LASER

Arpit Rathi 12D070027

Gaurav Patil 11D070021

Contents

• Why the interest in lasers

• Unique properties of lasers

• How such properties come about

• Operation of a simple laser

• Other issues/ problems

• Types of lasers

• Future

References: www.ocw.mit.edu, www.wikipedia.com, www.ieee.org, etc. 2

Why the interest in lasers

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Examples of laser applications

• Bar code readers

• Compact discs

• Computer printers

• Color copiers

• Laser “shows”

• Holography – 3D

• Position & motion control

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Examples of laser applications

• Sensors

• Fiberoptic communication

• Materials processing

• Non-destructive testing

• Spectroscopic measurements

• Chemical processing

• Military systems

• Medical procedures

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Where lasers are used

• Home

• Factory

• Hospital

• Laboratory

• Military

• Space

• Ocean

• theater

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Unique properties of lasers

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Properties of lasers

• High monochromaticity / Narrow spectral width

• High temporal coherence

• Highly collimated beam / Diffraction limited collimation

• Very small focussed spot / Diffraction limited focussing

• High spatial coherence

• High Power

• Wide tuning range

• Very short pulse width

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High monochromaticity

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Typical applications of narrow spectral width

• Communication

• Spectroscopy

• Interferometry

• Holography

• sensors

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High temporal coherence

• τ very long

• ∆f ~ 1/ τ very small

• Can predict amplitude & phase at any time, at a given position

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Highly collimated beam

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Typical applications of high degree of

collimation

• Alignment

• Bar code readers

• Communication

• Radar

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Diffraction limited focusing

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Typical applications of small focussed spot

• Compact discs

• Laser printers

• Materials processing

• Medical surgery

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High spatial coherence

• Wave is well behaved in space

• Can predict amplitude and phase at any position at a given time

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High power

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Typical applications of high power

• Materials processing

• Fusion

• Military

• Nonlinear optics

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Wide tuning range

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Typical applications of wide tuning range

• Interaction with specific atoms & molecules

• Spectroscopy

• Propagation

• Medical

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Very short pulse width

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Typical applications of very short pulses

• Fast phenomena

• Optical computers

• High resolution radar

• Imaging

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How such properties come about

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To make an oscillator we need

• A resonator (low loss) → fₒ

• A measure to overcome the loss at fₒ

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The laser resonator

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Optical amplifier

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Highly collimated beam

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High power

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Wide tuning range

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Very short pulse width

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Where can we find these frequencies

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Operations of a simple laser

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How does an optical amplifier work

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How to make an optical amplifier

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But how does a laser start ?

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Bandwidth of the amplifier

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Spectrum of laser light

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Optics of laser beams

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Other issues / problems

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Amplifier limitations

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Single frequency selection

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Laser frequency and intensity

variations

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∆f/f = ∆L/L ∆I/I depends on pump alignment etc.

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Transverse modes of a laser

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Types of lasers

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Types of lasers

• Gas

• Liquid

• Solid

• Semiconductor

• Chemical

• Excimer

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Types of lasers

• Gas dynamic

• TEA

• E-beam

• Free electron

• fiber

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Classification according to pumping

mechanism

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Electron-collision pump

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Chemical pump

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Electron current injection pump

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Future

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Future of lasers

• Semiconductor replacing He-Ne lasers

• Semiconductor pumped solid lasers

• Microchip lasers

• Fiberoptic lasers

• Thin film waveguide lasers

• VUV lasers

• X-ray lasers

References: www.ocw.mit.edu, www.wikipedia.com, www.ieee.org, etc. 123

Applications

• Fiberoptic communication

• Materials processing

• Medical procedures

• Data processing

• Sensors

• Fiberoptic sensors

References: www.ocw.mit.edu, www.wikipedia.com, www.ieee.org, etc. 124

Applications

• Distributed sensors

• Precision positioning

• Laser shows

• Computer interconnects

• Optical computers

• High density memories

• Color holography

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Thank You

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