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Laser. Lesson objectives What is laser? What is laser? Applications of laser around us Applications of laser around us Laser radiation hazards Laser radiation

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  • Laser

  • Lesson objectives What is laser?Applications of laser around usLaser radiation hazardsLaser classificationLaser safety

  • What is a laser?A laser is a device that emits light (electromagnetic radiation) through a process called simulated emission.The term laser is an acronym for light amplification by simulated emission of radiation.

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  • Overivew of laserIn 1917 Albert Einstein, Zur Quantentheorie der Strahlung (On the Quantum Theory of Radiation)The first working laser was demonstrated on 16 May 1960 by Theodore Maiman at Hughes Research Laboratories.Applications: optical storage devices such as compact disc and DVD players (largest), fiber-optic communication (second largest)Video (Record 5 events/applications of lasers)

  • Properties of laser Spatially coherent The electric fields at different positions oscillate in a totally correlated way Strong directionality of laser beamsMonochromatic (not for all lasers)Narrow wavelength spectrum

  • Design of laserGain mediumHigh reflectorEnergy supplyLaser output

  • Applications of laserMedicine: bloodless surgery, laser healingIndustry: Cutting, welding, material heat treatmentDefense: marking targets, missile defenseResearch: spectroscopy, laser scanningCommercial: laser printer, CDs, barcode scannersAesthetics: laser light shows

  • Laser radiation hazardsCoherent light, low divergence angle concentrate on a small spot on the retinaLaser radiation predominantly causes injury via thermal effects. A transient increase of only 10 C can destroy retinal photoreceptors.Some lasers are so powerful that even the diffuse reflection from a surface can be hazardous to the eye.

  • Laser classificationClass I: inherently safe (light enclosed), e.g. CD players

    Class II: safe during normal use (damage prevented by blink reflex of the eye) e.g. laser pointers

    Class IIIa/3R: up to 5mW, small risk of eye damage

  • Laser classificationClass III/3B: up to 500mW, immediate severe eye damage upon exposure, e.g. those in CD burners.

    Class IV: burn skin, even scattered light can cause eye damage. Many industrial and scientific lasers are in this class.

  • Laser safetyLaser safety is the avoidance of laser accidents, especially those involving eye injuries. Safety measures Everyone who uses a laser should be aware of the risks. Optical experiments should be carried out on an optical table with all laser beams travelling in the horizontal plane only, and all beams should be stopped at the edges of the table. Users should never put their eyes at the level of the horizontal plane where the beams are in case a reflected beam leaves the table.

  • Laser safetySafety measures (contd)Watches and other jewelry that might enter the optical plane should not be allowed in the laboratory. All non-optical objects that are close to the optical plane should have a matte finish.Adequate eye protection should always be required for everyone in the room if there is a significant risk for eye injury High-intensity beams that can cause fire or skin damage (mainly from class 4 and ultraviolet lasers) and that are not frequently modified should be guided through tubes Alignment of beams and optical components should be performed at a reduced beam power whenever possible

  • Laser safetyProtective eyewearSpectacles or goggles with appropriately filtering optics Eyewear must be selected for the specific type of laser, to block or attenuate in the appropriate wavelength range The protective specifications (wavelengths and optical densities) are usually printed on the goggles

  • Laser safetyLaser safety officerIn many jurisdictions, organizations that operate lasers are required to appoint a laser safety officer (LSO). The LSO is responsible for ensuring that safety regulations are followed by all other workers in the organization.

  • Group Activity4 people in a group (Individual responsibility)Poster Design for introduction of lasers15 minutes