Faraday Rotators & Isolators - Frequently Asked Questions
1. I have an EOT PAVOS 1010 nm to 1080 nm Faraday Rotator / Isolator. What is its bandwidth?
EOT's PAVOS 1010 nm to 1080 nm Faraday Rotators / Isolators can be optimized for any wavelength within the 1010 nm to 1080 nm region. The bandwidth for any given specific wavelength in that region is ± 13 nm. For example, if the Faraday Rotator / Isolator is optimized for 1053 nm, it has a useable wavelength range of 1040 nm to 1066 nm. Useable wavelength range is defined as the wavelength range over which the Faraday Rotator / Isolator will meet its published transmission and isolation specifications.
2. Can I use my 1010 nm to 1080 nm Faraday Rotator / Isolator at 980 nm or 800 nm?
No. The 1010 nm to 1080 nm Faraday Rotators / Isolators will not meet their published specifications at these wavelengths. The Verdet constant of TGG is wavelength-dependent. At shorter wavelengths, the Verdet constant of TGG increases. At 980 nm or 800 nm, Faraday rotation would be considerably higher than 45°, resulting in poor isolation and transmission.
3. Why am I seeing fringes on my beam after it passes through my Faraday Rotator / Isolator?
This is an indication that the beam is being clipped due to overfilling of the clear aperture of the Faraday Rotator / Isolator. EOT recommends that the 1/e2 diameter of your beam not exceed 2/3 of the clear aperture of your Faraday Rotator / Isolator. If you are seeing fringes, we recommend that you decrease the size of your beam.
4. Why is the isolation of my 1010 nm to 1080 nm Faraday Isolator decreasing over time?
This is usually a result of too much power being incident on the optical isolator or being rejected by the optical isolator. EOT's PAVOS 1010 nm to 1080 nm Faraday Isolators are designed to handle up to 50 W of average power. Beyond that, absorption in the TGG can result in thermal lensing or other thermal-related effects. EOT makes custom Faraday rotators specifically for lasers having >50 W of average power. Please see the Custom Products section of this website for more information.
If more than 0.5 W of average power is being rejected, EOT recommends that the escape ports be open to allow the rejected light to escape. If rejected powers of >0.5 W are not allowed to escape and are instead contained within the isolator body, the isolator can heat up and degrade the performance of your optical isolator. When using the escape ports to allow rejected light to escape, it is important to properly terminate the beam. Please consult EOT's PAVOS 1010 nm to 1080 nm Faraday Rotator/Isolator User Guide on this website for more information on the proper use of escape ports.
5. Why are the pulses from my femtosecond Ti:Sapphire laser being broadened after passing through my broadband Faraday Rotator / Isolator?
The pulse broadening is due to dispersion in the TGG. The Sellmeiers Equation for TGG can be found in the Faraday Rotator / Isolator Technical Notes section of this website.
6. Why is my Faraday Rotator / Isolator not meeting specification at an operating temperature of 50 °C when it was working fine at 25 °C?
Both the TGG and magnets used in EOT's Faraday Rotators / Isolators are temperature-dependent. As temperature increases, the Verdet constant of TGG decreases and the fields generated by the magnets weaken, resulting in lower Faraday rotation. As temperature decreases, the Verdet constant of TGG increases and the fields generated by the magnets strengthen, resulting in higher Faraday rotation. If you are going to use your Faraday Rotator / Isolator at a temperature other than room temperature or over a range of temperatures, we strongly encourage you to contact EOT to discuss this application.
7. Can I order an EOT laser diode isolator with an escape port for my injection locking application?
Yes. EOT offers our TORNOS laser diode isolators with PBS cubes rather than Polarcor polarizers for these applications. Please contact EOT for pricing and information on this option.
8. Can EOT do custom a base plate or beam height?
Yes. There will be an additional charge but customized base plates or special beam heights can be done. Please provide us with your specifications.
9. Are EOT's Faraday Rotators / Isolators vacuum-compatible or space-qualified?
EOT can make custom Faraday Rotators / Isolators that are vacuum-compatible or space-qualified. Please contact EOT for more information.