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EOT Broadband Faraday Rotator/Isolator
I. Faraday Rotator and Isolator Overview
Your EOT Faraday Isolator is essentially a uni-directional light valve or spectrally selective one-way mirror. It is used to protect a laser source from destabilizing feedback or actual damage from back-reflected light. Figure 1 below identifies the main elements of your Faraday Isolator.
Figure 1: EOT Broadband, 5mm Aperture Faraday Isolator
The 5mm aperture Faraday isolator is a rectangular shaped magneto-optic device. Strong Neodymium Iron Boron permanent magnets are used to generate high (>10,000 Gauss) axially oriented fields within the magnet housing. The strong longitudinal field causes 45 degrees of non-reciprocal polarization rotation for propagating light via the Faraday Effect in the Terbium Gallium Garnet ("TGG") crystal located within the magnet housing. Following the TGG crystal is a quartz reciprocal rotator with 45 deg. rotation. In the forward direction, the two rotations add up, resulting in 90 deg. of rotation. In the reverse direction, the two rotations are opposite and result in 0 deg. of rotation. The change in rotation as the wavelength shifts from the central wavelength is similar for both TGG and quartz, resulting in broadband operation. In operation, the magnet housing is sandwiched between input and output polarizers that have their transmission axis oriented 90 degrees relative to each other. In the reverse direction the backward traveling beam has a polarization orthogonal to the input polarizer and is therefore crossed with it, resulting in a rejected beam exiting the input polarizer.
Figure 2: EOT Broadband, 8mm Aperture Faraday Isolator
The 8mm aperture Faraday isolator is a cylindrically shaped magneto-optic device. The device operates similarly to the 5mm aperture device. However, the magnet body is cylindrical and the polarizers and mounts are different.
Figure 3: EOT Broadband, 10mm Aperture Faraday Isolator
The 10mm aperture Faraday isolator is a rectangular shaped magneto-optic device. The device operates similarly to the 5mm aperture device. However, the magnet body is rectangular and the polarizers and mounts are different. |
