Planar Waveguide Lens for Uniform Evanescent Field
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Solution Overview
Problem
Existing planar waveguide technologies face challenges in achieving a strong, uniform evanescent field for sample illumination while being insensitive to misalignment and optical properties of the chamber, particularly in multimode waveguides, which complicates fluorescence-based assays and optofluidic applications.
Innovation Solution
The integration of a plano-convex cylindrical lens within the planar waveguide allows for efficient light coupling and adjustment of the internal propagation angle, enabling a robust and uniform evanescent field with reduced sensitivity to misalignment and optical properties of the chamber, using a refractive volume to optically couple light and maintain consistent coupling across the waveguide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a multimode planar waveguide is used for fluorescence-based assays, then ease of manufacture and coupling are improved, but uniformity and field strength of the evanescent field deteriorate
Solution Approach 1:
The patent applies local quality by introducing a lens structure at a specific location within the waveguide to focus light and create a localized region of enhanced evanescent field strength and uniformity, while the rest of the waveguide maintains its multimode structure for ease of manufacture
Solution Approach 2:
The patent changes the optical parameters by incorporating a lens with specific focal length and positioning it at a defined distance from the waveguide surface, thereby transforming the non-uniform evanescent field into a uniform one in the detection region
2Manufacturing precision
If a single-mode planar waveguide is used, then uniformity and field strength of the evanescent field are improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent introduces a lens as an intermediary optical element that mediates between the simple multimode waveguide structure and the requirement for uniform evanescent field, avoiding the need for complex single-mode waveguide fabrication while achieving field uniformity
3Use of energy by moving object
If precise alignment is required for light coupling, then coupling efficiency is improved, but ease of operation deteriorates
Solution Approach 1:
The patent performs preliminary action by pre-positioning the lens within the waveguide structure during manufacturing, so that the optimal coupling geometry is established beforehand, eliminating the need for precise alignment during operation
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 configuration enhances the strength and uniformity of the evanescent field, improving fluorescence detection and assay efficiency by minimizing the impact of misalignment and optical property variations, facilitating effective illumination of samples and reducing background fluorescence.
Implementation Method 1
The integration of a plano-convex cylindrical lens within the planar waveguide allows for efficient light coupling
Implementation Method 2
Total internal reflection fluorescence (TIRF) is one method of reducing background fluorescence. In general, when light propagates from one medium to another, a portion of the light will be reflected at the interface. If the light is propagating into a material with a lower index of optical refraction, however, all of the light will be reflected if the angle at which the beam is incident on the surface is greater than the 'critical angle'
Implementation Method 3
Fluorescently labeled probes provide a convenient method of characterizing the content of biological samples. Since fluorophores typically absorb and re-emit Stokes-shifted radiation regardless of being bound or unbound to a species to be detected, the bound and unbound fluorophores must be separated
Data Source
AI summary
An apparatus for illuminating a sample includes a planar waveguide. The planar waveguide includes a first substrate, including a first outer surface and a first inner surface, and a second substrate, including a second outer surface and a second inner surface. The first and second inner surfaces of the first and second substrates, respectively, are spaced apart from each other and partly define a volume for confining the sample therein. The apparatus also includes a light source for providing light directed toward the planar waveguide, such that the light is optically coupled to and contained within the planar waveguide between the outer surfaces of the first and second substrates, while illuminating at least a portion of the sample confined within the volume.