LASER – History, Working, and Applications of LASER

History of LASER

• Hasan Ibn AL Haytham

The first progression in comprehending light was attempted in the Islamic Golden Age. In 1027 Muslim polymath Hasan Ibn AL Haytham, also known as Alhazen, wrote the Book of Optics.

He resolved the preferred idea that light originated from our eyes like torches. Rather, AL Haytham verified that it is released as well as mirrored from objects and travels directly to our eyes.

• Isaac Newton

Isaac Newton revealed that colour is a property of light and not the medium. Thomas Young exposed the wave nature of light.

• James Staff Maxwell

And James Staff Maxwell went further, mathematically explaining light as an electromagnetic wave.

And afterward came relativity and also quantum mechanics. Not just did these imposing concepts shape physics in the 20th century. They additionally revolutionized our understanding of light.

• Albert Einstein

Albert Einstein was the main one to changing our understanding. His special theory of relativity showed that the rate of light was a basic constant of nature. Einstein’s description of light in quantum mechanics caused among the best innovations of the 20th century: the LASER.

Working of Laser

The working of laser includes two most important phenomena:

• Stimulated emission and Spontaneous Emission
• Population Inversion

Stimulated Emission

When a photon of energy disrupts an electron in a metastable state, the electron drops to the lower-energy state and also gives off an additional photon, as well as the two photons proceed off together.

This procedure is called Stimulated emission. It occurs with a relatively high chance when the energy of the inbound photon equals the energy difference in between the excited and “de-excited” energy of the electron (ΔE= hf).

Thus, the incoming photon and the photon generated by de-excitation have the same energy, hf.

Spontaneous Emission

The excited atom may decay by spontaneous emission by discharging a photon of energy hf = E2 – E1 in any kind of arbitrary direction.

Population Inversion

Population inversion is a state of a system, for example, a laser gain medium, where higher-lying energy is much more strongly populated than a lower-lying. This cannot happen under conditions of thermal stability, where the degree populaces are described by a Boltzmann circulation.

Nevertheless, a populace inversion is frequently conveniently achieved by optical pumping at a suitable optical wavelength.

Populace Inversion and Laser Action

Let us consider a simple situation of material whose atoms can stay in three different states. E₁ is the ground energy state. E₃ is the excited state in which the atom can reside just for 10 ^-8 sec and also E₂ is called metastable state in which atom can live for 10^-3 sec.

A metastable state is an excited state in which an excited electron is typically more stable and from which the electron falls to a lower state after a relatively long time.

Let the incident photons of energy hf = E₃ – E₁ increased the atom to excited state E₃ from ground state E₁. The excited atoms do not decay back to E₁. However, the atom decay to E₂ automatically.

The atom reaches the state E₂ much faster than they leave state E₂.In this situation, the state E₂ consists of more atoms than E₁.

Applications

• Lasers are made use of in a wide variety of applications, such as in communication (fiber optics phone lines),
• entertainment (laser light shows),
• medical (removing lumps as well as cauterizing vessels in the retina),
• and in stores, grocery (bar code scanner).
• Lasers can likewise be created by a huge variety of products, including solids (for instance, the ruby crystal), gases (helium-gas mixture), as well as liquids such as organic dyes. Lately, a laser was even developed making use of jelly– an edible laser.

MCQs about LASER