Category: optics

Teaching LASERs – snapshots

Today, I will be teaching the origins of LASERs in my optics class. Some of the content may interest science enthusiasts here. I present some snapshots from my notes. As expected, it starts with Einstein introducing his A and B coefficients and the stimulated emission.

He introduced them in a paper written in German: Einstein, A. (1916). “Strahlungs-Emission und -Absorption nach der Quantentheorie”. Verhandlungen der Deutschen Physikalischen Gesellschaft. 18: 318–323.

The English translation of the paper: “Volume 6: The Berlin Years: Writings, 1914-1917 (English Translation Supplement) Page 212 (224 of 462).” Accessed November 3, 2023. https://einsteinpapers.press.princeton.edu/vol6-trans/224.

Under thermodynamic equilibrium, the detailed balance gives us the connection between the coefficients…and amplification and stimulated emission of radiation become a measurable prospect.

The pic shows the leading characters behind the invention of the Light Amplification by Stimulated Emission of Radiation (LASER) Charles Townes was the intellectual pioneer behind microwave variety… and Maiman….the freak behind the optical version..

The history of the invention is fascinating and dramatic. I did a podcast on this a few months ago. Check it out..

https://backscattering.wordpress.com/2023/06/23/new-episode-on-podcast-gripping-history-of-laser-inventionnew-episode-on-podcast/

2023 Nobel in Physics – Initial thoughts

One should not be surprised nowadays if a Nobel prize in physics goes to something related to light. As a person working in optics and light-matter interaction, I welcome any recognition of one of the most profound aspects of nature: light. This time, the prize has gone to some great experimental effort dating back to the late 1980s to early 2000s when amazing progress was made in three aspects related to the prize: a) higher harmonic generation of light in rare gases, b) production of a train of attosecond light pulses, and c) eventually production of single attosecond light pulses that can interact with matter, especially electrons in matter. Such an interaction can lead to the mapping of dynamics of quantum entities such as electrons and will have far-reaching consequences in probing the internal degrees of molecules and atoms. The scientific information published by the Nobel Committee has wonderful illustrations and is worth reading.

This time, the Nobel Prize website has published a fantastic set of illustrations to convey the relevance of the research. The above one shows the spectrum of temporal scales. It elegantly illustrates the breadth of the scale – attosecond to heartbeat:: Heartbeat to the age of the universe.. Oh, how beautiful science is!

Via Twitter, thanks to a student who was attending a lecture by Anne (one of the Nobel laureates), we got to see continuing her lecture even after a Nobel announcement. Now that is the spirit of academics!

This is the fundamental paper that triggered higher harmonic generation in gases and laid the foundation for attosecond pulse generation. of today, the impact factor of this journal is 1.6. The impact is not proportional to the impact factor of a journal