Laser and Its Applications

Many scientific, military, medical and commercial laser application have been developed since the invention of the laser in 1958. The coherency, high mono chromaticity, and ability to reach extremely high powers are all properties which allow for the specialized applications. LASER is Light Amplification by Stimulated Emission of Radiation, it is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiations. The first laser was built in 1960 by Theodore H. Maiman at Hughes laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Scawlow. A laser differs from other sources of light in a way that it emits light coherently. Spatial coherence allows a laser to be focused to a tight spot enabling applications such as laser cutting and lithography. Lasers are characterized according to their wavelength in a vacuum. Most “Single wavelength” laser actually produce radiation in several modes having slightly differing frequencies, often not in a single polarization. Although temporal coherence implies mono chromaticity, there are lasers that emit a broad spectrum of light or emit different wavelength of light simultaneously. There are some lasers that are not single spatial mode and consequently have light beams that diverge more than is required by the diffraction limit. Among their many applications, lasers are used in optical disk drives, laser pointers, barcode scanners, fiber optics and skin treatment, cutting and welding materials, military and low enforcement devices for marking targets and measuring range and speed. Some other uses are: 1. Medicine: Bloodless surgery, laser healing, surgical treatment, kidney stone treatment, eye treatment, dentistry. 2. Industry: Cutting, welding, material heat treatment, marking parts, non-contact measurement of parts. 3. Military: Marking targets, guiding munitions, missile defence, electro optical counter measures, alternative to radar, blinding troops. 4. Law Enforcement: Used for latent fingerprint detection in the forensic identification field. 5. Research: Spectroscopy, laser ablation, laser interferometry, laser capture microdissection, fluorescence microscopy, metrology. 6. Commercial: Laser printers, optical discs, barcode scanners, thermometers, laser pointers, holograms, bubblegrams. 7. Laser lighting displays: Laser light shows. 8. Cosmetic skin treatment: Acne treatment, cellulite and striac reduction and hair removal. Different applications need laser with different output powers. Lasers that produce a continuous beam or a series of short pulses can be compared on the basis of their average power. Lasers that produce pulses can also be characterized based on the peak power of each pulse. The peak power of a pulsed laser is many orders of magnitude greater than its average power. The average output power is always less than the power consumed.

Femtosecond lasers have great applications over conventional laser. Femtosecond lasers are very useful for the micromachining of many types of materials. They are equally good for hard as well as soft materials,eg. Metals , ceramics, plastics and biological tissues. Applications of femtosecond lasers are surprisively diverse. By the use of these lasers damage to the surroundings can be minimized to a large extent . they are very useful for ophthalmology , dentistry and gynecology. Other applications include human breath In Ophthalmology, it is possible to use one step technique. Transepithelial surface ablation (TESA) with the help of femosecond lasers. Eye surgeons want to minimize mechanical manipulation of the delicate cornea, surgical duration and dryness of eyes. This has become possible by the use of TESA Procedure. In this procedure there is no need of using scalpel so damage to delicate cornea is minimum. There is one more eye condition treatment for which femtosecond lasers are very useful- cataract surgery. In traditional method for this surgery, damage is more in tissue penetration. Traditional method is associated with temperature rise in aqueous parts of the eye, while femtosecond laser performs incisions with higher pedictibility and reducibility,visual quality increases and in night vision there is no issue, no double vision and no myopic shift or hyperopic shift. So we can conclude that conventional lasers are dominated by thermal processes (burning, coagulation) and acoustic damage while femtosecond lasers are dominated by non-thermal processes (Photodisruption). Collateral damage is more in conventional lasers while collateral damage is very less in femtosecond lasers. In conventional method absorption is within whole illuminated lasers while in femtosecond lasers absorption is focussed. Uncontrolled ablation is common with conventional lasers while predictable ablation is possible if femtosecond laser method is adopted.

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