000-10.000Hz; Rubies, alluminium with chromium ions, λ = 694,3 nm (red zone of white light); The semiconductor, the most common is the Gallium Arsen diot, λ = 890nm (near-infrared spectrum).Laser gas: He-Ne, Helium and Neon, λ = 632,8nm, (red light), low power from one to several tens of mW; Argon, argon, λ = 488 and 514,5 nm; CO2, λ = 10.600 nm (far-infrared spectrum), power up to megawatts (MW).
Liquid laser: the active medium is liquid, the most common is the color Laser, as the Laser uses a dye. Use solvents such as methane and ethane in addition to organic plant extracts (coumarin, rhomadine and florescene). The dye structure determines the working wavelength of the Laser.
The advent of Laser has created a great revolution in the development of science and technology in general and in the medical field in particular. Research on the application of the Laser in medicine was conducted quite early (1962). Overall, the development of Laser applications in medicine is an ongoing process that involves considerable progress and progress.
From Lasers to traditional treatments, Lasers have become independent means and have often yielded remarkable results. In fact, all over the world, a new medical science has been created: the Laser medicine industry, whose function is to research, develop and apply laser technology for human health.
Since 1974, the Laser World Medical Association has been organized with 10.000 members from more than 50 participating countries. In medicine, Lasers are studied in the following two directions: the Laser is used as a tool to study biological objects for diagnostic and test purposes; the Laser is used as a treatment tool.
Lasers have many applications in many areas of medicine, such as diagnosis; in traditional medicine; in surgery; in ophthalmology; in cosmetology; in the treatment of cancer, dental maxillofacial disease, otolaryngology, dermatological diseases…
When you shine a Laser light on an organism such as the human body, biological effects occur in the body. These biological effects are at the base of the use of Lasers in medicine for human use. When using a laser for treatment, the determining factor for the treatment effect is the dose, including the parameters: power, convergence (power density), projection duration, number of projections, distance between projections. In addition, the characteristics of the body where the body is projected are also an important factor contributing to the good results of the treatment.
Lasers used in diagnosis and treatment have a wavelength range of 193 nanometers – 10,6 micrometers, in the ultraviolet, visible and near infrared regions, can operate in pulsed or continuous mode. Many Laser devices used in diagnostics are: Dop Laser probes, blood flow measurement in the body; Laser tomograph, detectors to measure and guide the diagnosis.