Thin-Film Lithium Niobate Tap Coupler Stabilization
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Solution Overview
Problem
Conventional optical modulators with thin-film lithium niobate waveguides face challenges in maintaining a stable split ratio in tap couplers due to manufacturing errors, affecting light propagation and modulation efficiency.
Innovation Solution
The implementation of a delayed interferometer in the tap coupler, utilizing multi-mode interference couplers with optical length differences between waveguides to stabilize the split ratio, reduces the impact of manufacturing errors and ensures consistent light splitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a thin-film lithium niobate waveguide is used to increase optical confinement, then electric field application efficiency is improved and driving voltage is reduced, but manufacturing errors cause instability in the split ratio of the tap coupler
Solution Approach 1:
The patent changes the operating parameters of the tap coupler by introducing a delayed interferometer configuration with specific optical path differences. This allows the system to operate at points where the split ratio is less sensitive to manufacturing variations, thereby maintaining stability while preserving the high optical confinement benefits of thin-film lithium niobate waveguides
Solution Approach 2:
The delayed interferometer in the tap coupler provides a feedback mechanism where the optical path difference creates interference patterns that compensate for manufacturing errors. The system automatically adjusts the effective split ratio through constructive and destructive interference, stabilizing the output despite variations in waveguide dimensions
2Device complexity
If conventional directional couplers are used in the tap coupler, then the structure is simple, but the split ratio varies significantly due to manufacturing errors in waveguide width
Solution Approach 1:
The patent transforms the tap coupler from a simple directional coupler to a delayed interferometer configuration. This parameter change introduces optical path difference as a new degree of freedom, allowing the system to achieve split ratio stability through interference effects rather than relying solely on precise dimensional control
Solution Approach 2:
The patent adds the dimension of optical path difference to the traditional two-waveguide coupling structure. By controlling the relative optical paths in the delayed interferometer, the system achieves split ratio control through an additional parameter (optical length) rather than relying exclusively on waveguide width precision
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 stabilizes the split ratio of the tap coupler, even with strong optical confinement and manufacturing errors, enhancing the reliability and efficiency of light modulation in optical communication systems.
Implementation Method 1
a thin-film optical waveguide, in which an optical waveguide using a thin film made of an LN crystal is formed
Implementation Method 2
refractive indices of the optical waveguides are changed by the electric fields in the optical waveguides, and a phase of light is changed
Implementation Method 3
The tap coupler includes a delayed interferometer that splits a part of the light that passes through the optical waveguide, at a split ratio corresponding to a phase difference of light
Data Source
AI summary
An optical device includes a modulator and a tap coupler. The modulator includes an optical waveguide that is formed of a thin-film lithium niobate (LN) substrate and through which light passes, and an electrode that applies voltage to the optical waveguide, and modulates a phase of light that passes through the optical waveguide in accordance with an electric field in the optical waveguide, where the electric field corresponds to the voltage. The tap coupler includes at least a part formed of the thin-film LN substrate, and splits a part of the light that passes through an inside of the optical waveguide. The tap coupler includes a delayed interferometer that splits a part of the light that passes through the optical waveguide, at a split ratio corresponding to a phase difference of light that passes through an inside of the tap coupler from the optical waveguide.