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Optical modulation of polarization state based on an etched single mode fiber with azo-polymer overlay

A large modulation range of polarization state at 1550nm is achieved by using an etched single mode fiber (SMF) with azo-polymer overlay. With irradiation of polarized light, the photo-reorientation of azo-polymer occurs, causing the birefringence in the fiber. This optically induced birefringence results in the change of polarization state which is continuously recorded on the Poincare sphere, finally makes the state of polarization (SOP) tunable by the irradiation of 365nm polarized light. In our experiment the SOP changes from-handed elliptical polarization to left-handed elliptical polarization and the ellipticity varies from 16.2° to 55.6° during the irradiation. The trajectory of the SOP can also be recovered to the initial polarization state when irradiated by unpolarized light. The experimental results show that the modulation is not only in large range, but also dynamic, reversible.