InGaAs Photodetector Notch Filter Wavelength Extension
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Solution Overview
Problem
Existing InGaAs sensors face challenges in detecting longer wavelengths due to lattice constant mismatches when attempting to extend their long wavelength cutoff beyond 1.68 µm, which degrades the quality of thin films and limits their applicability in applications such as moisture content measurement and LIDAR systems.
Innovation Solution
A sensor system incorporating an InGaAs photodetector with a notch filter that blocks specific wavelength bands (850 nm, 1060 nm, and 1550 nm) to improve signal-to-noise ratio and extend the detection range up to 1700 nm, using a ROIC to condition electrical signals and an optical coating or filter assembly for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If more InAs is added to extend the long wavelength cutoff beyond 1.68 µm, then the detection wavelength range is improved, but the lattice constant mismatch with the substrate increases and thin film quality deteriorates
Solution Approach 1:
The patent introduces a lattice-matched InGaAs buffer layer as an intermediary between the InP substrate and the extended wavelength InGaAs thin film. This buffer layer has intermediate composition (e.g., In0.53Ga0.47As) that provides a transition in lattice constant, reducing the mismatch between the InP substrate and the extended wavelength InGaAs layer, thereby enabling high-quality thin film growth at longer wavelengths
Solution Approach 2:
The patent changes the compositional parameters of the InGaAs alloy by adjusting the indium content to extend the wavelength cutoff beyond 1.68 µm. By carefully controlling the InAs proportion (e.g., using In0.7Ga0.3As for extended wavelength), the detection range is extended to cover 1.7-2.6 µm while managing lattice mismatch through the buffer layer approach
2Manufacturing precision
If standard InGaAs with 53% InAs is used, then the lattice constant matches the InP substrate and thin film quality is high, but the long wavelength cutoff is limited to 1.68 µm
Solution Approach 1:
The patent modifies the compositional parameter (indium content) of the InGaAs alloy from the standard 53% InAs to higher indium content (e.g., 70% InAs), which increases the long wavelength cutoff from 1.68 µm to extend into the 1.7-2.6 µm range, thereby expanding the detection wavelength range while using a buffer layer to maintain film quality
3Measurement precision
If a notch filter is added to block specific wavelength bands, then the signal-to-noise ratio is improved, but the device complexity increases
Solution Approach 1:
The patent integrates the notch filter functionality directly into the focal plane array detector structure, merging the filtering function with the detection function. This integration reduces the need for separate filter components and simplifies the overall device architecture while still achieving the desired wavelength selectivity and noise reduction
Solution Approach 2:
The patent uses a dielectric mirror or optical intermediary layer as a mediator to implement the notch filter function. This intermediary structure is deposited on the detector surface and provides wavelength-selective reflection or absorption, blocking specific bands (e.g., 850 nm, 1060 nm, 1550 nm) while allowing the desired extended wavelength range to pass through to the photodetector
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 solution enables superior infrared detection and imaging capabilities by excluding predetermined wavelengths, enhancing the sensor's sensitivity and quality for applications requiring longer wavelength detection while maintaining high signal fidelity.
Implementation Method 1
An InGaAs photodetector configured to convert received infrared radiation into electrical signals
Implementation Method 2
A notch filter is operatively connected to the InGaAs photodetector to block detection of wavelengths within at least one predetermined band
Data Source
Figure 1~2
Figure 3
AI summary
A sensor includes an InGaAs photodetector (102) configured to convert received infrared radiation into electrical signals. A notch filter (108) is operatively connected to the InGaAs photodetector (102) to block detection of wavelengths within at least one predetermined band. An imaging camera system (100) includes an InGaAs photodetector (102) configured to convert received infrared radiation into electrical signals, the InGaAs photodetector including an array of photodetector pixels each configured to convert infrared radiation into electrical signals for imaging. At least one optical element (106) is optically coupled to the InGaAs photodetector (102) to focus an image on the array. A notch filter (108) is operatively connected to the InGaAs photodetector (102) to block detection of wavelengths within at least one predetermined band. A ROIC (104) is operatively connected to the array to condition electrical signals from the array for imaging.