High efficiency all-fiber cylindrical vector beam laser using a long-period fiber grating

Area of Science:

• Photonics and Optics
• Fiber Laser Technology

Background:

• Cylindrical vector beams (CVBs) offer unique polarization properties valuable in various optical applications.
• Existing methods for generating CVBs often involve complex setups or lack high efficiency.
• All-fiber laser systems provide advantages in terms of stability, compactness, and robustness.

Purpose of the Study:

• To develop a novel all-fiber laser capable of generating high-purity cylindrical vector beams.
• To achieve high slope efficiency and a low lasing threshold in the fiber laser system.
• To investigate the influence of key components, such as the two-mode fiber Bragg grating (TM-FBG), on laser performance.

Main Methods:

• Incorporation of a long-period fiber grating (LPFG) within the laser cavity for efficient mode conversion at ~1548 nm.
• Integration of a two-mode fiber Bragg grating (TM-FBG) for simultaneous mode selection and spectrum filtering.
• Utilizing an intra-cavity polarization controller to switch between radially and azimuthally polarized beam generation.

Main Results:

• The fiber laser successfully generated CVBs at a single wavelength of 1547.95 nm with a narrow 30 dB linewidth (<0.18 nm) and high side-mode suppression ratio (>56 dB).
• Achieved a low lasing threshold of 24.5 mW and a high slope efficiency of 35.41%.
• Demonstrated the generation of both high-purity radially and azimuthally polarized beams by adjusting the polarization controller.

Conclusions:

• The proposed all-fiber laser design, utilizing LPFG and TM-FBG, is an effective method for generating CVBs.
• The system exhibits excellent performance characteristics, including high efficiency, low threshold, and stable single-wavelength operation.
• The demonstrated ability to generate both radial and azimuthal polarization modes enhances the versatility of this fiber laser for advanced optical applications.