Where Does All the Energy Go?
/) Many lasers will become unstable under these conditions which for some, may even result in damage (e.g., where a light feedback loop attempts to maintain constant output power and increases current to an excessive value). The chance of this happening will be reduced or eliminated by always aligning for multiple fringes or using a Mach-Zehnder instead of a Michelson interferometer. The Mach-Zehnder is slightly more complex but all light exits in a forward direction.
Suppose we have a Michelson interferometer (see the section: Basics of Interferometry and Interferometers) set up with a perfectly collimated (plane wave source) and perfectly plane mirrors adjusted so that they are perfectly perpendicular to the optical axis (for each mirror) and the beam splitter is also of perfect construction and oriented perfectly. In this case, there won’t be multiple fringes but just a broad area whose intensity will be determined by the path-length difference between the two beams. Where this is exactly 1/2 wavelength (180 degrees), the result will be nothing at all and the screen will be absolutely dark! So, where is all the energy going? No, it doesn’t simply vanish into thin air or the ether, vacuum, the local dump, or anywhere else. 🙂 Your initial response might be: “Well, no system is ideal and the beams won’t really be perfectly planar so, perhaps the energy will appear around the edges or this situation simply cannot exist – period”. Sorry, this would
