Laser and its Applications
Laser and its Applications
A laser (Light Amplification by Stimulated Emission of Radiation) is a device which produces an intense, coherent, directional beam of light by stimulating electronic or molecular transitions to lower energy levels.
- A laser consists of a gain medium, a mechanism to supply energy to it, and something to provide optical feedback. The gain medium is a material with properties that allow it to amplify light by stimulated emission.
- Light of a specific wavelength that passes through the gain medium is amplified (increases in power).
- For the gain medium to amplify light, it needs to be supplied with energy. This process is called pumping.
- The energy is typically supplied as an electrical current, or as light at a different wavelength. Pump light may be provided by a flash lamp or by another laser.
- The most common type of laser uses feedback from an optical cavity—a pair of mirrors on either end of the gain medium. Light bounces back and forth between the mirrors, passing through the gain medium and being amplified each time.
- Typically one of the two mirrors, the output coupler, is partially transparent. Some of the light escapes through this mirror. Depending on the design of the cavity (whether the mirrors are flat or curved), the light coming out of the laser may spread out or form a narrow beam.
- This type of device is sometimes called a laser oscillator in analogy to electronic oscillators, in which an electronic amplifier receives electrical feedback that causes it to produce a signal.
- Most practical lasers contain additional elements that affect properties of the emitted light such as the polarization, the wavelength, and the shape of the beam.
PROPERTIES OF LASER LIGHT
Laser has certain unique properties, namely, high monochromaticity, coherence and directionality, compared to ordinary sources of light, though both are electromagnetic radiations.
- Monochromatic — It means laser light consists of essentially one wavelength, having its origin in stimulated emission from one set of atomic energy levels. This is possible because laser transition, in principle, involves well-defined energy levels. In contrast, ordinary white light is a combination of different wavelengths.
- Directional- laser light is emitted as a narrow beam and in a specific direction. This property is referred to as directionality.
- Coherence – The light from a laser is said to be coherent. This means that the wavelengths of the laser light are in phase. There are two types of coherence – spatial and Correlation between the waves at one place at different times, or along the path of a beam at a single instant, are effectively the same thing, and are called “temporal coherence”. Correlation between different places (but not along the path) is called “spatial coherence”.
APPLICATIONS OF LASERS
Many scientific, military, medical and commercial laser applications have been developed since the invention of the laser in 1958. The coherency, high monochromaticity, and ability to reach extremely high powers are all properties which allow for these specialized applications.
I. SCIENTIFIC APPLICATIONS
In science, lasers are used in many ways, such as, Raman spectroscopy, Laser induced breakdown spectroscopy, Atmospheric remote sensing, Laser based Light Detection And Ranging (LIDAR) technology has application in geology, seismology, remote sensing and atmospheric physics.
Lasers have been used aboard spacecraft such as in the Cassini-Huygens mission.
- Most types of laser are an inherently pure source of light; they emit near-monochromatic light with a very well defined range of wavelengths.
- 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).
- Material Processing
- Laser cutting, laser welding, laser brazing, laser bending, laser engraving or marking, laser cleaning, weapons etc.
- When the material is exposed to laser it produces intense heat, thus the material is heated and melted. Laser and its Applications
- Some laser systems can produce extremely brief pulses of light – as short as picoseconds or femtoseconds (10-12 – 10-15 seconds).
- Such pulses can be used to initiate and analyse chemical reactions, a technique known as photochemistry.
- This method is particularly useful in biochemistry, where it is used to analyse details of protein folding and function.
- Laser Cooling
- A technique that has recent success is laser cooling. This involves atom trapping, a method where a number of atoms are confined in a specially shaped arrangement of electric and magnetic fields.
- Confocal laser scanning microscopy and Two-photon excitation microscopy make use of lasers to obtain blur-free images of thick specimens at various depths.
II. MILITARY APPLICATIONS
Military uses of lasers include applications such as target designation and ranging, defensive countermeasures, communications and directed energy weapons.
- Directly as an Energy Weapon
- Directed energy weapons are being developed, such as Boeing’s Airborne Laser which was constructed inside a Boeing 747. Designated the YAL-1, it is intended to kill short- and intermediate-range ballistic missiles in their boost phase.
- Defensive Countermeasures
- Defensive countermeasure applications can range from compact, low power infrared countermeasures to high power, airborne laser systems.
- IR countermeasure systems use lasers to confuse the seeker heads on heat-seeking anti-aircraft missiles.
- High power boost-phase intercept laser systems use a complex system of lasers to find, track and destroy intercontinental ballistic missiles (ICBM). In this type of system a chemical laser, one in which the laser operation is powered by an energetic chemical reaction, is used as the main weapon beam (see Airborne Laser).
- The Mobile Tactical High-Energy Laser (MTHEL) is another defensive laser system under development; this is envisioned as a field-deployable weapon system able to track incoming artillery projectiles and cruise missiles by radar and destroy them with a powerful deuterium fluoride laser.
- LIDAR (Light detection and Ranging or Laser Imaging Detection and Ranging) is a technology that determines distance of an object/surface using laser pulses.
- It is similar to radar technology but it uses light as against radio-waves used in radar.
- The range of an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal.
- Laser Target Designator
- Another military use of lasers is as a laser target designator. This is a low-power laser pointer used to indicate a target for a precision-guided ammunition, typically launched from an aircraft.
- The guided ammunition adjusts its flight-path to home in to the laser light reflected by the target, enabling a great precision in aiming.
- The laser designator can be shined onto the target by an aircraft or nearby infantry. Lasers used for this purpose are usually infrared lasers, so the enemy cannot easily detect the guiding laser light.
- Laser Sight
- The laser has in most ‘firearms applications been used as a tool to enhance the targeting of other weapon systems.
- For example, a laser sight is a small, usually visible light laser placed on a handgun or a rifle and aligned to emit a beam parallel to the barrel.
- Since a laser beam has low divergence, the laser light appears as a small spot even at long distances; the user places the spot on the desired target and the barrel of the gun is aligned.
III. MEDICAL APPLICATIONS
- Lasers are widely used in Cosmetic surgery (removing tattoos, scars, stretch marks, sunspots, wrinkles, birthmarks, and hairs), eye surgery and refractive surgery, Soft tissue surgery, “No-Touch” removal of tumours, especially of the brain and spinal cord and in dentistry for caries removal, endodontic/periodontic procedures, tooth whitening, and oral surgery.
- Laser surgery has many advantages over conventional surgery. In laser surgery there is virtually no bleeding, far less trauma to the patients and healing is faster.
- Although use of lasers in surgery is widespread in the western countries, its application in India was limited mainly due to the high cost of imported surgical lasers.
- Centre for advanced technology (CAT) therefore decided to develop a surgical laser based on a 60W CO2.
- This surgical laser has an articulated arm with seven elbows to allow the surgeon to guide the laser beam. The laser is designed for Indian conditions and can withstand the extreme ambient.
IV. INDUSTRIAL AND COMMERCIAL APPLICATIONS
- Lasers have great applicability in industry as well. Lasers are used for cutting and preening of metals and other materials, welding, marking, etc. Laser line levels are used in surveying and construction.
- Lasers are also used for guidance for aircraft. Laser scanners are used to read barcodes on consumer goods and to inspect precision components in workshops.
- Diode lasers are used as a light switch in industry, with a laser beam and a receiver which will switch on or off when the beam is interrupted, and because a laser can keep the light intensity over larger distances than a normal light, and is more precise than a normal light it can be used for product detection in automated production.
- In consumer electronics, telecommunications, and data communications, lasers are used as the transmitters in optical communications over optical fibre and free space.
- Hence lasers have wide range of applications but due to limited availability of lasers, their components and cost effectiveness, the activities are still very slow in our country in comparison to other countries. Laser and its Applications