Shallow-Profile Optical Elements for Misalignment-Tolerant PD Coupling
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Solution Overview
Problem
In optical communication systems, achieving high-speed operation of photodetectors (PDs) is hindered by the small active area of PDs, making efficient light coupling from optical input devices challenging due to potential optical misalignment.
Innovation Solution
The use of small-diameter, small-aperture, shallow profile lenses and concave mirrors designed to pass the chief ray near the center of optical elements, such as lenses or mirrors, integrated with the PD, to enhance optical coupling and control back reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the active area of photodetector is reduced to achieve high-speed operation, then the operating speed increases, but the light coupling efficiency deteriorates due to smaller coupling area
Solution Approach 1:
An optical element (lens or mirror) is introduced as an intermediary component between the optical input device and the photodetector. This optical element focuses or directs light onto the small active area of the photodetector, enabling efficient light coupling despite the reduced detector size. The optical element acts as a mediator that bridges the gap between the larger optical input aperture and the smaller photodetector area.
Solution Approach 2:
The optical element utilizes spatial dimensionality to solve the coupling problem. By introducing an optical element with specific curvature (lens) or reflective surface (mirror), the system transforms the light propagation paths in three-dimensional space, focusing light from a larger area onto the smaller photodetector active area through focal points or focused beams.
2Productivity
If the photodetector size is reduced for high-speed operation, then the bandwidth increases beyond 25 Gb/s, but the alignment sensitivity increases making coupling more difficult
Solution Approach 1:
The optical element serves as a tolerant intermediary that can accommodate alignment variations. The optical element's focal properties allow it to maintain effective coupling over a range of alignment conditions, reducing the sensitivity to precise positioning requirements and making the system more robust to manufacturing tolerances and assembly variations.
Solution Approach 2:
The optical element changes the optical parameters (light convergence angle, focal position, beam size) to optimize coupling efficiency. By adjusting the optical element's position, orientation, or focal length, the system can maintain effective light coupling despite variations in alignment, effectively decoupling the data transfer rate performance from strict alignment requirements.
3Volume of moving object
If small-diameter optical elements are used with photodetectors, then the package size is reduced, but the optical coupling efficiency may deteriorate due to smaller aperture
Solution Approach 1:
The optical element is integrated directly with the photodetector structure, merging two components into a compact unified assembly. This integration eliminates the need for separate mounting structures and reduces the overall package volume while maintaining effective optical coupling through the closely coupled optical element and photodetector arrangement.
Solution Approach 2:
The optical element utilizes three-dimensional light focusing to achieve efficient coupling within a compact footprint. By focusing light in the vertical dimension (through focal points above or below the photodetector surface), the system achieves effective coupling without requiring large lateral dimensions, thus reducing package size while maintaining 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 configuration increases the reliability and efficiency of optical coupling while maintaining small package sizes, reducing sensitivity to optical misalignment and allowing for higher data transfer rates beyond 25 Gb/s.
Implementation Method 1
shallow profile lenses and concave mirrors designed to pass the chief ray near the center of optical elements
Implementation Method 2
shallow profile lenses and concave mirrors designed to pass the chief ray near the center of optical elements
Implementation Method 3
A carrier with such a high frequency is sometimes referred to as an optical signal, an optical carrier, a light wave signal, or, simply, light
Data Source
AI summary
An optical system can include a optical receiver comprising an optical waveguide, an optical lid adjacent the waveguide, and a reflective surface proximate an output of the optical waveguide to direct light from the waveguide towards an output of the optical lid. The optical system can also include a photodetector (PD) die comprising a substrate, a concave mirror, and a photodetector. The concave mirror is formed on a first side of the substrate and the photodetector is disposed on a second side of the substrate, the first side opposite the second side, wherein the photodetector is disposed on the second side of the PD die offset from the optical axis of the optical element.