Waveguide Optical Device Supplemental Plate Groove Formation
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Solution Overview
Problem
Waveguide type optical devices face issues with polarization dependence and coupling loss due to the formation of thin film insertion grooves, which can lead to chipping and degradation of propagation characteristics, and the use of adhesives introduces additional refractive index effects that increase light coupling loss.
Innovation Solution
A waveguide type optical device design where a supplemental plate is adhered to the substrate using an adhesive, with a groove forming part cut through the plate to reach the waveguide, ensuring the adhesive's influence on light modes is minimized by maintaining a distance between the waveguide and the supplemental plate within 0≦ΔW≦0.08×λ, and using materials with matching refractive index and thermal expansion coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a thin film insertion groove forming part is formed in the substrate to insert a functional thin film, then polarization non-independency is achieved, but chipping occurs in the substrate and waveguide leading to degradation of propagation characteristics
Solution Approach 1:
A process supplemental plate is adhered to the upper part of the substrate before forming the thin film insertion groove. This preliminary action provides mechanical support during the groove formation process, preventing chipping of the substrate and waveguide, thereby maintaining propagation characteristics while enabling polarization non-independency through subsequent functional film insertion
2Reliability
If a process supplemental plate is adhered to the substrate by adhesive to prevent chipping, then propagation characteristic is maintained, but light coupling loss increases due to refractive index mismatch of the adhesive
Solution Approach 1:
The adhesive layer is positioned only in the peripheral region surrounding the waveguide, not directly over it. This local quality approach allows the adhesive to provide mechanical support and prevent chipping while minimizing its optical interference with the guided light, thereby reducing light coupling loss caused by refractive index mismatch
Solution Approach 2:
The adhesive is placed in the lateral dimension (periphery) rather than directly in the optical path dimension. By moving the adhesive to a different spatial dimension (surrounding the waveguide rather than covering it), the solution maintains mechanical support functionality while eliminating harmful optical effects
3Loss of energy
If the adhesive layer is made thin to reduce light coupling loss, then light propagation is improved, but mechanical strength for fixing the supplemental plate is reduced
Solution Approach 1:
The adhesive layer is applied only in the peripheral region around the waveguide, creating a localized bonding area. This allows the adhesive to provide sufficient mechanical strength for fixing the supplemental plate while keeping the adhesive thickness minimal in the optical region, thereby reducing light coupling loss without compromising mechanical attachment
Data Source
AI summary
A waveguide type optical device includes a substrate where a waveguide is formed; a supplemental plate connected on the substrate by using an adhesive; and a groove forming part formed by cutting through the supplemental plate so as to reach the substrate and cut the waveguide, the groove forming part being where a functional thin film is inserted. The supplemental plate and the waveguide adhere to each other or come close to each other in a range not influencing a mode of light.