Optical Waveguide Structure With Oxygen-Deficient Light Attenuation
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Solution Overview
Problem
In optical waveguide devices using thin LN substrates, unnecessary light propagates through the substrate, leading to reduced extinction ratio and mechanical deformation due to stress accumulation from temperature fluctuations.
Innovation Solution
An optical waveguide device with an oxygen-deficient layer on the substrate surface, particularly on the rib and slab portions, to absorb and attenuate unnecessary light, reducing stress and mechanical deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conductive layer made of gold (Au) is provided on the substrate surface through which unnecessary light propagates, then the propagation of unnecessary light is suppressed by optical electric field absorption, but stress accumulates in the substrate due to difference in linear expansion coefficient between the underlayer and substrate
Solution Approach 1:
The patent changes the material parameter of the lossy layer from metal (gold) to oxide material with specific optical properties. The oxide layer has an absorption coefficient that is 10 times or more larger than the substrate in the wavelength range of unnecessary light, enabling effective absorption while having matching thermal expansion characteristics to avoid stress accumulation.
Solution Approach 2:
The patent uses a composite structure where an oxide lossy layer is formed on the substrate surface. This oxide layer combines the necessary optical absorption property with mechanical compatibility (matching linear expansion coefficient) to simultaneously suppress unnecessary light and avoid stress accumulation.
2Use of energy by moving object
If the substrate is thinned to increase electric field efficiency, then the interaction between signal electric field and guided light is enhanced, but unnecessary light leaks into the substrate and becomes noise light
Solution Approach 1:
The patent applies local quality by creating a lossy oxide layer specifically in the regions where unnecessary light propagates (on the substrate surface outside the waveguide path), while maintaining the thin substrate structure elsewhere to preserve electric field efficiency. The oxide layer is positioned locally to absorb unnecessary light without interfering with the waveguide function.
3Object-affected harmful factors
If a metal underlayer is used to absorb unnecessary light, then optical electric field absorption is achieved, but mechanical deformation such as warpage occurs due to stress accumulation
Solution Approach 1:
The patent changes the material parameters by replacing metal underlayers with oxide materials that have matching linear expansion coefficients. This parameter change maintains the optical absorption function while eliminating the stress mismatch that causes warpage and deformation.
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
Effectively attenuates unnecessary light while suppressing substrate stress, maintaining optical modulation performance and reducing mechanical deformation.
Implementation Method 1
the oxygen-deficient layer is disposed in a region, on the principal surface of the substrate, other than a waveguide path for light from an optical input end to an optical output end of the optical waveguide
Implementation Method 2
an optical modulation device using LiNbO3 (hereinafter also referred to as LN), which has an electro-optic effect, as a substrate
Data Source
AI summary
An optical waveguide device includes a substrate made of an oxide, and an optical waveguide formed on a principal surface of the substrate, in which the substrate includes an oxygen-deficient layer having a lower oxygen content than in other portions of the substrate, and the oxygen-deficient layer is disposed in a region, on the principal surface of the substrate, other than a waveguide path for light from an optical input end to an optical output end of the optical waveguide. The structure attenuates unnecessary light that propagates through the substrate while suppressing generation of substrate stress in an optical waveguide device.