laserinterferometrar

Laserinterferometrar are precision optical instruments that measure very small changes in distance, refractive index, or surface position by exploiting the interference of coherent laser light. The basic principle is to split a single laser beam into two or more paths, guide the beams along separate arms, and then recombine them to produce an interference pattern. The detected intensity depends on the phase difference between the beams, which in turn is proportional to the difference in optical path length. Small changes in length produce shifts in the interference fringes, from which displacement can be inferred with high sensitivity.

Common configurations include the Michelson interferometer, which uses two perpendicular arms; the Mach-Zehnder interferometer, which guides light along two separate paths to a common output; and the Fabry-Pérot interferometer, which uses a high-finesse cavity to amplify phase changes. The Sagnac arrangement is used for rotation sensing. In many modern instruments, heterodyne or homodyne detection is used to convert phase information into output intensity with high signal-to-noise.

Applications range from precision metrology and surface profiling to gravitational wave detection, fiber-optic sensing, and medical imaging techniques such as optical coherence tomography. Gas or vacuum environments and vibration isolation are often employed to reduce environmental noise, and active stabilization keeps the interferometer at a sensitive operating point.

Historically, laser interferometry emerged in the early 20th century and has become central to physics and engineering, with large-scale facilities like LIGO and Virgo using kilometer-scale Michelson configurations to measure minute spacetime distortions.