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Broadband Circular Polarizer Based on Chirped Double-Helix Chiral Fiber Grating
Linlin Xue1, Bras Samuel Malumba Timoteo1, Weiwei Qiu1
1School of Information and Electronic Engineering, Zhejiang University of Science and Technology, Hangzhou 310023, China.
Materials (Basel, Switzerland)
|May 20, 2022
Summary
We developed a novel all-fiber broadband circular polarizer using leaky mode coupling and a phase-matched turning point. This compact device achieves high extinction ratios over a wide bandwidth, enabling advanced optical applications.
Area of Science:
- Optics and Photonics
- Fiber Optics
- Materials Science
Background:
- Circular polarizers are crucial optical components.
- Existing designs often face limitations in bandwidth, size, or performance.
- All-fiber solutions offer advantages in integration and robustness.
Purpose of the Study:
- To propose and simulate a novel all-fiber broadband circular polarizer.
- To achieve a high extinction ratio over a broad spectral range.
- To enable a compact device design.
Main Methods:
- Utilizing a chirped, double-helix, chiral, long-period, fiber grating (CLPG).
- Employing leaky mode coupling by coating the CLPG with a high refractive index material.
- Applying complex coupled-mode theory to analyze coupling mechanisms.
- Leveraging a phase-matched turning point (PMTP) to optimize bandwidth and grating pitch.
Main Results:
- Simulated two broadband circular polarizers with extinction ratios exceeding 25 dB.
- Achieved a bandwidth of over 120 nm with a 3.5 cm device.
- Demonstrated a bandwidth exceeding 300 nm with an 8 cm device.
- The PMTP facilitated a large bandwidth with a small grating pitch, leading to a compact structure.
Conclusions:
- The proposed CLPG with leaky mode coupling and PMTP is an effective design for broadband circular polarizers.
- The demonstrated performance (bandwidth and extinction ratio) is suitable for various optical applications.
- The compact nature of the device enhances its practical utility in integrated optical systems.
