ONLINE ELECTRICAL ENGINEERING STUDY SITE

Laser | Types and Components of Laser

LASER

The acronym LASER stands for Light amplification by stimulated emission of radiation.
It is a device which produces lights. These lights have no existence in nature. The lights can be produced through a process of optical amplification based on the stimulated emission of electromagnetic radiation. It is different from conventional light in three ways. First, the lights from LASER contains only one color or wavelength that is why it is called ‘monochromatic’. Secondly, all the wavelengths are in phase- because of this, it is known as coherent. And thirdly, laser light beams are very narrow and can be concentrated on one tiny spot- this property makes it be known as ‘collimated’. These are also the characteristics of LASER.

For its operation, population inversion is much needed. When a group of atoms or molecules exist with more no electrons in an excited state than in lower energy states, population inversion takes place. Now, when an electron is in an excited state, it may decay to an empty lower energy state. If an electron decays without external influence, emitting a photon, that is known as spontaneous emission.
But if the electron is stimulated by a light wave (photon) and to emit the second wave and return to the lower level, then it is known as stimulated emission. Practically in stimulated emission, a photon hits an electron and two photons are produced. Now, if a significant population inversion exists, then stimulated emission can produce significant amplification of light. Photons which are produced in stimulated emission produce coherent light as they have definite phase relationship.
The principle of laser was first discovered by Einstein in 1917 but it was not until 1958 that laser was successfully developed.
It has many important applications. They are used in common consumer devices such as CD and DVD players, printers and scanners. They are used in medicine for surgical purposes and various skin treatments, and in industry for cutting and welding materials. They are used in military and law enforcement devices for marking targets and measuring range. Lasers also have many important applications in scientific research.

Components of LASER

Every LASER consists of three basic components. These are -
  1. Lasing material or active medium.
  2. External energy source.
  3. Optical resonator.
components of laser
  • The active medium is excited by the external energy source(pump source) to produce the population inversion. In the gain medium that spontaneous and stimulated emission of photons takes place, leading to the phenomenon of optical gain, or amplification. Semiconductors, organic dyes, gases (He, Ne, CO2, etc), solid materials (YAG, sapphire (ruby) etc.) are usually used as lasing materials and often LASERs are named for the ingredients used as a medium.
  • The excitation source, pump source provides energy which is needed for the population inversion and stimulated emission to the system. Pumping can be done in two ways - electrical discharge method and optical method. Examples of pump sources are electrical discharges, flash lamps, arc lamps, light from another laser, chemical reactions etc.
  • Resonator guide basically provides the guidance about the simulated emission process. It is induced by high-speed photons. Finally, a laser beam will be generated.

In most of the systems, it consists of two mirrors. One mirror is fully reflective and other is partially reflective. Both the mirrors are set up on optic axis, parallel to each other. The active medium is used in the optical cavity between the both mirrors. This arrangement only filters those photons which came along the axis and others are reflected by the mirrors back into the medium, where it may be amplified by stimulated emission.

Types of LASER

There are many types of LASERs available for different purposes. Depending upon the sources they can be described as below.

  1. Solid State LASER
    In this kind of LASERs solid state, materials are used as active medium. The solid state materials can be ruby, neodymium-YAG (yttrium aluminum garnet) etc.

  2. Gas LASER
    These LASERs contain a mixture of helium and Neon. This mixture is packed up into a glass tube. It acts as active medium. We can use Argon or Krypton or Xenon as the medium. CO2 and Nitrogen LASER can also be made.
  3. Dye or Liquid LASER
    In this kind of LASERs organic dyes like Rhodamine 6G in liquid solution or suspension used as active medium inside the glass tube.
  4. Excimer LASER
    Excimer LASERs (the name came from excited and dimers) use reactive gases like Chlorine and fluorine mixed with inert gases like Argon or Krypton or Xenon. These LASERs produce light in the ultraviolet range.
  5. Chemical LASER
    A chemical laser is a LASER that obtains its energy from a chemical reaction. Examples of chemical lasers are the chemical oxygen iodine laser (COIL), all gas-phase iodine laser (AGIL), and the hydrogen fluoride laser, deuterium fluoride laser etc
  6. Semiconductor LASER
    In these lasers, junction diodes are used. The semiconductor is doped by both the acceptors and donors. These are known as injection laser diodes. Whenever the current is passed, light can be seen at the output.




Closely Related Articles Op-amp | Working Principle of Op-ampAmplifier Gain | Decibel or dB GainIntegrated Circuits | Types of ICRegulated Power SupplyWork FunctionMobility of Charge CarrierWhat are Photo Electrons? Electron volt or eVEnergy Quanta | Development of Quantum Physics Schottky EffectHeisenberg Uncertainty PrincipleSchrodinger Wave Equation and Wave FunctionCyclotron Basic Construction and Working PrincipleSinusoidal Wave SignalCommon Emitter AmplifierRC Coupled AmplifierDifferential AmplifierWave Particle Duality PrincipleSpace ChargeInverting AmplifierMore Related Articles Vacuum Diode History Working Principle and Types of Vacuum DiodePN Junction Diode and its CharacteristicsDiode | Working and Types of DiodeDiode CharacteristicsHalf Wave Diode RectifierFull Wave Diode RectifierDiode Bridge RectifierWhat is Zener Diode?Application of Zener DiodeLED or Light Emitting DiodePIN Photodiode | Avalanche PhotodiodeTunnel Diode and its ApplicationsGUNN DiodeVaractor DiodeLaser DiodeSchottky DiodePower DiodesDiode ResistanceDiode Current EquationIdeal DiodeReverse Recovery Time of DiodeDiode TestingMOSFET | Working Principle of p-channel n-channel MOSFETMOSFET CircuitsMOS Capacitor | MOS Capacitance C V CurveApplications of MOSFETMOSFET as a SwitchMOSFET CharacteristicsPower MOSFETHalf Wave RectifiersFull Wave RectifiersBridge RectifiersClamping CircuitTheory of SemiconductorIntrinsic SemiconductorExtrinsic SemiconductorsEnergy Bands of SiliconDonor and Acceptor Impurities in Semiconductor Conductivity of SemiconductorCurrent Density in Metal and Semiconductor Intrinsic Silicon and Extrinsic SiliconP Type SemiconductorN Type SemiconductorP N Junction Theory Behind P N JunctionForward and Reverse Bias of P N JunctionZener BreakdownAvalanche BreakdownHall Effect Applications of Hall EffectGallium Arsenide SemiconductorSilicon SemiconductorTypes of TransistorsBipolar Junction Transistor or BJTBiasing of Bipolar Junction Transistor or BJTTransistor BiasingTransistor CharacteristicsCurrent Components in a TransistorTransistor Manufacturing TechniquesApplications of Bipolar Junction Transistor or BJT | History of BJTTransistor as a SwitchTransistor as an AmplifierJFET or Junction Field Effect Transistorn-channel JFET and p-channel JFETApplications of Field Effect TransistorDIAC Construction Operation and Applications of DIACTRIAC Construction Operation and Applications of TRIACPhototransistorNew Articles Ring CounterDischarging a CapacitorCharging a CapacitorElectric PotentialParity GeneratorElectric Flux