Laser is a device that stimulates atoms or molecules to emit light at a particular wavelength and amplifies that light, typically producing a very narrow beam of radiation. The emission generally covers an extremely limited range of visible, infrared,or ultraviolet wavelengths. Many different types of lasers have been developed, with highly varied characteristics. Laser is an acronym for “light amplification by the stimulated emission of radiation”.
Diagram of a LASER
Types of lasers
Crystals, glasses, semiconductors, gases, liquids, beams of high energy electrons, and even gelatin doped with suitable materials can generate laser beams.
In general hot gases near bright stars can generate strong stimulated emission at microwave frequencies, although these gas clouds lack resonant clarities, so they do not produce beams. In crystals and glass lasers, such as maiman’s first Ruby laser, light from an external source excites atoms, known as dopants, that have been added to a host material at low concentrations. Important examples include glasses and crystals doped with rare-earth element neodymium and glasses doped with erbium or ytterbium
Note: other types of lasers include due lasers, chemical lasers.
Application of lasers
Most lasers applications fall into one of a fair broad categories:
1) transmission and processing of information
Laser scanners: the ability to focus lasers beams onto very small spots and to switch them on and off billions of times per second makes lasers important tools in telecommunications and information processing. E.g In laser supermarket scanners; a rotating mirror scans a red beam while clerks move packages across the beam. The optical sensors detect light reflected from striped barcodes on packages, decode the symbol, and relay the information to a computer so that it can add the price to the bill.
LASER scanner use in supermarket
Barcodes on packages
Fibre optic cable
2)precise delivery of energy (industrial uses):laser energy can be focused in space and concentrated in time so that it heats, burns away, or vapourizers many materials. Although the total energy in a laser beam may be small, the concentrated power on small spots or during intervals can be enormous even though it cost much. These are applicable in:
medical purposes: surgical removal of tissue with a laser is a physical process similar to industrial lasers burn away tissue because their infrared beams are strongly absorbed by the water that makes up the bulk of living cells. It stops bleeding in blood rich tissues such as the female reproductive tract or the gums.
Note: ophthalmologists surgically correct visual defects by removing tissue from the cornea, reshaping the transparent outer layer of the eye with intense ultraviolet pulses.
Pictures based on the photodynamic therapy (PDT) fibre optic surgery
high energy lasers: major application for these high power levels are fusion research, nuclear weapons testing and missile defense.
Nuclear weapon design
3) alignment measurement and imaging(surveying):surveyors and construction workers use laser beams to draw straight lines through the air. The beam itself is not visible in the air except where scattered by dust or haze, but it projects a bright point on a distant object. Surveyors bounce the beam off a mirror to measure direction and angle.
4) interferometry and holography: holograms now can be mass-produced by an embossing process as used to credit cards and do not have to be viewed in laser light.
Holograms are made by splitting a laser beam into two identical halves, using one beam to illuminate an object. This object beam is then combined with the other half-the reference beam- in the plane of a photographic plate.
Dangers of LASER
|Photobiological spectral domain||Eye||Skin|
|Ultraviolet C (200nm-280nm)||Photokeratitis||Erythema (sunburn)Skin cancerAccelerated skin ageing|
|Ultraviolet B (280nm-315nm)||Photokeratitis||Increased pigmentation|
|Ultraviolet A (315nm-400nm)||Photochemical (cataract)||Pigment darkeningSunburn|
|Visible (400nm-780nm)||Photochemical and thermal retinal injury||Pigment darkeningPhotosensitive reactionsSkin burn|
|Infrared B (1.4mm-3.0mm)||Corneal burn only||Skin burn|
1.what does the acronym LASER stand for? (Wassce 2018)
Answer: light amplification by stimulated emission of radiation
2.define laser? (Wassce 2018)
Answer: laser is a device that stimulates atoms or molecules to emit light at a particular wavelength and amplifies that light, typically producing a very narrow beam of radiation.
Answer: holograms are made by splitting a laser beam into two identical beams then combined with the other half-the reference beam-in place of a photographic plate.
4.list the four(4) application of a LASER
a) interferometry and holography
b) alignment measurement and imaging
c) precise delivery of energy
d) transmission and processing of information
5. List the types of LASER we have.
Answer: a) crystals b) glasses c) semiconductors d) gases e) liquids f) beam of high energy electrons and gelatin doped with suitable materials can generate laser beams.