Self-mixing PM Sensor VCSEL Extrinsic Photodiode Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current self-mixing interferometers using vertical-cavity surface-emitting lasers (VCSELs) and semiconductor photodiodes are costly and complex due to the need for a monolithic manufacturing process, limiting the adoption of extrinsic photodiodes for particulate matter sensing.
Innovation Solution
Implementing extrinsic photodiodes separate from the VCSELs, either on the same chip or on a separate chip, with a beam-splitting element to couple laser light efficiently, and using a dual-emitting VCSEL to enhance signal-to-noise ratio without the need for a beam-splitter, allowing for a less complex and high-yield manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If VCSEL and semiconductor photodiode are implemented on the same semiconductor chip using monolithic manufacturing process, then measurement precision and reliability are improved, but manufacturing cost increases and manufacturing yield decreases
Solution Approach 1:
The patent divides the sensor system into two separate components: a VCSEL chip and an extrinsic photodiode chip. This segmentation allows each component to be manufactured independently using optimized processes, avoiding the complexity of monolithic integration while maintaining functional performance. The VCSEL chip focuses on light emission with optimized cavity structure, while the photodiode chip focuses on light detection with optimized junction design.
Solution Approach 2:
The patent introduces an intermediary coupling mechanism (optical coupling structure) between the VCSEL chip and extrinsic photodiode chip. This intermediary enables efficient light transmission from the VCSEL to the photodiode while allowing independent manufacturing and optimization of each component. The coupling structure serves as a bridge that maintains signal integrity without requiring monolithic integration.
2Reliability
If VCSEL and semiconductor photodiode are implemented on the same semiconductor chip using monolithic manufacturing process, then device reliability is improved, but manufacturing yield decreases
Solution Approach 1:
By segmenting the device into separately manufacturable VCSEL chip and photodiode chip, the patent enables high-yield manufacturing of each component using standard processes. The separate chips can be manufactured in high volumes independently, and then assembled with reliable bonding techniques, achieving both high yield and high reliability.
Solution Approach 2:
The patent performs preliminary optimization of each chip's structure and manufacturing process independently before final assembly. The VCSEL chip is optimized for light emission performance and the photodiode chip is optimized for detection performance, allowing each to be manufactured with high yield using specialized processes, then combined with reliable bonding.
3Ease of manufacture
If extrinsic photodiodes are used separate from VCSELs, then manufacturing cost decreases and manufacturing complexity reduces, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent introduces an optimized optical coupling structure as an intermediary between the extrinsic photodiode and VCSEL. This coupling structure maximizes light transmission efficiency from the VCSEL to the photodiode, ensuring strong signal coupling that maintains high signal-to-noise ratio despite the separate chip architecture.
Solution Approach 2:
The patent optimizes key parameters of the extrinsic photodiode including junction depth, active area size, and doping concentration to maximize sensitivity to the VCSEL light. The photodiode is specifically designed with parameters optimized for detecting the VCSEL's emission wavelength and power level, ensuring high signal-to-noise ratio in the separate-chip configuration.
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 reduces manufacturing costs and complexity while improving signal-to-noise ratio, enabling effective particulate matter sensing with enhanced accuracy and efficiency.
Implementation Method 1
light emitted by a coherent or partially coherent source, e.g., a laser
Implementation Method 2
reflected and/or scattered from a target
Implementation Method 3
reflected and/or scattered from a target
Implementation Method 4
the optical power emitted by the laser
Data Source
AI summary
Aspects of the subject technology relate to an apparatus for self-mixing particulate-matter sensing using a vertical-cavity surface-emitting laser (VCSEL) with extrinsic photodiodes. The apparatus includes a dual-emitting light source disposed on a first chip and to generate a first light beam and a second light beam. The first light beam illuminates a particulate matter (PM), and a light detector extrinsic to the first chip measures the second light beam and variations of the second light beam and generates a self-mixing signal. The variations of the second light beam are caused by a back-scattered light resulting from back-scattering of the first light beam from the PM. The light detector is coupled to the dual-emitting light source. The direction of the second light beam is opposite to the direction of the first light beam, and the second light beam is directed to a sensitive area of the light detector.