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PRESENTED BY:

IRADUKUNDA Gilbert PHYSICS TUTOR AT TTC ZAZA

CLASS: Y3 SME A&B

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�LASER�(Light Amplification by Stimulated Emission of Radiation)

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What Is Laser

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Properties Of Laser

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Basic Concept Of Laser

Absorption

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Spontaneous Emission

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Stimulated Emission

The operation of the Laser

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How a Laser Works

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Population Inversion

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Types of Laser

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Applications of laser

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Overview

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What is Laser?

Light Amplification by Stimulated Emission of Radiation

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  • A device produces a coherent beam of optical radiation by stimulating electronic, ionic, or molecular transitions to higher energy levels
  • Mainly used in Single Mode Systems
  • Light Emission range: 5 to 10 degrees
  • Require Higher complex driver circuitry than LEDs
  • Laser action occurs from three main processes: photon absorption, spontaneous emission, and stimulated emission.

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Properties of Laser

  • Monochromatic

Concentrate in a narrow range of wavelengths (one specific colour).

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  • Coherent

All the emitted photons bear a constant phase relationship with each other in both time and phase

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  • Directional

A very tight beam which is very strong and concentrated.

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Basic concepts for a laser

  • Absorption

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  • Spontaneous Emission

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  • Stimulated Emission

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  • Population inversion

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Absorption

  • Energy is absorbed by an atom, the electrons are excited into vacant energy shells.

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Spontaneous Emission

  • The atom decays from level 2 to level 1 through the emission of a photon with the energy hv. It is a completely random process.

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Stimulated Emission

  • Atoms in an upper energy level can be triggered or stimulated in phase by an incoming photon of a specific energy.

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Stimulated Emission

The stimulated photons have unique properties:

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    • In phase with the incident photon

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    • Same wavelength as the incident photon

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    • Travel in same direction as incident photon

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The operation of the Laser

Light: Coherent, polarized

The stimulating and emitted photons have the same:

frequency

phase

direction

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How a Laser Works

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Condition for the laser operation

If n1 > n2

  • radiation is mostly absorbed absorbowane
  • spontaneous radiation dominates.
  • most atoms occupy level E2, weak absorption �
  • stimulated emission prevails

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  • light is amplified

if n2 >> n1 - population inversion

Necessary condition:� population inversion

E1

E2

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Population Inversion

  • A state in which a substance has been energized, or excited to specific energy levels.
  • More atoms or molecules are in a higher excited state.
  • The process of producing a population inversion is called pumping.
  • Examples:

→by lamps of appropriate intensity

→by electrical discharge

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Types of Laser

  • According to the active material:

solid-state, liquid, gas, excimer or semiconductor lasers.

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  • According to the wavelength:

infra-red, visible, ultra-violet (UV) or x-ray lasers.

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Applications of laser

1. Scientific

  • Spectroscopy
  • Lunar laser ranging
  • Photochemistry
  • Laser cooling
  • Nuclear fusion �

2. Military

  • Death ray
  • Defensive applications
  • Strategic defense initiative
  • Laser sight
  • Illuminator
  • Rangefinder
  • Target designator

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Application

3. Medical

Eye surgery

Cosmetic surgery

4. Industry & Commercial

a. Cutting, welding, marking

b. CD player, DVD player

c. Laser printers, laser pointers

d. Photolithography

e. Laser light display

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THANK YOU