Introduction to the working principle of optical isolators

Optical isolators mainly use the Faraday effect of magneto-optical crystals. The Faraday effect is Faraday's first observation in 1845 that a non-optically active material rotates the polarization direction of light passing through the material under the action of a magnetic field, also known as the magneto-optical effect.

For polarized light propagating in the direction of the magnetic field, the rotation angle θ of the polarization direction and the product of the magnetic field strength B and the length L of the material are proportional. For the signal light that is incident in the normal direction, it becomes linearly polarized light after passing through the polarizer. The Faraday gyromagnetic medium and the external magnetic field rotate the polarization direction of the signal light by 45 degrees to the right, and just make the low-loss pass through the polarizer in 45 degrees. degree-placed analyzer.

For the reverse light, when the linearly polarized light exiting the analyzer passes through the medium, the deflection direction is also rotated 45 degrees to the right, so that the polarization direction of the reverse light is orthogonal to the direction of the polarizer, which completely blocks the transmission of the reflected light. .