The word LASER stands for light amplification by stimulated emission of radiation. It is a device that is used to produce the light beam concentrated to a fixed point and having a high power output ranging from Milliwatt to watts. The frequency of the laser beam is from 430 Tera Hz to 750 Tera Hz.
Actually, the laser is a device, which is designed to generate light with special and unique characteristics. The laser was developed by Dr. Theodore Maiman in the spring of 1960. He placed a photographic flash lamp next to a cylindrical crystal of pink ruby. The result of this action produced the first laser.
The laser is a powerful full light source and its light is monochromatic, which means that it consists of a single color and not a mixture of colors.
The force which is used to compel the electrons to move from a lower energy level toward a high energy level is known as pump input. This external force may be in the shape of a flash of light OR externally applied voltage OR magnetic force etc.
When the electrons move from the lower energy level to the high energy level due to pump input, they stay at the high energy band for movement. That movement at which the access of electrons is collected in the high band of energy level is known as population inversion.
Classes Of Laser
Safety standards have placed lasers into four classifications according to their potential hazards. These classifications are:
Class - I Lasers
These are those lasers that produce light below a dangerous level.
Class - II Lasers
The class II lasers can damage the human eye only if the eye is deliberately exposed to the beam for a time longer than the normal blinking of the eye. In other words, the brightness of the light would cause a normal eye to blink before injury occurs.
Class - III Lasers
The lasers in this class can produce light of high enough intensity to inure a human eye before the eye can blink.
Class - IV Lasers
All the lasers which are more power full than class III are ports of this class. They are great potential hazards to the eye and the exposed skin. They can produce enough light to burn any combustible materials that their beam strike. Thus they are also considered a fire hazard.
In any laser system, a hazard even more dangerous than the beam itself is the electrical power supply. Voltages in access of 1000 volts are present even in low-power lasers.
A class III laser will not produce any injury under normal use but a potential of up to 5000 volts is present in the power supply which could easily cause serious personal injury. Therefore the laser power supply should always be enclosed in a suitable housing.
Safety Precautions For laser Work
- Do not stare into the laser beam or the reflection of the beam from shining objects. For class III lasers reflection from a flat mirror-type surface is as dangerous as the beam itself. However, the reflection from a diffused surface such as a wall is not considered dangerous.
- Don't point the laser at the eye. To help avoid this always keep the laser below eye level when the laser is turned ON.
- Don't intentionally or unintentionally track vehicles or aircraft with any laser beam.
- Don't leave an operating laser unattended and be sure to disconnect it from its power source, when it is not in use.
- Don't operate the laser with the power supply exposed.
- Never attempt to remove the protective housing from the laser trainer. Any attempt to do this could result in a serious electrical shock.
Uses of laser:
There are so many uses/applications of laser such as:
The 1st uses of the laser were dedicated to military applications. which still constitute a major portion of laser use today. Laser mostly in military applications deals with:
- Laser-guided weapons - Laser designation is used to guide bombs, missiles, shells, and other munitions to their targets with high accuracy.
- Laser rangefinding - Handheld or vehicle-mounted lasers are used to determine the exact distance to targets for targeting and artillery purposes.
- Laser sights - Mounted on firearms to improve aiming accuracy. The laser dot shows exactly where the weapon is aimed.
- Targeting and tracking - Laser systems are used to detect, acquire, track, and engage enemy targets, missiles, etc. Highly accurate.
- Countermeasures - Lasers are used to detect, jam, confuse, or damage enemy sensors, guidance systems, and sights. Defensive laser countermeasures.
- Communications - Lasers are used for high-bandwidth tactical communications that are hard to intercept or jam compared to radio.
- Detection - Laser radar (lidar) and sensing allows the detection and imaging of targets through obscurants like smoke, haze, or camouflage.
- Satellite/missile defense - High-power lasers are researched for intercepting and destroying incoming missiles and satellites.
- Directed energy weapons - From low-power lasers to dazzle or blind, to high-power weapons intended to shoot down drones.
- Optical surveillance - Laser microphones can detect sound by reading vibrations off objects at a distance. Laser tripwires for intruder detection.
Lasers play major roles in precision guidance, rangefinding, targeting, tracking, communications, sensing, countermeasures, and directed energy applications in the military.
- Material processing - Cutting, welding, drilling, marking, engraving, heat treating, and surface treatment of materials like metals, plastics, wood, and composite materials. Very precise.
- Microprocessing - Lasers can do micron-precision manufacturing, machining, and manipulation for electronics, medical devices, MEMS, etc.
- Additive manufacturing - Laser powder bed fusion and directed energy deposition are used in 3D printing of metal parts.
- Inspection and measurement - Laser measurement systems are used for extremely precise dimensional analysis in manufacturing. Holography allows non-destructive testing.
- Communications - Lasers are used for high-bandwidth fiber optic communications for data, audio, and video transmission.
- Barcode scanning - Lasers scan and read barcodes on products for inventory management and supply chains.
Guidance - Laser guidance systems position and guide robots, vehicles, mining, and construction machinery for automation.
- Alignment - Lasers provide visual guide beams for aligning large machine components, civil structures like tunnels, etc.
- Printing - Laser printers and typesetters use lasers to form images on paper and plates for high-resolution printing.
- Surveying - Lasers are used for leveling, alignment, distance, and position measurement in surveying and construction.
- Security - Laser scanners, tripwires, and motion detectors are used extensively for security systems.
On the medical side, the laser has also so many applications such as:
- Surgery - Lasers are used for precise cutting, ablation, vaporization, and coagulation of tissue. Examples include LASIK eye surgery, tumor removal, and vascular and neural procedures.
- Aesthetic treatments - Lasers are used for skin resurfacing, tattoo/hair removal, acne treatment, skin rejuvenation, and other cosmetic procedures.
- Dentistry - Lasers can cut, shape, and drill teeth or perform soft tissue procedures like gum contouring. Used for cavity preparation and cleaning.
- Imaging - Laser scanning systems like OCT provide detailed 3D imaging of the eye and other tissues non-invasively.
- Biostimulation - Low-level laser therapy (LLLT) uses laser light to stimulate cellular function and promote the healing of injuries.
- Endoscopy - Laser flexible waveguides allow minimally invasive diagnosis and surgery inside the body through small openings.
- Cancer treatment - Lasers can destroy tumors through photodynamic therapy or selectively target cancer cells.
- Ophthalmology - In addition to LASIK, lasers treat conditions like diabetic retinopathy, glaucoma, and cataracts.
- Dermatology - Vascular and pigmented lesions, tattoos, scars, and other skin conditions are treated with lasers.
- Diagnostics - Laser spectroscopy is used to analyze blood chemistry, identify bacterial infections, and diagnose disease.
- Wound healing - Lasers help heal stubborn wounds and stimulate the regeneration of nerves, skin, bones, and other tissues.
More applications of lasers are found day by day with the help of scientific research.
Other uses of lasers are
- Nowadays it is widely used in communication in order to achieve high speed and more data transfer rate.
- For quality printing, we take the help of laser technology, and different types of laser printers are designed.
- laser technology is also used for the purpose of reading or writing text graphics etc. one example is the CD ROM drive of the computer.
- laser is also used to measure the distance and speed of the object.
- laser technology is used for manufacturing and etching ICs.
Types of laser:
lasers are designed in different types and shapes. A few types of lasers are explained below.
- Ruby Laser
- Gallium Nearside Laser (Ga As)
- Gallium Phosphate (Ga p)
- Gallium Arsenide Phosphate laser (Ga As p)
- Indium Gallium Arsenide Phosphate
- Aluminum Gallium Arsenide laser (Al Ga As)
The laser speckle makes a reflected laser beam appear to dance.
A low-power reflection of laser light appears to be made up of several dark and light spots that dance about almost as if flakes of glitter had been dropped into the beam. This appearance is known as a laser speckle and results from the coherence of laser light.
Each part of the reflection hit by the light acts as a point source of coherent light. Light from each of these point sources moves away from the point in a circular/spherical direction. If only two of these point sources are present a simple interference pattern results.
However, there are actually an infinite number of point sources in the reflecting spot, each sending out coherent waves interfering with each other. The result is a very complex interference pattern in space.
Now speckles are actually the dark and light spots within this complex interference pattern. As we move these spots also move and dance.
Something General about Laser
We know that lasers can produce very high concentrations of power in relatively small areas. The radiance of even small lasers can exceed that of the sun because the laser beam is so intense. The very bright or high radiance source and the coherent and directional properties of laser light allow the beam to be focused on extremely small spots.
When light energy is directed onto a target, then it is partly absorbed by that target. The observed energy raises the temperature of the target surface at the point of incident. The amount of this temperature increase depends on the concentration of the light energy or irradiance.
Now since the laser beam is brighter than the sun, therefore it greatly increases the temperature of the target upon which it falls.
When the laser beam is directed at human skin, the temperature of the skin will increase in the area struck by the beam. If the temperature becomes high enough then skin will burn. This occurs only when the laser power is very large.
Small lasers such as Health Kit ET-4200 will not cause skin burns. However, if the beam is focused on a very small spot then irradiance at the focal point increases and so burns the skin.
The human eye has a very good Lens system, which focuses incoming light to a very small spot on the back portion of the eye called the retina.
So the low power beams also when focused by the eye’s Lens then high irradiance values may reach and so it burns a spot on the Retina. This burn can result in a blind spot in a person’s field of vision.