The word "Photonics" comes from the elementary particle "Photon", which is a quanta of energy equivalent to hν, where h is the Planck's constant (6.6x10-34 J•sec) and hν is the frequency (Hertz) of light. So "Photonics" can be understood as the study of the particle called the "Photon".
"Photons" are present all around us, and because of their reflection or absorption we can see objects. "Photons" have no rest mass and they travel with the speed of light (3x108 m/sec in vacuum), in their propagation they exhibit wave like characteristics. These particles show electro-magnetic behavior i.e. a photon is associated with an electric component and a magnetic component which are perpendicular to each other and are mutually orthogonal to the direction of propagation.
In nature, the biggest sources of photons are the stars (The Milky Way), and in our solar system, it's the sun. The human eye can see only a fraction of the whole spectrum, namely the visible spectrum (400-800nm). Most of the radiation we see is polychromatic (contains many frequencies), the incandescent lamp or the fluorescent tube are some examples.
"Lasers" constitute a special class of devices which emit monochromatic light (single frequency). "Laser" is an abbreviation of "Light Amplification by Stimulated Emission of Radiation". As atoms (The building blocks of the universe) and molecules (The building blocks of most materials) contain energy levels which coincide with Photon energies, the coherent Photon source (Laser) becomes a powerful tool for probing them. Due to their high directionality and focus, lasers are used in numerous applications, one of the most common applications is in CD and DVD players.
Gradually but surely, man has been able to harness the power of this fantastic particle which has revolutionized today's world.
Come join us in the quest for knowledge of the seen and the unseen world.
Saumyabrata Banerjee, Doctoral Student
