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Introduction to Lasers
 

Introduction to Lasers

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Featuring the Laser principles and applications ..... Include figures & representations for more references .....

Featuring the Laser principles and applications ..... Include figures & representations for more references .....

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    Introduction to Lasers Introduction to Lasers Presentation Transcript

    • Visit www.ignitedmindsv2.tk Lasers Introduction to
    • Lecture Contents • • • • • • Laser Applications Definition of lasers Population Inversion Materials used for semiconducting laser Quantum dot devices Laser Safety Intro to lasers
    • Intro to lasers Laser Applications TELECOMMUNICATION 10 Gbits /s FLAG network From UK to Japan (Fiber-optic Link Around the Globe) 28OOOKM Flag Network owned by Reliance Globecom -UK Flag Network Collaboration In India Reliance Communications
    • Another Typical Application of Laser – Fibre Optics • An example of application is for the light source for fibre optics communication. • Light travels down a fibre optics glass at a speed, = c/n, where n = refractive index. • Light carries with it information • Different wavelength travels at different speed. • This induce dispersion and at the receiving end the light is observed to be spread. This is associated with data or information lost. • The greater the spread of information, the more loss • However, if we start with a more coherent beam then loss can be greatly reduced. Intro to lasers
    • Laser Applications MEDICINAL PURPOSE # Intro to lasers Fiber optic Endoscopeto Detect ulcers in the intestines. Lasers are used extensively in the treatment of eye-diseases ,particularly to reattach a detached retina. Bloodless Surgery. # The liver and lung diseases could be treated using lasers.
    • Laser Applications MEDICINAL PURPOSE Intro to lasers • To destroy cancerous and precancerous cells; at the same time, the heat seal off capillaries, To break up gallstones and kidney stones To remove plaque clogging human arteries
    • Laser Applications INDUSTRIAL PURPOSES Intro to lasers # lasers are used now for cutting, drilling and welding of metals and other materials. Laser light is used to collect the information about the prefixed prices of various products in shops and business establishments from the barcode printed on the product. • LIDAR –Light Detection & Ranging (Mines) • Leveling of Ceramic Tile Floor # For precision measurements & leveling
    • Laser Applications INDUSTRIAL PURPOSES PC-board CAD tools s 3D printers Latching tool Intro to lasers Milling tool A variety of 3D printing techniques have appeared in the last few years. SLA: Stereolithography: laser curing of liquid plastic. SLS: Selective Laser Sintering: similar, laser fuses powder. LOM: Layered Object Modeling: laser cuts paper one layer at a time. FDM: Fused Deposition Modeling: a thread of plastic is melted through a moving head.
    • Laser Applications DEFENCE & SECURITY Intro to lasers # LASTEC- HPL Researches (Laser Science & Technology Centre) # In sniper guns, for target acquisition & locking Dragunov SVD – Semi Automatic Sniper gun Under DRDO (Defence Research & Development Organisation) Indian ARM industry :- OFB (Ordinance Factories Board )
    • MILITARY USES THERMAL IMAGING THERMAL IMAGING • Laser guided munitions – Designated from air or ground Intro to lasers • Thermal homing missiles • Optical Guidance • Night Vision
    • Lasers – Military Applications • Targeting tool – Absorbed by target – thermal radiator – Reflected by target – selective radiator • Modulated – Different lasers of the same frequency to be deconflicted and limits enemy interference • Weapon Systems: Hellfire, Maverick, Rockeye • Laser Range finders, Beam riders, and laser target designators (LTD) • THEL & MHEL - Tactical High Energy Laser (Shoot down incoming) @ www.gizmag.com/millitarygadgets Intro to lasers
    • Intro to lasers Laser Applications HOLOGRAPHY • Holography is the production of holograms by the use of laser. @ www.pranavmistry.com
    • Laser Applications HOLOGRAPHY • Possible medical applications using the technology – Surgical procedures (using tracking capabilities) – Rehabilitation techniques & Gaming Intro to lasers
    • Typical Application of Laser The detection of the binary data stored in the form of pits on the compact disc is done with the use of a semiconductor laser. The laser is focused to a diameter of about 0.8 mm at the bottom of the disc, but is further focused to about 1.7 micrometers as it passes through the clear plastic substrate to strike the reflective layer. The reflected laser will be detected by a photodiode. Moral of the story: without optoelectronics there will no CD player! Intro to lasers
    • BASIC LASER Light Amplification by Stimulated Emission of Radiation Intro to lasers
    • Definition of laser • A laser is a device that generates light by a process called STIMULATED EMISSION. • The acronym LASER stands for Light Amplification by Stimulated Emission of Radiation • Semiconducting lasers are multilayer semiconductor devices that generates a coherent beam of monochromatic light by laser action. A coherent beam resulted which all of the photons are in phase. Intro to lasers
    • Electromagnetic Spectrum Gamma Rays 10-13 10-12 10-11 X-Rays 10-10 10-9 Ultra- Visible violet Infrared 10-8 10-5 10-7 10-6 Microwaves 10-4 10-3 10-2 Radar waves 10-1 TV waves 1 10 Radio waves 102 Wavelength (m) LASERS Retinal Hazard Region Ultraviolet 200 300 Visible 400 500 600 Near Infrared 700 800 900 1000 1100 Far Infrared 1200 1300 1400 1500 10600 Wavelength (nm) ArF 193 XeCl 308 KrF 248 Ar 488/515 HeNe Ruby 633 694 2w Alexandrite GaAs Nd:YAG 755 905 532 Nd:YAG 1064 Communication CO2 10600 Diode 1550 Lasers operate in the ultraviolet, visible, and infrared. Intro to lasers
    • Properties of Laser Light • Monochromaticity – Laser light is concentrated in a narrow range of wavelengths • Coherence – All the emitted photons bear a constant phase relationship with each other in both time and phase • Directionality – laser light is usually low in divergence • High Irradiance – Power of EM radiation Incident per unit area Intro to lasers
    • Types of LASERS LASERS Semiconductor Diode Laser Solid state Liquid Gas Lasers Solid state Liquid Neodymium Yag Laser Ruby laser Gaseous Intro to lasers
    • Market demand of QD lasers ( QUANTUM DOT ) Microwave/Millimeter wave transmission with optical fibers Datacom network Telecom network QD Lasers High speed QDL Directly Modulated Quantum Dot Lasers •Datacom Mode-Locked Quantum Dot Lasers Optics Advantages •Short InP Based Quantum Dot Lasers •Low @ www.fibers.org Intro to lasers application •Rate of 10Gb/s optical pulses •Narrow spectral width •Broad gain spectrum •Very low α factor-low chirp emission wavelength •Wide temperature range •Used for data transmission
    • DEFINITION OF MPE The level of laser light to which a person may be exposed without risk of injury. Intro to lasers
    • Mechanisms of Light Emission For atomic systems in thermal equilibrium with their surrounding, the emission of light is the result of:  Absorption  And subsequently, spontaneous emission of energy There is another process whereby the atom in an upper energy level can be triggered or stimulated in phase with the an incoming photon. This process is:  Stimulated emission  It is an important process for laser action Therefore 3 process of light emission: 1. Absorption 2. Spontaneous Emission 3. Stimulated Emission
    • Stimulated Emission •It is pointed out by Einstein that: “Atoms in an excited state can be stimulated to jump to a lower energy level when they are struck by a photon of incident light whose energy is the same as the energy-level difference involved in the jump. The electron thus emits a photon of the same wavelength as the incident photon. The incident and emitted photons travel away from the atom in phase.” Intro to This process is called stimulated emission. lasers
    • Intro to lasers Stimulated Emission Emitted photon Incident photon Excited electron Incident photon Unexcited electron Before emission After emission
    • Intro to lasers In order to obtain the coherent light from stimulated emission, two conditions must be satisfied: 1. The atoms must be excited to the higher state. That is, an inverted population is needed, one in which more atoms are in the upper state than in the lower one, so that emission of photons will dominate over absorption. Unexcited system Excited system E3 E2 E3 E2 E1 E1
    • Metastable State Intro to lasers 2. The higher state must be a metastable state – a state in which the electrons remain longer than usual so that the transition to the lower state occurs by stimulated emission rather than spontaneously. E3 Metastable state E3 E2 E2 Incident photon Photon of energy E 2  E1 E1 Metastable system E1 Emitted photon Stimulated emission
    • Common Laser System Intro to lasers
    • Intro to lasers BASIC LASER COMPONENTS ACTIVE MEDIUM Optical Resonator Solid (Crystal) Gas Semiconductor (Diode) Liquid (Dye) EXCITATION MECHANISM Optical Electrical Chemical OPTICAL RESONATOR HR Mirror and Output Coupler Active Medium High Reflectance Mirror (HR) Output Beam Output Coupler Mirror (OC) Excitation Mechanism The Active Medium contains atoms which can emit light by stimulated emission. The Excitation Mechanism is a source of energy to excite the atoms to the proper energy state. The Optical Resonator reflects the laser beam through the active medium for amplification.
    • Laser Wavelength Linewidth Intro to lasers
    • CDRH CLASS WARNING LABELS Laser Radiation Do Not Stare Into Beam Helium Neon Laser 1 milliwatt max/cw CLASS II LASER PRODUCT Class II Class IIIa with expanded beam VISIBLE LASER RADIATIONAVOID EYE OR SKIN EXPOSURE TO DIRECT OR SCATTERED RADIATION Argon Ion Wavelength: 488/514 nm Output Power 5 W CLASS IV Laser Product Class IIIa with small beam Class IIIb Class IV Intro to lasers
    • INTERNATIONAL LASER WARNING LABELS INVISIBLE LASER RADIATION AVOID EYE OR SKIN EXPOSURE TO DIRECT OR SCATTERED RADIATION CLASS 4 LASER PRODUCT WAVELENGTH MAX LASER POWER EN60825-1 Symbol and Border: Black Background: Yellow 10,600 nm 200 W 1998 Legend and Border: Black Background: Yellow Intro to lasers
    • Intro to NEODYMIUM YAG LASER lasers Courtesy of Los Alamos National Laboratory Rear Mirror Adjustment Knobs Safety Shutter Polarizer Assembly (optional) Coolant Beam Tube Adjustment Knob Output Mirror Beam Q-switch (optional) Beam Tube Nd:YAG Laser Rod Flashlamps Pump Cavity Laser Cavity Harmonic Generator (optional) Medium :- Neodymium-Doped Yttrium Aluminum Garnet Crystal State :- Solid Excitation :- Diode Laser Beam :- 1064 nm infrared Uses :- Cataract ,Glaucoma , Gingivectomy surgeries
    • Intro to lasers Light Absorption • Dominant interaction – Photon absorbed – Electron is excited to CB – Hole left in the VB • Depends on the energy band gap (similar to lasers) • Absorption (a) requires the photon energy to be larger than the material band gap hc  Eg  hc 1.24  m )   E g E g eV )
    • LASER HAZARD CLASSES Lasers are classified according to the level of laser radiation that is accessible during normal operation. Intro to lasers
    • CLASS 1 • Safe during normal use • Incapable of causing injury • Low power or enclosed beam CLASS I Laser Product Label not required Nd:YAG Laser Marker May be higher class during maintenance or service
    • CLASS 2 • • • • Staring into beam is eye hazard Eye protected by aversion response Visible lasers only CW maximum power 1 mW Laser Scanners Laser Radiation Do Not Stare Into Beam Helium Neon Laser 1 milliwatt max/cw CLASS II LASER PRODUCT
    • CLASS 3R (Formerly 3a) • Aversion response may not provide adequate eye protection • CDRH includes visible lasers only • ANSI includes invisible lasers • CW maximum power (visible) 5 mW Expanded Beam Laser Pointers Laser RadiationDo Not Stare Into Beam or View Directly With Optical Instruments Helium Neon Laser 5 milliwatt max/cw CLASS IIIa LASER PRODUCT LASER RADIATIONAVOID DIRECT EYE EXPOSURE ND:YAG 532nm 5 milliwatts max/CW CLASS IIIa Laser Product Small Beam
    • CLASS 3B DPSS Laser with cover removed • Direct exposure to beam is eye hazard • Visible or invisible • CW maximum power 500 mW LASER RADIATIONAVOID DIRECT EXPOSURE TO BEAM 2w ND:YAG Wavelength: 532 nm Output Power 80 mW CLASS IIIb Laser Product Courtesy of Sam’s Laser FAQ, www.repairfaq.org/sam/lasersam.htm, © 1994-2004
    • CLASS 4 • Exposure to direct beam and scattered light is eye and skin hazard • Visible or invisible • CW power >0.5 W • Fire hazard VISIBLE LASER RADIATIONAVOID EYE OR SKIN EXPOSURE TO DIRECT OR SCATTERED RADIATION Photo: Keith Hunt - www.keithhunt.co.uk Copyright: University of Sussex, Brighton (UK) 2w Nd:YAG Wavelength: 532 nm Output Power 20 W CLASS IV Laser Product
    • TYPES OF LASER EYE EXPOSURE INTRABEAM VIEWING EYE LASER SPECULAR REFLECTION LASER DIFFUSE REFLECTION LASER REFLECTED BEAM MIRROR SCATTERED LIGHT ROUGH SURFACE Intro to lasers
    • VISIBLE and/ or INVISIBLE LASER RADIATION-AVOID EYE OR SKIN EXPOSURE TO DIRECT OR SCATTERED RADIATION. ND:YAG 1064 nm 100 Watts Max. Average Power CLASS 4 LASER Controlled Area Warning Sign
    • Intro to lasers LABORATORY DOOR INTERLOCK
    • Intro to lasers ENTRYWAY WARNING LIGHTS
    • Intro to lasers LASER PROTECTIVE BARRIERS
    • Intro to lasers CURBS ON OPTICAL TABLE
    • Intro to lasers BEAM CONTROL
    • Intro to lasers COMPUTERS IN RESEARCH LABS Allowing a direct view from a computer workstation into a laser experimental setup increases the risk of eye exposure to reflected beams. Laser-Professionals.com
    • LASER SAFETY EYEWEAR Intro to lasers
    • EYEWEAR LABELS Intro to lasers All eyewear must be labeled with wavelength and optical density.
    • Visit www.ignitedmindsv2.tk