An all-fiber laser using polarization-maintaining and ring-core fibers that are capable of automatically generating stable TE and TM modes is proposed and demonstrated experimentally. Two vector-mode coupling long-period fiber gratings (LPFGs) fabricated by a high-frequency CO laser are used in the fiber laser to realize efficient coupling between HE mode and TE/TM mode. The polarization dependence of the LPFGs is simulated using the coupled-mode theory and verified by experiments. A ring-core fiber is employed to support the stable propagation of TE and TM modes. By carefully aligning the polarization direction of the input light, the mode coupling ratios of both LPFGs exceed 15 dB. The mode purities of TE and TM modes are 92.4% and 97.3%, respectively. Owing to the all-polarization-maintaining structure, the laser output is highly stable under environmental disturbance. This laser can be used as a stable cylindrical vector beam source for a wide range of applications, including surface plasmon excitation, optical tweezers, high-resolution metrology and so on.
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http://dx.doi.org/10.1364/OE.395757 | DOI Listing |
We propose and demonstrate an ultra-wide tunable mode-locked all-fiber laser based on nonlinear amplifying loop mirror (NALM) with the output of cylindrical vector beams (CVBs). The tuning range covers from 1029 nm to 1098 nm through the intracavity nonlinear polarization evolution (NPE) filter effect. The switchable CVBs between radially and azimuthally polarized beams with mode purity above 90% are generated by incorporating a broadband few-mode long-period fiber grating (LPFG).
View Article and Find Full Text PDFJ Opt Soc Am A Opt Image Sci Vis
August 2024
We study properties of a light field at the tight focus of the superposition of two different-order cylindrical vector beams (CVBs). In the source plane, this superposition has a polarization singularity index amounting to the half-sum of the numbers of two constituent CVBs, while having neither spin angular momentum (SAM) nor transverse energy flow. We show that if the constituent CVBs have different-parity numbers, in the focal plane there occur areas that have opposite-sign longitudinal SAM projections, alongside areas of opposite-handed energy flows rotating on closed paths (clockwise and anticlockwise).
View Article and Find Full Text PDFA 1645 nm end-pumped dual-channel Er:YAG vector laser that could generate two cylindrical vector (CV) beams simultaneously with different polarization orders is demonstrated. The laser is designed in a two-arm structure, wherein each arm places a q-plate (QP) to introduce intra-cavity spin-orbital angular momentum conversion, leading to the oscillation of two various CV modes in two arms, and finally output along two directions, respectively. The favorable experimental results illustrate high power stability and polarization mode purity.
View Article and Find Full Text PDFOptical misalignment between transmitter and receiver leads to power loss and mode crosstalk in a mode division multiplexing (MDM) free-space optical (FSO) link. We report both numerical simulations and experimental results on the propagation performance of two typical vector beams, C-point polarization full Poincaré beams (FPB), and V-point polarization cylindrical vector beams (CVB), compared to homogeneous polarization scalar vortex beams (SVB) under optical misalignment. The FSO communication performance under misalignment using different transmit beams is evaluated in terms of power loss, mode crosstalk, power penalty, etc.
View Article and Find Full Text PDFFree-space optical (FSO) communication has the advantages of large bandwidth and high security and being license-free, making it the preferred solution for addressing the "last kilometer" of information transmission. However, it is susceptible to fluctuations in the received optical power (ROP) due to atmospheric turbulence and pointing errors, resulting in the inevitable free-space optical communication transmission performance degradation. In this work, we experimentally verified the turbulence resistance of the cylindrical vector beam (CVB) over a 3 km long free-space field trial link.
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