What is the theory of stimulated emission?

Stimulated emission is the process by which an incoming photon of a specific frequency can interact with an excited atomic electron (or other excited molecular state), causing it to drop to a lower energy level.

What is a photon in QFT?

A photon (from Ancient Greek φῶς, φωτός (phôs, phōtós) ‘light’) is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force.

Who proposed concept of stimulated emission?

Albert Einstein
This process is called “stimulated emission.” Albert Einstein first broached the possibility of stimulated emission in a 1917 paper, having turned his attention the year before from general relativity to the interplay of matter and radiation, and how the two could achieve thermal equilibrium.

Why does stimulated emission occur?

If a laser-active atom or ion is in an excited state (quantum-mechanical energy level) (e.g. by optical pumping), it may after some time spontaneously decay into a lower energy level, releasing energy in the form of a photon, emitted in a random spatial direction.

What is the difference between quantum and photon?

A photon has the properties of both wave like and particle like, but quantum does not. Quantum can be compared to a measure of quantity, but a photon is not about a measure of quantity.

Why stimulated emission is coherent?

A single photon interacting with an excited atom can therefore result in two photons being emitted. If the emitted photons are viewed as a wave, the stimulated emission will oscillate at the incoming light’s frequency and be in phase (coherent), resulting in amplification of the original light wave’s intensity.

What are the important features of stimulated emission?

5.3. The stimulated emission process is based on four basic phenomena that occur in the laser generator: pumping, spontaneous emission of radiation, stimulated emission of radiation, and absorption. Pumping: This is the result of excitation of the active medium.