Lecture on Laser Instrumentation

Kalyan Kumar Mistry, CSIR-CMERI, Durgapur

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LASER

L - Light

A - Amplification

S - Stimulated

E - Emission

R - Radiation

Laser beam is �Monochromatic �Coherent�Parallel

Perfect

mirrorEnergy input

PUMPING

Laser

Beam

Partial

mirror

What is LASER?LASER is a device that emits light through a specific mechanism for which the term laser is an acronym.


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The first working laser was demonstrated in May

1960 by Theodore Maiman at Hughes Research

Laboratories.

Presently lasers have become a multi-billion dollar

industry

The most widespread use of lasers is in storage devices such as CD/DVD and optical communication.

History Of LASER


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Common Components of all Lasers

1. Active Medium

Ruby, Nd:YAG, liquid dyes, gas or semiconductor. Active mediums contain atoms whose electrons may be excited to a metastable energy level by an energy source.

2. Excitation Mechanism

Excitation mechanisms pump energy into the active medium by optical, electrical or chemical.

3. High Reflectance Mirror

A mirror which reflects essentially 100% of the laser light.

4. Partially Transmissive Mirror

A mirror which reflects less than 100% of the laser light and transmits the remainder.


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Inversion of the active medium

1. Electron gas discharge� Optical pumping� Electron beam irritation� Chemical reaction

2. Solid-state� Flash lamp� Optical pumping with semiconductor laser

3. Liquid laser� Flash lamp� Optical pumping with another laser

4. Semiconductor laser

5. Injection current


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Incandescent vs. Laser Light

1. Many wavelengths

2. Multidirectional

3. Incoherent

1. Monochromatic

2. Directional

3. Coherent


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Measurement :

� Distance time of light� Velocity (Doppler)� Length (interferometer)� Rotation (gyro)� Alignment (straight Line)� Holography

Optical communication

Material processing: cutting welding, surface finishing

Spectroscopy : chemical, medical, surgery, scanning

Laser fusion : heat compress

Laser Application


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Conditions of producing Laser

�Active laser medium must be transparent.

�The atoms in the medium must attain excited states efficiently.

Let’s consider a system with two energy levels(E1 & E2) :

To produce laser, we have to achieve population inversion i.e.no. of atoms in excited states(N1) > no. of atoms in some lower energy states(N2)

If the group of atoms is in thermal equilibrium, the ratio N2/N1 satisfy the following equation:

E1 : ground state energy

E2 : excited state energy

k : Boltzmann’s constant

T : temperature of the group of atoms


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Atom at lower energy state

Atom at excited state

Photon emitted by

Pumping process

�First, some of atoms under go stimulated.

�the photons emitted rebound between the two ends

� Excited atom emit photons.

�As a result, more and more atoms attain excited state.

� more and more photons are emitted

� Finally, a beam of laser is emitted.


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Types of Laser

� Gas laser(He- Ne Laser, CO2 Laser)

� Liquid laser

� Solid laser(Ruby Laser, NdYag)

� X-ray laser

� Semiconductor laser

� Free electron laser


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Solid-state laser* Diode-pumped solid-state laser

laser diodes emit at wavelengths from 375 nm to 1800 nm, are used in laser printers ,CD/DVD players.

* Fiber laser

* Disk laser

Type and operating principle of Laser

Gas LaserGas lasers using many gases have been built and used for many purposes. Gas laser are one of the oldest types of laser.

•Carbon dioxide lasers•helium-neon laser (HeNe) •Carbon monoxide •Argon-ion lasers


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Scientific Use

1. Spectroscopy

Laser (LADAR) technology has application in geology, seismology, remote sensing and atmospheric physics.

2. Lunar laser ranging (LLR)LLR measures the distancebetween the Earth and the Moon. Lasers on Earth are aimed at retro reflectors and the time delay for the reflected light to return is determined.

Application of LASER for Instrumentation


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3. Photochemistry

4. Laser cooling5. Microscopy

Nuclear fusion World's most powerful and complex arrangements are multiple lasers and optical amplifiers.


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Cosmetic surgeryremoving scars, stretch marks, sunspots, wrinkles, birthmarks.

LASIK (Laser-Assisted in Situ Keratomileusis) A type of refractive laser used in eye surgery for correcting myopia, hyperemia, and astigmatism.

Laser scalpelA laser scalpel is a scalpel for surgery, cutting tissue by the energy of laser light.

PhotobiomodulationPhotobiomodulation known as laser therapy, is a controversial medical and veterinary technique to enhance tissue growth.

LASER in Medical Instrumentation


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� Laser cuttingLaser cutting is a technology that uses a laser to cut materials with a high quality surface finish

� Rangefinder

� LIDAR (Light Detection and Ranging)

is a remote sensing technology that measures the properties of scattered light.

� Laser engraving of printing plates � Laser accelerometer � Optical communication� Laser lighting display

A laser lighting display or laser light show involves the use of laser light to entertain an audience.

Laser in Industrial & commercial Instrumentation


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� Biomedical Instrumentation

Laser induced fluorescence spectroscopy of human tissues for cancer diagnosis

several research is going on towards development and evaluation of laser induced fluorescence

spectroscopy for the diagnosis of cancer

Present Research on Laser Instrumentation


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The laser characterized for malaria diagnosis, diagnosis of neuronal growth cones, 3-D viewing of dividing chloroplasts, microinjection of impermeable dyes into cells.

� Laser micromanipulation of microscopic objectsOptical imaging



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Laser Materials Processing

�Laser Induced Surface Improvement (LISI)

�LISI Process and Applications

�Finite Element Modeling of the LISI Process

�Laser Patterning of Diamond Microelectronics

�Laser Induced Surface Modification of Aluminum Alloys

�Laser Induced Reaction Coatings of Ceramics



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Types of Laser Hazards

1. Eye : Exposure of lasers on eye can cause corneal or retinal burns.

2. Skin : Acute exposure to high levels of optical radiation may cause skin burns.

3. Chemical : Some lasers require hazardous or toxic substances to operate (i.e., chemical dye, Excimer lasers).

4. Electrical : Most lasers utilize high voltages that can be dangerous.

5. Fire : The solvents used in dye lasers are flammable. High voltage pulse or flash lamps may cause ignition.


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Lecture on Laser Instrumentation

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