An optical isolator is a device that allows light to pass through in one direction while blocking it in the opposite direction. This is important in laser systems, where unwanted feedback can disrupt the operation of the laser. By preventing light from reflecting back into the laser, optical isolators help maintain stable performance and improve the quality of the output beam. Typically, optical isolators use the principle of Faraday rotation, which involves a magneto-optic effect. This effect changes the polarization of light as it passes through the device, allowing it to be transmitted in one direction while absorbing or reflecting light coming from the other direction.