LASER SAFETY Texas State University | San Marcos

Objectives IDENTIFY what the acronym LASER means and briefly DESCRIBE how a laser performs it function. (LST.OBJ.001) LIST the characteristics of a laser beam. (LST.OBJ.002) DIFFERENTIATE between a Continuous Wave Laser and a Pulsed Laser. (LST.OBJ.003)

Objectives (continued) LIST the five types of lasers and briefly DESCRIBE their attributes. (LST.OBJ.004) LIST several types of laser excitation sources. (LST.OBJ.005) IDENTIFY the American National Standards Institute Laser Classifications. LST.OBJ.006

Objectives (continued) LIST three areas in which lasers have been used. (LST.OBJ.007) Describe the two common types of laser pointers. (LST.OBJ.008) List the criteria used by the FDA to determine laser pointer classification and the required labeling on each class of laser pointer. (LST.OBJ.009)

Objectives (continued) IDENTIFY the three primary mechanisms of tissue injury associated with laser radiation exposure. LST.OBJ.010 MATCH the specified laser wavelength to the part of the eye that is most affected. LST.OBJ.011

Objectives (continued) IDENTIFY the two mechanisms by which laser radiation may potentially cause skin injury. LST.OBJ.012 IDENTIFY the three basic categories of controls used in laser environments to provide a degree of protection from possible laser radiation injury and GIVE several examples of each type of control. LST.OBJ.013

Objectives (continued) IDENTIFY other non-beam hazards that are possible in laser environment and GIVE an example of each. LST.OBJ.014 MATCH the following laser related terms to their corresponding meaning: –Accessible Exposure Limit -Nominal Hazard Zone –-iffuse Reflection -Specular Reflection –Intrabeam Exposure -Radiant Exposure –Irradiance -Peak Power –Maximum Permissible Exposure LST.OBJ.015

TxState Laser Safety Program Laser Safety Training Manual Laser Safety Manual Texas Department of State Health Services Bureau Radiation Control –25 TAC §

LASER Acronym for: –Light –Amplification by the –Stimulated –Emission of –Radiation.

Laser Emits non-ionizing electromagnetic radiation that is ultraviolet, visible, or infrared light. Lasers now capable of emission in X-ray frequency.

Laser Light Monochromatic –One wavelength or color Directional –Does not expand as quickly as ordinary light Coherent –Waves of light generated in phase with each other.

Basic Operating Concept Electrons moved from ground state to higher energy state. When electrons descend to ground state, photons emitted of specific wavelength. Photons oscillate in mirrored resonator Increases intensity by stimulating emission of additional photons of same wavelength and phase. Photons escape via output coupler

Continuous Wave Lasers Operated in a continuous mode for at least a period of.25 seconds. Output expressed as the average power (watts).

Irradiance (Power Density) Expressed in W/cm 2 Function of the beam power divided by beam area Beam area a function of: –Beam size at aperture –Beam divergence –Distance from aperture > irradiance > potential hazard

Pulsed Lasers Delivers energy in the form of a: –single pulse –train of pulses Delivered in less than.25 seconds. Output expressed as the total energy per pulse (joules).

Radiant Exposure (Energy Density) Normally expressed in Joules/cm 2 Function of: –Pulse Density –Pulse duration –Pulse frequency > radiant exposure > potential hazard

Laser Types Solid state –Ruby crystals and neodymium-doped glasses and crystals most common solid laser media. Gas –A pure gas or mixture of gases (i.e. Helium- Neon or Carbon dioxide) Liquid –Inorganic dyes contained in glass vessels most common.

Laser Types Excimer –Uses reactive gas with inert gas. Dimer produced which when lased produce UV Semi-conductor (most common laser) –Gallium arsenide most common semiconductor material

Excitation Sources Types –Flash lamps –Plasma discharge tubes –High voltage current –Radio frequency –Some lasers used to “pump” other lasers. Excitation device can present serious non-beam hazard

ANSI Classification ANSI (and LIA) - ANSI 2000 has developed four categories of hazard potential. Based on the ability of optical emissions from a laser system to produce injury to personnel. The higher the classification number, the greater the hazard potential.

Class I May produce visible or invisible laser radiation. Do NOT pose a hazard under normal operating conditions.

Class II Low-power visible light lasers or laser systems that: –Do NOT normally present a hazard because of the normal human aversion response Blinking eye movement, etc. –Potential for hazard if viewed directly for extended period of time similar to many conventional light sources

Class IIIa Normally not injure the eye if viewed for momentary period (within the aversion response period) with the unaided eye May present a greater hazard if viewed using collection optics. Must carry a caution label.

Class IIIa Another group of Class IIIA lasers have DANGER labels Capable of exceeding permissible exposure levels for the eye in 0.25 seconds. Still poses a low risk of injury.

Class IIIb Produce eye damage if viewed directly. Includes intrabeam viewing of specular reflections. Normally do not produce a hazardous diffuse reflection.

Class IV Produce retinal damage from direct or specular reflections. May also produce hazardous diffuse reflections. May produce significant eye and skin radiation hazards as well as fire hazards.

Laser Applications Industry –Can be used to melt, vaporize, drill material in precise manner –Many other Scientific Research –Used to study molecular structure –Selectively induce chemical reactions Medicine –Cut and cauterize without damaging healthy tissue –Eye surgery

Laser Applications Military –Guidance systems for missles, aircraft, and satellites Communication –Laser light can carry 1000 times number television channels now carried by microwave –Play audio compact discs and videodiscs

Laser Pointers Not dangerous when used properly. Looking directly into beam for > 1 ½ minutes can result in eye injury. Flashblindness –Split second look –Similar to effect in flash photography –Vision returns to normal after few moments –No long term effect

Red Laser Pointers 670 nm –1000’ range –Rarely sold today 650 nm –2000’ range –Adequate most purposes 635 nm –4000’ range –Usefule outdoors unless sun brightly shining

Green Laser Pointers 532 nm –Eye more sensitive to green light –Reason for exceptionally brilliant visibility Frequency doubled diode –Uses infrared diode (2 x 1064) –Low efficiency 500 mW into diode Few mW out of diode

FDA Regulation Laser pointers are regulated according to their power output. Class II laser Pointers –< 1 mW –CAUTION Label required Class IIIb Laser Pointers –1 to 5 mW –WARNING Label required

Biological Effects Tissues at risk are: –Eyes –Skin Three mechanisms of injury –Thermal effects –Photochemical effects –Acoustical transient effects

Eye Injury Potential Related to laser wavelength – 1400 nm Cornea –> 300 < 400 nm Aqueous Humor Iris Lens Vitreous humor –> 400 < 1400 nm Retina

Eye Injury Potential Retinal Injury –May be severe due to focal magnification –Optical gain ~ 10 5 –Example 1 mW/cm 2 into eye ≈100 W/cm 2 on retina Lesions –Caused when choroids blood flow cannot regulate retina heat loading

Picture of burned retina.

Skin Injury Potential Thermal Injury –Acute exposures to high power lasers beams –Direct contact with beam or specular reflection –Not usually serious Photochemically induced –Chronic exposure to scattered UV radiation –Direct contact with UV beam, specular reflection, or diffuse reflection –Can cause minor or severe sunburn –May promote formation of cancer

Photobiological Spectral Domain Eye EffectsSkin Effects UV-C (200 to 280 nm) PhotokeratitisErythema (sunburn) UV-B (280 to 315 nm) PhotokeratitisAccelerated skin aging Increased pigmentation Skin cancer UV-A (315 to 400 nm) Photochemical UV cataract Pigment darkening Skin burn Visible (400 to 780 nm) Photochemical and thermal retinal injury Photosensitive reactions Skin burn Infrared A (780 to 1400 nm) Cataract, retinal burnsSkin burn Infrared B (1400 to 3000 nm) Corneal burn Aqueous flare IR cataract Skin burn Infrared C (3000 to 10 6 nm) Corneal burnSkin burn

Laser Safety Responsibility of each individual Three categories of controls –Engineering –Administrative and Procedural –Personal Protective Equipment Work better together than singly.

Engineering Controls Normally designed and built into laser equipment –Protective housing –Master key switch –Beam stops/attenuators –Activation warning system –Interlocked doors –Airborne emissions controls

Administrative & Procedural Controls No physical barrier Examples –Area postings –Standard Operating procedures –Maintenance procedures –Administrative procedures –Alignment procedures

Personal Protective Equipment Eye protection –Essential for beam alignments –Must be marked with: Optical Density Laser Wavelength –Must be comfortable Skin protection –Gloves –UV face shield –Lab coat

Non-Beam Hazards Industrial Hygiene –Associated with compressed gases, cryogenic materials, toxic & carcinogenic materials –Adequate ventilation to reduce fumes & vapors Explosion Hazards –High pressure arc lamps, filament lamps, or laser welding equipment –Laser targets and elements of optical train

Non-Beam Hazards Non-beam Optical Radiation Hazards –Laser discharge tubes, pumping lamps, and laser welding plasma Electrical Hazards –Installation and connection –Conduit versus flexible cord Noise Hazards –High noise levels during operation

Non-Beam Hazards - Physical Factors that contribute to injury are: –Fire –Explosions –electrocutions From –arc and filament lamps –capacitors –wiring –power supplies –circuits –solvents –gases

Non-Beam Hazards - Chemical Various chemical agents: –Dyes –Solvents –Gases Laser-generated airborne contaminants –Dusts –Mists –Fumes –Smokes

Mastering Light: An Introduction to Laser Safety and Hazards

Objectives IDENTIFY what the acronym LASER means and briefly DESCRIBE how a laser performs it function. (LST.OBJ.001) LIST the characteristics of a laser beam. (LST.OBJ.002) DIFFERENTIATE between a Continuous Wave Laser and a Pulsed Laser. (LST.OBJ.003)

Objectives (continued) LIST the five types of lasers and briefly DESCRIBE their attributes. (LST.OBJ.004) LIST several types of laser excitation sources. (LST.OBJ.005) IDENTIFY the American National Standards Institute Laser Classifications. LST.OBJ.006

Objectives (continued) LIST three areas in which lasers have been used. (LST.OBJ.007) Describe the two common types of laser pointers. (LST.OBJ.008) List the criteria used by the FDA to determine laser pointer classification and the required labeling on each class of laser pointer. (LST.OBJ.009)

Objectives (continued) IDENTIFY the three primary mechanisms of tissue injury associated with laser radiation exposure. LST.OBJ.010 MATCH the specified laser wavelength to the part of the eye that is most affected. LST.OBJ.011

Objectives (continued) IDENTIFY the two mechanisms by which laser radiation may potentially cause skin injury. LST.OBJ.012 IDENTIFY the three basic categories of controls used in laser environments to provide a degree of protection from possible laser radiation injury and GIVE several examples of each type of control. LST.OBJ.013

Objectives (continued) IDENTIFY other non-beam hazards that are possible in laser environment and GIVE an example of each. LST.OBJ.014 MATCH the following laser related terms to their corresponding meaning: –Accessible Exposure Limit -Nominal Hazard Zone –-iffuse Reflection -Specular Reflection –Intrabeam Exposure -Radiant Exposure –Irradiance -Peak Power –Maximum Permissible Exposure LST.OBJ.015