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Compact hybrid five-mode multiplexer based on asymmetric directional couplers with constant bus waveguide width
Optics Letters
|May 15, 2023
Summary
This study presents a novel hybrid mode division multiplexer (MDM) using asymmetric directional couplers without transition tapers. The device efficiently couples five hybrid modes, achieving a 140 nm working bandwidth.
Area of Science:
- Photonics
- Optical Communications
- Integrated Optics
Background:
- Mode division multiplexing (MDM) is crucial for increasing optical fiber communication capacity.
- Existing MDM devices often require complex structures like transition tapers, increasing fabrication challenges and insertion loss.
- Efficiently coupling multiple spatial modes into a single waveguide is a key challenge in integrated photonics.
Purpose of the Study:
- To demonstrate a simplified hybrid mode division multiplexer (MDM) design.
- To enable arbitrary add-drop functionality for multiple hybrid modes in a single bus waveguide.
- To achieve a wide operational bandwidth for the proposed MDM device.
Main Methods:
- Experimental demonstration of a hybrid mode division multiplexer (MDM) utilizing asymmetric directional couplers (ADCs).
- Elimination of transition tapers between cascaded ADCs by maintaining a constant bus waveguide width.
- Introduction of a partially etched subwavelength grating to control the effective refractive index of the bus waveguide.
Main Results:
- Successfully coupled five fundamental modes (TE0, TE1, TE2, TM0, TM1) as hybrid modes into the bus waveguide.
- Achieved arbitrary add-drop functionality without requiring transition tapers.
- Demonstrated a wide working bandwidth of up to 140 nm for the hybrid MDM.
Conclusions:
- The proposed hybrid MDM based on ADCs offers a simplified and effective solution for mode multiplexing.
- The integration of subwavelength gratings provides a viable method for controlling effective refractive index and enabling add-drop functionality.
- This compact and wide-bandwidth device holds significant potential for future high-capacity optical communication systems.
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