Halogenated Silicon Optical Filters for Wide-Angle Stability

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Solution Overview

Problem

Conventional optical filters face challenges in maintaining high optical properties at wide angles of incidence due to refractive index changes with polarization, and hydrogenated amorphous silicon films struggle with controlling hydrogen diffusion, leading to inconsistent optical properties and low reflectivity at near-infrared wavelengths.

Innovation Solution

The use of halogenated amorphous silicon layers in a multilayer structure with controlled gas ratios during deposition, combined with high refractive index materials, to achieve stable optical properties across a wide range of incidence angles and low extinction coefficients in the 800 nm to 1100 nm band.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional high and low refraction materials are used in optical filters, then normal incidence optical properties can be achieved, but the refractive index changes with polarization at wide angles of incidence (±15 degrees or more)

Engineering Contradiction:

Improveoptical propertiesVSAvoidangle of incidence range

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the material parameter from conventional high/low refraction materials to halogenated amorphous silicon, which has a high refractive index (3.0 or more) and low extinction coefficient (0.001 or below) that remains stable across wide angles of incidence. This material parameter change resolves the polarization-dependent refractive index variation at wide angles.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a multilayer structure comprising alternating high refraction material layers and low refraction material layers, where the high refraction layers are made of halogenated amorphous silicon. This composite structure combines the high refractive index of halogenated silicon with low refraction materials to achieve both high optical performance and wide angle adaptability.

Inventive Principle:

Principle #40Composite materials

2Measurement precision

If hydrogenated amorphous silicon is used to achieve high refractive index, then optical properties can be improved, but hydrogen diffusion is difficult to control precisely leading to inconsistent optical properties

Engineering Contradiction:

Improverefractive indexVSAvoidoptical property consistency

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the material composition from hydrogenated amorphous silicon to halogenated amorphous silicon. This parameter change in chemical composition eliminates the hydrogen diffusion control issues while maintaining the high refractive index property, thereby improving optical property consistency.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If hydrogen concentration is increased to minimize optical absorption, then extinction coefficient is reduced, but refractive index decreases

Engineering Contradiction:

Improveoptical absorptionVSAvoidrefractive index

Core Design Contradiction:

Loss of energyVSMeasurement precision

Solution Approach 1:

The patent changes the material from hydrogenated amorphous silicon to halogenated amorphous silicon. This fundamental material parameter change allows achieving low extinction coefficient (0.001 or below) without the trade-off of reduced refractive index, as halogenated silicon maintains high refractive index (3.0 or more) while minimizing optical absorption.

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 optical filter maintains high refractive index and low extinction coefficient properties, accommodating a wide range of incidence angles with minimal band shift, enhancing sensor system performance.

Implementation Method 1

TiO2, Nb2O5, Ta2O5, Si3N4 and the like as high refraction optical deposition materials, and SiO2, MgF2, Al2O3 and the like as low refraction optical deposition materials

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

must be able to block other bands through reflection or absorption processes

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 3

absorb light in the near-infrared range of about 800 nm to 1100 nm and requires high transmittance

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 4

method for preparing halogenated amorphous silicon thin film for optical filter

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Data Source

PatentUS12372688B2Optical filter and sensor system comprising the same, and method for preparing halogenated amorphous silicon thin film for optical filter

Publication Date: 2025.07.29 SONG YOUNG JIN

AI summary

An optical filter according to an embodiment of the present invention comprises a first mirror layer where a first high refraction material layer and a first low refraction material layer are alternately deposited, a spacer layer continuously deposited above one side surface of the first mirror layer, and comprises a plurality of second high refraction material layers, and a second mirror layer located to face the first mirror layer with the spacer layer interposed therebetween, and where a third high refraction material layer and a third low refraction material layer are alternately deposited.