VCSEL Self-Mix Sensor with Integrated Fabry-Perot Filter
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Solution Overview
Problem
Self-mixing sensors, particularly those using Vertical Cavity Surface Emitting Lasers (VCSELs), face limitations in achieving high signal levels, which restrict their scalability and sensitivity, making them inadequate for various consumer and industrial applications.
Innovation Solution
The use of a Fabry-Perot filter in the optical path of the monitoring signal, combined with VCSELs designed for bottom emission, allows for enhanced signal amplification and efficient packaging, eliminating the need for a separate beam-splitter component and enabling direct integration of the filter into the VCSEL structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional VCSELs are used in self-mixing sensors, then the device complexity is reduced and packaging is simplified, but the achievable signal levels remain low
Solution Approach 1:
The patent merges the VCSEL and detector into a single integrated device structure, where the detector is positioned to receive light emitted from the VCSEL. This integration eliminates the need for separate beam-splitter components and reduces overall device complexity while maintaining compact packaging. The filter is integrated into the VCSEL structure itself, further simplifying the system architecture.
Solution Approach 2:
The patent introduces a filter as an intermediary element within the VCSEL structure to enhance the signal level. The filter is positioned to selectively transmit or block specific wavelengths of light, thereby amplifying the self-mixing signal without requiring additional external components. This intermediary filter enables higher signal levels while maintaining the simplicity of the integrated VCSEL-detector architecture.
2Measurement precision
If signal levels are increased for longer range applications, then the measurement precision improves, but the device complexity and cost increase
Solution Approach 1:
The patent combines multiple functions into the integrated VCSEL-detector structure, eliminating the need for separate beam-splitter components and external filters. This merging approach achieves the signal enhancement needed for longer range applications and improved measurement precision without increasing device complexity. The integrated design maintains a compact form factor suitable for consumer applications.
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 significantly amplifies the output signal, reduces sensor size and cost, and improves sensitivity, enabling the use of self-mixing sensors in longer range applications and consumer markets.
Implementation Method 1
The use of a Fabry-Perot filter in the optical path of the monitoring signal, combined with VCSELs designed for bottom emission, allows for enhanced signal amplification
Implementation Method 2
Self-mixing in VCSELs is known. However, VCSELs suffer from many of the same limitations as traditional lasers, namely the low achievable signal levels
Implementation Method 3
Self-mixing, or optical feedback interferometry as it is also known, in lasers and laser diodes is a sensitive mechanism for sensing physical phenomena related to motion
Data Source
AI summary
A system and method for generating, enhancing, and detecting the amplitude and phase modulation of a laser under a condition of self-mixing is provided. The system may comprise a laser and a detector to extract the characteristic self-mix signal, which is then interpreted using algorithms implemented in hardware or software. In the case of the laser being a Vertical Cavity Surface Emitting laser (VCSEL), the output signal can be detected by monitoring the surface light emission by means of a beam splitter, or in some embodiments as emission from the bottom surface of the laser. In some embodiments, the system may further comprise a wavelength filter such as an etalon in the signal path.