Introduction to Laser Technology
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Questions and Answers

What does LASER stand for?

Light Amplification by Stimulated Emission of Radiation

The MASER amplifies electromagnetic radiation in the visible portion of the electromagnetic spectrum.

False

What is the name of the first laser, which was demonstrated in 1960?

T.H. Maiman

What can be used to amplify and generate electromagnetic radiation in the MASER?

<p>subatomic</p> Signup and view all the answers

Laser light is highly directional.

<p>True</p> Signup and view all the answers

What is the unit of measurement for the wavelength of light?

<p>Å (angstrom)</p> Signup and view all the answers

Which of the following is NOT a property of laser light?

<p>Scattering</p> Signup and view all the answers

The intensity of a laser beam is very high.

<p>True</p> Signup and view all the answers

A laser beam is strictly monochromatic, meaning it only contains a single frequency.

<p>True</p> Signup and view all the answers

The coherence of a laser beam is low.

<p>False</p> Signup and view all the answers

What are the two types of coherence?

<p>Temporal and spatial coherence</p> Signup and view all the answers

The coherence length of a He-Ne laser is about 600 km.

<p>True</p> Signup and view all the answers

Ordinary light spreads in all directions.

<p>True</p> Signup and view all the answers

How is the angular spread of a laser beam related to the diameter of the aperture and the wavelength of the light?

<p>The angular spread is given by the angle Δθ=λ/d</p> Signup and view all the answers

What is the term that describes a condition where there is a large number of atoms in a higher energy state compared to a lower energy state?

<p>Population Inversion</p> Signup and view all the answers

What are the three main components of a laser?

<p>Amplifying medium, pumping method, optical resonator</p> Signup and view all the answers

In normal conditions, the number of atoms in the lower energy state is greater than the number of atoms in the upper excited state.

<p>True</p> Signup and view all the answers

What is the main function of the optical resonator?

<p>To provide optical feedback to the amplifier and to act as a source of laser radiation.</p> Signup and view all the answers

What are the three key phenomena that occur when electromagnetic radiation interacts with the energy levels of atoms?

<p>Stimulated Absorption, Spontaneous Emission, Stimulated Emission</p> Signup and view all the answers

Explain the process of stimulated absorption.

<p>An incoming photon with a frequency corresponding to the energy difference between two energy levels of an atom interacts with an atom in the lower energy level. The energy from the photon is absorbed, and the atom transitions to the higher energy level.</p> Signup and view all the answers

What is the difference between spontaneous emission and stimulated emission?

<p>Spontaneous emission is the emission of a photon by an atom without any external stimulus, While stimulated emission is the emission of a photon by an atom that is induced by an incoming photon.</p> Signup and view all the answers

Laser action can be achieved under thermal equilibrium.

<p>False</p> Signup and view all the answers

What is population inversion?

<p>Population inversion is a state where the majority of atoms are in an excited state rather than in the ground state.</p> Signup and view all the answers

Which of the following is NOT a method for achieving population inversion in a laser?

<p>Mechanical vibration</p> Signup and view all the answers

The most common way to achieve population inversion is through optical pumping.

<p>True</p> Signup and view all the answers

In the electrical discharge method, electrons are accelerated using a magnetic field.

<p>False</p> Signup and view all the answers

What is the role of an active medium in a laser?

<p>The active medium is where the energy is stored and the population inversion is created.</p> Signup and view all the answers

Why is the active centre important during laser operation?

<p>The active centre provides the energy levels that are required for population inversion in the active medium.</p> Signup and view all the answers

A 100% reflecting mirror and a partially reflecting mirror are part of the optical resonator.

<p>True</p> Signup and view all the answers

What is the purpose of an optical resonator?

<p>To create optical feedback, which is essential for amplifying the laser beam and increasing its intensity.</p> Signup and view all the answers

What are the two main categories of solid-state lasers?

<p>3-level lasers and 4-level lasers</p> Signup and view all the answers

What is the advantage of using a 4-level laser over a 3-level laser?

<p>A 4-level laser is more efficient and easier to operate compared to a 3-level laser.</p> Signup and view all the answers

Which type of laser is used widely in fiber optic communications?

<p>Semiconductor laser</p> Signup and view all the answers

A high refractive index for a material can act as an optical resonator in a semiconductor laser.

<p>True</p> Signup and view all the answers

What is the main advantage of using a gas laser over a solid-state laser?

<p>Gas lasers are capable of operating continuously without needing cooling.</p> Signup and view all the answers

What is the main application of lasers in electronic industry?

<p>Material processing including scribing, soldering, trimming, and welding.</p> Signup and view all the answers

What is the main difference between a pulsed laser and a continuous wave laser?

<p>A pulsed laser emits light in short bursts, while a continuous wave laser emits a continuous beam of light.</p> Signup and view all the answers

What is the principle of holography?

<p>Holography is a technique that records and reconstructs the amplitude and phase of light waves to create a three-dimensional image.</p> Signup and view all the answers

Holography is used only for creating artistic displays.

<p>False</p> Signup and view all the answers

Study Notes

Laser Introduction

  • Laser is an acronym for Light Amplification by Stimulated Emission of Radiation
  • Stimulated emission amplifies light waves
  • Lasers produce a highly focused, intense, monochromatic beam
  • No other light source compares to its ability to concentrate energy into a narrow beam

Albert Einstein's Prediction

  • In 1917, Albert Einstein predicted two types of emission processes in atoms: spontaneous and stimulated
  • Spontaneous emission occurs randomly while stimulated emission amplifies existing light

MASER Development

  • In 1950, Schawlow-Townes (USA) and Basov-Prokhorov (USSR) developed MASER (Microwave Amplification by Stimulated Emission of Radiation)
  • This technology used stimulated emission to amplify microwaves

Laser Development

  • Following MASER, efforts focused on extending the amplification to optical frequencies.
  • In 1960, T.H. Maiman demonstrated the first laser (using ruby)
  • This led to rapid advancements in laser technology across various materials (glasses, solids, liquids, etc.)

Electromagnetic Spectrum

  • Electromagnetic radiation exists in different forms within a range of frequencies and wavelengths.
  • Lasers operate in the optical region of the spectrum, which includes visible light.

Interaction with Matter

  • Atoms and molecules have specific energy levels
  • Electrons can occupy discrete energy levels
  • Light interacts with matter, affecting its energy levels, either by absorption or emission
  • Absorption promotes electrons to higher energy states while stimulated emission causes electrons to return to lower energy levels emitting light

Laser Scheme

  • Key components of a laser include: an amplifying medium, a pumping mechanism, and an optical resonator
  • Amplifying medium, consists of atoms, molecules, or ions, which enhance light waves
  • The pumping method furnishes energy to the medium, leading to population inversion
  • The optical resonator, typically a pair of reflecting mirrors, provides feedback to amplify light through reflections

Laser Beam Characteristics

  • Directionality: Laser beams travel as parallel beams over long distances before spreading. This contrasts with ordinary light beams, which diverge
  • Intensity: Lasers exhibit high intensity, containing a significant number of photons in a tightly focused beam.
  • Monochromaticity: Lasers produce light at a single wavelength or with a very narrow spectrum range unlike ordinary light sources
  • Coherence: Laser light waves maintain a consistent phase relationship along a given beam, creating coherent light. This contrasts with incoherent light from ordinary sources.

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Description

Explore the basics of laser technology, including the principles of light amplification and the historical development of lasers. Learn about Albert Einstein's predictions related to light emissions and the evolution from MASER to the first laser demonstration in 1960.

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