What is a Laser?

A laser (which is an acronym for Light Amplification by Stimulated Emission of Radiation) is a device that sends out a single wavelength, narrow beam of light with a help of a process known as stimulated emission as shown in Figure 1. In a laser, a special substance called a gain medium gets excited by either an electric current or another laser. This activation causes the atoms in the substance to emit light waves that are all coherent, have the same polarization state, and are in phase with each other. The light bounces back and forth between mirrors on both sides of a device. This amplifies the light and produces a highly focused beam of photons. We can use this kind of light for things like cutting, welding, and measuring far-away distances. The devices are also used in the field of medicine, science, engineering, and research.

Basic working of a laser and how lasers are used for cutting
Figure 1: Basic working of a laser and how they are used for cutting.

A laser uses a gain material like a solid, liquid, or gas that has tiny particles (atoms or molecules) which can be excited to produce light. This excitation can come in different forms such as by electricity, another light source, or raising the temperature of the gain material. When these atoms and molecules in the gain material return to their original state from the excited state, they give off photons. Depending upon the energy released, the wavelength of the photons can be calculated using the formula mentioned below.



E is the energy in joules,

h is Planck’s constant,

f is the frequency in hertz (Hz),

v is the speed of light in m/s, and

lambda is wavelength in m.

In a laser, the light that comes out is not like the light that comes out of a regular light bulb because it all travels in phase and is organized. Instead, they all go in the same direction and phase, creating a strong and directed beam of light. This happens when you put something called a gain medium in between two mirrors. One of the mirrors lets some light through, but not all of it. When atoms or molecules get excited, they release photons. These photons bounce between two mirrors, making the light stronger and more focused. Then the light comes out through a see-through mirror.

The type of laser beam (wavelength and polarization) depends on the material it comes from and the mirrors it bounces off of. They can produce light of different colors by using certain materials and mirror coatings. They can make light that is invisible to our eyes, like infrared or ultraviolet, or colors that we can see, like purple. These devices can do many things like cutting and joining things in factories, helping doctors during operations, and being very accurate in science and engineering in order to take measurements.

Lasers are extremely special for the advancement of the human race because they have different properties that can be helpful in many different jobs. For instance, they can concentrate on tiny areas, making it possible to cut or drill with great accuracy. They can make really bright light that helps us understand how things behave when they are really hot or under a lot of pressure. These devices can send messages far away through thin cables because they have all their particles moving together and at the same speed.

Applications of Lasers

These devices can find their application for many different things in various regimes. Some of the most usual ways people use them are given below.

1. Manufacturing: These devices help make many things by cutting, welding, drilling, or marking different materials such as metal, plastic, and wood. Laser cutting and welding are very helpful in making things like cars and planes where accuracy is very important.

2. Medical: Doctors use lasers for different things like surgeries, skin treatments, eye exams, and dental work. During surgeries, doctors use them to make accurate and clean cuts that result in less bleeding and faster healing.

3. Communication: Lasers are used for sending information through light in long-distance communication systems. These things are used to talk to people far away, go on the internet, and send information.

4. Research: Lasers are powerful tools that scientists use for very accurate tests and research in different areas of science. They are really good at measuring distances very accurately, studying how atoms and molecules behave, and making really hot and pressurized conditions.

5. Entertainment: They are used in concerts, shows, and theme parks to create cool special effects like laser light shows, 3D images, and holograms. They are also used in games such as laser tag.

6. Defense and security: These devices are used by soldiers for finding how far away things are, aiming at things and help them go in the right direction. Lasers are also used by normal people for looking at things to make sure they’re safe and for scanning barcodes.

7. Environmental: Lasers are helpful in checking the environment. They can find things like dirty air and greenhouse gases. They can also study the earth’s land and water using LIDAR systems.

8. Spectroscopy: Scientists use lasers to learn how light and matter interact in a process called spectroscopy. Using lasers to study substances can tell us what they are made of, help us understand what materials are like, and examine the world around us.

9. Scientific research: Scientists use lasers a lot in their research, particularly in the areas of physics, chemistry, and biology. Lasers can move around small things like particles, and also make things very hot and squished for testing.

10. Printing: These devices are special tools that help with printing. They can be found in machines like printers, copiers, and engravers. Laser printing is a fast and good way to print things in businesses.

11. Astronomy: Scientists use lasers in space exploration to fix the problems caused by Earth’s atmosphere. Adaptive optics systems use them to make a fake star in the sky. This helps measure the changes in the air and adjust the telescope’s lenses.

12. Metrology: These devices are a tool used to make very accurate measurements of things like how far away something is, what angle it’s at, and where it’s located. Laser interferometry is a fancy way to use them to accurately measure how much two things move compared to each other.

13. Military: Lasers are shiny things that the army uses to help aim and guide their weapons, and also to protect themselves from missiles and hurt people.

14. Art conservation: Lasers help clean paintings and artworks without harm. They take off dirt and grime but don’t harm the artwork.

15. Hair removal: Cosmetic companies use lasers to remove hair. The light from the device hits the hair roots and stops them from making new hair grow.

16. Agriculture: Lasers help farmers measure how tall their crops are and create maps of how much they produce. They can also help get rid of weeds and make watering plants more effective.

17. Forensics: Lasers are special tools that can help investigators to solve crimes by looking closely at fingerprints, finding tiny clues left behind at a crime scene, and checking if money is real or fake.

18. Archaeology: Lasers help archaeologists make really detailed pictures of old things and buildings. This helps them learn more about history and take better care of places that are important.

19. Automotive: Lasers are used in cars to do things like stick parts together, cut things, and figure out how big things are. The laser detectors can help stop crashes and help drivers control their speed.

20. Energy: Lasers are used in different ways to make energy. One way is called nuclear fusion. In this way, they heat and squeeze fuel to make plasma.

21. Aerospace: Laser beams are helpful in aerospace for various jobs such as checking how the air flows over airplane wings, recognizing air turbulence, and examining materials to see if they can be used in space.

22. Cutting: High-power devices are also used in cutting. Laser cutting is efficient since it can be used for various materials as it can also pass through various materials, depending upon the wavelength.

Focused Applications of Lasers

Laser tag

This is a fun game where people use laser guns and special sensors to pretend that they are in a battle. Players put on protective vests or other equipment that have sensors on them. Then, they use these guns to aim and fire at one another.

Here’s how it works:

1. Laser guns: These guns shoot light rays that we can’t see with our eyes. When a player pulls the trigger of their gun, it releases a beam of special light called infrared light. The gun also shoots out a beam of light that looks like a laser to simulate it.

2. Sensors: Each person playing the game wears a special vest or equipment that has sensors on it. If a player gets hit by a laser, a detector senses it and records that they were hit. The sensor tells the player’s gun to shake or light up when they get hit.

3. Scoring: If a player gets hit, they will lose points. The person who gets the most points wins the game.

You can play laser tag inside or outside in different places. You can play the game with different guns and sensors. The rules and modes of the game may vary depending on where you play. In general, this is a fun and thrilling game that lets you pretend to be in a battle without anyone getting hurt.

Uses in the medical field

Doctors use lasers to do certain things in medicine, like removing fat, commonly known as liposuction, or doing surgery on the eyes, referred to as laser eye surgery. The usage of laser light in these two procedures is given below.


Laser-assisted liposuction (LAL) is a way to remove fat from the body. It uses a laser to turn the fat into liquid before it is taken out of the body as shown in Figure 2 (a). A small tube is put into a specific part of the body in this process. The doctor uses a special tool called optic fiber to melt the fat cells so they can be taken out more easily. The liquid fat is removed from the body using a thin tube. LAL is a gentler way of removing fat than regular liposuction. It uses smaller cuts and causes less bleeding. There are two methods of performing laser liposuction, contact method, and non-contact method. In the contact method, the laser goes in deeper and can melt more fat, but it lacks wide area coverage and therefore, the beam has to be traversed along the intended liposuction area to melt fat. In the non-contact method, the light covers a wider area but does not diffuse deeper into the fatty area.

Applications of Laser, Laser Pointer, Laser Cutter, Laser Liposuction, and Laser Hair Removal
Figure 2: Applications of Laser, (a) Liposuction, (b)Pointer, (c) Cutter, and (d) Hair Removal.

Eye surgery

Doctors use these devices in different eye surgeries like LASIK (laser-assisted in situ keratomileusis), PRK (photorefractive keratectomy), and cataract surgery. The laser is used to change the shape of the cornea in the eye, so people can see better and don’t need to wear glasses or contacts. During cataract surgery, a laser light is used to make a very careful cut in the eye and to break apart and take out the hazy lens. This beam is used to get the eye ready for a new lens to be put in.

These beam from these devices is now used a lot in medicine. This is because they help doctors do surgeries that don’t need big cuts, they help them be more accurate, and they can help patients feel better faster.

Uses in Technology

Lasers are a type of tool that is used in things like laser pointers, printers, and CDs. Here is a basic explanation of how lasers work in different technologies.

1. Pointers: Laser pointers shoot a straight and thin line of light using a special part called a laser diode as shown in Figure 2 (b). A small electronic piece called a diode works when it gets energy from a battery and a device that manages how much electricity goes through it. When electricity goes through the diode, it makes the electrons get excited and they give off light. The light in the laser pointer bounces back and forth between two mirrors in a tiny device called a diode. This makes the light beam stronger and it comes out of the pointer in one direction. Laser pointers are small devices that shoot out a light beam. The light is easy to see, even if you are far away.

2. Printers: Laser printers use a special beam of light to put ink on paper. The printer has a light that shines on a spinning drum with special material on it. The beam makes the drum sticky so that the toner can stick to it. The ink goes on the paper and gets stuck there by heating it up. These printers are machines that can quickly make really good-looking prints. People like to use them in their workplaces and houses.

3. Discs: Laser discs use a special light to get information from them. The disc has small holes and lines that a the light from this device reads. When we shine a light on a disc, it bounces off little bumps and dips that have been made on the disc. This makes a special pattern that we can use to hear or see things, like music or movies. The beam is made very small and shines on the disc with the help of a lens. A special tool makes sure the light emitting device stays in the right place as the disc spins around. In the old days, people used these discs to keep movies and music. But now, people use different ways to store them instead of these discs.

4. Cutter machine: A laser cutter is a tool that uses a strong beam to cut or make designs on things like wood, plastic, metal, paper, and acrylic as shown in Figure 2 (c). The light goes through a lens and is pointed at a piece of material that is usually fixed on a bed that moves around horizontally and vertically. This makes the material hot and turns it into vapor, which makes a small opening or design. This cutter is very good at cutting things very accurately and precisely. This means it can make really detailed designs and cuts that regular cutting tools can’t do as well. Laser cutters are machines that can cut objects for different purposes like making objects, buildings, jewelry, and signs. They can use tools to cut things in special shapes and sizes, write words or symbols on them, and create complicated designs without difficulty. Apart from cutting and carving, these specially designed cutters can also do etching, drilling, and welding. Fancy laser machines can slice through thick stuff or build 3D things by cutting and stacking many sheets of the material.

This high intensity beam is a useful tool in many fields, like making things or talking with people far away. They help us work precisely and quickly.

Hair removal (cosmetic procedure)

Laser hair removal is when a special light is used to get rid of hair that you don’t want on different parts of your body as shown in Figure 2 (d). To start the process, a specialist will talk to the patient about their skin and hair and check their medical history for any concerns. This helps them understand any risks and make a plan.

Before the hair removal treatment, the patient is told not to get a tan and to shave the part of the body that will be treated. The doctor might put medication on your skin to make it numb and lessen any pain while they work.

During the treatment, a person uses a special light beam that shines on specific hairs to remove them. The light is taken in by the color in our hair roots (melanin), which makes the hair get hot and break down. High temperatures can harm the hair follicle and prevent new hair from growing.

After the hair removal treatment, the patient might feel some pain, swelling, or redness in the area that was treated. The doctor or therapist can put on a cold cream or gel to make the skin feel better. After the treatment, the person should stay away from sunlight and not take hot baths or showers for a little while to prevent making the irritation worse.

To remove hair , it usually takes more than one visit for the best outcome. Hair grows in cycles, and lasers work best when the hair is in the active growth phase. Patients usually need 4-6 hair reduction treatments that are spread out by a few weeks to get long-lasting results. Getting hair removal is a good and safe way to get rid of hair you don’t want on your body. It’s important to pick a good doctor and take care of yourself after getting treatment so you get the best results and don’t have any problems.


[1]. Wikipedia

Further Readings

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