Multiband IR Detector with Frequency Selective Slots
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Solution Overview
Problem
Conventional IR detectors face challenges in achieving dual or multiband imaging response due to low quantum efficiency and the inability to combine frequency-selective surfaces, limiting their broad band coverage and imaging capabilities.
Innovation Solution
A multiband sub-wavelength IR detector array with frequency-selective slots is developed, featuring resonant apertures and detectors that allow simultaneous detection of multiple frequency bands within a single pixel element, utilizing mercury cadmium telluride as the IR absorber material and a manufacturing process involving epitaxial growth and dry etching to create sub-wavelength absorber mesas and metallic surfaces with dipole antennas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional IR detectors use single-band detection structures, then manufacturing is simpler, but multiband imaging capability is lost
Solution Approach 1:
The detector surface is segmented into multiple frequency-selective slots, each tuned to detect specific frequency bands. This segmentation allows simultaneous multiband detection within a single pixel element while maintaining manageable manufacturing complexity through modular slot design
Solution Approach 2:
The detector structure is designed with universal sub-wavelength resonant elements that can be configured for multiple frequency bands. The same basic slot geometry and resonant structure serve multiple detection functions across different frequency ranges, enabling multiband capability without proportionally increasing complexity
2Reliability
If extrinsic doping is used in GaN and GaAs/AlGaAs QWIP technologies, then broad band LWIR response is achieved, but quantum efficiency at 10 μm becomes significantly low
Solution Approach 1:
The invention changes the detection mechanism from extrinsic doping-dependent QWIP to resonant cavity-enhanced absorption. By adjusting slot dimensions, resonant frequencies, and cavity depths, the system achieves high quantum efficiency at 10 μm while maintaining broad band LWIR response through parameter optimization rather than material doping
3Adaptability or versatility
If frequency-selective surfaces are not combined with detectors, then device complexity is reduced, but dual or multiband detection capability is lost
Solution Approach 1:
The frequency-selective slots are merged directly into the detector structure, with resonant apertures positioned above detector elements. This integration combines frequency selection and detection functions into a unified structure, achieving multiband capability while minimizing additional complexity through direct structural integration
Solution Approach 2:
The invention adds vertical dimensionality by stacking frequency-selective slots above detector elements in a layered configuration. This three-dimensional arrangement enables frequency discrimination and detection in separate spatial layers, achieving multiband capability without significantly increasing planar complexity
4Measurement precision
If resonant apertures are used to collect and focus radiation, then quantum efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The invention uses parameter optimization in the resonant slot design, where tolerances are relaxed by adjusting slot dimensions, frequencies, and geometries. By changing design parameters such as slot width, length, and resonant frequency, the system achieves high quantum efficiency with reduced sensitivity to manufacturing variations
Solution Approach 2:
The resonant structures are designed with excessive dimensions or frequencies that provide tolerance buffering. By oversizing certain features or using lower-frequency resonances with broader bandwidths, the system maintains high quantum efficiency even with moderate manufacturing imprecision
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 efficient detection of multiple frequency bands with higher quantum efficiency and reduced noise, allowing for the generation of high-performance imaging systems with improved producibility and integration capabilities.
Implementation Method 1
resonant apertures that collect energy incident on a portion of the pixel area and resonantly transmit the light in a distinct frequency band to a detector element positioned below the aperture
Implementation Method 2
sub-wavelength absorber mesas and metallic surfaces with dipole antennas
Data Source
Figure 1
Figure 2~2D
Figure 3
AI summary
In one embodiment, a multiband infrared (IR) detector array includes a metallic surface having a plurality of periodic resonant structures configured to resonantly transmit electromagnetic energy in distinct frequency bands. A plurality of pixels (10) on the array each include at least first and second resonant structures (14A,14B) corresponding to first and second wavelengths. For each pixel (10), the first and second resonant structures (14A,14B) have an associated detector (12A,12B) and are arranged such that essentially all of the electromagnetic energy at the first wavelength passes through the first resonant structure (14A) onto the first detector (12A), and essentially all of the electromagnetic energy at the second wavelength passes through the second resonant structure (14B) onto the second detector (12B). In one embodiment, the resonant structures (14A,14B) are apertures or slots, and the IR detectors may be mercad telluride configured to absorb radiation in the 8-12 µm band. Detection of more than two wavelengths may be achieved by proper scaling. A method of forming an IR detector array is also disclosed.