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EOT Broadband Faraday Rotator/Isolator
IV. Using your Faraday Isolator
Observe the guidelines for safe use of your Faraday Isolator found in Section II above when removing your isolator from its shipping container. Do not remove the protective dust covers from the polarizer mounts until the device is in a clean, relatively dust free environment.
Save the packaging material and containers in the event that the device should ever need to be returned to EOT.
Verify that the Input and Output polarization states are consistent with the intended mode of operation as described by the Purchase Order Model Number. If not, either send the device back to EOT (see Section VI) or, if desired, re-adjust the isolator as required (see Section V).
With the source laser off, or running at very low power (less than 250mW), position the Faraday Isolator such that the source laser beam can be directed through the Input Aperture.
Critical alignment of the Faraday Isolator should be done at low power (less than 250mW) in order to prevent optical damage to your isolator or laser source.
Use IR cards or viewers to ensure that the source laser beam is centered on the input and Output Apertures. It is also preferable to use an IR viewer to ensure that weak reflections from AR coated optical surfaces in the Faraday Isolator are not being directed back into the source laser. The Optical surfaces in the Faraday Isolator are angled slightly to reduce these reflections. Increasing the distance between the Faraday Isolator and the source laser can also help ensure that no reflections couple back into the source laser if necessary.
At this point the Faraday Isolator should be secured to the work surface with two to four ΒΌ - 20 or M6 screws –one for each slot in the baseplate flanges. Steel (ferromagnetic) ball drivers or other such wrenches will be attracted to the external magnetic field surrounding the device. If possible use anti-magnetic stainless steel or titanium tools. If ferromagnetic tools are used it is desirable to introduce the slowly towards the device from the sides along the direction of the baseplate flange slots.
If the Faraday Isolator will be used with average powers in excess of 25W transmitted or 0.5W rejected backward propagating radiation the Polarizer Covers will need to be removed so that the Escape Ports allow rejected polarization light to be safely dumped onto a beam dump. Failure to allow these rejected polarizations to escape can cause the device to heat up. Such heat can degrade the performance of the Faraday Isolator, or in severe cases, cause damage to optical components in the isolator. While working with low alignment level power and wearing safety glasses, remove the screw holding the dust cover in place for both the input and output. Any rejected polarized beams (in either the forward or backward propagating directions) can now exit the polarizer assembly. Use an IR viewer or IR card to locate these beams. Ensure that they are terminated on beam dumps consistent with the maximum amount of power that may be in such beams. If the Faraday Isolator is used in applications where strong reflections and/or optical gain elements (amplifiers) exist there may be very high power rejected beams for backward propagating light at the input polarizer. If the average power levels used do not exceed 25W transmitted or 0.5W of backward propagating power then the Polarizer Covers may be kept in their factory positioned orientation –that it with all rejected beams blocked by the Polarizer Cover. However, if the Faraday Isolator is to be used with very high peak intensities it is prudent to allow rejected beams to escape on to external beam dumps to prevent any ablation damage to the Nickel plated Polarizer Covers. Follow the same procedure above as for high average powers in order to safely terminate all rejected beams. |
