Laser

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

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

Overivew of laser In 1917 Albert Einstein, Zur Quantentheorie der Strahlung (On the Quantum Theory of Radiation) In 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. 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) Applications: optical storage devices such as compact disc and DVD players (largest), fiber- optic communication (second largest) Video (Record 5 events/applications of lasers) Video (Record 5 events/applications of lasers) Video

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

Design of laser Gain medium Gain medium High reflector High reflector Energy supply Energy supply Laser output Laser output

Applications of laser Medicine: bloodless surgery, laser healing Medicine: bloodless surgery, laser healing Industry: Cutting, welding, material heat treatment Industry: Cutting, welding, material heat treatment Defense: marking targets, missile defense Defense: marking targets, missile defense Research: spectroscopy, laser scanning Research: spectroscopy, laser scanning Commercial: laser printer, CDs, barcode scanners Commercial: laser printer, CDs, barcode scanners Aesthetics: laser light shows Aesthetics: laser light shows

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

Laser classification Class I: inherently safe (light enclosed), e.g. CD players Class 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 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 Class IIIa/3R: up to 5mW, small risk of eye damage

Laser classification Class III/3B: up to 500mW, immediate severe eye damage upon exposure, e.g. those in CD burners. Class 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. Class IV: burn skin, even scattered light can cause eye damage. Many industrial and scientific lasers are in this class.

Laser safety Laser safety is the avoidance of laser accidents, especially those involving eye injuries. Laser safety is the avoidance of laser accidents, especially those involving eye injuries. Safety measures Safety measures Everyone who uses a laser should be aware of the risks. 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. 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 safety Safety measures (cont’d) Safety measures (cont’d) 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. 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 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 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 Alignment of beams and optical components should be performed at a reduced beam power whenever possible

Laser safety Protective eyewear Protective eyewear Spectacles or goggles with appropriately filtering optics Spectacles 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 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 The protective specifications (wavelengths and optical densities) are usually printed on the goggles

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

Group Activity 4 people in a group (Individual responsibility) Poster Design for introduction of lasers 15 minutes