Group III Nitride Acoustooptic Device for UV Imaging
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Solution Overview
Problem
Conventional acoustooptic devices face challenges with light in the ultraviolet region due to absorption issues, require high-frequency signal power sources, suffer from poor performance, and are prone to dust adhesion and laser damage, leading to inefficiencies and maintenance challenges in optical imaging applications.
Innovation Solution
An acoustooptic device utilizing a Group III nitride crystal as the acoustooptic medium, which converts high-frequency signals into mechanical vibrations, creating a diffraction grating for light and improving refractive index variation, thus enhancing performance and resistance to dust and laser damage, while reducing the size of the driving circuit and improving moisture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional acoustooptic media (PbMoO4, TeO2, quartz glass, KDP) are used, then the device can operate with visible light, but the absorption edge wavelength limits transmission of ultraviolet light with wavelength of 380 nm or shorter
Solution Approach 1:
The patent changes the fundamental optical parameter (absorption edge wavelength) by selecting a different crystal material system. AlN has an absorption edge at 210 nm and GaN at 380 nm, which are significantly shorter than conventional materials, enabling UV light transmission while maintaining acoustooptic functionality.
Solution Approach 2:
The patent employs composite material strategy by using Group III nitride crystals (AlN, GaN, InN) which combine wide bandgap properties with excellent acoustooptic characteristics, achieving both UV transparency and high acoustooptic performance that neither conventional materials nor single materials could provide alone.
2Illumination intensity
If TeO2 crystal is used for ultraviolet acoustooptic device, then the absorption edge wavelength is around 330 nm, but it is not suitable for high pulse peak power applications
Solution Approach 1:
The patent uses Group III nitride crystals that combine wide bandgap properties (providing UV transparency) with high damage threshold characteristics. These materials simultaneously satisfy both requirements: transmission of ultraviolet light and resistance to high pulse peak power, which TeO2 cannot achieve alone.
Solution Approach 2:
The patent changes the material's intrinsic parameters by selecting Group III nitride crystals with wider bandgaps and higher thermal conductivity compared to TeO2, thereby improving both UV transmission and laser damage resistance without compromise.
3Ease of manufacture
If quartz glass, quartz crystal, or KDP crystal is used for acoustooptic device, then the device can be manufactured, but it delivers poor acoustooptic performance requiring high-frequency signal power source and water-cooling
Solution Approach 1:
The patent changes the acoustic velocity parameter by using Group III nitride crystals with lower acoustic velocity compared to conventional materials. This parameter change directly improves the acoustooptic figure of merit, enabling efficient operation at lower frequencies without requiring high-power sources or water-cooling systems.
Solution Approach 2:
The patent employs Group III nitride crystals that provide a unique combination of properties: adequate manufacturability through established semiconductor fabrication techniques, superior acoustooptic performance, and inherent thermal management capabilities that eliminate the need for external water-cooling.
4Illumination intensity
If conventional acoustooptic device is used with light having short wavelength, then the device can operate, but dust adheres to light incident surface and light emitting surface causing continuous use problems
Solution Approach 1:
The patent changes the surface energy parameters by using Group III nitride crystals with different surface chemistry characteristics. These materials exhibit reduced dust adhesion properties, particularly when produced in controlled environments, enabling continuous operation with short wavelength light without dust accumulation on optical surfaces.
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 use of Group III nitride crystals in acoustooptic devices provides excellent performance, resistance to laser and optical damage, and reduced dust adhesion, enabling continuous operation with improved heat dissipation and cost-effectiveness for optical imaging applications.
Implementation Method 1
a high-frequency signal input from the high-frequency signal input part is converted into a mechanical vibration by the transducer part
Implementation Method 2
an optical characteristic of the acoustooptic medium varies depending on the mechanical vibration
Implementation Method 3
creates a diffraction grating for light
Data Source
AI summary
The present invention provides an acoustooptic device usable even with light in the ultraviolet region, free from laser damage and optical damage, and excellent in acoustooptic performance and an optical imaging apparatus using the same. The acoustooptic device according to the present invention includes a high-frequency signal input part (65), a transducer part (64), and an acoustooptic medium (6). A high-frequency signal input from the high-frequency signal input part (65) is converted into a mechanical vibration by the transducer part (64), and an optical characteristic of the acoustooptic medium (6) varies depending on the mechanical vibration. The acoustooptic medium is formed of a Group III nitride crystal. The optical imaging apparatus according to the present invention includes a light source, an acoustooptic device, a driving circuit, and an image plane. Light from the light source is diffracted by the acoustooptic device in accordance with a signal from the driving circuit and the resultant diffracted light forms an image on the image plane. An acoustooptic medium of the acoustooptic device is formed of a Group III nitride crystal.