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EOT 1030 - 1080nm Faraday Isolators
III. The EOT 1030 - 1080nm Faraday Isolator
With the polarizer covers off a polarizing beamsplitter cube ("PBSC") can be seen at each end of the device. The inscribed arrow on the baseplate shows the transmission direction. The output PBSC is seen to be oriented with its transmission axis rotated 45 degrees relative to the input PBSC. The input polarization shown is horizontal. The central magnet housing together with the TGG crystal residing in its center forms a Faraday Rotator. The Faraday Rotator rotates the input horizontal transmission axis by 45 degrees so that transmitted light has a polarization aligned with the output transmission axis. The input and output PBSC's work in conjunction with the central Faraday Rotator to form a Faraday Isolator as described previously in Section I.
Figures 3 and 4 below show Input views of an EOT 1030 - 1080nm Faraday Isolator.
Figure 3 shows a device aligned for a horizontal input polarization. The "dot" superimposed on one of the polarization transmission axis scribe lines on the endplate of the input polarizer mount denotes the side of the input PBSC that backward propagating (i.e. isolation direction) light will get directed to. In the case shown this direction is to the right.
Figure 4 shows a device aligned for a vertical input polarization. Since the "dot" is on the top side of the polarizer, backward propagating light will get directed downward as shown.
Figures 5 and 6 below show Output views of an EOT 1030 - 1080nm Faraday Isolator. In both cases the Faraday Isolators have been adjusted for Horizontal Input polarization.
Figure 5 shows a Faraday Isolator configured for Negative z rotation. Coarse wavelength tuning adjustment can be made by aligning the polarization transmission scribe lines to the appropriate scribe line on the Polarizer Clamp Ring. When the polarization transmission axis scribe line is aligned with the line labeled "1055" the device is nominally adjusted to operate optimally at 1055nm. If the polarization transmission axis scribe line is aligned with the line labeled "A" then the device is nominally adjusted to operate optimally at 1030nm. If the polarization transmission axis scribe line is aligned with the line labeled "B" then the device is nominally adjusted to operate optimally at 1080nm. Again, the "dot" on the Output Polarizer mount denotes the side of the Output PBSC that backward propagating (i.e. isolation direction) light will get directed to. In the case shown this direction is upward and to the left.
Figure 6 shows a Faraday Isolator configured for Positive z rotation. Again, when the polarization transmission axis scribe line is aligned with the line labeled "1055" the device is nominally adjusted to operate optimally at 1055nm. However, if the polarization transmission axis scribe line is aligned with the line labeled "A" then the device is nominally adjusted to operate optimally at 1080nm. Conversely, if the polarization transmission axis scribe line is aligned with the line labeled "B" then the device is nominally adjusted to operate optimally at 1030nm. Again, the "dot" denotes the side of the Output PBSC that backward propagating (i.e. isolation direction) light will get directed to. In the case shown this direction is upward and to the right.
EOT Faraday Isolators are factory aligned as per the Model Number specified in a Purchase Order. The information below shows the range for each field in the Model Number together with the definition of the coordinate axis system which defines the z rotation sense.
Numbering Fields and Coordinate System for EOT 1030 - 1080nm Faraday Isolator
General Format for Numbering Field: A-B-CCCC-DDD-E-FFF
| Field Description: |
| 1. |
"A" is the aperture size, e.g. 8 mm. |
| 2. |
"B" is "I" for isolator, or "R" is for rotator. |
| 3. |
"CCCC" is the wavelength in nm. If not selected by the customer, 1064 will be assigned. |
| 4. |
"DDD" is the input polarization axis angle. A right hand x,y,z Cartesian coordinate system is used, where the direction of beam propagation away from the laser source is along the positive z axis. The x axis is in the plane of the baseplate. The y axis is vertical, normal to the plane of the baseplate. The xy plane forms the plane of polarization. The xz plane forms the plane of the baseplate. As an example, a horizontal input polarization is 000 or 0 degrees. A vertical polarization is 090, or 90 degrees. If no polarization is selected by the customer, 000 will be assigned. |
| 5. |
"E" is the sense of faraday rotation, being viewed in the direction of propagation. "1" is for positive z rotation while "2" is for negative z rotation. An example of a positive rotation would be a device with an input polarization of 0 degrees, or horizontal polarization and an output polarization of 45 degrees, using the conventions established above. The rotation sweeps from the positive x axis towards the y axis in the xy plane for positive z rotation. The default assignment is "1". |
| 6. |
"FFF" is the output polarization if a waveplate is used. If there is no waveplate, "N/U" is used. If there a waveplate but no polarization is specified, the default setting is the input polarization. The angle convention is the same as described for "DDD". |
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