Immersion Grating Structure for Wide-Bandwidth Diffracted Reflection
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Solution Overview
Problem
Conventional diffraction gratings face limitations in achieving high spectral bandwidth and efficiency due to the physical constraints imposed by their dispersion characteristics, particularly in reflection-only immersion gratings, which often require high-dispersion substrates that compromise bandwidth.
Innovation Solution
The use of a dielectric layer with a higher refractive index than the substrate, coupled with a substrate that supports low optical loss and high transparency, allows for a lower dispersion grating design that increases spectral bandwidth by optimizing the grating parameters to suppress transmitted orders and enhance reflected orders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-dispersion substrate is used in reflection-only immersion gratings, then diffraction efficiency is improved, but spectral bandwidth is reduced
Solution Approach 1:
The patent changes the refractive index parameter of the immersion medium from conventional values to higher values (n>1.7), which fundamentally alters the dispersion characteristics of the grating. This parameter change enables the system to achieve high diffraction efficiency while simultaneously maintaining wide spectral bandwidth, resolving the traditional trade-off between these two parameters.
Solution Approach 2:
The patent employs composite material structures combining high-refractive-index dielectric layers (such as TiO2, Ta2O5, or HfO2) with substrate materials, creating an immersion grating system that achieves both high efficiency and wide bandwidth through the synergistic properties of the composite structure.
2Adaptability or versatility
If the refractive index at the grating/ambient interface is increased, then spectral bandwidth is improved, but manufacturing complexity increases
Solution Approach 1:
The patent introduces a high-refractive-index dielectric layer as an intermediary between the substrate and the ambient environment. This intermediary layer enables the system to achieve high spectral bandwidth without directly modifying the substrate, thereby simplifying the manufacturing process while still achieving the desired optical performance.
3Reliability
If transmitted orders are suppressed to enhance reflected orders, then diffraction efficiency is improved, but spectral bandwidth is reduced
Solution Approach 1:
By changing the refractive index parameter of the immersion medium to high values (n>1.7), the patent modifies the phase matching conditions for transmitted and reflected orders. This parameter change allows the system to suppress transmitted orders effectively while maintaining wide spectral bandwidth, overcoming the traditional limitation where suppressing transmitted orders narrows the bandwidth.
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
This approach results in a wider spectral bandwidth and higher diffraction efficiency, enabling high-power laser applications without thermal damage, by reducing dispersion and maintaining high refractive index at the grating/ambient interface.
Implementation Method 1
The grating generates multiple diffracted beams (called orders) when a single beam is incident upon the structure
Implementation Method 2
In embodiments in which the transmitted orders are suppressed, the reflected orders are governed by the total internal reflection (TIR) condition
Implementation Method 3
The use of a dielectric layer with a higher refractive index than the substrate, coupled with a substrate that supports low optical loss and high transparency, allows for a lower dispersion grating design that increases spectral bandwidth
Data Source
AI summary
A method of forming a diffracted order includes providing an immersion grating having a dielectric substrate having an incident light surface and a second surface opposing the incident surface and directing a light beam to be incident on the incident light surface of the dielectric substrate. The method also includes propagating the light beam through the at least one dielectric layer, diffracting the light beam to form a reflected order, and propagating the reflected order through the at least one dielectric layer.