Therefore, the light leaves the isolator with a POP of 45°. Finally, the light exits through the output polarizer which has its axis at 45°. The Faraday rotator will rotate the plane of polarization (POP) by 45° in the positive direction. Laser light, either polarized or unpolarized, enters the input polarizer and becomes vertically polarized. In this example, we will assume that the input polarizer's axis is vertical (0° in Figure 2). Light propagating in the reverse direction is rejected by the input polarizer.
A single-stage, polarization-dependent isolator.
This light's polarization is now perpendicular to the transmission axis of the input polarizer, and as a result, the energy is either reflected or absorbed depending on the type of polarizer.įigure 2. In the reverse direction, the Faraday rotator continues to rotate the light's polarization in the same direction that it did in the forward direction so that the polarization of the light is now rotated 90° with respect to the input signal. The output light is now rotated by 45° with respect to the input signal. The Faraday element rotates the input light's polarization by 45°, after which it exits through another linear polarizer. The input polarizer works as a filter to allow only linearly polarized light into the Faraday rotator. V: the Verdet Constant, a property of the optical material, in radians/T ĭ: the path length through the optical material in meters.Īn optical isolator consists of an input polarizer, a Faraday rotator with magnet, and an output polarizer. Faraday Rotator's Effect on Linearly Polarized Light Faraday Rotation