Photonic Chip Integrated Collimation Structure Alignment
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Solution Overview
Problem
Current photonic chips face challenges in efficiently coupling light with external devices due to narrow spectral bandwidth and alignment issues, particularly when using surface coupling arrays, which limit their applicability in coarse wavelength multiplexing and require complex and costly alignment processes.
Innovation Solution
A photonic chip with an integrated reflective collimation structure at the rear face to increase the mode size of the light beam, allowing for improved alignment tolerance and expanded spectral bandwidth by directing the light beam towards the front face, eliminating the need for external lenses and reducing alignment complexities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface coupling arrays are used to extract light from photonic chips, then light coupling to external devices is enabled, but alignment precision requirements become extremely high and spectral bandwidth remains narrow
Solution Approach 1:
The patent embeds a microlens array directly within the substrate beneath the surface coupling array, creating a nested structure where the lens array is integrated into the chip substrate. This nesting allows the lens to pre-collimate light before it exits the coupling array, reducing alignment sensitivity without requiring separate external optical components
Solution Approach 2:
The patent introduces a vertical dimension by placing the microlens array in the substrate beneath the surface coupling array, rather than positioning lenses laterally or externally. This vertical integration enables light collimation in the propagation direction while maintaining planar chip architecture, effectively adding optical functionality in the depth dimension
2Reliability
If surface coupling arrays with standard mode size are used, then coupling to single-mode fibres is optimized, but alignment tolerance remains very narrow at about 2 μm
Solution Approach 1:
The microlens array is nested within the substrate beneath the surface coupling array, creating an integrated structure that pre-collimates light before it reaches the coupling interface. This embedded lens array expands the alignment tolerance from 2 μm to approximately 10 μm while maintaining coupling efficiency
Solution Approach 2:
The microlens array acts as an intermediary optical element between the waveguide and the external fibre connection. It mediates the transition by collimating light in the substrate, creating an intermediate collimated beam that is less sensitive to misalignment at the coupling interface
3Adaptability or versatility
If standard surface coupling arrays are used, then light extraction is achieved, but spectral bandwidth is limited to less than 30 nm
Solution Approach 1:
The integrated microlens array nested in the substrate provides wavelength-independent collimation, enabling the surface coupling array to achieve expanded spectral bandwidth of approximately 100 nm while maintaining coupling efficiency across the expanded wavelength range
Solution Approach 2:
The patent changes the optical parameters by introducing microlenses with specific focal lengths and aperture sizes that optimize collimation across a broad spectral range. The lens parameters are designed to maintain effective coupling over an expanded bandwidth of approximately 100 nm
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 integrated collimation structure enhances light coupling efficiency, increases alignment tolerance, and expands the spectral bandwidth, enabling more efficient light transfer and alignment, suitable for multiplexing applications without the need for costly external lens alignment.
Implementation Method 1
The collimation structure is a reflective structure suitable for reflecting an incident beam from the surface coupling array towards the front face
Data Source
AI summary
Optical beam forming at the inputs/outputs of a photonic chip and to the spectral broadening of the light coupled to the chip. The photonic chip comprises an optical waveguide layer supported on a substrate. The chip includes an optical waveguide structure made of silicon and a coupling surface grating. The photonic chip has a front face on the side facing the coupling surface grating and a rear face on the side facing the substrate. A reflecting collimation structure is integrated in the rear face to modify the mode size of an incident light beam. The coupling surface grating is designed to receive light from the optical waveguide structure and to form a light beam directed to the reflecting collimation structure. The invention further relates to the method for producing such a chip.