Laser to Chip Coupler with Multi-Mode Section for Relaxed Alignment
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Solution Overview
Problem
Current methods for coupling light between photonic chips and semiconductor laser diodes face challenges due to stringent alignment tolerances, high manufacturing costs, and reduced coupling efficiency, particularly due to the mismatch in dimensions and polarization sensitivity of existing coupling techniques.
Innovation Solution
The apparatus employs a multi-mode section on the photonic chip that converts misalignment into a slowly varying phase front distortion, allowing efficient coupling of light from a single laser diode to multiple single mode optical paths, even when misaligned, by mapping the misalignment onto internal degrees of freedom, and utilizing a multi-mode interferometer to stabilize the intensity distribution and phase front.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If grating couplers are used to couple light to and from the photonic chip, then alignment tolerances are relaxed, but polarization sensitivity increases and bandwidth is limited
Solution Approach 1:
The waveguide is segmented into multiple sections with different cross-sectional dimensions. The input waveguide has larger dimensions to accept the laser beam, while output waveguides have smaller dimensions for single-mode operation. This segmentation allows the system to benefit from both relaxed alignment tolerances (due to larger input waveguide) and single-mode performance (at output), without the polarization sensitivity and bandwidth limitations of grating couplers.
Solution Approach 2:
The waveguide dimensions are changed along its length, transitioning from larger cross-section at the input to smaller cross-section at the output. This parameter change enables mode transformation and allows the waveguide to accept broader beams with relaxed alignment while maintaining single-mode operation at the output, avoiding the polarization and bandwidth constraints of grating couplers.
2Loss of energy
If the waveguide dimensions are reduced to match laser beam dimensions, then coupling efficiency improves, but alignment tolerances become more stringent
Solution Approach 1:
The waveguide is divided into an input section with larger dimensions (matching laser beam) and output sections with smaller dimensions (single-mode). This segmentation allows efficient coupling from the laser while maintaining single-mode operation, and the larger input dimensions provide relaxed alignment tolerances compared to uniformly small waveguides.
Solution Approach 2:
The waveguide dimensions are changed in the transverse dimension along its length, creating a tapered or stepped structure. This dimensional change allows the waveguide to match the laser beam dimensions at the input for efficient coupling with relaxed alignment, while maintaining smaller single-mode dimensions at the output.
3Manufacturing precision
If active optical alignment is used to achieve high alignment accuracy, then coupling efficiency improves, but manufacturing cost increases
Solution Approach 1:
The waveguide structure is segmented with larger input dimensions that provide inherent alignment tolerance, reducing the need for expensive active optical alignment. The segmentation allows passive alignment methods to achieve sufficient accuracy while maintaining efficient coupling and single-mode operation at the output.
Solution Approach 2:
The invention uses a waveguide structure that is robust to alignment errors, effectively making the coupling process less sensitive to misalignment. This allows the use of cheaper passive alignment methods instead of expensive active optical alignment, reducing manufacturing cost while maintaining performance.
4Manufacturing precision
If single mode waveguides with small dimensions are used, then alignment tolerance is reduced, but coupling efficiency to laser diodes decreases
Solution Approach 1:
The waveguide is segmented into an input section with larger dimensions for efficient laser coupling and output sections with smaller single-mode dimensions. This segmentation resolves the contradiction by providing both relaxed alignment tolerance (at input) and single-mode performance (at output), achieving both improved alignment tolerance and maintained coupling efficiency.
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 approach relaxes alignment tolerances, increases coupling efficiency, and reduces manufacturing costs by enabling passive alignment with machine vision, while maintaining high alignment accuracy and efficient heat sinking, particularly suitable for silicon-on-insulator (SOI) material.
Implementation Method 1
utilizing a multi-mode interferometer to stabilize the intensity distribution and phase front
Implementation Method 2
The dimensions and compositions of the final waveguide are 450 nm wide, 250 nm high silicon waveguide surrounded by silicon dioxide
Data Source
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AI summary
A method and an apparatus for butt-coupling an input beam incoming from a photonic device of a second optical element to a primary photonic chip at an input interface of the primary photonic chip is disclosed. The primary photonic chip comprises a coupling apparatus. The light from the input beam is butt-coupled to the coupling apparatus. The coupling apparatus comprises a plurality of more than one single mode optical paths on the primary photonic chip. The single mode optical paths are strongly coupled to each other at the input interface of the primary photonic chip. Regions of strongly coupled single mode optical paths can correspond to one or both of distinct but highly coupled waveguides or waveguides fully merged into a multi-mode section.