Note that you can also receive the articles in the form of a newsletter or with an RSS feed. You may link to this page and cite it, because its location is permanent. DK Photonics from Shenzhen, China, offers high quality fiber-optic components for applications in. This article is a posting of the Photonics Spotlight, authored by Dr. RP Photonics Encyclopedia and Buyers Guide. The degree of isolation possible with that setup can be substantially higher than with a Faraday isolator alone.īut of course this works only when your setup can work with circularly polarized light and does not change the polarization of back-reflected light. Normally, it would get through this and be blocked only by the input polarizer. There is a way to combine both methods: just place a λ/4 waveplate after a Faraday isolator, again with 45° of its axis against the polarization direction.Īssuming that the polarization state of the back-reflected light has not been changed, the waveplate will transform that into linearly polarized light such that the light cannot pass even the output polarizer of the isolator. Its polarization direction is rotated by 90°, so that it will be blocked by the polarizer and thus cannot get back to the laser source. Send the beam through a polarizer first, then through a λ/4 waveplate, with the waveplate's axis being oriented at 45° against the polarization direction.Īny light reflected back after the waveplate will do a double pass through it, so that it effectively sees a λ/2 plate. Mostly, Faraday isolators are used for this purpose.īut there is a simple substitute, which will do the job in some cases: in Q switches and other optical modulators. Sometimes we need an optical isolator for suppressing back reflections from a device which might, for example, disturb a laser source. Note that thermal lensing may occur not only in the laser gain medium, but also in other optical components, e.g. EDFA Applications EDFA uses Er-Doped Fiber (EDF) as the gain medium. Ref.: encyclopedia articles on Faraday isolators and waveplates DK Photonics offers a large selection of passive optical components use for fiber laser.Such as 1064nm high power isolator,Cladding Power Stripper,Pum. However, this approach has its limitations. Rüdiger Paschotta, RP Photonics AGĪbstract: It is explained that a simple combination of a polarizer and a quarter waveplate can sometimes be used instead of a Faraday isolator. Posted on as a part of the Photonics Spotlight (available as e-mail newsletter!)Īuthor: Dr.
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