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)The Laser (II •Types of Lasers • Applications • Safety موزه بنت محمد الربان أستاذ مشارك فيزياء ذرية و ليزر Types of Lasers Most lasers consist of a column of active material with a partly reflecting mirror at one end and a fully reflecting mirror at the other. The active material can be solid (ruby crystal), liquid or gas ( HeNe, CO2 etc.). Types of Lasers • Crystal lasers, also known as “solid state” lasers. • Liquid lasers • Gas lasers • Semiconductor lasers, sometimes called diode lasers. Types of Lasers 1 • Crystal lasers, also known as “solid state” lasers, use a rod of crystal material positioned between a pair of mirrors. Flash lamps are the most common power source. • The Nd:YAG laser emits infrared light at 1.064 nm. The Ruby Laser • Maiman’s first laser consisted of a rod of synthetic ruby with reflective coatings at each end that served as mirrors. • A high power flash lamp pumped energy into the rod. • When fired, the device generated a pulsed red laser beam that was powerful enough to pierce a razor blade. • Since then, hundreds of exotic crystal types have been successfully used in lasers The Ruby Laser Invented in 1960 by Ted Maiman at Hughes Research Labs, it was the first laser. Ruby is a three-level system, so you have to hit it hard. Types of Lasers 2 • Liquid lasers (Dye Lasers) use fluorescent dyes to produce laser beams of many different colors. The dye is flowed through a glass tube with laser mirrors positioned on each end. • Dye lasers can be tuned to produce almost any color of light by changing the type and concentration of the dye used, and by using special mirror arrangements designed to allow only a specific wavelength of light to circulate within the laser.. • Dye lasers find widespread use in scientific research and in medicine where different types of living tissue respond to different wavelengths of laser light. Dyes cover the visible, near-IR, and near-UV ranges. Types of Lasers 3 Gas lasers are physically different than solid or liquid lasers. They consist of a laser tube made of quartz, glass, ceramic, or in special cases, even metals. At each end of the tube are the laser mirrors, and the tube is also fitted with electrodes for applying a high voltage to the gas. Types of Lasers 3 Gas lasers Gas laser tubes are electrically similar to common fluorescent lights or neon signs. When high voltage is applied, the gas in the tube ionizes and produces a glowing light. , the perfectly aligned mirrors gather and concentrate a specific wavelength of light produced by the gas into an intense laser beam. Gas lasers produce extremely high quality laser beams, many of which are of very high power, suitable for cutting, welding and even some military applications. The HeliumNeon Laser Energetic electrons in a glow discharge collide with and excite He atoms, which then collide with and transfer the excitation to Ne atoms, an ideal 4-level system. Carbon Dioxide Laser The CO2 laser operates analogously. N2 is pumped, transferring the energy to CO2. Types of Lasers 4 Semiconductor lasers, sometimes called diode lasers, are pn junctions. Current is the pump source. Today, the most widespread lasers are of the semiconductor type. These lasers use semiconductor materials similar to those found in transistors, integrated circuit chips and light emitting diodes that are commonplace in today’s electronic equipment. Applications: laser printers or CD players. Types of Lasers 4 • Semiconductor lasers are very small, often the size of a grain of salt, so they are mounted in larger packages for protection and efficient cooling. In most cases they do not use separate mirrors as larger lasers do. Rather, the ends of the semiconductor material are cut so that the end faces are perfectly parallel, and then coated to enhance reflectivity. • Unlike gas lasers, they do not need dangerous high voltages to operate. ..Some Laser Applications.. Now that we have seen how lasers work and some of the basic types, lets look at some interesting laser applications… Lasers have affected almost every aspect of our lives, and yet many of us do not even realize it. much more intense, directionality, coherency, high monochromatic , and ability to reach extremely high powers are all properties which allow for wide range of applications.. Applications.. http://www.repairfaq.org/sam/laserlia.htm • Scientific – – – – – – Spectroscopy Material processing Photochemistry Laser cooling Nuclear fusion Microscopy • Industrial and commercial • Images • Military – Defensive countermeasures – Targeting • Ranging • Target designator – Firearms • Laser sight • Eye-targeted lasers • Medical Universal Product Code, or UPC Communications Communications Lasers and fiber optics will soon replace most wires A single strand of glass optical fiber can carry more than half a million telephone conversations, or thousands of computer connections and TV channels. Thinner than a human hair, fiber optics promised unlimited expansion for the future. Fiber optics has been the driving force in the enormous growth of the internet, arguably the single most influential social and technological development of the 20th century… a development that was made possible by the semiconductor laser. “free space” optics Some everyday applications of diode: The common laser printer Laser Printer CD and DVD Players and writers shorter wavelengths can be focused to smaller spots than longer wavelengths A CD burner The smaller the spot size, the more pits can be stored and read from a CD or DVD Laser measurement and quality control Contractors use laser leveling equipment Mapping laser scan data collected during construction onto 3D design model of the building. Surveying, mining and tunneling applications • Because lasers generate beams that are perfectly straight, they can ensure a tunnel or mine shaft remains straight during boring. • The English Channel tunnel relied heavily on laser alignment during its construction. Because separate tunnels were started from both the English and French sides of the channel, it was imperative that accurate alignments be maintained throughout the digging if they were to meet in the middle of the channel. Laser welding and.. Cutting Laser are an excellent choice for fine cutting of a wide variety of metals, ceramics and silicon materials. Near-IR wavelengths are commonly used. Material processing Laser cutting, laser welding, laser brazing, laser bending, laser engraving or marking, laser cleaning, weapons etc. lasers have found application in a very wide range of high precision micromachining applications including sintering, ablation, fine pitch soldering, trimming, direct metal deposition and many more. Using mid-IR laser light to shoot down missiles Wavelength = 3.6 to 4.2 mm The Tactical High Energy Laser uses a high-energy, deuterium fluoride chemical laser to shoot down short range unguided (ballistic flying) rockets. Spectroscopy Monochromaticity, makes the laser a very useful source for spectroscopy. Many spectroscopic techniques based on lasers can be used to make extremely sensitive detectors of various molecules, able to measure molecular concentrations in the parts-per-trillion (ppt) level. The high intensity of light that can be achieved in a small, well collimated beam can also be used to induce a nonlinear optical effect in a sample, which makes techniques such as Raman spectroscopy possible. Due to the high power densities achievable by lasers, beam-induced atomic emission is possible: this technique is termed Laser induced breakdown spectroscopy (LIBS). Laser Technology Could Instantly Identify Environment Hazards New research indicates that a novel laser technique may provide tremendous assistance in strengthening homeland security. Laser breakdown spectroscopy (LIBS) has the power to instantly detect and identify a wide variety of target materials, including chemical substances in environment as well as explosives and biological agents. Laser and Photonics Solutions for Environmental Sensing and Spectroscopy Laser Induced Breakdown Spectroscopy In LIBS, a short laser pulse is focused on a sample. Laser energy heats, vaporizes, atomizes and ionizes sample material generating small area of plasma. Excited atoms and ions in plasma emit secondary light which is collected, spectrally resolved by spectrophotometer and analyzed by light detector. Each chemical element has a unique “spectral signature” which can be discriminated from the obtained spectra and therefore the multielemental composition of the sample can be determined. Photolithography • Photolithography (also called optical lithography) is a process used in microfabrication to selectively remove parts of a thin film (or the bulk of a substrate). • It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical (photoresist, or simply "resist") on the substrate. A series of chemical treatments then engraves the exposure pattern into the material underneath the photoresist. shorter wavelengths can be focused to smaller spots than longer wavelengths. Extreme Ultraviolet Sources for Lithography Tomorrow’s Lithography will use EUV sources Year 2010 Wavelength λ=13 nm (EUV) Completely new optics for lithography Use mirrors instead of lenses 1.0 0.8 Mo-Si multilayer mirror Reflectivity 68% at 13.5nm 0.6 0.4 0.2 0.0 12.5 13.0 13.5 14.0 Wavelength (nm) 14.5 Laser Produced Plasmas We proposed mass-limited droplet technology many years ago Laser Produced Plasmas Moving from Xe to Tin moves the UTA to 13.5 nm Moreover, instead of just one ion species participating in this UTA, many ions species emit at 13 – 14 nm Gerry O’Sullivan, Physics Department, University College Dublin 3 rd EUVL Symposium, Miyazaki, 2nd-4th November 2004 In Medicine!! Laser Light Show Laser safety As we have seen, lasers are powerful and highly versatile tools, but just like working with any other tool, one must keep safety foremost in mind. Lasers can pose a number of hazards depending on the wavelength and power levels involved. Laser safety • The semiconductor lasers used in communications systems can produce power levels that can cause eye damage, and that damage may not be immediately noticed. • Special protective glasses are available for every laser wavelength in use today, and must be worn when working around lasers. • The dangers of high power lasers include eye damage by beam energy reflected from smooth surfaces as well as the possibility of burns to clothing and skin. • Eximer lasers that produce ultraviolet beams can trigger skin cancers if the beam is allowed to reach unprotected flesh. • High power lasers can also start fires many meters away from the laser if the beam path is not completely enclosed. Because of these potential hazards, all countries now have stringent safety codes that must be followed when working with lasers. http://www.safety.vanderbilt.edu/safety_links/laser.htm So… Take care Thank you