Metasurface Diffractive Optical Element for TIRF Excitation
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Solution Overview
Problem
TIRF microscopy requires high-numerical-aperture objectives that are expensive and introduce significant aberrations, and the alignment of these objectives is complex.
Innovation Solution
A diffractive optical element comprising a substrate with a metasurface made of dielectric material, which diffracts light to generate evanescent waves without the need for high-numerical-aperture objectives, using a patterned structure that redirects light into specific diffraction orders to achieve total internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-numerical-aperture objectives are used to generate evanescent waves for TIRF microscopy, then the excitation efficiency and spatial resolution are improved, but the cost increases significantly and alignment complexity increases
Solution Approach 1:
The patent extracts the TIRF generation function from the complex high-NA objective lens and implements it through a simplified diffractive optical element (grating) on the substrate surface. This separates the evanescent wave generation capability from the expensive, complex objective lens, allowing standard objectives to be used while maintaining TIRF functionality.
Solution Approach 2:
The patent creates a periodic pattern (grating) on the substrate that copies the optical function of a high-NA objective lens for generating evanescent waves. This diffractive structure replicates the essential TIRF-generating capability without requiring the expensive, complex lens system, thereby simplifying alignment and reducing cost while maintaining spatial resolution.
2Reliability
If high-numerical-aperture objectives are used for TIRF microscopy, then evanescent wave generation is achieved, but the cost of the system increases significantly
Solution Approach 1:
The patent replaces the expensive, fragile high-NA objective lens with a inexpensive diffractive optical element (grating pattern) that can be directly fabricated on the substrate using standard lithography techniques. This disposable-like approach to generating evanescent waves dramatically reduces system cost while maintaining reliable TIRF functionality.
Solution Approach 2:
The patent substitutes the mechanical/optical complexity of a high-NA objective lens with a static diffractive pattern on the substrate. This replacement eliminates the need for expensive, precision-mechanized lens systems while achieving the same evanescent wave generation through diffraction physics, thereby reducing system cost and simplifying manufacturing.
3Measurement precision
If high-numerical-aperture objectives are used to achieve total internal reflection, then the penetration depth control is improved, but significant optical aberrations are introduced
Solution Approach 1:
The patent introduces a diffractive optical element (grating) as an intermediary between the light source and the sample. This intermediate structure modifies the incident light to generate evanescent waves with controlled penetration depths without requiring high-NA objectives that introduce aberrations. The grating acts as a mediator that achieves precise penetration control through diffraction geometry rather than through high-angle refraction.
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
Enables high-resolution TIRF microscopy with reduced background noise and cost, while simplifying alignment and eliminating the need for expensive high-NA objectives.
Implementation Method 1
said metasurface being suitable for diffracting light radiation of wavelength λ comprised in said spectral range, and incident with an angle of incidence, to form diffracted radiation
Implementation Method 2
said diffracted radiation being formed in such a way that it propagates through the substrate, and strikes said second surface of the substrate at a diffracted angle θd larger than or equal to a limit angle θc of total internal reflection
Implementation Method 3
an evanescent wave OE appears in the ambient medium MA. This evanescent wave has an intensity that decreases exponentially with distance z from the surface S: I(z)=I0e−z/δ
Implementation Method 4
The evanescent wave excites the fluorophores contained in the ambient medium, but only over a thickness of the order of δ
Data Source
AI summary
Disclosed is a diffractive optical element includes a substrate (BS) having a first surface and a second surface opposite the first surface, being transparent to light in at least one spectral range and having, in the spectral range, a refractive index that is greater than that of water, at least one metasurface able to diffract light radiation of wavelength λ within the spectral range, incident with an angle of incidence, according to a diffracted radiation, so that the diffracted radiation propagates in the substrate and reaches the second surface of the substrate at a diffracted angle θd that is greater than or equal to a limit angle (θc) of total internal reflection between the substrate and water, the metasurface being designed to have, for the angle of incidence, a transmission with a 0 order of diffraction below 5% and a transmission of the diffracted radiation corresponding to a −1 or +1 order of diffraction above 50%.