Dual-Surface Diffractive Optical Element for Lower Light Loss

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Solution Overview

Problem

Diffractive optical elements suffer from high light loss rates, typically around 40%, which is a significant drawback in applications requiring efficient light utilization.

Innovation Solution

A diffractive optical element is designed with a substrate and two diffractive structure layers, where the refractive index difference between the layers is greater than 0.25, and the layers are made of materials like silicon oxide or silicon nitride, with one layer configured to depress noise at zero order, and the other to generate a desired light pattern, using nanoimprint technology for patterning.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a conventional diffractive optical element is used, then the optical function is achieved, but the light loss rate is high (about 40%)

Engineering Contradiction:

Improvelight loss rateVSAvoidoptical function performance

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The diffractive optical element is divided into multiple diffractive structure layers (first diffractive structure layer and second diffractive structure layer) with different refractive indices. Each layer performs a portion of the diffraction function, distributing the optical workload and reducing energy loss at each interface.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite material structure by combining multiple diffractive structure layers made of different materials (semiconductor layers or glue material layers) with distinct refractive indices on opposite surfaces of the substrate. This composite approach optimizes light transmission and reduces overall light loss while maintaining the required optical diffraction function.

Inventive Principle:

Principle #40Composite materials

2Loss of energy

If multiple diffractive structure layers with different refractive indices are used, then light loss is reduced, but the device complexity increases

Engineering Contradiction:

Improvelight loss rateVSAvoidstructure complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The substrate serves multiple functions: it provides mechanical support, positions the diffractive structure layers, and acts as an optical element itself. The diffractive structure layers simultaneously perform diffraction and wavelength filtering functions, reducing the need for additional separate components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The diffractive structure layers are positioned on opposite surfaces of the substrate, with each layer nested within the overall optical element structure. The protection layer is further nested on top of the first diffractive structure layer, creating a compact integrated design that minimizes overall device complexity.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Loss of energy

If the refractive index difference between diffractive structure layer and protection layer is greater than 0.25, then light loss is reduced, but manufacturing precision requirements increase

Engineering Contradiction:

Improvelight loss rateVSAvoidrefractive index control precision

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The patent specifies a quantitative parameter threshold (refractive index difference greater than 0.25) to ensure optimal light loss reduction. By establishing this clear parameter criterion, the design guides material selection and manufacturing processes to achieve the desired optical performance while providing a measurable target for quality 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 design significantly reduces light loss, enhancing the efficiency of light utilization and enabling precise light pattern generation on a target.

Implementation Method 1

A diffractive optical element is a well-known optical element that utilizes light diffraction phenomenon to achieve various optical functions

Methodology Applied

Scientific EffectLight diffraction: Diffraction

Implementation Method 2

A difference between a refractive index of the first diffractive structure layer and a refractive index of the protection layer is bigger than 0.25

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS12416749B2Diffractive optical element and method for fabricating the diffractive optical element

Publication Date: 2025.09.16 HIMAX TECH LTD

AI summary

A diffractive optical element and method for fabricating the diffractive optical element are provided. The diffractive optical element includes a substrate, a first diffractive structure layer and a second diffractive structure layer. The substrate has a first surface and a second surface opposite to the first surface. The first diffractive structure layer is disposed on the first surface of the substrate. The second diffractive structure layer is disposed on the second surface of the substrate. In the method for fabricating the diffractive optical element, at first, the substrate is provided. Then, a first glue material layer/first semiconductor layer is formed and patterned on the first surface of the substrate. Thereafter, a second glue material layer/second semiconductor layer is formed and patterned on the second surface of the substrate.