Amplifying the energy within a laser, over and over, won’t get you an infinite amount of energy. There’s a fundamental limit due to physics.
Back in the middle of the 20th century, there was really no good way to create purely monochromatic light: light where every one of the photons that are part of that beam possess precisely the same wavelength. Sure, you could break up white light into its component colors, such as by passing it through a prism or color filter, and selecting for only a narrow range of wavelengths, but that wouldn’t be truly monochromatic. However, the fact that atoms, molecules, lattices, and other structures only admit a specific set of electron transitions brought forth a fascinating possibility: if you could stimulate the same transition (or sets of transitions) over and over, without creating any other transitions in the process, you could produce truly monochromatic light.
Since 1958, we’ve managed to do precisely that with the invention of the laser. Over time, lasers have become more powerful, more widespread, and have been engineered to produce an enormous variety of wavelengths for their emitted light. By having photons of a specific wavelength build up in the lasing cavity, that same-frequency…
