Metasurface Phase Modulation for Autofocusing Laser Beams
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current laser surgery devices lack the ability to change output spatial modes, resulting in inadequate penetration and focusing of light into tissues, especially in deep tissue applications, due to their inability to create high intensity hotspots without diffraction.
Innovation Solution
A metasurface-based device utilizing a metasurface phase modulation element with nano-structures on an optical emitting surface generates abrupt autofocusing (AAF) beams, which maintain hollow shapes and concentrate energy effectively, allowing for precise focusing without damaging surrounding structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional laser beams are used for deep tissue penetration, then the light source can be positioned close to the tissue, but the light intensity cannot be concentrated sufficiently at depth due to diffraction
Solution Approach 1:
The patent transforms a conventional Gaussian beam into an Airy beam by modifying the spatial phase distribution of the light field. This parameter change in the beam's wavefront structure enables the light to maintain its intensity profile over extended propagation distances and achieve autofocusing at depth without additional optical elements, thereby resolving the contradiction between penetration depth and focal intensity concentration.
2Illumination intensity
If high numerical aperture focusing is used to concentrate light, then the focal spot size is reduced, but the working distance becomes too small and axial confinement is poor
Solution Approach 1:
The invention changes the fundamental parameters of the light beam from a conventional focused Gaussian profile to an Airy beam profile with cubic phase modulation. This parameter transformation creates a non-diffracting beam that maintains its shape and intensity over long propagation distances, achieving both deep penetration and tight focal confinement without requiring high numerical aperture lenses that would limit working distance.
3Illumination intensity
If conventional beams are focused deep into tissue, then the focal spot is diffuse due to diffraction, but creating a high intensity hotspot requires complex optical systems
Solution Approach 1:
The patent applies a cubic phase modulation parameter to the incident Gaussian beam to generate an Airy beam. This single parameter change in the wavefront structure enables the beam to naturally autofocus at depth with high intensity contrast between the focal hotspot and surrounding regions, eliminating the need for complex multi-element optical focusing systems.
Solution Approach 2:
The Airy beam possesses intrinsic autofocusing properties that enable it to self-concentrate at the desired depth without requiring external focusing optical elements. The beam's unique phase structure causes it to naturally form a tight focal spot deep within the tissue, making the system self-focusing and significantly reducing overall optical system complexity.
4Illumination intensity
If focused light is delivered to deep tissue, then the surrounding tissue may be damaged by scattered light, but reducing focus intensity reduces treatment effectiveness
Solution Approach 1:
The transformation to an Airy beam with cubic phase modulation creates a light field with a hollow core structure during propagation, where the majority of energy is confined to a narrow region. This parameter change in beam structure minimizes light scattering and energy deposition in surrounding tissues while maintaining extremely high intensity at the focal plane, thus protecting surrounding tissue from damage.
Solution Approach 2:
The Airy beam creates a highly localized energy distribution where the intense focal hotspot is spatially separated from the propagation path. The beam's structure concentrates energy delivery precisely at the target depth while the regions along the propagation path contain minimal energy, providing selective energy deposition that treats the target without damaging surrounding healthy tissue.
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 AAF beam achieves high intensity at the focal plane, enabling effective medical procedures by maintaining hollow beam shapes and concentrating energy, thus preventing damage to cells or structures along the propagation path while ensuring efficient energy delivery.
Implementation Method 1
a metasurface phase modulation element having a plurality of nano-structures formed on an optical emitting surface
Implementation Method 2
modulating the incident beam into a diffracted light beam
Implementation Method 3
The focus lens is configured to perform optical Fourier transform of the diffracted light field from the metasurface phase modulation element for forming an AAF beam
Implementation Method 4
During free-space propagation, the AAF beam naturally gets focused without any focusing optical components
Implementation Method 5
since the focal position of the AAF beam has Bessel effect, the energy could be concentrated so that the optical process, such as medical operation or treatment, could be performed on the object effectively
Implementation Method 6
The sudden increase in the light intensity at the focal plane is the most striking feature, very similar to the Bragg effect in proton beam
Data Source
AI summary
The present invention provides a device for generating an abrupt autofocusing beam, comprising a light source module, a metasurface phase modulating element, and a focus lens, wherein the light source module generates an incident light beam, the metasurface modulating element has a first optical receiving surface for receiving the incident light beam, and an optical emitting surface having a plurality of dielectric nano-structures formed thereon for modulating the incident light beam into a diffracted light beam wherein the plurality of nano-structures respectively corresponding to optical-phase mask patterns, and the focus lens is arranged at a side of the optical receiving surface for performing optical Fourier transform of the diffracted light beam obtained from the metasurface phase modulating element.