[Physics Class Notes] on Laser Pdf for Exam

It is basically a device that can stimulate atoms or electrons to  emit electromagnetic radiation of a specific wavelength and then amplify it producing a narrow spectrum of light. Laser is different from other lights because the light which the laser device emits has identical frequencies and wavelengths in it as a result a narrow tight beam of light is produced.

Laser Physics

The branch of optical physics that deals with the theory and application of lasers is called laser physics. This branch of physics lays the foundation of quantum electronics. 

 

What Are Lasers?

The word laser is an acronym and can be expanded as “light amplification by stimulating the emission of radiation.”The laser beams have a property similar to that of light waves emitted all at once. They are coherent, and usually of one wavelength (or colour).

There are many types of lasers, varying from giant lasers that emit high energy pulses of radiation like X-rays to a small device that are used in semiconductor chips to produce infrared lights.

Further, a laser is a device that increases the intensity of light by focusing in a particular direction.

Lasers not only increase the intensity of light but also generate light. Lasers emit light by stimulated emission of radiation, which increases the intensity of radiation. Some lasers produce visible light, and some produce ultraviolet or infrared rays.

Lasers are different from conventional light sources. Lasers have some properties which are not found in traditional light sources like sun, electric bulb, and incandescent lamp.

It also deals with the physics of laser beam propagation, particularly that of Gaussian beams, laser applications, nonlinear and quantum optics.

Further, a laser is a device that increases the intensity of light by focusing in a particular direction.

Lasers not only increase the intensity of light but also generate light. Lasers emit light by stimulated emission of radiation, which increases the intensity of radiation. Some lasers produce visible light, and some produce ultraviolet or infrared rays.

Lasers are different from conventional light sources. Lasers have some properties which are not found in traditional light sources like sun, electric bulb, and incandescent lamp.

Characteristics of Lasers

You can find a number of characteristics of laser light over ordinary light source:

• Coherence

• Directionality

• Monochromatic

• High intensity

1. Coherence

Visible light receives its emission from excited electrons (electrons of the higher energy level) are moved down to the lower energy level (ground state).

 

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2. Directionality

In conventional light sources like lamps, torchlights, electric bulbs, etc, photons move at random points. As such, these sources scatter light in all possible directions. The lasers emit light in a particular focused direction.

 

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3. Monochromatic

Monochromatic light means a light beam which contains a single wavelength. Photons that originate from natural light sources contain a range of energies, wavelengths, and colors. 

The Properties of Laser Similar to That of Monochromatic Light Are

1. Frequency

2. Wavelength

3. Color

4. High Intensity

Wave intensity is the energy flowing through a unit normal area per unit time. Light from an ordinary source spreads out in all directions. The light of a laser is focused in a particular direction.

How Does a Laser Work?

You can take a normal laser (like a ruby laser) to see the action that is done. 

Check out the image below; the device contains all the components required to make a laser function properly. The ruby laser has a medium in the form of a ruby crystal, a set of mirrors on either end (one of which is more transparent as compared to the other) and a flash tube stimulant. When current is passed through the ruby crystal  electrons are excited and then the excited electrons excite more electrons and the collective electrons all reach the high energy state. When the electron ultimately comes to the ground state energy they emit photons which are collected to form a strong beam of light called a laser.

Here’s How the Process Will Work Here:

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1. First, an electric current is supplied to turn the flash lamp on and off, which excites the electrons of the ruby crystals.

2. These excited electrons of the high energy state return to the ground state, thereby emitting a photon of light by spontaneous emission.

3. These photons move in the medium, bouncing off the mirrors and exciting other electrons into the high energy states. This process emits more photons by stimulating emission. 

Since now you have more number of excited electrons than the ground electrons, so it creates a population inversion.

4. The photons keep bouncing back and forth between the two mirrors of the medium, but one of the mirrors is a little less reflective and lets some photons through it.

5. Photons that emerge from the mirror are concentrated as a powerful beam of laser light.

Laser Types and Uses

There are many types of lasers, and they are categorized based on the type of medium at which they are used. This can be solid, liquid, gas, or semiconductor.

1. Solid-State Lasers

These lasers are made up of solid media, like ruby or crystalline. The lasers have a flash tube wrapped around it to excite the electrons.

These types of lasers are typically used for target destination systems by military applications and also to drill holes in metals.

 

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2. Gas Lasers

These types of lasers are made out of helium or helium-neon. They are used to produce characteristic red laser light. 

These lasers are powerful and efficient and are used for industrial cutting and welding applications.

 

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3. Liquid Dye Lasers

The liquid dye lasers use liquid dyes like rhodamine in a liquid solution as their medium. In these lasers, the electrons are ex
cited either by an arc lamp, flash lamp, or another laser.

Liquid dye lasers can produce a broader band of light frequencies as compared to solid-state or liquid lasers and are used in a variety of applications.

 

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4. Semiconductor Lasers

These types of lasers are very cheap to produce and hence found in several electronic devices like laser printers and barcode scanners.

These are also called diode lasers, as they use LEDs to generate light in a monochromatic pattern.

 

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Laser Type and Wavelength (nm)