Dielectric Grating Reflective Color Pixel on Lossy Metal Substrates

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Solution Overview

Problem

Existing reflective color pixel technologies are limited by the use of metals with high optical loss and moderate reflectivity, which restricts CMOS compatibility, chemical functionality, and stability, necessitating a strategy to diversify structural colors using a wider range of metals, including highly lossy metals.

Innovation Solution

A reflective color pixel is developed using a dielectric grating formed on a lossy metal substrate, such as Cu, Ni, Co, Pd, or W, which enhances color vibrancy, sRGB color gamut coverage, and allows passive control over the visible range by varying the period and etch width of the dielectric grating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If lossy metals (e.g., Cu, Ni, Co, Pd, W) are used as substrates, then CMOS compatibility, chemical functionality, and stability are improved, but optical loss increases and reflectivity decreases

Engineering Contradiction:

Improvemetal selection rangeVSAvoidoptical loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

A dielectric grating layer is introduced as an intermediary between the lossy metal substrate and the incident light. This dielectric layer mediates the optical interaction, enabling the system to use lossy metals while maintaining high color vibrancy through grating-mediated resonance effects rather than direct metal-light interaction.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention creates a composite structure combining lossy metal substrate with dielectric grating material. This composite approach allows the system to leverage both the chemical stability and CMOS compatibility of lossy metals and the optical advantages of dielectric materials, achieving high color vibrancy despite metal losses.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If conventional metals (Ag, Al) are used, then optical performance and color vibrancy are improved, but oxidation resistance and chemical stability deteriorate

Engineering Contradiction:

Improvecolor vibrancyVSAvoidoxidation resistance

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The dielectric grating serves as a protective intermediary layer that prevents direct exposure of the metal substrate to oxidizing environments. This mediator allows the use of oxidation-prone metals like Ag and Al while maintaining their optical advantages and improving their chemical stability through physical protection.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The dielectric grating layer acts as a sacrificial protective layer that can be optimized for optical performance while protecting the underlying metal. This approach allows using metals that would otherwise be unsuitable due to oxidation, effectively extending the usable lifetime and reliability of the structural color device.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Illumination intensity

If dielectric gratings are formed on lossy metal substrates, then color vibrancy and sRGB color gamut coverage are improved, but manufacturing complexity increases

Engineering Contradiction:

Improvecolor vibrancyVSAvoidstructure complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The device is segmented into distinct functional layers: the lossy metal substrate providing chemical stability and the dielectric grating layer providing optical functionality. This segmentation allows independent optimization of each layer for its specific function, simplifying the overall design despite the multi-layer structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention controls optical properties by adjusting grating parameters (period, depth, duty cycle) rather than changing material properties. This parameter-based control allows fine-tuning of color output and optimization of manufacturing processes, reducing complexity compared to material composition control.

Inventive Principle:

Principle #35Parameter changes

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 reflective color pixel achieves higher color vibrancy, wider sRGB color gamut, improved spectral purity, and high contrast through cross-polarized reflection, utilizing lossy metals like Pt or W, while maintaining CMOS compatibility and thermal stability.

Implementation Method 1

metal gratings or array structures have been widely used for diffractive excitation of SPPs and promotion of their interference

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

Efforts to produce vivid structural colors have been mostly developed based on the use of localized surface plasmons, surface plasmon polaritons (SPPs) and Mie resonance

Methodology Applied

Scientific EffectSurface plasmon polaritons: