Diffractive Optical Element Multi-Stage Grating Zeroth-Order Suppression

Solution Overview

Problem

Diffractive optical elements struggle to effectively reduce zeroth-order diffraction light while maintaining the efficiency of first-order diffraction light, particularly when using laser light sources, as existing designs often result in excessive zeroth-order diffraction light interference.

Innovation Solution

A diffractive optical element with a diffraction layer featuring a high refractive index part with multi-stage projections and a low refractive index part with recesses, where the projections have a sawtooth or multi-stage shape and a concave curved plane, optimizing the area ratios and shape to minimize zeroth-order diffraction light while preserving first-order diffraction efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a sawtooth shape (blaze) is configured on the diffraction grating to concentrate and diffract a specific wavelength to a specific order, then first-order diffraction efficiency is improved, but zeroth-order diffraction light remains excessively large

Engineering Contradiction:

Improvefirst-order diffraction efficiencyVSAvoidzeroth-order diffraction light interference

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The diffraction grating is divided into multiple regions with different blaze angles. The first region has a blaze angle of 30-60 degrees while the second region has a blaze angle of 0-30 degrees, creating segmented zones that differentially control zeroth-order and first-order diffraction light respectively

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the diffraction grating are assigned different local optical properties (blaze angles) to perform different functions. The first region's steeper blaze angle targets first-order diffraction efficiency while the second region's shallower blaze angle suppresses zeroth-order diffraction light

Inventive Principle:

Principle #3Local quality

2Object-generated harmful factors

If the zeroth-order diffraction light is reduced by adjusting the diffraction grating parameters, then zeroth-order light interference is suppressed, but the necessary first-order diffraction light is also decreased

Engineering Contradiction:

Improvezeroth-order diffraction light interferenceVSAvoidfirst-order diffraction efficiency

Core Design Contradiction:

Object-generated harmful factorsVSPower

Solution Approach 1:

The diffraction grating is divided into multiple regions with different blaze angles. The first region has a blaze angle of 30-60 degrees while the second region has a blaze angle of 0-30 degrees, creating segmented zones that differentially control zeroth-order and first-order diffraction light respectively

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the diffraction grating are assigned different local optical properties (blaze angles) to perform different functions. The first region's steeper blaze angle targets first-order diffraction efficiency while the second region's shallower blaze angle suppresses zeroth-order diffraction light

Inventive Principle:

Principle #3Local quality

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 solution significantly reduces zeroth-order diffraction light intensity while suppressing the reduction of first-order diffraction efficiency, achieving improved optical performance by configuring the diffraction grating with a concave curved plane imitated by a multi-stage shape, as demonstrated through simulations and actual measurements.

Implementation Method 1

This is an application of the diffraction phenomenon when light passes through a location where materials having different refractive indexes are arranged with periodicity

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

a diffraction layer including: a high refractive index part in which a plurality of projections are arranged side by side; and a low refractive index part having a refractive index lower than that of the high refractive index part

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS11366256B2Diffractive optical element

Publication Date: 2022.06.21 DAI NIPPON PRINTING CO LTD

AI summary

A diffractive optical element capable of further reducing zero-order diffraction light includes a diffraction layer including: a high refractive index part in which a plurality of projections are arranged side by side in a cross-sectional shape; and a low refractive index part that has a lower refractive index than the high refractive index part and that includes a recess formed at least between the projections. The projections have a sawtooth shape or a shape that imitates a sawtooth shape by a multi-stage outline shape. An inclined plane that is inclined with respect to a sheet surface of the diffractive optical element, which has a sawtooth shape or a sawtooth shape imitated by a multi-stage outline shape, has a concave curved plane that is concave toward the projections.