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 If you do not see an isolator that suits your application, please refer to the Custom Isolators tab for information on our build-to-order options, or contact Tech Support.įigure 1. Please use the Selection Guide table above for more information. Thorlabs also manufactures free-space isolators and fiber isolators designed for the infrared range.
In addition, each unit is tested before shipment to ensure compliance with our specifications and a complete test report comes with every serialized part. There is 0.8 m to 1 m of fiber built into each side of the isolator, and an arrow on the body indicates the transmission direction. Our high-power units are built using a specialized fiber end face process that increases the maximum power. In contrast, our polarization-dependent IR isolators are designed to connect to polarization-maintaining (PM) fibers. Thorlabs' polarization-independent IR isolators, sold on this page, are compatible with single mode (SM) fibers. The IOT-H-1550A dual-stage isolator includes an additional Faraday rotator, half-wave plate, and birefringent beam displacer compared to a single-stage isolator in order to achieve greater isolation. Click the schematic to show polarization states. See the Isolator Tutorial tab for more details and for a comparison to dual-stage isolators. Light is deflected away from the input path and stopped by the housing. This schematic shows a single-stage, polarization-independent isolator. Please see the Isolator Tutorial tab for an explanation of the operating principles of a Faraday isolator. Optical isolators, also known as Faraday isolators, are magneto-optic devices that preferentially transmit light in the forward direction while absorbing or displacing light propagating in the reverse direction (see the schematic below). Custom Isolators Available (See the Custom Isolators tab)įiber isolators protect light sources from back reflections and signals that can cause intensity noise and optical damage.
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