Adiabatic Optical Coupler Structure for Low Insertion Loss
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Solution Overview
Problem
Conventional optical couplers experience higher than desired losses due to optical energy being emitted in free space and coupling into undesired modes.
Innovation Solution
The optical coupler design includes cores with specific surface spacings and widths that taper adiabatically to minimize loss, using cladding with a lower refractive index, allowing for efficient coupling and reduced radiation into undesired modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional optical coupler designs are used, then device simplicity is maintained, but insertion loss increases due to energy emission in free space and coupling into undesired modes
Solution Approach 1:
The optical coupler is divided into multiple distinct portions: a first portion for receiving input signals, a second portion for coupling between cores, and a third portion for output signals. This segmentation allows each portion to be optimized for its specific function, with the second portion specifically designed as a coupling region with controlled spacing and tapered dimensions to minimize energy loss while maintaining manageable structural complexity.
Solution Approach 2:
Different portions of the optical coupler are given different local properties: the first and third portions have larger core dimensions for efficient signal reception and output, while the second coupling portion has reduced core dimensions and controlled spacing to maximize coupling efficiency. The spacing between cores is specifically tapered in the coupling region to achieve optimal mode matching and minimize radiation losses locally where coupling occurs.
2Loss of energy
If adiabatic tapering is implemented to reduce losses, then insertion loss decreases, but manufacturing precision requirements increase
Solution Approach 1:
The optical coupler structure is designed with predetermined spacing and dimensional parameters that are calculated in advance to achieve adiabatic tapering. The spacing between cores and the dimensions of each portion are specified a priori to ensure that the tapering occurs smoothly through the coupling region, allowing light to adapt gradually to the changing mode profile without abrupt transitions that would cause radiation losses. This preliminary design approach reduces the need for extremely tight manufacturing tolerances during fabrication.
3Loss of energy
If core dimensions are reduced in the coupling region, then coupling efficiency improves, but signal power decreases
Solution Approach 1:
The optical coupler employs dynamic dimensional variation along its length, with the core dimensions and spacing changing gradually through the coupling region. The second portion has reduced core dimensions compared to the first and third portions, creating a dynamic transition zone where the mode profile evolves smoothly. This dynamic structure allows efficient power transfer between cores during the coupling process while maintaining adequate signal power levels in the input and output regions where larger core dimensions are restored.
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 design achieves lower insertion loss and broader bandwidth, enabling the creation of resonators with higher quality factors that require less optical power, thus using lower-cost and less powerful sources.
Implementation Method 1
a first spacing between the first surface along the first portion of the first core and the second surface along the first portion of the second core adiabatically tapers narrower towards the second portions of the first and the second cores
Implementation Method 2
each of the first and the second cores has an index of refraction higher than an index of refraction of the cladding
Implementation Method 3
each of the first and the second cores has an index of refraction higher than an index of refraction of the cladding
Data Source
AI summary
Techniques are provided for implementing a low insertion loss optical coupler utilizing adiabatic tapering of spacings between two adjacent optical waveguides and tapering of a portion of one of the optical waveguides. An optical resonator with a higher quality factor may be formed using two of the low insertion loss optical couplers.