The Laser

A Brief History

In 1900, Max Planck deduced the relationship between energy and the frequency of radiation, essentially saying that energy could be emitted or absorbed only in discrete chunks — which he called quanta — even if the chunks were very small.
In 1905, Einstein released his paper on the photoelectric effect, which proposed that light also delivers its energy in chunks, in this case discrete quantum particles now called photons.
In 1917, Einstein proposed the process that makes lasers possible, called stimulated emission. But it would take nearly 40 years before scientists would be able to amplify those emissions, proving Einstein correct.
Jump forward some 44 years and the Lasers begins to appearing on the commercial market.
In 1961, The first medical treatment using a laser on a human patient is performed by Dr. Charles J. Campbell of the Institute of Ophthalmology at Columbia-Presbyterian Medical Center and Charles J. Koester of the American Optical Co. at Columbia-Presbyterian Hospital in Manhattan. An American Optical ruby laser is used to destroy a retinal tumour.
In 1962, Fred J. McClung, Hellwarth proves his laser theory, generating peak powers 100× that of ordinary ruby lasers. Important first applications include the welding of springs for watches.
In 1964, The carbon dioxide laser is invented by Kumar Patel at Bell Labs. The most powerful continuously operating laser of its time, it is now used worldwide as a cutting tool in surgery and industry.
In 1965, TWI (The Welding Institute) became aware that a 300W CO2 gas laser was operational at the Services Electronic Research Laboratory in Harlow, just down the road from TWI.
That same year Peter Houldcroft, Deputy Scientific Director at The Welding Institute, had visited BMC (British Motor Company), where he was told some preliminary cutting trials had been undertaken using a plasma torch and an articulated arm robot, for the application of body panel trimming during press tool development. The problem was that the system was not accurate enough and produced burning. Peter was asked if he could think of any other suitable cutting process. On the drive back to Cambridge, the idea of combining an oxygen-jet with a focused laser beam began to form. The necessary catalyst for this idea was provided by the availability of 300W of CO2 laser power at SERL.
In 1966, Charles K. Kao, working with George Hockham at Standard Telecommunication Laboratories in Harlow, UK, makes a discovery that leads to a breakthrough in fiber optics.
In 1967, Peter Houldcroft, Deputy Scientific Director at The Welding Institute, used an oxygen assist gas to cut 1mm thick steel sheet with a focused CO2 laser beam. This marked the beginning of using lasers for industrial material processing 50 years on, laser cutting machines account for the largest percentage of metal cutting processes which includes high pressure Water Jet and Plasma cutting.

References:  https://www.photonics.com/Articles/A_History_of_the_Laser_1960_-_2019/a42279
https://www.twi-global.com/technical-knowledge/published-papers/the-early-days-of-laser-cutting-august-2007