Spectrally Tunable Infrared Detector With Stacked Dual-Band Filters
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Solution Overview
Problem
Current hyperspectral imaging systems in the infrared wavelength band face limitations in spectral tuning range, particularly with Fabry Perot filters, which are typically restricted to one octave in bandwidth, making it impossible to effectively cover the 1.0-2.5 μm range, a band of significant practical interest.
Innovation Solution
A spectrally tunable infrared detector system featuring a dual-band detector configuration with an interferometer filter, comprising two dielectric mirrors and flexible supports, allowing for adjustable spacing to pass and detect wavelengths across a broader range, including the 1.0-2.5 μm range, by using chirped Bragg mirrors to extend the high reflectivity band and modify the phase response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a Fabry Perot filter is used for spectral tuning, then the system achieves wavelength selectivity, but the spectral tuning range is limited to one octave in bandwidth
Solution Approach 1:
The patent divides the spectral detection into multiple bands by stacking multiple detectors (first wavelength detector for 1.0-1.4 μm, second wavelength detector for 1.5-2.3 μm) with separate Fabry Perot filters for each band. This segmentation allows each filter to be optimized for its specific band while collectively covering a wider spectral range beyond the one-octave limitation of a single filter.
Solution Approach 2:
The patent transitions from a single-band detection approach to a multi-band stacked detector architecture, adding the dimension of spectral band multiplication. By stacking detectors and filters vertically, the system achieves extended spectral coverage without increasing the horizontal footprint, effectively solving the bandwidth limitation through vertical integration.
2Adaptability or versatility
If a single F-P cavity filter is used, then the device structure is simple, but it cannot tune over the wavelength range of 1.0-2.5 μm
Solution Approach 1:
The patent segments the 1.0-2.5 μm wavelength range into two distinct bands (1.0-1.4 μm and 1.5-2.3 μm), each handled by a separate detector-filter combination. This segmentation enables comprehensive wavelength coverage while maintaining relatively simple individual components that can be independently optimized and fabricated.
Solution Approach 2:
The patent implements a nested structure where multiple detector layers and their associated Fabry Perot filters are stacked vertically within a single device package. The first wavelength detector with its filter is positioned beneath the second wavelength detector with its filter, creating a compact nested arrangement that achieves extended spectral coverage without proportionally increasing device footprint.
3Adaptability or versatility
If the spectral width of reflectors is increased, then the tuning range expands, but the resonance peaks become broader and less precise
Solution Approach 1:
The patent assigns different spectral ranges to different detector-filter pairs, allowing each filter to be designed with optimal reflector width for its specific band. The first filter operates in the 1.0-1.4 μm band while the second operates in 1.5-2.3 μm, enabling precise resonance peaks for each band without requiring excessively broad reflectors that would degrade precision across the entire range.
Solution Approach 2:
The patent changes the operational parameters of multiple detector-filter systems simultaneously, with each system tuned to its optimal wavelength range. By adjusting the reflector designs and detector characteristics independently for each band, the system achieves both extended tuning range and maintained precision through parameter optimization rather than uniform broadening.
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
Enables detection across a wide range of infrared wavelengths, achieving hyperspectral imaging capabilities beyond the limitations of conventional single-band detectors, with the interferometer filter providing high reflectivity and narrow resonance peaks, allowing for efficient detection of both short and long wavelengths within the SWIR band.
Implementation Method 1
an interferometer filter formed over the top wavelength detector layer and the bottom wavelength detector layer. The interferometer filter is operatively configured to pass a first wavelength associated with a first portion of a predetermined band and a second wavelength associated with a second portion of the predetermined band
Implementation Method 2
The F-P filters use dielectric mirrors in the form of distributed Bragg reflectors, which are formed from alternating layers of high and low refractive index, low loss materials such as Ge and SiOx
Implementation Method 3
Each of the flexible supports is operatively configured to receive an electrical or mechanical input and to move the first mirror from the first predetermined distance to a second predetermined distance over the second mirror
Data Source
AI summary
A tunable infrared detector is provided that includes a substrate, a bottom wavelength detector formed over the substrate, a top wavelength detector formed over the first wavelength detector layer, and an interferometer filter formed over the top wavelength detector layer and the bottom wavelength detector layer. The interferometer filter is operatively configured to pass a first wavelength associated with a first portion of a predetermined band and a second wavelength associated with a second portion of the predetermined band to the top wavelength detector. The top wavelength detector is operatively configured to detect each wavelength associated with the first portion of the predetermined band and to transmit each wavelength associated with the second portion of the predetermined band to the bottom wavelength detector. The bottom wavelength detector is operatively configured to detect each wavelength associated with the second portion of the predetermined band.