Maarg Manthan · Topic 8.11

Types and Applications of Lasers

Science & Technology › Physics – Mechanics, Waves and Thermodynamics · Topic 8.11

LASER stands for light amplification by stimulated emission of radiation. A laser makes a narrow, intense beam of light in which all the waves have the same wavelength and move in step, called monochromatic and coherent light. It works by stimulated emission, an idea from Albert Einstein in 1917, in which an excited atom is triggered by a passing photon to emit an identical photon. A population inversion, with more atoms in the excited state than in the ground state, and an optical cavity of mirrors, give amplification. Theodore Maiman built the first working laser, a ruby laser, in 1960. Charles Townes, Nikolay Basov and Aleksandr Prokhorov received the Nobel Prize in 1964 for the principle. Lasers are used in medicine, industry, communication, defence and research.

5 min read · UPSC Prelims · Science & Technology · Physics – Mechanics, Waves and Thermodynamics

At a Glance

Full form Light Amplification by Stimulated Emission of Radiation
First laser Maiman, ruby, 1960
Properties Monochromatic, coherent, directional
Eye surgery Excimer laser (LASIK)
Gravitational waves LIGO uses lasers
Exam link UPSC Prelims, Science & Technology: Physics – Mechanics, Waves and Thermodynamics

Where Does It Fit?

This is the last topic of the macro on physics. It joins light, energy and quantum ideas into a technology with wide uses, and the next macro moves to modern physics and the universe. Previous topic: Applications of Superconductors. Next topic: Theories and Laws of Physics, Including the Theory of Relativity.

What Are the Types of Lasers?

Type	Features and uses
Ruby laser	Solid-state, red light, pulsed. The first laser. Used in tattoo removal and holography
Helium-neon laser	Gas laser with red beam. Barcode scanners, alignment and teaching labs
Carbon dioxide laser	Gas laser in the infrared with high power. Cutting and welding metals, and surgery as a bloodless knife
Nd:YAG laser	Solid-state, infrared. Industry, surgery, range finding and military use
Semiconductor (diode) laser	Small and cheap. Laser pointers, CD and DVD players, printers and optical fibre communication
Excimer laser	Ultraviolet pulses that remove thin layers of tissue. Used in LASIK eye surgery
Fibre laser	Light amplified in doped optical fibre. Precise industrial cutting and high-power uses

How Does a Laser Work and Why Is the Light Special?

Stimulated emission: a photon passing an excited atom causes the atom to emit a second photon with the same wavelength, direction and phase.
Population inversion: energy is pumped into the medium, by light or electrical discharge, so that more atoms are excited than not.
Optical cavity: mirrors at the ends make light pass many times through the medium, so that it builds up, and one mirror is partly transparent to let out the beam.
Monochromatic: a single wavelength, unlike white light.
Coherent: waves in phase, which gives sharp interference patterns and a very narrow beam.
Directional and intense: the beam spreads very little, so it can be focused to a tiny spot of very high energy density.

What Else Should You Remember?

Medicine: LASIK reshapes the cornea to correct vision, lasers treat kidney stones, remove tumours, seal blood vessels and clear tattoos. They are also used in dentistry and skin treatment, as in Light and Optics.
Industry: laser cutting, welding, engraving and 3D printing of metals give precise work on materials.
Communication: diode lasers send signals along optical fibres at high speed, as in ionosphere Space…">Electromagnetic Wave Behaviour.
Science: LIGO uses laser beams in 4-kilometre arms to detect gravitational waves, as in Gravitational Waves, and laser cooling of atoms led to Bose-Einstein condensates.
Defence: laser range finders, target designators, guided weapons and directed energy weapons. India’s DRDO has tested a laser-based directed energy weapon system, according to reports in 2025.
Space and Chandrayaan: laser-induced breakdown spectroscopy was used on the Chandrayaan-3 rover to study the elements in lunar soil.
Everyday uses: barcode scanners, laser printers, pointers and optical drives.
Safety: lasers can damage the eyes and skin, so they are graded in classes and users wear protective glasses.
Nobel Prize 2018: Arthur Ashkin, Gerard Mourou and Donna Strickland won it for optical tweezers and chirped pulse amplification, which gives extremely short high-power laser pulses.
Coherent light: coherent light is the reason a laser beam can travel long distances with little spreading, as seen in range finders and in laser reflectors left on the Moon.
Semiconductor laser: a semiconductor laser is a tiny diode that is pumped by electric current, and it is the most common type, found in phones, printers and optical drives.

Why Does It Matter for the Exam?

Principle questions: what stimulated emission and population inversion mean.
Properties questions: why laser light is coherent and monochromatic.
Application questions: which laser is used for eye surgery, communication or cutting.
Defence link: directed energy weapons and laser guidance.
Common errors: saying that a laser creates light from nothing or that it is ordinary light made bright.

As an analytical point, a laser is light organised in wavelength, phase and direction. This order is what makes it useful from the operating theatre to the observatory.

Why Is This Topic Important?

Facts Full form and first laser asked
Properties Coherence
Use Medicine and defence

What Came Next?

The next macro covers modern physics and astrophysics. Next topic: Theories and Laws of Physics, Including the Theory of Relativity.

Key People and Terms

Stimulated emission Photon triggers identical photon
Population inversion More excited than ground-state atoms
Coherent Waves in phase
Monochromatic Single wavelength
Optical cavity Mirrors around the medium
LASIK Laser eye surgery

Exam Corner

Points to Remember

First laser: Maiman, 1960, ruby.
Stimulated emission: Einstein, 1917.
Excimer laser for LASIK.
CO2 laser for cutting.
Diode laser for fibre communication.

Do Not Confuse With

Laser and ordinary light Coherent versus random phases
Stimulated and spontaneous emission Triggered versus random
Maser and laser Microwave versus light

Memory Hook

Stimulated emission, population inversion, mirrors in a cavity; coherent, mono, narrow beam; ruby sixty, LASIK, fibre and LIGO.

Mains Angle

Questions ask about lasers in medicine, industry and defence. These points add depth.

Principle Stimulated emission
Properties Coherent beam
Uses Many fields

A Question You May Face

An original practice question, not a past paper question.

“Explain the working principle and properties of lasers and discuss their applications in medicine, industry and defence.”

How to Answer

Principle Stimulated emission.
Setup Pump, cavity.
Types Ruby to diode.
Uses Medicine, defence.

GS Relevance

Prelims: principle, properties, types and uses, medical and defence applications. GS Paper 3: science and technology, defence.

Frequently Asked Questions

What does LASER stand for?

LASER stands for light amplification by stimulated emission of radiation. It is a device that makes an intense, narrow beam of light in which all waves have the same wavelength and move in step, and the first working laser was built by Theodore Maiman in 1960 using a ruby crystal.

What is stimulated emission?

Stimulated emission is the process in which an excited atom is struck by a photon of the right energy and releases a second photon that has the same wavelength, direction and phase as the first. Albert Einstein proposed it in 1917, and it is the basis for the amplification of light in lasers.

What is population inversion?

Population inversion is a condition in which more atoms of a material are in an excited energy state than in the lower energy state. It is needed for a laser to work, since only then does stimulated emission dominate over absorption, and it is created by pumping energy into the material with light or electric discharge.

What are the properties of laser light?

Laser light is monochromatic, with a single wavelength, coherent, with all waves in phase, and highly directional, spreading very little over distance. It can also be extremely intense when focused, and these features make it different from light from a bulb, which has many wavelengths and spreads in all directions.

How are lasers used in medicine?

Lasers are used in LASIK surgery to reshape the cornea and correct vision, to treat kidney stones, remove tumours, seal bleeding vessels and treat skin conditions, and in dentistry. Their narrow, controlled beams cut or heat tissue with great precision and cause little damage to nearby areas.

PYQ Practice — Statement Analysis

1 The first laser was built by Theodore Maiman in 1960.

True

It was a ruby laser.

2 Laser light contains many different wavelengths.

False

It is monochromatic.

3 Excimer lasers are used in LASIK eye surgery.