Silicon Waveguide Meta-Surface Mode Converter for Low-Loss Compact Coupling
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Solution Overview
Problem
Existing silicon waveguide mode converters are large in size, have limited working bandwidth, and high insertion loss, which restricts the efficiency of mode division multiplexing in optical communication systems.
Innovation Solution
An ultra-compact silicon waveguide mode converter based on a meta-surface structure with periodical oblique subwavelength perturbations is developed, which changes the traditional constant mode coupling coefficient to a variable one, enabling efficient mode conversion from the fundamental mode to higher order modes with reduced loss and crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional mode converter structures are used, then mode conversion can be achieved, but the device size becomes large and insertion loss increases
Solution Approach 1:
The patent changes the geometric parameters of the waveguide structure by introducing oblique subwavelength perturbations with specific angles and periods. This modifies the mode coupling coefficient from constant to variable, enabling efficient mode conversion in a compact length while reducing insertion loss through optimized geometric parameters
Solution Approach 2:
The patent introduces oblique perturbations that add a spatial dimensionality to the mode conversion process. The oblique angle θ creates coupling in a directional manner, allowing mode conversion to occur over a shorter propagation distance compared to traditional straight-waveguide configurations
2Length of stationary object
If mode conversion is achieved in a compact structure, then device size is reduced, but working bandwidth becomes limited
Solution Approach 1:
The patent creates a dynamically adjustable mode converter where the oblique perturbation parameters (angle θ, period Λ) can be tuned to optimize performance for different wavelength ranges. The variable coupling coefficient allows the device to adapt to different operating conditions, expanding the effective working bandwidth despite the compact size
3Reliability
If traditional mode coupling is used, then mode conversion occurs, but crosstalk between modes increases
Solution Approach 1:
The patent applies local quality by introducing oblique perturbations only in specific regions of the waveguide rather than uniformly throughout. This localized modification creates controlled coupling zones that convert modes efficiently while minimizing unwanted crosstalk, achieving high conversion purity without excessive structural complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves significant reduction in mode conversion lengths and insertion loss, with conversion lengths of 3.96 μm, 3.686 μm, and 3.564 μm for TE0-TE1, TE0-TE2, and TE0-TE3 modes respectively, and maintains low insertion loss (<1 dB) and crosstalk (<−10 dB) in the 1500-1625 nm wavelength range.
Implementation Method 1
The meta-surface is a two-dimensional artificial structure with subwavelength characteristics, which can control the phase, amplitude and polarization of the beam effectively
Implementation Method 2
κab and κba represent the exchange coupling coefficient between waveguide modes a and b, namely the mode coupling coefficient
Implementation Method 3
an all-medium meta-surface structures with oblique subwavelength perturbations is adopted
Implementation Method 4
The phase matching condition of the mode converter meets the equation
Data Source
AI summary
A compact silicon waveguide mode converter, a dielectric meta-surface structure based on periodical oblique subwavelength perturbations, including a top silicon structure with oblique subwavelength perturbations etched in certain periods with period length of Λ, a duty cycle and an oblique angle θ on the SOI substrate. The invention adopts an all-dielectric meta-surface structure with oblique subwavelength perturbation, which can achieve a compact mode conversion from fundamental mode to arbitrary high-order mode of silicon waveguide, and can improve the optical communication capacity greatly.