How LASERs work! (Animation with Einstein)

the stimulated emission of light was a discovery by Einstein around 1916 all we need is an atom which possesses the electrons just like any other item in our world and a photon that is a quantum of light the atom has electrons orbiting the atoms nucleus for better understanding the Bohr model of the hydrogen atom will be used the hydrogen atom has only one electron the atom and the electron on the ground state namely a zero however an electron may have other discrete values of energy for this example two energy levels will suffice II won and e2 and the electron can be excited to a higher energy level by absorbing a photon whose energy is equal to the energy difference between the levels the electron is said to be excited however after a very short time the excited electron will go to the lower energy level by emitting a photon equal to the energy difference this is called spontaneous emission but when an atom absorbs a photon and after a short time another photon is absorbed a stimulated emission will be the result the newly created photon has the same face frequency polarization and direction as the second photo so it's a copy the operation of lasers is based on the process of stimulated emission here we will discuss a three energy level design a photon is absorbed by the atoms the photon has enough energy to live the electron from energy level e zero to energy level e to shortly afterwards the electron jumps into energy level e 1 this can occur without emission of a photon a laser device is made up of several components first of all Amuro with a reflectivities 100% is installed at one end off the device furthermore we need to gas a liquid or a solid that serves as the gain medium and creates identical photons another mirror with a reflectivity of about 98% must be installed at the other end of the gain medium another part we need is an energy source in order to use photons to raise electrons from a lower energy level to a high one a process called optical pumping now let's have a look at the inside of the gain medium the atom and the electron are on the ground state now optical pumping that is emitting energy in the form of photons is used to raise the electron into a higher energy level in this case its energy level is e to F a short period of time the electron jumps into energy level e 1 without emission of a photon consequently the process of optical pumping cannot cause stimulated emission because there are two different amounts of energy present the electron will maintain its energy level e 1 for some time then the atom will spontaneously emit a photon in a random direction as it relaxes to a lower electronic state this photon may interact with an excited atom that hasn't emitted a photon yet so the photon hits the excited atom and causes a stimulated emission because the photon has the exact amount of energy to do that only photons emitted in a direction perpendicular to the mirrors will be reflected the reflected photons initiate is Cheyne reaction to produce more and more photons of the same kind for the mole only photons with the same amount of energy and the same amount 'm will be part of the chain reaction that's the reason why laser beams are strongly coherent and monochromatic a very important aspect is the fact that many atoms must be in an excited state for laser to work more atoms must be in an excited state than in lower energy states this is called population inversion the semi-transparent Murrell allows some of the laser energy to be emitted while bouncing most of it back through the laser there are many other cool things about lasers but for now that's all you

Channel: Thomas Schwenke

Views: 355,335

Rating: 4.8588834 out of 5

Keywords: albert einstein, laser, how laser work, how lasers work, stimulated emission

Id: 1LmcUaWuYao

Length: 5min 26sec (326 seconds)

Published: Tue Mar 25 2014