How Lasers Work

Simplified explanation of laser physics principles: atomic energy levels, spontaneous and stimulated emission, gain, three- and four-level schemes. Also explained are various types of laser: ruby, Neodymium, Helium-Neon, Semiconductor/Diode, Capillary Discharge and Free Electron Lasers. Contents 00:00 - Introduction 02:04 - Atomic processes 04:54 - Laser gain 06:43 - CW and Q-switching 09:14 - Population inversion 13:12 - Ruby, Neodymium 14:24 - HeNe 15:00 - Diode lasers 17:00 - Unconventional 18:27 - Free Electron 19:47 - LWI 20:33 - Summary References [1] “Raman spectroscopy has shed light on the structure of difficult to analyse sulphur-rich polymers”, Central Laser Facility https://www.clf.stfc.ac.uk/Pages/Raman-spectroscopy-has-shed-light-on-the-structure-of-difficult-to-analyse-sulphur-rich-polymers.aspx [2] 3D animation of the Rutherford atom (User: Damek) https://commons.wikimedia.org/wiki/File:3D_anamation_of_the_Rutherford_atom.ogv [3] Y. Diouf et al., “Numerical Study of Density Functional Theory of Multi-electronic Atoms: Case of Carbon and Helium”, American Journal of Nanomaterials 9, 12 (2021). [4] Xenon Flashtube by Nathan Boor (User: NapoleonoftheNow) https://en.wikipedia.org/wiki/File:Xenon_Flash_Wiki.ogv [5] S. Hooker and C. E. Webb, “Laser Physics”, (OUP 2010). ISBN: 978-0198506928 [6] Black Marble 2016, NASA's Goddard Space Flight Center https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=30878 [7] 3D cut of the LHC dipole, CERN, OPEN-PHO-ACCEL-2014-003-8 https://home.cern/resources/image/accelerators/lhc-images-gallery [8] L. Yuan et al., “Transient lasing without inversion via forbidden and virtual transitions”, Physical Review A 89, 013814 (2014).