Optoelectronic Package Inverted Photodetector Alignment
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Solution Overview
Problem
Conventional optoelectronic packages with mirrors for light reflection result in significant signal loss, optical cross-talk, alignment issues, and sourcing challenges due to the need for custom components.
Innovation Solution
The optoelectronic package design eliminates the need for a mirror by orienting the photodetector upside-down in direct line of sight with the light source, using an inner package with external bond pads connected via wire bonds to terminals in an outer package, allowing for simplified alignment and reduced assembly costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mirror is used to reflect light from the light source to the photodetector, then the photodetector can be positioned on the same substrate or laterally offset, but this causes significant signal loss, optical cross-talk, alignment issues, and increased device complexity
Solution Approach 1:
The patent removes the mirror component from the optical path entirely. By inverting the photodetector orientation, the light source and photodetector are positioned in direct line of sight without requiring reflective surfaces, thereby eliminating the source of signal loss and optical cross-talk associated with mirror reflections.
Solution Approach 2:
The photodetector is inverted (oriented upside-down) relative to conventional configurations. This inversion allows the photodetector active area to face directly toward the light source, creating a direct optical path that eliminates the need for mirrors and resolves the alignment and signal quality issues inherent in conventional designs.
2Reliability
If a mirror is used to reflect light, then light can be directed to the photodetector, but this results in significant signal loss
Solution Approach 1:
The mirror is extracted from the system, eliminating the reflective interface that causes optical signal loss. The direct line-of-sight configuration allows light to travel unreflected from the light source to the photodetector, preserving signal strength.
Solution Approach 2:
By inverting the photodetector, the active detection area is positioned to receive light directly from the source without reflection. This eliminates the energy loss that occurs during mirror reflection, where some light is always absorbed or scattered at the reflective surface.
3Reliability
If a mirror is used for light reflection, then the photodetector can receive light, but this causes optical cross-talk
Solution Approach 1:
The mirror is removed from the optical path, eliminating the mechanism that causes optical cross-talk. In conventional designs, reflected light can bounce off the mirror and reach unintended photodetector areas or adjacent detectors, creating cross-talk signals that degrade detection accuracy.
Solution Approach 2:
The inverted photodetector configuration creates a direct, unreflected optical path. Light travels straight from the source to the detector without bouncing off mirrors, thereby eliminating the possibility of reflected light causing cross-talk with other detectors or detector regions.
4Reliability
If conventional mirror-based alignment is used, then light can be directed to the photodetector, but this increases alignment complexity and assembly cost
Solution Approach 1:
The mirror component and its associated alignment mechanisms are extracted from the system. Without mirrors, the complex multi-degree-of-freedom alignment procedures required to position reflective surfaces correctly are eliminated, significantly simplifying the assembly process and reducing costs.
Solution Approach 2:
The inverted photodetector creates a direct line-of-sight configuration that is inherently more tolerant to misalignment than mirror-based systems. This direct path requires minimal alignment precision compared to the delicate angular adjustments needed for mirror positioning, thereby simplifying manufacturing and reducing assembly costs.
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 design simplifies alignment, reduces assembly costs, and minimizes signal loss and optical cross-talk, while enabling the use of off-the-shelf photodetector dies and hermetic sealing, supporting a wide range of applications including atomic clocks and magnetometers.
Implementation Method 1
The PD can be on the same substrate as the light source, or on the other side of the package laterally offset from the light source
Implementation Method 2
A first wire bond connects the first external bond pad of the PD die to a first terminal of the outer package. A second wire bond connects the second external bond pad of the PD die to a second terminal of the outer package.
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2A
AI summary
In described examples, an optoelectronic package (200) includes an inner package (100) with a dielectric substrate having at least a first dielectric level with a photodetector (PD) die (110) on a die attach area, first routing connecting a first contact to a first external bond pad (FEBP 111), and second routing connecting a second contact to a second external bond pad (SEBP 112). An outer package (OP 170) includes a ceramic substrate (171) including a light source die (180) on a base portion (171a) in direct line of sight with the PD including a first electrode (181) and second electrode (182). A first wire bond (161) connects the FEBP (111) to a first terminal (191), a second wire bond (162) connects the SEBP (112) to a second terminal (192), a third wire bond (165) connects the first electrode to a third terminal (193), and a fourth wire bond (166) connects the second electrode to a fourth terminal (194).