======================LASER=========================== Apertur small opening which electromagnetic radiation pass. Beam Diamete diameter of circular beam at certain point where intensity drop to fraction of maximum value. common definitions are 1/e (0.368) and 1/e2 (0.135) of maxvalue. Beam Divergenc Angle of beam spread,in (milli)radians. approximated for small angle by ratio beam diameter to distance from laser aperture. Divergenc Increase in beam diameter with distance from aperture Coherence electromagnetic waves in phase in both time space. Coherent light Monochromaticity low beamdivergence, canconcentrated to high power densities. Diffraction wave property create deviation from straight line when beam pass near an edge of an opaque object. Irradiance (E Radiant flux (radiant power) per unit area in Watts per square centimeter. (Sometimes referred to as power density, although not exactly correct). Laser acronym for Light Amplification by Stimulated Emission of Radiation. an optical cavity, with mirrors at ends, filled with crystal, glass, liquid, gas or dye. produces an intense beam of light with the unique properties of coherence, collimation monochromaticity. Amplification process which electromagnetic radiation inside active medium within laser optical cavity increase by process of stimulated emission. Amplitude maximum value of a wave, measured from its equilibrium. Anode positive electrode ofgas laser, used for excitation of the gas in tube. Argon Lase gas laser which argon ions arethe active medium. emits blue-green visible spectrum, primarily 448 and 515nm Brewster Window Windows at ends of gas laser, used to produce polarized electromagnetic radiation. window at Brewster angle to optical axis of the laser, only polarization can pass through. Carbon Dioxide (CO2) Lase gas laser which CO2 molecules emits infrared spectrum, primarily at 9-11 [µm], strongest emission line at 10.6 [µm]. Cathod negative electrode gas laser, for excitation of gas in tube. Diode Laser Semiconductor Laser Excimer Lase gas laser emits in UV spectrum. active medium is "Excited Dimer" does not have stable ground state. Gas Laser laser i active medium is a gas. gas can be composed of molecules (like CO2), Atoms (like He-Ne), ions (Ar+). Ground State Lowest energy level of an atom or molecule. Helium-Neon (He-Ne) Laser A gas laser Helium (He) and Neon (Ne) atoms active medium. emits primarily in Visible spectrum, primarily 632.8 [nm], some lines in near Infrared. Hologram interference phenomena on plate (or film). contain enormous amount information 3 dimensional image constructed from it. Injection Laser laser which produces output from semiconductor materials such as GaAs. Injection Lase See Diode Laser. Ion Laser active medium is composed of ions of a Nobel gas (like Ar+ or Kr+). excited by high discharge voltage at the ends of a small bore tube. Laser Accessorie hardware and options available for lasers, as Brewster windows, Q-switches optical components to control laser radiation. Laser Mediu (See Active Medium) Laser Ro solid-state, rod-shaped active medium which excitation caused byintense light (optical pumping),as flash lamp. used for the rod, the earliest of which was synthetic ruby crystal (see Solid State Laser). Laser Pulse discontinuous burst of laser radiation, a true laser pulse achieves higher peak powers than that attainable in a CW output. Limit Accessible Emission Level (AEL permitted within a particularly class. In ANSI Z-136.1, AEL is product Accessible Emission Maximum Permissible Exposure limit (MPE) and area limiting aperture (7mm for visible and near infrared lasers). Limiting Apertur maximum circular area which radiance and radiant exposure can be averaged when determining safety hazards. Longitudinal (Axial) Mode Specific wavelengths in laser output, determined by standing waves within laser cavity. Only longitudinal modes under the laser gain curve, above laser threshold found in laser output. Maximum Permissible Exposure (MPE may be exposed without hazardous effect or adverse changes in eye or skin. Metastable Stat The upper laser level. excited state of atom or molecule, which have a long lifetime. Micro Micro-meter, one millionth of a meter (10-6 [m]). Milliradia unit to measure angles, one thousandth of a radian. 1 milliradian [mrad] = 0.057°. Mode locke method controlling the length of output laser pulse . Produce very short (10-12 [sec]) burst of pulses. Monochromatic Ligh Theoretically, light at one specific wavelength. with very narrow bandwidth. light out of a laser most monochromatic source known to man. Nanometer [nm one billionth of a meter (10-9 [m]). Nd:Glass Lase A solid-state laser in which a Nd dope active medium, to produce 1064 [nm] wavelength. Nd:YAG Lase solid-state laser which Neodymium doped Yttrium Aluminum Garnet used as active medium, produce 1064 [nm] wavelength YAG is a synthetic crystal. Neodymium (Nd rare earth element is active element in Nd:YAG laser and Nd:Glass lasers. Optical Cavity (Resonator Space between laser mirrors where lasingoccurs. Optical Densit logarithmic expression for attenuation produced by an attenuating medium, such as an eye protection filter. Optical Fibe filament of quartz or other optical material, capable of transmitting light by multiple internal reflection and emitting it at the end. Optical Pumpin excitation of active medium r by the application of light, rather than electrical discharge. can be from a conventional source like Xenon or Krypton lamp, or laser. Optical Radiatio Ultraviolet, visible and infrared spectrum (0.35-1.4 mm) in the region of transmittance of the human eye. Optical Resonato mirrors (or reflectors) making up laser cavity including laser rod or tube. mirrors reflect back and forth to up amplification. Output Couple part of laser which enable light come out of laser. Usually a partially reflecting mirror at end of laser optical cavity. Output Powe energy per second (measured in Watts) emitted from laser form of coherent light. Pulse Duratio "On" time of pulsed laser. Pulsed Lase Laser delivers in single or train of laser pulses. Pumpin (See Optical Pumping). Addition of energy (thermal, electrical, or optical) active laser medium. to produce a state of population inversion. Q-Switch Laser laser which store energy in active medium, produce short pulse with high energy. by blocking resonatorability to oscillate, keeping the "Q-Factor" of optical cavity low. Ruby Laser first laser type. use a crystal of sapphire (aluminum oxide) containing trace amounts of chromium oxide as an active medium. Scanning Laser laser having a time-varying direction, origin or pattern propagation with respect to a stationary frame reference. Semiconductor Laser (see diode laser) produces its output from semiconductor materials such as GaAs. Solid State Laser laser in which the active medium is solid state (usually not including semiconductor lasers). Spontaneous Emission Random emission of photon by decay of an excited state to a lower level. Determined by lifetime of the excited state. Spot Size diameter of the beam of laser radiation. Stimulated Emission Coherent emission of radiation, stimulated by a photon absorbed by an atom (or molecule) in its excited state. Transverse Mode geometry of power distribution in cross section of laser beam. Transverse Electro-Magnetic (TEM) Mode Used to designate shape of cross section of laser beam. TEM00 lowest order transverse mode possible. power distribution across beam is of a gaussian shape. Tunable Laser laser system can be "tuned" to emit laser light over continuous range of wavelengths or frequencies. Tunable Dye Laser laser whose active medium a liquid dye, pumped by another laser or flash lamps, produce various colors of light. color may be tuned by adjusting optical tuning elements and/or changing the dye used. Radian measurement of angles. 2p [rad] = 360°, 1 [rad] = 57.3°. Radiant Energy (Q) Energy in form of electromagnetic waves usually ex units of Joules (watt-seconds). Radiant Exposure (H) total energy per unit area upon a given surface. express exposure to pulsed laser radiation inJ/cm2. Reflection return radiant energy (incident light) by surface, with no change in wavelength. Refraction change of direction of propagation of wave, when it passes from one medium to another in which the wave velocity is different. Len curved transparent material which depending on its shape, is used to either converge or diverge light. Ligh visible spectrum. 400 to 700 nanometers. Excitatio Energizing active medium to state of populationinversion. Fluorescenc Emission light particular wavelength, result ofabsorption light shorter wavelength. a property of some materials, each material has wavelength of absorption and emission. Frequency (n) (nu number times wave oscillates per second (The number of periods of oscillations per second). Electromagnetic Radiation (Spectrum wave propagate vacuum with speedlight, simultaneous oscillations of electric field and magnetic field perpendicular each other perpendicular to direction of propagation Created by accelerating electric charge, X-rays, visible spectrum, infrared , microwave etc. Electron Volt [eV Unit of energy: energyelectron accuire while accelerating through 1 [Volt].1 [eV] = 1.6*10-19 [Joule] Photon The elemental unit of light. Qu proportional to wavelength (l) (lambda) (or frequency f). E = hf = hc / l (lambda). ( l (lambda) = wavelength, c = speed of light, h = Planks constant). Polarizatio Vibration of electric field vector in specific direction perpendicular to direction of propagation of wave. Population Inversio excited state of matter, imore atoms (or molecules) in upper state than ilower one. a required for a laser action. Powe rate energy delivery in unit of time, expressed in Watts (Joules per second). Thus: 1 [Watt] = 1 [Joule]/1 [sec]. Infrared Spectrum (IR between 0.7-1,000 [µm]. Solid Angle ratio of area on surface of sphere to square of radius of that sphere. in steradians (sr). Ultraviolet (UV) Radiation Electromagnetic radiation with wavelengths between soft X-rays and visible violet light, broken down into UV-A (315-400 [nm]), UV-B (280-315 [nm]), and UV-C (100-280 [nm]). Visible Spectrum (light) can be detected by the human eye. wavelengths which lie in the range between 400 nm and 700-780 nm. Wavelength (l) (Lamda length of light wave. shortest distancewhich wave pattern fully repeats itself, from crest to crest. wavelength of light in visible spectrum determines color. units of measurement are micrometer (micron),nanometer, and (old unit) the Angstrom unit. YAG Yttrium Aluminum Garnet widely used solid-state crystal composed of yttrium and aluminum oxide doped with a small amount of rare-earth neodymium.