Bi-spectral Infrared Detector Meta-surface Pixel Segmentation
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Solution Overview
Problem
Current bi-spectral IR detectors face challenges in achieving spatial coherence between MWIR and LWIR images due to poor optical coupling and complex contact structures, leading to low sensitivity and resolution.
Innovation Solution
A bi-spectral detector with a meta-surface configuration that focuses different infrared wavelengths on separate pixels, using a stack of semiconductor layers and dielectric resonators to enhance optical coupling and reduce crosstalk, allowing for improved sensitivity and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a Bayer matrix with interference filters is used to detect MWIR and LWIR images, then the detector can capture both spectral bands, but the spatial coherence between the two images is lost and the sensitivity and resolution are low
Solution Approach 1:
The detector is segmented into distinct pixel regions: first pixels for MWIR detection and second pixels for LWIR detection. This segmentation allows each pixel type to be optimized for its specific spectral band while maintaining spatial coherence within each band, resolving the contradiction between multi-band detection capability and spatial coherence.
2Measurement precision
If two superposed absorbing layers (QWIP technology) are used to maintain spatial coherence, then spatial coherence is achieved, but the optical coupling is poor and the device complexity increases due to multiple contacts
Solution Approach 1:
The patent extracts the optical coupling function from the complex multi-layer QWIP structure and implements it through a simplified single-substrate architecture with selective pixel regions. This extraction eliminates the need for complex inter-layer optical coupling and multiple contact structures, reducing device complexity while preserving spatial coherence.
Solution Approach 2:
Instead of using vertical superposition of absorbing layers (three-dimensional stacking requiring multiple contacts), the patent transitions to a planar two-dimensional arrangement where first and second pixels are distributed on the same substrate plane. This dimensional change simplifies the contact structure to a single plane while maintaining spatial coherence through proper pixel positioning.
3Ease of manufacture
If a mesa structure with air contact is used for QWIP detectors, then the pixel structure is simplified, but dark current increases and passivation becomes problematic
Solution Approach 1:
The patent applies homogeneous passivation material covering all pixel surfaces uniformly, including the mesa structures. This homogeneous passivation approach simplifies the manufacturing process compared to selective passivation while effectively reducing dark current generated at air-contact interfaces, resolving the contradiction between manufacturing ease and dark current reduction.
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 achieves better spatial coherence and sensitivity by focusing MWIR and LWIR beams on distinct pixels, improving the Modulation Transfer Function (MTF) and gain, while simplifying the detector's manufacturing process.
Implementation Method 1
a plurality of dielectric resonators on the upper face of said substrate forming an upper surface called meta-surface, the meta-surface being configured to diffuse, deflect and focus in the pixels of the detector in a resonant manner
Implementation Method 2
the meta-surface being configured to diffuse, deflect and focus in the pixels of the detector in a resonant manner, when illuminated by the incident light
Implementation Method 3
an absorbent structure arranged on an underside of a substrate and comprising a stack of at least one absorbent layer of semiconductor material, sensitive in the two spectral bands and able to photo-generate carriers by absorption of an incident beam on an upper face of said substrate
Implementation Method 4
able to photo-generate carriers by absorption of an incident beam
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The invention relates to an optical detector (10) that is sensitive in at least two infrared wavelength ranges denoted first spectral band (SB1) and second spectral band (SB2), and having a set of pixels, comprising: - an absorbent structure (Sabs) disposed on a lower face (11) of a substrate (Sub) and comprising a stack of at least one absorbent layer (AL, AL1, AL2) made of semi-conductor material; - the detector further comprising a plurality of dielectric resonators (Res) on the upper surface (12) of said substrate forming an upper surface denoted metasurface (13), the metasurface being configured to diffuse, deflect and focus in the pixels of the detector in a resonant manner, when illuminated by the incident light (IL), a first beam (FL1) having at least one first wavelength (A1) included in the first spectral band (SB1) and a second beam (FL2) having at least one second wavelength (A2) included in the second band, the metasurface also being configured so that said first (FL1) and second (FL2) beams are focused on different pixels of the detector.