Sub-Wavelength Acoustic Waveguide for Non-Suspended Acousto-Optic Modulators
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acousto-optic modulators face challenges in achieving high conversion efficiency and stability due to the lack of piezoelectric effect in silicon materials and the complexity of suspending devices, which complicates the design and manufacturing process, limiting microwave-to-optical wave conversion.
Innovation Solution
An acousto-optic modulator enhanced by a sub-wavelength acoustic waveguide, utilizing a sapphire underlayment and silicon dioxide layer with a lithium niobate thin film, includes a transducer region, tapered transition region, and acoustic-photonic crystal cavity, allowing for non-suspended operation and efficient acoustic resonance mode excitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If suspended thin-film silicon is used to make an acoustic-photonic crystal cavity, then high opto-mechanical coupling rate is achieved, but the lack of piezoelectric effect limits microwave-to-optical wave conversion
Solution Approach 1:
The patent employs a hybrid structure combining silicon waveguide (for optical confinement) with lithium niobate thin film (for piezoelectric effect and acoustic wave generation). This composite material approach allows the device to simultaneously achieve high opto-mechanical coupling through the silicon portion and effective microwave-to-optical conversion through the lithium niobate portion, resolving the contradiction between coupling rate and conversion capability.
2Adaptability or versatility
If acoustic levitation cavity is designed under crystalline cavity to solve lack of piezoelectric effect, then acoustic resonance can be induced, but optical Q value must exceed 10^7 and manufacturing becomes difficult
Solution Approach 1:
The patent extracts the piezoelectric function from a separate acoustic levitation cavity and integrates it directly into the waveguide structure through lithium niobate thin film deposition. This eliminates the need for a complex suspended acoustic cavity while maintaining acoustic resonance capability, significantly simplifying the manufacturing process by removing the requirement for ultra-high optical Q values and complex suspension structures.
Solution Approach 2:
The patent merges the acoustic wave generation function (previously requiring a separate acoustic levitation cavity) with the optical waveguide structure by depositing lithium niobate thin film directly on the silicon waveguide. This integration combines multiple functions into a single structure, reducing manufacturing complexity while maintaining the desired acoustic resonance and microwave-to-optical conversion capabilities.
3Productivity
If sub-wavelength acoustic waveguide is used to bind acoustic modes, then coupling efficiency is enhanced, but device must be suspended and preparation process becomes difficult
Solution Approach 1:
The patent changes the dimensional parameters of the acoustic waveguide to sub-wavelength scale (width and height both less than acoustic wavelength) to achieve strong acoustic mode confinement and high coupling efficiency. Despite this stringent dimensional requirement, the device is implemented as a non-suspended planar structure that can be fabricated using standard thin-film deposition and lithography techniques, making the preparation process feasible while maintaining high acoustic coupling efficiency.
4Device complexity
If traditional acousto-optic modulation device is used, then simple structure is maintained, but conversion efficiency is unsatisfactory due to dimensional and physical properties
Solution Approach 1:
The patent applies local quality enhancement by confining both optical and acoustic modes to a sub-wavelength scale within the waveguide structure. This localized confinement creates intense field interactions between photons and phonons in a small region, dramatically improving conversion efficiency. The device maintains a relatively simple overall structure while introducing localized sub-wavelength features that enhance performance without requiring complex suspended configurations.
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 high modulation efficiency and strong acousto-optic interactions with broad application prospects, overcoming the limitations of previous designs by enhancing microwave-to-lightwave conversion and reducing manufacturing complexity.
Implementation Method 1
lithium niobate materials (LiNbO3) have attracted much attention in the industry because of their outstanding electro-optical, nonlinear optical, acousto-optical, piezoelectric properties
Implementation Method 2
acousto-optic modulators occupy an important position in microwave-to-lightwave conversion, which changes the refractive index of a medium through phonon-photon interactions to realize a modulation of an optical field
Implementation Method 3
bind the acoustic modes to a mechanical waveguide at the sub-wavelength scale and couple to the acoustic-photonic crystal cavity; this significantly enhances the coupling efficiency of acoustic wave
Data Source
AI summary
An acousto-optic modulator enhanced by a sub-wavelength acoustic waveguide is provided. The acousto-optic modulator comprising: a substrate, wherein the substrate includes a sapphire underlayment and a silicon dioxide layer disposed on the sapphire underlayment; the substrate further including a lithium niobate thin film, wherein the lithium niobate thin film includes a transducer region and a tapered transition region that are etched, the sub-wavelength acoustic waveguide, an acoustic-photonic crystal cavity, and a side-coupled photonic crystal; wherein the etched transducer region is provided with an interdigital transducer, the sub-wavelength acoustic waveguide is connected with the etched transducer region via the tapered transition region that is etched, the acoustic-photonic crystal cavity is connected with a non-suspended sub-wavelength acoustic waveguide and is arranged parallel to a suspended side-coupled photonic crystal.