WHAT IS LASER AND HOW DOES IT WORK?

As we read in the article about everything about light, the nature of ordinary light and laser light is the same, and both consist of electromagnetic waves that contain photon packets of different wavelengths, which causes the difference in the radiation of the two.

Lamp Amplification by Stimulated Emission of Radiation

 

What does the word LASER mean?

In order to understand the use of laser and how it S produced, we must first know its meaning: LASER is the abbreviation of the following words:

Light Amplification by Stimulated Emission of Radiation

We will discuss it more!

How does the laser work?

A laser is a device that emits light as a narrow beam with a specific wavelength. By irradiating a photon to a particle, another photon releases, and these two photons are of the same frequency.

Imagine hitting the surface of the water with the same waves, the more and faster the number of waves, the stronger the wave will produced. As a result, the laser light starts from a weak beam, and this beam strengthened by the back and forth of the photons.

What is inductive emission?

Consider a red light bulb. What kind of photons does this lamp emit? Photons with the wavelength of red light, in which direction is this radiation emitted. In all directions.

 

Now, if we make all these monochromatic photons to emit in exactly the same direction, we have made a red laser. Laser emits lights with the same wavelength; it phase and in a specific direction. We do this in the induction laser. Albert Einstein first proposed induced emission in 1917.

If we have an electron with a low energy level, it can go to higher energy levels by absorbing energy and become so-called excited. If a photon hits the atom, the electron can take the photon’s energy and go to a higher energy level. We call this phenomenon-stimulated absorption.

Now, if the atom receives another photon in the excited state, the probability that the electron will go to a higher energy level is low, and the atom will release the new photon and the previous photon it took together and return to the energy base state. That is, it releases two photons with equal energy. This process called inductive emission. Because an external agent and a photon stimulated the atom was emitted. In induced emission, an incoming photon stimulates the excited electron to change its energy level and go to a lower level.

 

Spontaneous release

If the atom returns from the excited state to the ground state, it releases a photon in an unknown direction. This state called spontaneous emission, because the external agent did not force the atom to emit, and the electron naturally prefers to go to a lower energy state.

How many parts does the laser consist of?

A normal laser consists of two main parts:

1. Blower: It creates the necessary energy to create photons in the laser.
2. Amplifying medium: It is an important part of laser, which is a light source, in this part, photons are excited and it can be gas, liquid or solid and it determines the wavelength of laser radiation.

What is the application of laser in different industries?

Medical application

 

Lasers use for many medical purposes, and because the beam is so small and precise, it allows doctors to safely treat the target tissue without harming the surrounding areas.

Treatment of varicose veins , improvement of vision during corneal and LASIK surgery and eye LASIK operation , repair of detached retina , removal of prostate , kidney stones , tumor removal and skin surgery are among the cases used in medicine.

Treatment of skin spots, types of rejuvenation and removal of unwanted hair are other uses.

Dental application

 

10 applications of laser in dentistry are:

• Facilitating orthodontic movements
• Frenectomy: to close the spaces between the frenum of the tooth for orderly laminate and composite
• Teeth bleaching
• Improving gum color (removing black gums)
• Improvement of gum hyperplasia with gum lift or gingivectomy: The act of removing excess gum tissue called gingivectomy, gum lift or crown lengthening in dental terms.
• The term gummy smile with laser
• Reducing the recovery period after implant surgery
• Eliminating gum soft tissue lesions
• Reduce or eliminate bacterial accumulations
• They exposed or revealed hidden and semi-hidden teeth

Application in industry

Laser cutting: from cutting light materials such as fabric to hard metals and precious stones such as diamonds, you can cut with a laser.

Laser engraving: The laser beam physically removes the surface of the material and creates a cavity in a process. The laser generates a lot of heat during engraving, which vaporizes the material. Laser engraving is very fast because the material vaporizes with each stroke.

Laser drilling: drilling or laser drilling is creating a depression or hole on a material. In this method, the desired material is steamed and melted layer by layer until the drilling hole created. This process will vary depending on the thickness of the material, the number of holes to make and the size of these holes. The whole process of laser drilling achieved without any direct contact with the surface of the material.

Application in military weapons

 

 

Laser range finder: Laser range finder based on the same principles that used in normal radars. A short laser pulse (typically 10 to 20 nanoseconds in duration) aimed at the target and a suitable optical receiver that includes an optical detector records the backscattered pulse.

Marking: Illuminates the target. Due to the intense brightness of the light, the target will appear as a bright spot when viewed through a narrow strip optical filter. The weapon, which may be a bomb, missile or other explosive weapon, is equipped with a suitable sensing system. In its simplest form, this sensor can be a lens that transmits the image of the target to a quarter-circle optical detector that controls the weapon’s motion control system and can therefore direct it to the target. In this way, it is possible to target with great accuracy.

Energy Directed Weapons: Considerable effort is now being devoted in both the United States and Russia to the development of lasers that can be used as energy directed weapons. In the case of strong laser systems with a power of probably around megawatts (at least for a few tens of seconds), an optical system directs the laser beam to the target (aircraft-satellite or missile) to cause irreparable damage to its sensing devices. On the other hand, to cause such damage to its surface that eventually flying objects will damaged. Ground-based laser systems do not seem very practical now due to the well-known effect of thermal bloom that occurs in the atmosphere.

Application of laser in space achievements

 

Since years ago, NASA scientists tried to use lasers on the moon in order to obtain changes in the atmosphere and on the moon using lasers.

Finally, in 2020, with their French colleagues, they managed to receive the first reflection. They did this using a laser the size of a storybook page, which is 350.000 km from the Earth. They used the mission. This rover has been in operation since 2009. One of the reasons scientists used this rover was that it could be kept on the surface of the moon for 50 years as a new target.

Another fact that revealed during this period was that the distance between the moon and the earth increased by 3.8 cm. The reason for this is the attractive interactions of these two. ُ

There are 5 reflective panels on the lunar surface that placed on the lunar surface by Apollo 11 and 14. Each of them consists of 100 mirrors. The advantage of using these panels is that they can return the light from any angle to the same direction. The laser light that is emitted takes about 2.5 seconds to return to the ground. The new system not only offers higher data transfer rates, but also optimizes the size, weight and power of missions, Trudy Cortes, director of NASA’s Space Technology Mission Directorate, said in a teleconference. Compared to current technologies, this technology will be smaller, smaller, lighter, and less energy consuming.

The largest laser in the world

 

The largest laser in the world, which called Hercules at the University of Michigan, currently emits a beam with a power of 300 terawatts, but by replacing certain old components, its power can increased to 1000 terawatts. With this power, the laser can make progress in astrophysics research. And make medical X-rays more accurate, faster and cheaper.

The Hercules laser, which started its operation in 2007, has the Guinness record for high-intensity focused laser by creating a focused laser beam with an intensity of 20 sextillion watts (10 to the power of 21) per square centimeter.

The world’s largest handheld laser

 

“Krypton” laser considered one of the most powerful hand-held lasers, which has a range of 136 km. It is powerful enough to set a piece of paper on fire from one side of the room to the other side of the room, or other objects. Which are located outside the earth’s atmosphere.

Looking directly at this laser, which introduced in the Guinness Book of Records as the brightest handheld laser in the world, can be very dangerous because the shine of this laser beam has the effect of a sun eight thousand times brighter than the normal sun on the human eye. . Therefore, safety glasses used when using this laser.

The smallest laser in the world

 

The smallest laser in the world is made of a sphere with a diameter of 44 nm. Lasers can used as a light source in imaging with near-field light microscopes to reveal details beyond the power of standard light microscopes. This device can work ten times faster than microelectronic chips. Solid materials such as ruby, etherium, neodymium, garnet and aluminum use for its mechanism.
American physicist and electrical engineer who succeeded in making the first solid state laser in 1960 at the Hughes Company in Los Angeles.

 

 

Types of solid lasers:

YAG laser

Currently, the most practical solid-state laser used for processing and machining materials is 1% ion. In medicine, it used to treat eye diseases or eye surgeries.

Laser (ER)

 

ER lasers are important because they have two specific wavelengths, but they are not as remarkable in terms of output energy as YAG. They use to treat skin problems and deep spots, which are usually painful and use with local anesthesia.

Gas laser

It consists of a mixture of helium and neon or argon, krypton, xenon, nitrogen and carbon dioxide. It is a type of laser which electric current is discharged to produce light in a gaseous medium.

 

Ali Javan

 

The inventor of the gas laser is a person named Ali Javan, an Iranian scientist who the first person made this type of laser with the help of neon and helium gas. This device registered in 1961.

Neutral atomic lasers

The most common lasers are gas and the gas used in them is helium and neon. This type of laser used in physics labs and other research cases and has a very reasonable price.

Ion laser

The function of ion lasers is that in ion lasers, the ionized atomic energy levels expand and ionize the neutral atom with the first collision.

Molecular laser

The performance of molecular lasers is also such that the transition between molecular energy levels used as the driving force of the laser.

Excimer laser

Excimer lasers, meaning excited dimer, actually use diatomic molecules that are stable in the excited state and unstable in the ground state.

Co2 laser

Carbon dioxide gas laser also used in industries for cutting and welding.

 

Color lasers are a type of lasers that use *organic materials* in its structure as the active laser medium, which is usually in liquid form. This color is made of a carbon-based material that is often fluorescent, after that with the compatible solvent combined and allows the molecules to spread evenly throughout the environment. The dye solution is circulating at a high speed, which prevents the degradation of the dye or its absorption.

What is organic matter?

Organic matter is a substance of organic compounds that formed from the remains of dead organisms from the category of plants and animals and waste materials and their discards in the environment. Organic matter or organic matter refers to a large group of carbon-based compounds that exist in different environments such as water and soil environments or that made in laboratories with the help of synthesis methods. In another definition, organic matter refers to materials obtained from living organisms such as plants and animals and their remains. In addition, organic matter is not limited to living organisms, but organic molecules can produced by chemical reactions in which there are no remains of living organisms. Cellulose, protein, lignin, lipid and carbohydrate can mentioned among the important organic substances. Organic matter plays a very important role in the food cycle of the environment and the remaining water on the surface of plants.

This type of laser mostly used in the field of medicine to improve skin spots, or even out the skin, and to remove unwanted hair. They also used to treat port wine stains and other blood vessel disorders, scars and kidney stones. They can be compatible with various inks for tattoo removal as well as a number of other applications.

They are the makers of the first liquid or color laser that independently discovered this type of laser in 1996.

Semiconductor diode lasers are the best-selling type of laser in the world, and this type of laser as first made in 1962. The purpose of making these types of lasers is to use them in the telecommunications industry, but data storage, CD reading, and use in industrial machines have peaked in recent years.

Their use in medicine is also significant. Today, doctors use this type of laser to analyze blood factors, for example, to measure blood glucose levels without injection.

Robert Noel and General Electric

 

Two groups, one led by Robert and the other for General Electric, started researching the construction of a diode laser, which they finally succeeded in building in 1962. General Electric registered its data earlier and was able to register this invention under its own name.

What are the characteristics of laser beam?

Monotony

Natural light consists of a series of wavelengths ranging from ultraviolet to infrared. Instead, a laser is a single wavelength band of light. This feature called monochrome. Monochrome has the advantage of allowing more flexibility in optical design.

HIGH ORIENTATION

Directivity is the property of maintaining the direction of light when moving in space; high directivity indicates that the direction maintained with high accuracy and low expansion. Natural light is a series of bands of light that spread out in all directions, while laser light is directional, making it easy to design optical systems that prevent light from spreading.

HIGH COHERENCE

Coherence explains how much light interferes with itself, and considering light as a wave, it can said that the more uniform the light beam, the greater its coherence. Because the phase, wavelength and direction of the light of this device do not change, a strong wave can maintained to transmit the rays of this device over a long distance without emission. This means that light can focused into a small area with the lens.

HIGH DENSITY

Because lasers have excellent monochromatic, directivity, and coherence, they can focused into a very small area, resulting in high-density light. By focusing the light of this tool in a very small area, you can increase its intensity (power density) even to obtain enough energy to cut metal. Due to these characteristics, the light of this tool used in many fields of modern machining of materials. The intensity maintained for a long time thanks to the coherence and can directed even more with the help of lenses.

The laser beam engraves the surface of the material, is absorbed and heats the material. This heat generation causes the complete removal or vaporization of the material. It engraves marks or cuts a wide range of materials.