Tapered Directional Waveguide Coupler for Thick-Silicon Light Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical couplers face challenges in achieving high coupling efficiency, particularly when dealing with thick-silicon waveguides, where tightly confined modes require stringent processing tolerances and result in inefficient light transfer between waveguides.
Innovation Solution
A directional coupler design featuring tapers in the coupler shoulder and ridges, allowing for adiabatic expansion and compression of electromagnetic radiation, which enhances coupling efficiency by guiding light from one waveguide to another through a combination of evanescent and direct coupling mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional optical coupler designs are used with thick-silicon waveguides, then manufacturing is simpler, but coupling efficiency is poor due to tightly confined modes requiring stringent processing tolerances
Solution Approach 1:
The patent modifies the geometric parameters of the coupler structure by introducing tapers with specific width variations along the propagation direction. The taper regions have gradually changing cross-sectional dimensions that transform the mode confinement characteristics, allowing efficient coupling without requiring extremely tight processing tolerances. This parameter change enables the coupler to work effectively with thick-silicon waveguides while maintaining relaxed manufacturing requirements.
2Reliability
If tapers are added to the coupler shoulder and ridges to enable adiabatic expansion and compression of electromagnetic radiation, then coupling efficiency increases, but device complexity increases
Solution Approach 1:
The coupler structure is segmented into distinct functional regions: straight waveguide sections, taper regions with expanding/compressing cross-sections, and coupling regions. Each segment performs a specific function - the straight sections guide light, the taper sections adiabatically transform the mode profiles, and the coupling sections enable energy transfer. This segmentation allows the complex adiabatic transformation to be achieved through a series of simpler, manageable structural transitions rather than a single complex element.
Solution Approach 2:
The tapers introduce curved, gradual transitions in the waveguide geometry rather than abrupt changes. The cross-sectional dimensions vary continuously along the propagation direction, creating a smooth adiabatic transformation of the electromagnetic modes. This curved geometric approach enables efficient coupling by gradually adapting the mode profiles to match between the input and output waveguides.
3Reliability
If stringent processing tolerances are used to achieve high coupling efficiency with thick-silicon waveguides, then coupling efficiency improves, but manufacturing complexity and cost increase
Solution Approach 1:
The patent deliberately designs the taper parameters (width, length, gradient) to transform the sensitivity characteristics of the coupler. By changing the geometric parameters to include gradual tapers, the coupling efficiency becomes less sensitive to variations in fabrication dimensions. This parameter optimization allows the coupler to maintain high efficiency even with moderate processing tolerances, significantly easing manufacturing requirements compared to conventional designs.
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 directional coupler design significantly increases coupling efficiency and reduces manufacturing complexities, enabling efficient light transfer between thick-silicon waveguides while providing flexible manufacturing tolerances and minimizing attenuation.
Implementation Method 1
An optical waveguide directs radiation in the visible, infrared, and/or ultra-violet portions of the radiation spectrum by total internal reflection
Implementation Method 2
a certain percentage of light from the first waveguide transitions to the second waveguide through sides of the waveguides
Data Source
Figure 1~3
Figure 4
Figure 5
AI summary
An optical, directional coupler has a first input, a second input, a first output, and a second output. The coupler is made with a shoulder disposed on a substrate and a first ridge and a second ridge disposed on the shoulder. The first ridge extends from the first input to the first output. The second ridge extends from the second input to the second output. The shoulder, the first ridge, and the second ridge taper to provide coupling and are modified to select a coupling ratio. Further, a tunable laser has a first mirror, a second mirror, a gain medium, and a directional coupler. The first mirror and the second mirror form an optical resonator. The gain medium and the directional coupler are, at least partially, in an optical path of the optical resonator. The directional coupler provides an output coupler for the tunable laser.