Optical Phase Modulator Trenches for Thermal Confinement
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Solution Overview
Problem
Thermo-optical modulators in optical phased arrays suffer from limited efficiency due to heat spreading in all directions, which is not confined effectively, leading to inefficient power consumption and integration challenges.
Innovation Solution
An optical phase modulator design featuring dielectric trenches above and beside the waveguide and heater, thermally coupled to the waveguide, with a second dielectric layer covering the trenches to maintain thermal insulation during integration, reducing heat loss and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If insulation trenches are added to confine heat, then thermal efficiency is improved, but device complexity increases and integration becomes difficult
Solution Approach 1:
The insulation structure is segmented into multiple functional layers: a first dielectric layer forming initial insulation, a suspended section creating an air gap for enhanced thermal isolation, and a second dielectric layer providing additional insulation and structural support. This segmentation allows effective heat confinement while maintaining manufacturability through standard semiconductor processing steps.
Solution Approach 2:
The invention introduces vertical dimensionality by suspending the waveguide section between two dielectric layers, creating a three-dimensional insulated structure. The air gap formed by suspension provides thermal isolation in the vertical dimension, complementing the lateral insulation trenches, thereby achieving superior thermal confinement without excessive lateral complexity.
2Loss of energy
If the modulator is suspended by etching the substrate, then heat confinement is improved, but manufacturing complexity increases
Solution Approach 1:
The suspension structure is formed as an integrated part of the device fabrication process rather than as a post-processing step. The dielectric layers and suspended section are created during standard semiconductor manufacturing, allowing heat confinement to be achieved without requiring complex post-fabrication suspension techniques.
3Ease of manufacture
If a simple Ti/TiN heater structure is used, then ease of manufacture is improved, but thermal efficiency deteriorates due to heat spreading
Solution Approach 1:
Multiple dielectric layers and air gaps are introduced as intermediary thermal insulation structures between the heater and the surrounding environment. These intermediary layers redirect heat flow primarily into the waveguide core, reducing lateral heat spreading while maintaining the simplicity of the Ti/TiN heater structure itself.
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
The modulator achieves a four-fold reduction in power required for phase modulation, improving efficiency and enabling integration without performance degradation.
Implementation Method 1
thermo-optical modulators that utilise the temperature dependence of the refractive index of a material (thermo-optic coefficient). Thus, by heating (or cooling) this material, its refractive index will be modified which, as with electro-optical modulators, results in a change of phase for a signal propagating in this material.
Implementation Method 2
Each of the first, second and third trenches thermally insulates each heater and each waveguide from the external environment. In this way, the heat generated by the heater that is not transferred to the waveguide is reduced.
Implementation Method 3
Ti/TiN heater (above the waveguide) in which an electric current is circulated to heat the heater (and therefore the waveguide) by the Joule effect.
Data Source
AI summary
An optical phase modulator includes a first layer made of dielectric material with a waveguide and a heater extending therein; at least one upper trench arranged above the heater and side trenches arranged on either side of the waveguide and the heater, and a second layer made of dielectric material extending over the first layer made of dielectric material and covering each first, second and third trench.