Photonic Chip Collimation Structure for Alignment Tolerance
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Solution Overview
Problem
Current photonic chips face challenges in efficiently coupling light beams with external devices due to limited alignment tolerance, narrow spectral band, and polarization sensitivity, particularly with surface grating couplers, which restrict their application in multiplexing and free propagation scenarios.
Innovation Solution
A photonic chip design incorporating a light guiding layer with a vertical coupler and a collimation structure on the rear face, featuring a digital or Fresnel lens with trenches of invariable thickness, which expands and collimates the light beam, allowing for improved alignment tolerance and expanded spectral band, enabling efficient coupling with external devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface grating couplers are used for light coupling, then coupling between waveguides and fibres is achieved, but alignment tolerance is limited and spectral band is narrow
Solution Approach 1:
The patent combines the surface grating coupler with a lens structure into an integrated photonic chip component. The lens is formed by etching trenches in the substrate beneath the grating coupler, creating a merged structure that performs both coupling and beam collimation functions simultaneously, thereby expanding alignment tolerance and spectral band while maintaining coupling efficiency
Solution Approach 2:
The lens structure acts as an intermediary element between the surface grating coupler and external fibres. It receives the coupled light from the grating coupler, collimates and expands the beam, then directs it towards external fibres, thereby mediating the transition and improving both alignment tolerance and spectral compatibility
2Ease of operation
If surface grating couplers are used, then vertical coupling to fibres is enabled, but polarization sensitivity restricts application
Solution Approach 1:
The integrated lens-grating coupler structure is designed to be polarization-insensitive, enabling it to handle both TE and TM polarizations equally. This universal design maintains the vertical coupling capability while removing the polarization restriction, allowing the component to function effectively in diverse photonic applications regardless of input polarization state
3Adaptability or versatility
If collimation structure with trenches of invariable thickness is used, then alignment tolerance is enhanced, but device complexity increases
Solution Approach 1:
The lens structure is segmented into an array of discrete trenches etched in the substrate. Each trench has an invariable thickness that is optimized for collimation, while the collective arrangement of these segmented trenches creates the overall lens function. This segmentation approach enhances alignment tolerance through the array configuration while keeping individual trench fabrication relatively simple
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 proposed design enhances alignment tolerance and spectral band, facilitating efficient light coupling and multiplexing, overcoming the limitations of traditional surface grating couplers by providing a collimated and expanded light beam with reduced polarization sensitivity.
Implementation Method 1
a lens (15) integrated at the level of the rear face and configured to collimate a light beam incident on said structure from the vertical coupler and to expand a mode size of this beam
Implementation Method 2
a vertical coupler configured to receive light from the light guiding structure and to form therefrom a light beam in the direction of the lens
Data Source
AI summary
The present disclosure relates to shaping of optic beams at the inputs/outputs of a photonic chip, the spectral widening of the light coupled to this chip, and a method for manufacturing the chip. The photonic chip includes a light guiding layer supported by a substrate. The chip includes at least one light guiding structure made of silicon coupled on one side to a vertical coupler and on another side to an optical component integrated in the light guiding layer. The photonic chip has a front face on the vertical coupler side and a rear face on the substrate side. A collimation structure of digital lens type is integrated at the level of the rear face to collimate the mode size of the light beam incident on the lens and coming from the vertical coupler.