Optical Waveguide Vertical Grating Separation Design
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Solution Overview
Problem
Existing optical density measuring apparatus using the ATR method require large diffraction gratings for light input and output, limiting the design freedom and efficiency of the optical waveguide due to the need for long light propagation distances and corresponding large sizes, which restricts the placement and arrangement of elements on the substrate.
Innovation Solution
The optical density measuring apparatus separates the diffraction grating unit and the core layer in the thickness direction of the optical waveguide, allowing for increased design freedom by setting a specific separation distance that suppresses evanescent coupling and reduces light loss, enabling more efficient placement and arrangement of elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the diffraction grating size is increased to accommodate light source and photodetector, then light input and output efficiency is improved, but the overall device area increases
Solution Approach 1:
The patent introduces a vertical separation between the diffraction grating and core layer in the thickness direction, transitioning from a planar two-dimensional arrangement to a three-dimensional stacked configuration. This allows the diffraction grating to be positioned above or below the core layer, enabling compact lateral arrangement while maintaining effective optical coupling through the vertical dimension.
Solution Approach 2:
The optical waveguide structure is segmented into distinct functional layers: the diffraction grating unit and the core layer are separated as independent components in the thickness direction. This segmentation allows each component to be optimized independently while reducing the lateral footprint of the overall device.
2Measurement precision
If the light propagation distance is increased to improve measurement sensitivity, then detection precision is improved, but the device area increases
Solution Approach 1:
The patent utilizes the vertical thickness direction to separate optical components, enabling the light propagation path to be configured in a three-dimensional space rather than constrained to a two-dimensional plane. This allows for extended propagation distances without proportionally increasing the lateral device area.
3Adaptability or versatility
If the diffraction grating and core layer are separated in the thickness direction, then design freedom and placement efficiency are improved, but light loss may occur due to separation distance
Solution Approach 1:
The patent optimizes the separation distance between the diffraction grating and core layer as a critical parameter. By carefully controlling this distance, the design achieves a balance between gaining design freedom through separation and minimizing light loss through evanescent coupling, allowing the system to operate effectively at optimized separation distances.
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 sensitivity of the sensor by preventing light loss and allowing for a more compact and efficient optical waveguide design, improving the interaction between the evanescent wave and the substance to be measured.
Implementation Method 1
A diffraction grating for bending the optical axis of the light is therefore often provided between the light source and the optical waveguide and between the photodetector and the optical waveguide
Implementation Method 2
When the light propagating through the structure is totally reflected at the interface, the light extends to the outside, which has a smaller refractive index. Such an extension is referred to as an evanescent wave
Implementation Method 3
An evanescent wave EW may be absorbed by a substance 52 adjacent to the structure 51 while light L is propagating. This enables detection and identification of the substance 52 in contact with the structure 51 based on a change in the intensity of the light L propagating through the structure 51
Data Source
AI summary
An optical density measuring apparatus and an optical waveguide capable of increasing the degree of design freedom are provided. The optical density measuring apparatus is for measuring density of a gas or a liquid to be measured and includes a light source capable of irradiating light into a core layer, a detector capable of receiving light propagated through the core layer, and an optical waveguide. The optical waveguide includes a substrate and the core layer, which includes a diffraction grating unit and a light propagation unit capable of propagating light in an extending direction of the light propagation unit. The diffraction grating unit and a portion of the core layer are separated in the thickness direction of the optical waveguide.