An optical isolator is a device that allows light to pass in one direction while preventing it from traveling in the opposite direction. This is particularly useful in laser systems, where back reflections can destabilize the laser operation. By blocking unwanted light, optical isolators help maintain the performance and reliability of laser applications. These devices typically use the principles of polarization and Faraday rotation. When light enters the isolator, it is polarized and then passed through a Faraday rotator, which rotates the light's polarization. If any light attempts to return, it is blocked by a polarizer, ensuring that only forward-moving light can pass through.