Coaxial Acousto-Optic Modulator for Mediator-Free Laser Focusing
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Solution Overview
Problem
Current methods for optical imaging, such as photoacoustic imaging, face limitations in penetration depth and resolution due to the use of mediators like air bubbles or oil droplets, and perpendicular alignment of ultrasound (US) waves with light, which do not provide time-stable focusing.
Innovation Solution
A coaxial acousto-optic modulator system that uses co- or counter-propagating US waves to modify the refractive index of the medium, allowing for mediator-free, time-stable focusing and amplification of laser beams without cavitation or temperature changes, enhancing penetration depth and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If mediators like air bubbles or oil droplets are used for optical modulation, then light penetration is enhanced, but device complexity and potential harmful effects increase
Solution Approach 1:
The patent removes the mediator (air bubbles or oil droplets) from the system entirely. Instead of using these auxiliary substances to modulate light, the invention uses direct acousto-optic interaction between ultrasound waves and laser beams in a clear medium, eliminating the need for mediators while maintaining optical modulation capability
Solution Approach 2:
The patent introduces ultrasound waves as a new intermediary to achieve optical modulation without using traditional mediators like air bubbles. The ultrasound field acts as the mediating element that couples acoustic energy to optical energy through refractive index modulation, providing a cleaner and more controllable interaction mechanism
2Illumination intensity
If perpendicular alignment of US waves with light is used, then optical modulation is achieved, but time-stable focusing is not provided
Solution Approach 1:
The patent inverts the traditional perpendicular alignment configuration and uses coaxial (parallel) alignment of ultrasound and light propagation directions. This inversion enables time-stable focusing because the acoustic field creates a stationary refractive index distribution along the optical path, allowing the laser to be continuously focused at a specific depth without temporal fluctuations
Solution Approach 2:
The patent changes the geometric parameter of wave alignment from perpendicular to coaxial (parallel). This parameter change fundamentally alters the interaction mechanism, enabling the acoustic field to create a stable optical lens effect that maintains focusing over time, whereas perpendicular alignment only provides transient modulation
3Shape
If auxiliary media or additional hardware are used for focusing, then focusing is achieved, but mediator-free property and system simplicity are compromised
Solution Approach 1:
The patent enables the system to focus light using only the ultrasound field itself, without requiring auxiliary media or additional focusing hardware. The acoustic standing wave pattern creates a self-formed optical lens through refractive index modulation, allowing the system to focus light at different depths by simply adjusting the acoustic parameters
Solution Approach 2:
The patent makes the ultrasound transducer serve multiple functions: it generates the acoustic field for modulation, creates the focusing effect through refractive index variation, and eliminates the need for separate focusing optics. This multi-functionality simplifies the overall system while maintaining versatile focusing capability
4Force
If US transducer is used as passive element for photoacoustics, then vibration reception is achieved, but active transmission and control are limited
Solution Approach 1:
The patent inverts the passive role of the ultrasound transducer and uses it as an active transmitter. Instead of merely receiving vibrations generated by incident laser (photoacoustics), the transducer actively generates and transmits ultrasound waves to modulate and focus the laser beam, providing full control over the acoustic field parameters
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 system achieves a 450-fold reduction in beam diameter, two orders of magnitude increase in power density, and maintains time-stable focusing over a deep dynamic control range, overcoming previous limitations in optical modulation and focusing.
Implementation Method 1
The phenomenon of acoustic modulation on propagation of light through scattering media by polarization modulation, optical phase conjugation, wave front shaping
Implementation Method 2
A coaxial acousto-optic modulator system that uses co- or counter-propagating US waves to modify the refractive index of the medium, allowing for mediator-free, time-stable focusing and amplification of laser beams
Data Source
AI summary
A co/counter propagating acousto-optic modulator is provided that creates a low-intensity focused ultrasound (FUS) wave on a laser beam in a medium such as water without any auxiliary mediators or special software/hardware. The main optical effect of the FUS is the controllable focusing of the laser beam through modification of the refractive index of the medium in a time-stable and dynamic fashion. The laser beam and the FUS wave are coaxially mixed and propagated through each other. The FUS pressure field highly amplifies the power density, highly amplifies the intensity, sharpens the diameter, and reduces the full width at half maximum (FWHM) of the laser beam. The FUS pressure field keeps the laser beam's lensing power positive, with small fluctuations, as long as the ultrasound wave is coaxially propagated with the laser beam.