Waveguide End Structure Thin Protective Film
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Solution Overview
Problem
Coupling loss becomes significant when connecting fibers or waveguides with an end cap buffer layer, as the light propagation mode changes from waveguide to diffusion mode, leading to increased loss and complexity in optical circuits handling visible and ultraviolet light.
Innovation Solution
A thin protective film, 0.5 to 3 μm thick, made of nitride, oxide, or fluoride materials such as Si3N4 or Al2O3, is applied to the end surface of the transmission lines to prevent core bulging and reduce coupling loss without using adhesives, allowing for closer core alignment and minimizing beam shape degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If an end cap buffer layer is provided on the fiber end surface to prevent core bulging, then the lifetime of optical output is extended, but coupling loss increases to 10 dB or more due to light spreading in diffusion mode
Solution Approach 1:
A protective film made of nitride, oxide, or fluoride materials is introduced as an intermediary layer between the fiber core and the external environment. This film prevents core bulging without causing light diffusion, thereby maintaining low coupling loss while extending the lifetime of optical output.
Solution Approach 2:
The invention changes the material parameters at the fiber end surface by applying a protective film with specific optical and mechanical properties. This film has different characteristics from both the core and cladding materials, providing protection against core bulging while maintaining optical transmission efficiency.
2Shape
If a buffer layer is provided on the fiber end surface to suppress core bulge, then beam shape degradation is prevented, but spatial optical components such as lenses are required, increasing device complexity
Solution Approach 1:
The invention extracts the essential function of the buffer layer (preventing core bulge) and implements it directly on the fiber end surface through a protective film. This eliminates the need for separate buffer layers and spatial optical components, thereby preventing beam shape degradation while reducing device complexity.
Solution Approach 2:
A thin protective film is applied to the fiber end surface to prevent core bulging. This thin film approach achieves the protective function without requiring bulky buffer layers or additional optical components, thus maintaining beam shape while simplifying the device structure.
3Stability of the object's composition
If adhesive is used to connect fibers or waveguides, then connection is achieved, but coupling loss increases due to adhesive deterioration
Solution Approach 1:
The protective film serves as a durable, non-deteriorating alternative to adhesive. Unlike adhesive which deteriorates over time, the protective film provides stable connection and protection without degrading, thereby maintaining low coupling loss while ensuring connection stability.
Data Source
AI summary
An end portion structure of a transmission line of the present invention is a structure in which a protective film with a thickness of 0.5 μm to 3.0 μm is formed on the end surface of the transmission line in place of an end cap formed in an end portion of a transmission line in the related art, and no adhesive is used in a portion through which light passes. The protective film on the end surface works to suppress a bulge of the core. The thickness of the protective film is significantly thinner than the end cap, and thus waveguides facing each other can be brought close to each other. It is possible to reduce the connection loss between two fibers or waveguides facing each other to be 0.5 dB or less. Since no adhesive is used, there is no loss increase caused by adhesive deterioration.