Index-Matched Optical Epoxy for Waveguide Edge Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical coupling into and out of waveguides in photonic integrated structures is inefficient due to light leakage at the edge of the structure, caused by differences in refractive indices between the waveguide, insulator layers, and encapsulating oxides, particularly when silicon substrates are used.
Innovation Solution
A substrate with an opening adjacent to its edge, featuring a layer of insulator forming a bridge and a waveguide with a tapered region, where optical epoxy indexed matched to the insulator is used to replace encapsulating insulators and oxides, thereby containing optical signals and reducing refractive index differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If encapsulating insulators and oxides are used to protect the waveguide, then structural protection is provided, but optical signal losses increase due to refractive index mismatches
Solution Approach 1:
The patent changes the refractive index parameter of the encapsulating material by replacing standard insulators and oxides with index-matched epoxy resin. This material has a refractive index specifically selected to match the waveguide core, eliminating refraction losses at the interface while maintaining protective encapsulation.
Solution Approach 2:
The patent introduces an intermediary material (index-matched epoxy resin) between the waveguide and the external environment. This intermediary serves dual purposes: it provides structural protection like traditional encapsulants while simultaneously matching the optical properties to prevent signal loss through refraction.
2Reliability
If standard insulator layers are used between waveguide and substrate, then electrical insulation is provided, but optical coupling efficiency decreases due to refractive index differences
Solution Approach 1:
The patent modifies the refractive index parameter of the insulator layer by replacing standard electrical insulators with index-matched epoxy resin. This change maintains the electrical insulation function while optimizing the optical parameter to match the waveguide, thereby improving coupling efficiency.
Solution Approach 2:
The patent uses composite material strategy by employing epoxy resin that combines both electrical insulating properties and optical index-matching characteristics. This single composite material replaces separate functional layers, achieving both electrical insulation and optical efficiency simultaneously.
3Strength
If silicon substrates are used, then mechanical strength and thermal stability are improved, but optical losses increase at the waveguide edge
Solution Approach 1:
The patent applies local quality principle by maintaining the silicon substrate for bulk mechanical strength while locally replacing the edge encapsulation materials with index-matched epoxy. This localized material substitution addresses the specific optical loss problem at the waveguide edge without compromising the overall mechanical integrity of the silicon substrate.
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
This configuration reduces signal losses by eliminating refractive index mismatches, enhancing the efficiency of optical coupling into and out of the waveguide.
Implementation Method 1
The losses occur mainly due to differences in indices of refraction between the waveguide, the insulator layers and the encapsulating oxides
Data Source
AI summary
A device that includes an optical coupler with a waveguide and waveguide index matched materials at an edge of a substrate, and a method of forming the device, is provided herein. The device comprises: a substrate having an edge, and an opening formed therein adjacent the edge; a layer of insulator on the substrate, which forms a bridge across the opening at the edge; a waveguide on the layer of insulator, the waveguide comprising a constant-width region and a tapered region terminating at the edge in a region of the opening; a first layer of optical epoxy in the opening, the optical epoxy indexed matched to the layer of insulator; and, a second layer of the optical epoxy on the tapered region, such that the optical epoxy optically contains an optical signal leaking from the waveguide in the tapered region.