2D Grating Waveguide Coupler for Polarization-Independent Multiplexing
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Solution Overview
Problem
High refractive index contrast optical waveguide systems face significant coupling losses when interfacing with optical fibers, and existing solutions like one-dimensional grating couplers are polarization dependent and have limited bandwidth, making them unsuitable for applications requiring multiple wavelengths over a large wavelength span, such as Fiber-To-The-Home networks.
Innovation Solution
An integrated waveguide coupler and multiplexer/demultiplexer system utilizing a diffraction grating structure that can couple optical signals over a large wavelength span, with a two-dimensional grating structure providing polarization-independent operation by diffracting light from intersecting dielectric waveguides into the same coupling direction, allowing for efficient coupling of distinct wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a one-dimensional grating coupler is used to improve coupling efficiency, then coupling efficiency is improved, but polarization independence deteriorates and bandwidth is limited
Solution Approach 1:
The patent transitions from a one-dimensional grating structure to a two-dimensional grating structure. This dimensional change enables the grating to interact with both TE and TM polarizations equally, achieving polarization independence. The 2D periodic structure creates diffraction orders in multiple directions, allowing efficient coupling for various polarization states and expanding the operational bandwidth beyond what 1D gratings can achieve.
2Adaptability or versatility
If a two-dimensional grating structure is used to achieve polarization independence, then polarization independence is improved, but device complexity increases
Solution Approach 1:
The two-dimensional grating structure serves multiple functions simultaneously: it acts as a coupling interface for both TE and TM polarizations, functions as a wavelength demultiplexer, and provides a compact integrated solution. This multi-functionality justifies the increased structural complexity by eliminating the need for separate polarization-specific components and achieving broader operational versatility.
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 high coupling efficiency and polarization independence, enabling effective multiplexing and demultiplexing of optical signals across a broad wavelength range, suitable for applications like Fiber-To-The-Home networks, by spatially separating or combining radiation beams into a single optical coupling element.
Implementation Method 1
a diffraction grating structure formed at the intersection. The diffraction grating structure is adapted for diffracting light of a first predetermined wavelength from the at least one first dielectric waveguide in a coupling direction, and for diffracting light of a second predetermined wavelength from the at least one second dielectric waveguide in substantially the same coupling direction
Data Source
Figure 1~2a
Figure 2b~3
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AI summary
An optical device for optically multiplexing or demultiplexing light of different predetermined wavelengths is provided, the optical device comprising at least one first waveguide (11) and at least one second waveguide (12) formed on a substrate (10), wherein the at least one first waveguide and the at least one second waveguide intersect at an intersection, comprising a diffraction grating structure (13) formed at the intersection. There exists a first wavelength or wavelength band travelling within the first waveguide (11) exciting the grating structure and being diffracted an angle corresponding to an outcoupling direction and there exists a second wavelength or wavelength band, different from the first wavelength or wavelength band, travelling within the second waveguide (12) exciting the grating structure and being diffracted at an angle corresponding to the same outcoupling direction. The two radiation beams comprising radiation of two different wavelengths or wavelength bands are spatially separated into the optical waveguides (11 and 12) or combined into single outcoupling direction, e.g. into a single optical element, e.g. a single optical fiber (21). An optical device may be used in local access communications such as fiber to the home, office or curb applications.