Light Modulator Conductive Oxide Layer Plasmonic Interface
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Solution Overview
Problem
Conventional light modulators face limitations in achieving high-speed modulation due to small changes in refractive index and phase matching conditions, leading to low modulation depth and increased insertion loss, especially when miniaturized.
Innovation Solution
A light modulator configuration with a waveguide, a metal layer, a conductive oxide layer, and an insulating layer, where the interface between the conductive oxide and insulating layers is formed at a distance shorter than the guided light wavelength, allowing significant refractive index changes and enhanced phase matching conditions when a voltage is applied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the length of the modulator is increased to improve the degree of modulation, then the modulation depth increases, but the insertion loss increases
Solution Approach 1:
The patent changes the physical and chemical parameters of the modulator by introducing a conductive oxide layer with specific electron density (10^19 to 10^21 cm^-3) and controlling the distance from the metal layer surface (less than one wavelength of guided light). This enables strong refractive index modulation without increasing modulator length, thereby achieving high modulation depth with low insertion loss.
Solution Approach 2:
The patent employs a composite structure consisting of a metal layer, a conductive oxide layer, and an insulating layer. This composite material approach combines the plasmonic properties of metal with the high electrical conductivity and tunable refractive index of conductive oxide, creating a system that achieves strong light modulation in a compact configuration with reduced insertion loss.
2Illumination intensity
If conventional electro-optic materials are used to achieve phase modulation, then the refractive index changes, but the change amount is very small (about 0.001)
Solution Approach 1:
The patent achieves large refractive index changes by controlling the electron density of the conductive oxide layer (10^19 to 10^21 cm^-3) and its proximity to the metal layer (within one wavelength distance). This parameter control enables the conductive oxide to exhibit much stronger refractive index modulation compared to conventional electro-optic materials, without requiring complex high-voltage electric field application systems.
Solution Approach 2:
The conductive oxide layer acts as an intermediary between the metal layer and the guided light. It converts the electromagnetic field from the metal layer into significant refractive index modulation, thereby achieving strong light-matter interaction and large phase modulation without the limitations of conventional electro-optic materials.
3Volume of moving object
If the modulator is miniaturized to reduce size, then the device becomes compact, but the phase matching condition control becomes difficult
Solution Approach 1:
The patent maintains effective phase matching control in miniaturized devices by precisely controlling the distance between the conductive oxide layer and the metal layer surface (less than one wavelength of guided light). This distance control, combined with electron density adjustment in the conductive oxide, enables strong refractive index modulation in a compact footprint, achieving both miniaturization and precise phase matching control.
Solution Approach 2:
The patent concentrates the modulation function in a localized region by positioning the conductive oxide layer adjacent to the metal layer surface within one wavelength distance. This local concentration of optical interaction enhances the modulation efficiency per unit length, allowing the modulator to be miniaturized while maintaining effective phase matching control through localized material property optimization.
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 enables increased modulation depth and high-speed modulation even in compact designs, reducing parasitic capacitance and improving light modulation efficiency.
Implementation Method 1
the electron density of the conductive oxide layer near the interface between the conductive oxide layer and the insulating layer changes, thereby the refractive index of the conductive oxide layer near the interface changes significantly
Implementation Method 2
a plasmon coupling type that modulates the amount of transmitted light utilizing coupling between surface plasmon polariton (hereinafter simply referred to SPP) and guided light
Data Source
AI summary
A light modulator (101) includes a waveguide (112) through which guided light propagates, a metal layer (113) formed adjacent to the waveguide (112), a conductive oxide layer (114) having electrical conductivity and formed on a surface of the metal layer (113) which is not adjacent to the waveguide (112), an insulating layer (115) formed adjacent to the conductive oxide layer (114), and a modulation circuit (102) that applies a voltage between the metal layer (113) and one of the conductive oxide layer (114) and the insulating layer (115). An interface (11) at which the conductive oxide layer (114) and the insulating layer (115) are adjacent to each other is formed at a distance shorter than a wavelength of the guided light in vacuum, from the surface of the metal layer (113) which is not adjacent to the waveguide (112).