Lasers - Civil Engineering (CE) PDF Download

Lasers
Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. Laser is a highly “monochromatic coherent beam of light of very high intensity”. In 1960 Mainmann built the first “LASER” using Ruby as active medium.

Interaction of Radiation with matter
1. Stimulated Absorption:
When an atom in the ground state say E1 absorbs a photon of energy (E− E1) it makes transition into exited state E2. This is called Stimulated or Induced absorption. It is represented as follows,
Photon + Atom = Atom*.

2. Spontaneous Emission:
Spontaneous emission is one in which atom in the excited state emits a photon when it returns to its lower energy state without the influence of any external energy.
Lasers - Civil Engineering (CE)

Consider an atom in the excited state E2. Excited state of an atom is highly unstable. With in a short interval of time, of the order of 10−8 sec,atom returns to its lower energy state say E1 and emits difference in energy in the form of photon of energy hν = E2 - E1 spontaneously.

If the two atoms are in the same excited state and returns to some lower energy states two photons of having same energy are emitted. These two photons may not travel in the same direction. They produce in-coherent beam of light. Spontaneous emission is represented as follows,
Atom* = Atom + Photon.

3. Stimulated Emission:
Consider an atom in the excited state E2. If a photon of energy E2 - E1 is made to incident on the atom in the excited state E2.

The incident photon forces (stimulates) the atom in the excited state to make transition in to ground state E1 by emitting difference in energy in the form of a photon. This type of emission in which atom in the excited state is forced to emit a photon by the influence of another photon of right energy is called stimulated emission. Stimulated emission can be represented as follows.

Photon + atom* = Atom + (photon + photon).

When stimulated emission takes place, incident photon and the emitted photon are in phase with each other and travel along the same direction. Therefore they are coherent.

 

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FAQs on Lasers - Civil Engineering (CE)

1. What are lasers used for?
Ans. Lasers are used in various applications such as telecommunications, medical procedures, scientific research, industrial manufacturing, and even in everyday consumer products like DVD players and barcode scanners.
2. How do lasers work?
Ans. Lasers work by emitting a concentrated beam of light through a process called stimulated emission. This process involves the excitation of atoms or molecules in a gain medium, which then release photons that are all of the same frequency and phase, resulting in a coherent and focused beam of light.
3. Are lasers harmful to human health?
Ans. Yes, lasers can be harmful to human health if used improperly. High-power lasers can cause eye injuries, burns, and even skin damage. It is important to follow safety guidelines and use appropriate protective measures when working with lasers.
4. What is the difference between continuous-wave lasers and pulsed lasers?
Ans. Continuous-wave lasers emit a continuous beam of light, while pulsed lasers emit light in short bursts or pulses. Continuous-wave lasers are typically used for applications that require a constant and steady beam, such as laser pointers, while pulsed lasers are used in applications that require high power and precision, such as laser cutting or laser surgery.
5. Can lasers be used for non-medical cosmetic procedures?
Ans. Yes, lasers are commonly used for non-medical cosmetic procedures such as hair removal, tattoo removal, skin rejuvenation, and scar reduction. These procedures involve the use of specific laser wavelengths that target the desired area, providing effective and precise results.
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