Evanescent Field Coupler Thin Film Coating Wavelength Equalization
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Solution Overview
Problem
Opto-electronic devices face challenges in achieving equalized coupling efficiency for different wavelengths of light into and out of an open dielectric resonator, as the optimal distance for coupling one wavelength significantly impairs the coupling of another, resulting in varying loaded quality factors and bandwidths by orders of magnitude.
Innovation Solution
An evanescent field coupler with a thin film coating is used, comprising alternating layers of different materials with specific refractive indices and thicknesses, designed to increase reflection of one wavelength while allowing another to pass through, thereby equalizing coupling efficiency and boosting the loaded quality factor of the resonator for both wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the distance between the coupler and WGMR is optimized to maximize coupling of light at a first wavelength, then coupling efficiency for the first wavelength is improved, but coupling efficiency for light at a significantly different second wavelength deteriorates
Solution Approach 1:
The patent applies local quality by introducing a wavelength-selective coating on the coupler surface that differentially affects different wavelengths. The coating creates locally different optical properties (reflectivity) for different wavelength ranges, allowing the same physical distance to provide optimal coupling for multiple wavelengths simultaneously. This resolves the contradiction by making the coupling interface wavelength-dependent through localized modification rather than changing the global distance parameter.
Solution Approach 2:
The patent changes the optical parameters (reflectivity, phase) of the coupler surface through the wavelength-selective coating. By modifying the effective refractive index and reflectivity characteristics at the coupler-resonator interface for different wavelengths, the system achieves wavelength-independent coupling efficiency without altering the physical distance. This parameter transformation allows simultaneous optimization for multiple wavelengths.
2Device complexity
If the distance between the coupler and WGMR is fixed, then device complexity is reduced, but coupling efficiency varies by orders of magnitude across different wavelengths
Solution Approach 1:
The patent transforms the coupling problem from a geometric parameter (distance) to an optical parameter (reflectivity) by introducing the wavelength-selective coating. This allows the fixed physical distance to provide variable effective coupling strength for different wavelengths through the coating's wavelength-dependent optical properties, maintaining simple device structure while achieving reliable coupling across wavelengths.
3Adaptability or versatility
If a wavelength-selective coating is added to the coupler, then coupling efficiency equalization across wavelengths is achieved, but device complexity increases
Solution Approach 1:
The wavelength-selective coating acts as an intermediary element between the coupler and the resonator modes. This intermediate layer mediates the interaction by providing wavelength-dependent coupling without requiring complex mechanical adjustment mechanisms. The coating translates the single-distance constraint into multi-wavelength optimization through its optical mediation properties.
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 thin film coating effectively reduces the coupling efficiency of longer wavelengths, matching the loaded quality factor of shorter wavelengths, ensuring that the resonator's quality factor values for different wavelengths are within a factor of four of each other, despite a fixed coupler-resonator distance.
Implementation Method 1
the refractive index of the first material, the refractive index of the second material, and a selected thickness of each layer of the plurality of layers cause constructive interference of light of the first wavelength at the thin film coating to increase reflection of light of the first wavelength
Implementation Method 2
the thin film coating is configured to increase reflection of light of a first wavelength
Implementation Method 3
an evanescent field coupler having a first surface configured to evanescently couple light between the evanescent field coupler and an open dielectric resonator
Data Source
AI summary
One feature pertains to an apparatus that includes apparatus that includes an evanescent field coupler having a first surface that evanescently couples light between the evanescent field coupler and an open dielectric resonator. The apparatus also includes a thin film coating covering at least a portion of the first surface of the evanescent field coupler. The thin film coating is specifically designed so that the thin film coating reflects light of a first wavelength.