Optical Microresonator Thermal Isolation via Cladding
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Solution Overview
Problem
Optical microring-resonator-based thermal sensors face performance degradation due to significant optical losses along bus waveguides in large-sized arrays, which affect the sensitivity and accuracy of infrared radiation detection.
Innovation Solution
The introduction of a cladding structure with a refractive index greater than 1.0 to encase portions of the optical waveguide and resonator, reducing scattering losses and enhancing evanescent coupling efficiency, allowing for the formation of larger-sized arrays with improved thermal isolation and mechanical support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If optical microring-resonator-based thermal sensors are used in large-sized arrays, then the coverage and detection capability are improved, but optical losses along the bus waveguides increase and degrade sensor performance
Solution Approach 1:
A cladding structure with refractive index greater than 1.0 is introduced as an intermediary between the waveguide and the surrounding environment. This cladding layer reduces scattering losses by providing a gradual refractive index transition, thereby minimizing optical energy loss while enabling larger array configurations.
Solution Approach 2:
The refractive index parameter of the surrounding medium is changed from air (n=1.0) to a cladding material with higher refractive index (>1.0). This parameter change reduces scattering losses at the waveguide interface, allowing for extended waveguide lengths and larger array sizes without significant performance degradation.
2Reliability
If the waveguide and resonator are exposed to air for evanescent coupling, then coupling efficiency is maintained, but scattering losses increase significantly
Solution Approach 1:
The cladding structure serves as an intermediary layer that surrounds the waveguide and resonator. It maintains the evanescent field coupling mechanism while reducing scattering losses by providing a controlled refractive index environment, thus preserving coupling efficiency without the penalty of high scattering losses.
Solution Approach 2:
The cladding structure is applied locally to the waveguide and resonator regions where optical fields are present. This localized modification provides scattering loss reduction precisely where needed, while maintaining the evanescent coupling functionality in the same region.
3Temperature
If thermal isolation from substrate is implemented, then temperature excursion is maximized, but mechanical support and structural stability are reduced
Solution Approach 1:
The support structure is segmented into discrete support beams or posts that provide mechanical support only in specific locations. This segmentation allows the resonator to be thermally isolated from the substrate while maintaining structural integrity through the distributed support points, maximizing temperature excursion without compromising mechanical strength.
Solution Approach 2:
Thin film structures and flexible support beams are used to provide mechanical support while minimizing thermal conduction paths to the substrate. These thin structures maintain structural stability but present minimal thermal resistance, allowing the resonator to achieve maximum temperature excursion while remaining mechanically supported.
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 significantly reduces scattering losses, maintains high sensitivity to temperature changes, and suppresses thermally-induced buckling, enabling more efficient detection of infrared radiation with reduced fabrication tolerances and the ability to form larger arrays without cryogenic cooling.
Implementation Method 1
a cladding structure disposed to surround and encase a section of the optical waveguide located proximate to the optical resonator and an adjacent portion of the optical resonator
Implementation Method 2
an optical waveguide located proximate to the optical resonator to couple light from the optical waveguide into the optical resonator
Implementation Method 3
an optical resonator suspended above a substrate (the optical resonator having a resonant frequency which changes in response to heating of the optical resonator by the infrared radiation)
Implementation Method 4
The sensors are based on the thermo-optic effect and are fabricated in a manner to be thermally isolated from an underlying silicon wafer substrate
Data Source
AI summary
A thermal microring optical sensor is configured such that a portion of the optical resonator and its associated waveguide are encased within a cladding structure to minimize scattering losses along the waveguide and also provide improved evanescent coupling efficiency between the waveguide and the resonator. Functioning as a thermal sensor, incoming radiation modifies the temperature of the resonator, which changes its resonant frequency and, as a result, the percentage of light that it evanescently couples from the waveguide. The cladding structure also functions as a mechanical support for the resonator disk, eliminating the need for a pedestal to suspend the disk above the support substrate. Thermally-induced buckling of the optical waveguide is also reduced by encasing the susceptible portion of the waveguiding within the cladding structure.