What Is a Laser?
Apr 08, · Lasers are used for recording and retrieving information. They are used in communications and in carrying TV and internet signals. We also find them in laser printers, bar code scanners, and DVD players. They also help to make parts for computers and other electronics. Lasers are also used in instruments called spectrometers. Jan 23, · Lasers are used in practically every major industry, from medicine and computers to entertainment and construction. A power rating, usually in watts, determines the strength of the laser. Some can cut through metal, while others read tiny bits of information without damaging the surface.
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for " light amplification by stimulated emission of radiation ". A laser differs from other sources of light in that it emits light which is coherent. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography.
Spatial coherence also allows a laser beam to stay narrow over great distances collimationenabling applications such as laser pointers and lidar. What is a v code can also have high temporal coherencewhich allows what province is pei in to emit light with a very narrow spectrumi.
Alternatively, temporal coherence can be used to produce pulses of light with a broad spectrum but durations as short as a femtosecond " ultrashort pulses ". Lasers are used in optical disk driveslaser printersbarcode scannersDNA sequencing instrumentsfiber-opticsemiconducting chip manufacturing photolithographyand free-space optical communicationlaser surgery and skin treatments, cutting and welding materials, military and law enforcement devices for marking targets and measuring range and speed, and in laser lighting displays for entertainment.
They have been used for car headlamps on luxury cars, by using a blue laser and a phosphor to produce highly directional white light. Lasers are distinguished from other light sources by their coherence. Spatial coherence is typically expressed through the output being a narrow beam, which is diffraction-limited.
Laser beams can be focused to very tiny spots, achieving a very high irradianceor they can have very low divergence in order to concentrate their power at a great distance. Temporal or longitudinal coherence implies a polarized wave at a single frequency, whose phase is correlated over a relatively great distance the coherence length along the beam.
Lasers are characterized according to their wavelength in a vacuum. Most "single wavelength" lasers actually produce radiation in several modes with slightly different wavelengths. Although temporal coherence implies monochromaticity, there are lasers that emit a broad spectrum of light or emit different wavelengths of light simultaneously.
Some lasers are not single spatial mode and have light beams that diverge more than is required by the diffraction limit. All such devices are classified as "lasers" based on their method of producing light, i. Lasers are employed where light of the required spatial or temporal coherence can not be produced using simpler technologies. The word laser started as an acronym for "light amplification by stimulated emission of radiation".
In this usage, the term "light" includes electromagnetic radiation of any frequency, not only visible lighthence the terms infrared laserultraviolet laserX-ray laser and gamma-ray laser. Because the microwave predecessor of the laser, the maserwas developed first, devices of this sort operating at microwave and radio frequencies are referred to as "masers" rather than "microwave lasers" or "radio lasers".
In the early technical literature, especially at Bell Telephone Laboratoriesthe laser was called an optical maser ; this term is now obsolete. A laser that produces light by itself is technically an optical oscillator rather than an optical amplifier as suggested by the acronym.
It has been humorously noted that the acronym LOSER, for "light oscillation by stimulated emission of radiation", would have been more correct. The back-formed verb to lase is frequently used in the field, meaning "to produce laser light,"  especially in reference to the gain medium of a laser; when a laser is operating it is said to be "lasing".
Further use of the words laser and maser in an extended sense, not referring to laser technology or devices, can be seen in usages such as astrophysical maser and atom laser.
A laser consists of a gain mediuma mechanism to energize it, and something to provide optical feedback. Light of a specific wavelength that passes through the gain medium is amplified increases in power. Feedback enables stimulated emission to amplify predominantly the optical frequency at the peak of the gain-frequency curve. As stimulated emission grows, eventually one frequency dominates over all others, meaning that a coherent beam has been formed. The screech one hears is audio oscillation at the peak of the gain-frequency curve for the amplifier.
For the gain medium to amplify light, it needs to be supplied with energy in a process called pumping. The energy is typically what did scooter libby do as an electric current or as light at a different wavelength. Pump light may be provided by a flash lamp how to get a marriage license in massachusetts by another laser.
The most common type of laser uses feedback from an optical cavity —a pair of mirrors on either end of the gain medium. Light bounces back and forth between the mirrors, passing through the gain medium and being amplified on what day is halloween time. Typically one of the two mirrors, the output coupleris partially transparent. Some of the light escapes through this mirror. Depending on the design of the cavity whether the mirrors are flat or curvedthe light coming out of the laser may spread out or form a narrow beam.
In analogy to electronic oscillatorsthis device is sometimes called a laser oscillator. Most practical lasers contain additional elements that affect properties of the emitted light, such as the polarization, wavelength, and shape of the beam. Electrons and how they interact with electromagnetic fields are important in our understanding of chemistry and physics.
In the classical viewthe energy of an electron orbiting an atomic nucleus is larger for orbits further from the nucleus of an atom. However, quantum mechanical effects force electrons to take on discrete positions in orbitals. Thus, electrons are found in specific energy levels of an atom, two of which are shown below:. An electron in an atom can absorb energy from light photons or heat phonons only if there is a transition between energy levels that matches the energy carried by the photon or phonon.
For light, this means that any given transition will only absorb one particular wavelength of light. Photons with the correct wavelength can cause an electron to jump from the lower to the higher energy level. The photon is consumed in this process. Conserving energy, the electron transitions to a lower energy level how to earn extra cash from home is not occupied, with transitions to different levels having different time constants.
This process is called " spontaneous emission ". Spontaneous emission is a quantum-mechanical effect and a direct physical manifestation of the Heisenberg uncertainty principle. The emitted photon has random direction, but its wavelength matches the absorption wavelength of the transition.
This is the mechanism of fluorescence and thermal emission. A photon with the correct wavelength to be absorbed by a transition can also cause an electron to drop from the higher to the lower level, emitting a new photon.
The emitted photon exactly matches the original photon in wavelength, phase, and direction. This process is called stimulated emission.
The gain medium is put into an excited state by an external source of energy. In most lasers this medium consists of a population of atoms which have been excited into such a state by means of an outside light source, or an electrical field which supplies energy for atoms to absorb and be transformed into their excited states. The gain medium of a laser is normally a material of controlled purity, size, concentration, and shape, which amplifies the beam by the process of stimulated emission described above.
This material can be of any state : gas, liquid, solid, or plasma. The gain medium absorbs pump energy, which raises some electrons into higher-energy " excited " quantum states. Particles can interact with light by either absorbing or emitting photons. Emission can be spontaneous or stimulated. In the latter case, the photon is emitted in the same direction as the light that is passing by.
When the number of particles in one excited state exceeds the number of particles in some lower-energy state, population inversion is achieved. In this state, the rate of stimulated emission is larger than the rate of absorption of light in the medium, and therefore the light is amplified. A system with this property is called an optical amplifier.
When an optical amplifier is placed inside a resonant optical cavity, one obtains a laser. In a few situations it is possible to obtain lasing with only a single pass of EM radiation through the gain medium, and this produces a laser beam without any need for a resonant or reflective cavity see for example nitrogen laser. The optical resonator is sometimes referred to as an "optical cavity", but this is a misnomer: lasers use open resonators as opposed to the literal cavity that would be employed at microwave frequencies how do you torture someone a maser.
The resonator typically consists of two mirrors between which a coherent beam of light travels in both directions, reflecting back on itself so that an average photon will pass through the gain medium repeatedly before it is emitted from the output aperture or lost to how to add numbers in your head or absorption. If the gain amplification in the medium is larger than the resonator losses, then the power of the recirculating light can rise exponentially.
But each stimulated emission event returns an atom from its excited state to the ground state, reducing the gain of the medium. With increasing beam power the net gain gain minus loss reduces to unity how to crochet a purse youtube the gain medium is said to be saturated.
In a continuous wave CW laser, the balance of pump power against gain saturation and cavity losses produces an equilibrium value of the laser power inside the cavity; this equilibrium determines the operating point of the laser. If the applied pump power is too small, the gain will never be sufficient to overcome the cavity losses, and laser light will not be produced.
The minimum pump power needed to begin laser action is called the lasing threshold. The gain medium will amplify any photons passing through it, regardless of direction; but only the photons in a spatial mode supported by the resonator will pass more than once through the medium and receive substantial amplification.
In most lasers, lasing begins with spontaneous emission into the lasing mode. This initial light is then amplified by stimulated emission in the gain medium. Stimulated emission produces light that matches the input signal in direction, wavelength, and polarization, whereas the phase of emitted light is 90 degrees in lead of the stimulating light.
The fundamental laser linewidth  of light emitted from the lasing resonator can be orders of magnitude narrower than the linewidth of light emitted from the passive resonator. Some lasers use a separate injection seeder to start the process off with a beam that is already highly coherent. This can produce beams with a narrower spectrum than would otherwise be possible. InRoy J. Glauber showed that coherent states are formed from combinations of photon number states, for which he was awarded the Nobel Prize in physics.
As a result, the arrival rate of photons in a laser beam is described by Poisson statistics. Many lasers produce a beam that can be approximated as a Gaussian beam ; such beams have the minimum divergence possible for a given beam diameter. Some lasers, particularly high-power ones, produce multimode beams, with the transverse modes often approximated using Hermite — Gaussian or Laguerre -Gaussian functions.
Some high power lasers use a flat-topped profile known as a " tophat beam ". Unstable laser resonators not used in most lasers produce fractal-shaped beams. Near the "waist" or focal region of a laser beam, it is highly collimated : the wavefronts are planar, normal to the direction of propagation, with no beam divergence at that point. However, due to diffractionthat can only remain true well within the Rayleigh range. The beam of a single transverse mode gaussian beam laser eventually diverges at an angle which varies inversely with the beam diameter, as required by diffraction theory.
Thus, the "pencil beam" directly generated by a common helium—neon laser would spread out to a size of perhaps kilometers when shone on the Moon from the distance of the earth. However even such a divergent beam can be transformed into a similarly collimated beam by means of a lens system, as is always included, for instance, in a laser pointer whose light originates from a laser diode. That is possible due to the light being of a single spatial mode.
In manufacturing, lasers are used for cutting, engraving, drilling and marking a broad range of materials. There are many applications for laser technology including the following: Laser Range Finding. Information Processing (DVDs and Blu-Ray) Bar Code Readers. Laser Surgery. Aug 29, · The laser is used to perform minor surgeries and promote regeneration in tissue. Programs exist that offer LLLT as an aid to quit smoking, but . Laser pointers are tools used for pointing out objects or locations, and are defined as "surveying, leveling, and alignment laser products" in an FDA regulation.
There are many applications for laser technology including the following:. Learn The Fundamentals of Laser Technology. What is a Laser? A laser is a device that emits a beam of coherent light through an optical amplification process. There are many types of lasers including gas lasers, fiber lasers, solid state lasers, dye lasers, diode lasers and excimer lasers. All of these laser types share a basic set of components.
Laser Components Gain medium capable of sustaining stimulated emission Energy source to pump the gain medium Total reflector to reflect energy Partial reflector Laser beam output The gain medium and resonator determine the wavelength of the laser beam and the power of the laser.
History of Laser Technology. ULS History of Innovation. Laser Material Processing Laser Cutting. Laser Engraving. Laser Marking. List of Laser Processes. How is Laser Technology Used? Lasers are key components of many of the products that we use every day. Consumer products like Blu-Ray and DVD players rely on laser technology to read information from the disks.
Bar code scanners rely on lasers for information processing. In manufacturing, lasers are used for cutting, engraving, drilling and marking a broad range of materials.
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