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 inefficiency in optical applications.
Innovation Solution
A diffractive optical element design featuring a substrate with two diffractive structure layers on opposite surfaces, where the refractive index difference between these layers is greater than 0.25, and one layer is configured to suppress noise at zero order, using materials like silicon oxide or silicon nitride, and fabrication methods such as nanoimprint technology to create precise microstructures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional diffractive optical element is used, then it can achieve light converging, diverging, distribution, wavelength filtering, or spectroscopic functions, but it suffers from high light loss rate (about 40%)
Solution Approach 1:
The patent transitions from conventional single-surface diffractive structures to a dual-surface diffractive optical element with microlens arrays on both the incident and exit surfaces. This dimensional expansion from one surface to two surfaces enables simultaneous light control at entry and exit, significantly reducing light loss while maintaining optical functions.
Solution Approach 2:
The patent employs composite material structures combining diffractive optical elements with microlens arrays made of transparent materials (resin, glass, or semiconductor) having specific refractive indices (1.3-2.5). The combination of diffractive structures on both surfaces with microlens arrays creates a composite optical system that minimizes light loss through coordinated refraction and diffraction.
2Manufacturing precision
If diffractive optical element structures are fabricated using conventional methods, then basic optical functions can be achieved, but manufacturing precision and control over noise at zero order are insufficient
Solution Approach 1:
The patent segments the optical control function into two separate diffractive structure layers on opposite surfaces of the substrate. One layer is specifically configured to depress noise at zero order while the other generates the desired optical pattern. This segmentation allows independent optimization of each layer's function, improving manufacturing precision and reducing harmful zero-order noise.
Solution Approach 2:
The patent applies different local qualities to different regions of the diffractive structures. Specifically, one diffractive structure layer is designed with parameters optimized for suppressing zero-order noise, while the other layer is optimized for generating the target optical pattern. This local differentiation enables precise control over both desired optical functions and unwanted noise.
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 optical efficiency 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
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
Data Source
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.