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EOT Broadband Faraday Rotator/Isolator
III. The EOT 1030 - 1080nm Faraday Isolator
Figure 4: View of a 5mm aperture, EOT Broadband Faraday Isolator with polarizer covers removed.
With the polarizer covers off, a polarizer can be seen at each end of the device. For the 5mm aperture devices, glan laser calcite polarizers are used. The arrow stickers on the top indicate the transmission direction. The input polarization shown is horizontal. The central magnet housing together with the TGG and quartz crystals residing in its center form a broadband Faraday rotator. The input and output polarizers work in conjunction with the central Faraday rotator to form a Faraday Isolator as described previously in Section I.
Figures 5 shows the input view of the isolator, note that the aperture is displaced to one side. This is due to the displacement of the beam after transmission through the glan laser calcite input polarizer. The output polarizer creates a similar magnitude of displacement. However, the beam is shifted vertically rather than horizontally. This is apparent in figure 2. A more detailed illustration of the aperture locations is in figure 4.
Figure 5: Input View of 5mm Aperture Broadband Faraday Isolator
Figure 6 shows a diagram with multiple views of the 5mm aperture broadband Faraday isolator.
Figure 6: Diagram View of 5mm Aperture Broadband Isolator
Another option is to use a Broadband Faraday Rotator. Optically, this device is composed of a Faraday rotator and a quartz rotator. Figure 7 shows a view of the device. Rather than polarizer mounts, this device has a set of trim pieces with a central aperture. The quartz is mounted to the interior of the output trim piece. Figure 8 shows a detailed diagram of the rotator.
Figure 7: View of 5mm Aperture Broadband Rotator
Figure 8: Diagram View of 5mm Aperture Broadband Rotator
Figure 9: View of 8mm Aperture Broadband Isolator without polarizer covers
Referring to figure 9, with the polarizer covers off, a polarizer can be seen at each end of the device. For the 8mm aperture devices, polarizing beam splitter cubes are used. The arrow on the side indicates the transmission direction. The input polarization shown is horizontal and the output is vertical. The central magnet housing together with the TGG and quartz crystals residing in its center form a broadband Faraday rotator. The input and output polarizers work in conjunction with the central Faraday rotator to form a Faraday isolator as described previously in Section I. Figure 10 shows a more detailed, diagram view of the device. Note that unlike the 5mm aperture isolator, the input and output apertures are in-line and centered on the magnet body. Unlike the 5mm and 10mm models, this device may be adjusted readily for any input polarization. The polarization adjustment screw shown in figure 9 may be loosened and the entire magnet housing along with input and output polarizers will rotate freely in the base clamp as a single assembly. Once the device is oriented for optimal input polarization, the screw is tightened again. Further details for this procedure are provided in section V.
The input view is observed in figure 2. Note that the polarizer covers are in the open position here, allowing rejected beams to exit the device. The user may close these ports by simply rotating the polarizer cover, shown in figure 2, until the port is in the closed position. This cover is held in place by an o-ring located between its inner surface and the polarizer mount.
Figure 10: Diagram View of 8mm Aperture Broadband Isolator
Figure 11 provides a detailed diagram of the 8mm aperture broadband rotator. Note the in-line configuration and square cross-section. Note the mounting holes located on the bottom of the device.
Figure 11: Diagram View of 8mm Aperture Broadband Rotator
Figure 12: View of 10mm Aperture Broadband Isolator without polarizer covers
Figure 12 shows the 10mm aperture broadband isolator without polarizer covers. Note that the device uses pbs cubes for polarizers and the apertures are located in-line through the device. As in the previous models, the arrows on top indicate the transmission direction. The quartz rotator may be observed mounted to the output polarizer mount on the output end of the Faraday rotator assembly (magnet housing).
Figure 13 shows a reverse view of the 10mm aperture broadband isolator with polarizer covers in place. They may be rotated between the open position (shown) and the closed position (with the covers rotated 90 deg.). Unlike the 8mm aperture isolator, the polarizer cover is fixed in position by a single screw that is tightened into the polarizer cover screw hole shown in figure 12.
Figure 13: View of 10mm Aperture Broadband Isolator with polarizer covers
Figure 14 shows a diagram view of the 10mm aperture broadband faraday rotator. Note its very similar construction to the 8mm aperture device. Note the mounting screw holes located on the endplates of the device.
Figure 14: Diagram View of 10mm Aperture Broadband Faraday Rotator
The polarization of EOT Faraday Isolators are factory set as per the Model Number specified in a Purchase Order. The information below shows the range for each field in the Model Number. EOT provides an online build-your-own service for ordering standard devices that will produce a model number based on the following system. A horizontal input polarization combined with a vertical output polarization is default in the event it is not specified by the customer. However, a customer may specify a vertical input polarization and a horizontal output polarization instead.
Numbering Fields and Coordinate System for EOT Broadband Faraday Isolators/Rotators
General Format for Numbering Field: BB-A-CC-D-EEE
Field Description:
1. "BB" designates the device as a broadband and is common for all broadband units.
2. "A" is "8" for 800nm center wavelength and "9" is for 900nm center wavelength.
3. "CC" designates the aperture size: 05,08,09 correspond to 5,8, and 9mm diameters, respectively.
4. "D" designates whether the device is a rotator, "R" or an isolator, "I".
5. "EEE" designates the input polarization, "000" for horizontal, "090" for vertical.
This applies only to isolators. For rotators, this field does not apply.
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