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/Rama...
[2] 3D animation of the Rutherford atom (User: Damek)
https://commons.wikimedia.org/wiki/Fi...
[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:Xe...
[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/det...
[7] 3D cut of the LHC dipole, CERN, OPEN-PHO-ACCEL-2014-003-8
https://home.cern/resources/image/acc...
[8] L. Yuan et al., “Transient lasing without inversion via forbidden and virtual transitions”, Physical Review A 89, 013814 (2014).