Light Multiplexer Athermalization Structure
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Solution Overview
Problem
The existing light multiplexers face issues with grating pitch displacement due to temperature changes, leading to changes in diffraction angles and increased coupling loss, as the diffraction grating is secured to supporters with different thermal expansion coefficients than the substrate, causing misalignment and improper multiplexing or demultiplexing of light beams.
Innovation Solution
A light multiplexer design where a diffraction grating is held by a holder that is not in contact with the substrate, with a supporter conducting heat directly to the holder, reducing the adverse influence of thermal expansion on the grating, and using materials with similar thermal expansion coefficients to minimize displacement and maintain alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the diffraction grating is secured to the substrate through supporters, then the grating is firmly fixed and supported, but thermal expansion coefficient differences cause grating pitch displacement and diffraction angle changes
Solution Approach 1:
An athermalization structure is introduced as an intermediary component between the supporter and the diffraction grating. This structure compensates for thermal expansion differences, preventing grating pitch displacement while maintaining firm fixation. The athermalization structure acts as a mediator that decouples the thermal expansion of the substrate from the grating, resolving the contradiction between firm fixing and pitch accuracy.
2Stability of the object's composition
If the diffraction grating is directly contacted with the substrate, then thermal expansion is minimized, but alignment precision and diffraction performance deteriorate
Solution Approach 1:
The athermalization structure serves as an intermediary that isolates the diffraction grating from direct thermal contact with the substrate. This allows the grating to maintain its precise alignment and diffraction performance while the athermalization structure absorbs thermal expansion, preventing direct transmission of thermal stress to the grating.
3Ease of manufacture
If supporters with different thermal expansion coefficients are used, then mounting compatibility is improved, but grating pitch displacement increases
Solution Approach 1:
The athermalization structure is positioned between the supporter and the diffraction grating to compensate for thermal expansion coefficient mismatches. This intermediary component allows the use of easily mountable supporters while preventing their thermal expansion from displacing the grating pitch, thus resolving the contradiction between mounting compatibility and pitch accuracy.
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 reduces grating pitch displacement and diffraction angle changes, resulting in lower coupling loss and improved light multiplexing or demultiplexing performance, even under temperature variations.
Implementation Method 1
a diffraction grating having numerous vertical grooves regularly arranged on a glass substrate in parallel to each other. When light beams are incident into the diffraction grating, the transmitted or reflected light beams are diffracted and interfere with each other
Implementation Method 2
the substrate 1 is generally made of metal such as Kovar, and therefore, it has a different thermal expansion coefficient from those of the supporters 6 and 7 mounted directly on the substrate 1 and the diffraction grating 5. As a consequence, when the temperature of the substrate 1 is increased, a portion of each of the supporters 6 and 7 in contact with or near the upper surface of the substrate 1 is more largely displaced than portions remote therefrom
Data Source
AI summary
One side surface of a diffraction grating is securely held by a holder, and further, the holder is securely supported on a substrate by a supporter in such a manner that the diffraction grating held by the holder is not brought into contact with the substrate. In this manner, the diffraction grating is fixed only onto one side surface to the supporter via the holder, and further, the diffraction grating is not brought into contact with the substrate. Therefore, the lower portion of the supporter is displaced by heat generated in the substrate, however, the displacement of the supporter cannot adversely influence directly on the diffraction grating since the holder is interposed between the displaced portion and the diffraction grating.