LaserLaser

Lesson objectives Lesson objectives

What is laser?What is laser?Applications of laser around usApplications of laser around usLaser radiation hazardsLaser radiation hazardsLaser classificationLaser classificationLaser safetyLaser safety

What is a laser?What is a laser?

A laser is a device that emits light A laser is a device that emits light (electromagnetic radiation) through a (electromagnetic radiation) through a process called process called simulated emissionsimulated emission..

The term The term laserlaser is an acronym for is an acronym for light light amplificationamplification by by simulated emission of simulated emission of radiation. radiation.

(from (from http://en.wikipedia.org/wiki/laserhttp://en.wikipedia.org/wiki/laser ) )

Overivew of laserOverivew of laser

In 1917 In 1917 Albert EinsteinAlbert Einstein, Zur Quantentheorie der , Zur Quantentheorie der Strahlung (On the Quantum Theory of Radiation)Strahlung (On the Quantum Theory of Radiation)

The first working laser was demonstrated on 16 The first working laser was demonstrated on 16 May 1960 by May 1960 by Theodore MaimanTheodore Maiman at Hughes at Hughes Research Laboratories.Research Laboratories.

Applications: optical storage devices such as Applications: optical storage devices such as compact disc and DVD players (largest), fiber-compact disc and DVD players (largest), fiber-optic communication (second largest)optic communication (second largest)

Video (Record 5 events/applications of lasers)Video (Record 5 events/applications of lasers)

Properties of laser Properties of laser

Spatially coherent Spatially coherent The electric fields at The electric fields at

different positions different positions oscillate in a totally oscillate in a totally correlated way correlated way

Strong directionality of Strong directionality of laser beamslaser beams

Monochromatic (not for Monochromatic (not for all lasers)all lasers) Narrow wavelength Narrow wavelength

spectrumspectrum

Design of laserDesign of laser

Gain mediumGain mediumHigh reflectorHigh reflectorEnergy supplyEnergy supplyLaser outputLaser output

Applications of laserApplications of laser

Medicine: bloodless surgery, laser healingMedicine: bloodless surgery, laser healing Industry: Cutting, welding, material heat Industry: Cutting, welding, material heat

treatmenttreatmentDefense: marking targets, missile defenseDefense: marking targets, missile defenseResearch: spectroscopy, laser scanningResearch: spectroscopy, laser scanningCommercial: laser printer, CDs, barcode Commercial: laser printer, CDs, barcode

scannersscannersAesthetics: laser light showsAesthetics: laser light shows

Laser radiation hazardsLaser radiation hazards

Coherent light, low divergence angle Coherent light, low divergence angle concentrate on a small spot on the concentrate on a small spot on the retinaretina

Laser radiation predominantly causes Laser radiation predominantly causes injury via thermal effects.injury via thermal effects.

A transient increase of only 10 °C can A transient increase of only 10 °C can destroy retinal photoreceptors.destroy retinal photoreceptors.

Some lasers are so powerful that even the Some lasers are so powerful that even the diffuse reflection from a surface can be diffuse reflection from a surface can be hazardous to the eye.hazardous to the eye.

Laser classificationLaser classification

Class I: inherently safe (light Class I: inherently safe (light enclosed), e.g. CD playersenclosed), e.g. CD players

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

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

Laser classificationLaser classification

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

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

Laser safetyLaser safety

Laser safety is the avoidance of laser accidents, Laser safety is the avoidance of laser accidents, especially those involving eye injuries. especially those involving eye injuries.

Safety measures Safety measures Everyone who uses a laser should be aware of the Everyone who uses a laser should be aware of the

risks. risks. Optical experiments should be carried out on an Optical experiments should be carried out on an

optical tableoptical table with all laser beams travelling in the with all laser beams travelling in the horizontal plane only, and all beams should be horizontal plane only, and all beams should be stopped at the edges of the table. stopped at the edges of the table. Users should never Users should never put their eyes at the level of the horizontal planeput their eyes at the level of the horizontal plane where the beams are in case a reflected beam leaves where the beams are in case a reflected beam leaves the table. the table.

Laser safetyLaser safety Safety measures (cont’d)Safety measures (cont’d)

Watches and other jewelry that might enter the optical Watches and other jewelry that might enter the optical plane should not be allowed in the laboratory. All non-plane should not be allowed in the laboratory. All non-optical objects that are close to the optical plane optical objects that are close to the optical plane should have should have a matte finisha matte finish..

Adequate eye protectionAdequate eye protection should always be required should always be required for everyone in the room if there is a significant risk for everyone in the room if there is a significant risk for eye injury for eye injury

High-intensity beams that can cause fire or skin High-intensity beams that can cause fire or skin damage (mainly from class 4 and ultraviolet lasers) damage (mainly from class 4 and ultraviolet lasers) and that are not frequently modified should be and that are not frequently modified should be guided guided through tubes through tubes

Alignment of beams and optical components should Alignment of beams and optical components should be performed be performed at a reduced beam powerat a reduced beam power whenever whenever possible possible

Laser safetyLaser safety

Protective eyewearProtective eyewearSpectacles or goggles with appropriately Spectacles or goggles with appropriately

filtering optics filtering optics Eyewear must be selected for Eyewear must be selected for the specific the specific

type of lasertype of laser, to block or attenuate in the , to block or attenuate in the appropriate wavelength range appropriate wavelength range

The protective specifications (wavelengths The protective specifications (wavelengths and optical densities) are usually printed on and optical densities) are usually printed on the goggles the goggles

Laser safetyLaser safety

Laser safety officerLaser safety officer In many jurisdictions, organizations that In many jurisdictions, organizations that

operate lasers are required to appoint a laser operate lasers are required to appoint a laser safety officer (LSO). safety officer (LSO).

The LSO is responsible for ensuring that The LSO is responsible for ensuring that safety regulations are followed by all other safety regulations are followed by all other workers in the organization. workers in the organization.

Group ActivityGroup Activity

4 people in a group (Individual responsibility)

Poster Design for introduction of lasers15 minutes