# A report on Stimulated emission, Einstein coefficients and Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.

- LaserThe Einstein A coefficients are related to the rate of spontaneous emission of light, and the Einstein B coefficients are related to the absorption and stimulated emission of light.

- Einstein coefficientsAccording to the American Physical Society, the first person to correctly predict the phenomenon of stimulated emission was Albert Einstein in a series of papers starting in 1916, culminating in what is now called the Einstein B Coefficient.

- Stimulated emissionSuch a gain medium, along with an optical resonator, is at the heart of a laser or maser.

- Stimulated emissionIn the cases of thermodynamic equilibrium and of local thermodynamic equilibrium, the number densities of the atoms, both excited and unexcited, may be calculated from the Maxwell–Boltzmann distribution, but for other cases, (e.g. lasers) the calculation is more complicated.

- Einstein coefficientsIn 1917, Albert Einstein established the theoretical foundations for the laser and the maser in the paper Zur Quantentheorie der Strahlung (On the Quantum Theory of Radiation) via a re-derivation of Max Planck's law of radiation, conceptually based upon probability coefficients (Einstein coefficients) for the absorption, spontaneous emission, and stimulated emission of electromagnetic radiation.

- Laser1 related topic with Alpha

## Spontaneous emission

0 linksProcess in which a quantum mechanical system transits from an excited energy state to a lower energy state (e.g., its ground state) and emits a quantized amount of energy in the form of a photon.

Process in which a quantum mechanical system transits from an excited energy state to a lower energy state (e.g., its ground state) and emits a quantized amount of energy in the form of a photon.

Lasers start via spontaneous emission, then during continuous operation work by stimulated emission.

According to the American Physical Society, the first person to correctly predict the phenomenon of spontaneous emission was Albert Einstein in a series of papers starting in 1916, culminating in what is now called the Einstein A Coefficient.