Segmented-Electrode Optical Modulator for Leaked-Light Interference Control
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Solution Overview
Problem
The variation in optical characteristics of optical modulation devices using protruding optical waveguides with segmented electrodes is caused by interference of leaked light beams between segments, leading to deteriorated optical characteristics such as extinction ratio.
Innovation Solution
The optical modulation device is designed with a multilayer substrate structure where the optical waveguide layer and support layers have specific refractive index relationships (n0 > n1 > n2) and controlled clearance and thickness to suppress interference between leaked light beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a segmented electrode is used to achieve impedance matching and velocity matching, then modulation performance is improved, but interference between leaked light beams occurs leading to deterioration of optical characteristics
Solution Approach 1:
A resin layer is introduced as an intermediary substance between the substrate and the protruding optical waveguide. This resin layer has a refractive index lower than both the substrate and the waveguide, creating a refractive index gradient that suppresses the interference of leaked light beams while maintaining the benefits of the segmented electrode structure
Solution Approach 2:
The refractive index distribution is modified by introducing the resin layer with a specific refractive index value that is lower than both the substrate and waveguide. This parameter change in the optical path creates conditions that reduce light beam interference without compromising the modulation performance achieved through segmented electrodes
2Manufacturing precision
If the protruding portion is formed with high accuracy in wafer process, then manufacturing precision is improved, but variation in optical characteristics such as extinction ratio still occurs
Solution Approach 1:
The resin layer acts as a compensating intermediary that reduces the impact of manufacturing variations in the protruding portion. By controlling the refractive index of this intermediate layer, the system becomes less sensitive to precise dimensional control of the waveguide structure
Solution Approach 2:
The refractive index parameter of the resin layer is optimized to reduce sensitivity to manufacturing tolerances. This parameter change creates a more robust system where optical characteristics remain consistent even when protruding portion dimensions vary within normal manufacturing ranges
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 design effectively reduces the intensity of leaked light beams, minimizing their impact on signal light and improving optical characteristics by suppressing interference, thereby enhancing the modulation performance.
Implementation Method 1
a refractive index n0 of the optical waveguide layer, a refractive index n1 of the first support layer, and a refractive index n2 of the second support layer have a relationship of n0>n1 and n2>n1
Implementation Method 2
forming the protruding portion (that is, a rib or a ridge) constituting the optical waveguide with high accuracy in a wafer process still poses an issue of variation in optical characteristics such as a modulation extinction ratio. A factor or a solution of the issue has not been found for a long time
Implementation Method 3
an optical modulator incorporating an optical modulation device as an optical waveguide device including an optical waveguide formed on a semiconductor substrate of InP or the like or on a substrate of LiNbO3 (hereinafter, referred to as LN) or the like having an electro-optic effect
Data Source
AI summary
An optical modulation device includes a substrate including a multilayer portion, an optical waveguide layer on which an optical waveguide is formed in the multilayer portion, and a modulation electrode formed to be divided into a plurality of segments along a propagation direction of the optical waveguide to control a light wave propagating through the optical waveguide, in which in all sections of the electrode or a section excluding a part of the sections, a clearance, measured in an extending direction of the optical waveguide, between gaps between adjacent segments is constant, the multilayer portion includes the optical waveguide layer, a first support layer, and a second support layer, and a refractive index n0 of the optical waveguide layer, a refractive index n1 of the first support layer, and a refractive index n2 of the second support layer have a relationship of n0>n1 and n2>n1.