Optical Modulator Rib Waveguide Lateral PN Junction
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Solution Overview
Problem
Optical modulator elements generate higher-order modes, leading to reduced extinction ratio, increased bit errors, and optical loss, which deteriorate the quality of optical signals and increase energy transition from the fundamental mode.
Innovation Solution
An optical modulator element with a rib optical waveguide, a first thin film, and high-concentration doped regions, where the thin film is formed on the P-type and N-type slab regions with electron affinity different from the material, and the metal electrode is connected to these regions, reducing electric field extension and optical absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the electric field of the guided mode is extended in an optical modulator element, then the optical modulation intensity is improved, but higher-order modes are generated which reduce the extinction ratio and increase bit errors
Solution Approach 1:
The patent applies local quality by creating a lateral PN junction structure where the P-type and N-type doped regions are positioned adjacent to each other in the slab portion. This localized doping configuration creates a controlled electric field distribution that provides sufficient modulation intensity in the rib portion while preventing field extension that would generate higher-order modes, thus resolving the contradiction between modulation intensity and extinction ratio.
Solution Approach 2:
The patent changes the electrical parameters by introducing high-concentration doped regions with specific doping concentrations (e.g., 1×10^19 to 1×10^21 atoms/cm³) in the slab portion. This parameter modification allows the electric field to be confined appropriately, maintaining high modulation intensity while preventing higher-order mode generation, thereby improving both optical modulation intensity and extinction ratio.
2Power
If the electric field of the guided mode is extended in an optical modulator element, then the optical modulation intensity is improved, but optical loss increases due to energy transition from fundamental mode to higher-order modes
Solution Approach 1:
The lateral PN junction structure with locally positioned P-type and N-type doped regions creates a controlled electric field that is concentrated where needed for modulation while avoiding field extension into regions that would cause higher-order mode generation and associated optical loss.
Solution Approach 2:
By adjusting the doping concentration parameters in the slab portion to high levels (1×10^19 to 1×10^21 atoms/cm³), the patent modifies the electrical characteristics to confine the electric field appropriately, achieving high modulation intensity while minimizing energy transition to higher-order modes and reducing optical loss.
3Device complexity
If a conventional optical modulator structure is used, then the device complexity is low, but the quality of optical signals deteriorates due to higher-order mode generation
Solution Approach 1:
The patent maintains relatively simple device structure by implementing only a lateral PN junction in the slab portion without adding complex three-dimensional structures. This localized doping approach achieves high optical signal quality by preventing higher-order mode generation while keeping the device structure simple and suitable for conventional manufacturing processes.
Solution Approach 2:
The patent achieves improved optical signal quality by modifying the doping concentration parameters in the slab portion to high levels, creating a lateral PN junction that confines the electric field effectively. This parameter change approach maintains structural simplicity while significantly improving extinction ratio and reducing bit errors.
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 reduces the generation of higher-order modes, decreases optical loss, and improves the quality of optical signals by minimizing electric field extension and absorption, thereby enhancing the reliability and productivity of optical modulators.
Implementation Method 1
The first thin film is formed on the P-type slab region and has electron affinity different from electron affinity of a material for the P-type slab region
Implementation Method 2
The rib optical waveguide includes a rib portion having a PN junction, a P-type slab region connected to a P-type region of the rib portion, and an N-type slab region connected to an N-type region of the rib portion
Data Source
AI summary
An optical modulator element includes a rib optical waveguide, a first thin film, a first high-concentration doped region, and a first metal electrode. The rib optical waveguide includes a rib portion having a PN junction, a P-type slab region connected to a P-type region of the rib portion, and an N-type slab region connected to an N-type region of the rib portion. The first thin film is formed on the P-type slab region and has electron affinity different from electron affinity of a material for the P-type slab region. The first high-concentration doped region is a region in the P-type slab region, the region being at a position separate from the rib portion. The first metal electrode is electrically connected to the first high-concentration doped region positioned outward in the P-type slab region having the first thin film formed over the P-type slab region.