Dielectric Microspheres for Photodetector Light Collection
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Solution Overview
Problem
Conventional photodetector focal plane arrays (FPAs) face challenges in achieving high sensitivity and large angle-of-view (AOV) due to limited pixel area fill factor and inefficient light collection, particularly in mid-IR imaging applications where COTS microlenses provide insufficient AOV and refractive index contrast.
Innovation Solution
The integration of an array of dielectric microspheres above the photosensitive regions of FPAs, which focus electromagnetic power through the 'photonic nanojet' effect, enhancing light collection efficiency and increasing AOV by optimizing the refractive index and diameter of the microspheres, allowing for reduced dark current and improved frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional COTS microlenses are used for light collection, then light collection efficiency is improved, but angle-of-view (AOV) is limited to insufficient levels
Solution Approach 1:
The patent changes the refractive index parameter from conventional microlense materials to high-index dielectric materials (n>2.0), enabling both high light collection efficiency and large AOV (>20 degrees) by optimizing the optical parameters of the microsphere array system
Solution Approach 2:
The patent introduces dielectric microspheres as intermediary optical elements that couple incident radiation to the photosensitive regions, acting as mediators that simultaneously achieve efficient light collection and large angular acceptance through their photonic nanojet effect
2Manufacturing precision
If pixel size is reduced to improve resolution and reduce dark current, then spatial sampling and frequency response are enhanced, but area fill factor decreases to a few percent
Solution Approach 1:
The patent employs spherical microsphere structures that provide curved optical surfaces for efficient light coupling, allowing small pixel dimensions for high resolution while the spherical geometry maintains effective light collection across the reduced pixel area
Solution Approach 2:
The dielectric microspheres serve as intermediary structures that compensate for the reduced pixel area by enhancing light coupling efficiency through their spherical geometry and high refractive index, effectively increasing the optical cross-section without increasing physical pixel size
3Loss of energy
If area fill factor is increased to improve light collection, then sensitivity is enhanced, but pixel size must be increased reducing resolution
Solution Approach 1:
The patent changes the optical parameters by using high refractive index dielectric materials (n>2.0) for the microspheres, enabling enhanced light collection efficiency through increased optical path length and reduced reflection losses without requiring larger physical pixel areas
Solution Approach 2:
The spherical shape of the microspheres provides optimal curved surfaces for light coupling with high collection efficiency while maintaining compact size, allowing enhanced light collection without increasing pixel footprint and thus preserving high spatial sampling resolution
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 enhances light collection efficiency and AOV, achieving up to 50-60% efficiency advantage and AOVs greater than 20 degrees, outperforming bare structures and COTS microlenses, while maintaining reduced dark current and increased frequency response.
Implementation Method 1
The integration of an array of dielectric microspheres above the photosensitive regions of FPAs, which focus electromagnetic power through the 'photonic nanojet' effect, enhancing light collection efficiency
Implementation Method 2
The pixels of such FPAs are represented by a semiconductor pin structure operating in a photovoltaic or photoconductive mode
Implementation Method 3
The pixels of such FPAs are represented by a semiconductor pin structure operating in a photovoltaic or photoconductive mode
Implementation Method 4
The layered quantum structures are represented by quantum well (QWIP), quantum dot (QDIP), or strained-layer superlattice (SLSIP) IR photodetectors
Data Source
AI summary
A photodetector focal plane array system, comprising: a substrate comprising a plurality of photosensitive regions; and a microcomponent disposed adjacent to each of the plurality of photosensitive regions operable for receiving incident radiation and directing a photonic nanojet into the associated photosensitive region. Optionally, each of the microcomponents comprises one of a microsphere and a microcylinder. Each of the microcomponents has a diameter of between ˜λ and ˜100λ, where λ is the wavelength of the incident radiation. Each of the microcomponents is manufactured from a dielectric or semiconductor material. Each of the microcomponents has an index of refraction of between ˜1.4 and ˜3.5. Optionally, high-index components can be embedded in a lower index material. The microcomponents form an array of microcomponents disposed adjacent to the substrate.