| Title |
Study on Control of Output Polarization States at Individual Lasing Wavelengths in Fiber Bragg Grating Laser |
| Authors |
Seul-Lee Lee ; Yong Wook Lee |
| DOI |
http://dx.doi.org/10.5207/JIEIE.2019.33.9.025 |
| Keywords |
Optical Fiber Laser; Polarization-Diversified Loop; Fiber Bragg Gratings |
| Abstract |
In this paper, we realized an optical fiber Bragg grating (FBG) laser based on a polarization-diversified loop structure (PDLS) whose dual lasing lines can control its output polarization state at individual resonance. The PDLS-based inline filter of the fiber laser consists of a polarization beam splitter, three quarter-wave plates (QWPs), and two FBGs with different resonances. At proper orientation angle sets of the three QWPs, the inline filter can have its polarization-dependent transmittance, enabling the reflection spectra of two FBGs to control its output states of polarization (SOPs) between two orthogonal SOPs of linear horizontal polarization (LHP) and linear vertical polarization (LVP) according to input SOPs. Therefore, by controlling the input SOPs at specific QWP angles, the output SOPs of two FBG reflection spectra can be selected independently, having orthogonal or parallel relationship each other. Consequently, the PDLS-based FBG laser could provide four types of dual lasing lines with switchable output SOPs of LHP or LVP at each Bragg wavelength, including two orthogonal output SOPs (e.g., LHP at one lasing wavelength and LVP at the other one, and vice versa) and two parallel ones (e.g., LHP or LVP at both lasing wavelengths). By properly controlling a cavity polarizer and three QWPs, four switchable output SOP sets of dual lasing lines could be obtained with a polarization extinction ratio (PER) more than 20.1dB without changing the filter structure. |