Laser Beam Homogenization Using Diffractive Optics and Multimode Fiber
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Solution Overview
Problem
Existing laser-based light sources struggle to achieve both angular and spatial uniformity, leading to non-uniform illumination and speckle patterns in optical applications like microscopy, due to their coherent nature and Gaussian/Lorentzian power distributions.
Innovation Solution
A system comprising deflection mirrors, diffractive optics, and multi-mode fibers is used to deflect and diffract laser beams, providing a uniform extended light source with substantial angular and spatial uniformity, while minimizing speckle and light losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a laser beam is used directly as an extended light source, then the system is simple and monochromatic, but the illumination is non-uniform with Gaussian/Lorentzian distribution and coherent speckle patterns form
Solution Approach 1:
The patent segments the laser beam into multiple discrete diffraction orders using a multi-lens array, where each lens creates a separate focused spot. This segmentation transforms the single Gaussian beam into multiple uniform spots arranged in a grid pattern, achieving spatial uniformity while maintaining system simplicity
Solution Approach 2:
The patent introduces a multi-lens array as an intermediary element between the laser source and the target plane. This intermediary diffracts and redistributes the laser energy into multiple uniform spots, acting as a mediator that converts non-uniform illumination into uniform illumination while preserving the monochromatic nature of the laser
2Illumination intensity
If a square fiber waveguide is used to couple a laser beam, then angular uniformity is improved through mode mixing, but the system design is complicated and NA range is limited
Solution Approach 1:
The patent replaces the mechanical alignment system required by square fiber waveguides with an optical diffraction system using a multi-lens array. This substitution eliminates the need for precise alignment between the fiber end face and imaging-system symmetry, simplifying the mechanical design while achieving angular uniformity through optical diffraction and mode mixing in the fiber
3Device complexity
If direct coupling of laser into fiber is used, then the system is simple, but high power density causes laser-induced damage and coupling loss
Solution Approach 1:
The patent segments the concentrated laser power into multiple discrete spots using the multi-lens array before coupling into the fiber. This segmentation distributes the power density across multiple focal points, preventing any single point from experiencing excessive power density that would cause laser-induced damage or coupling loss, while maintaining system simplicity
Solution Approach 2:
The multi-lens array acts as an intermediary that redistributes the laser power before fiber coupling. This intermediary element ensures that the power is evenly distributed across multiple diffraction orders, preventing concentration of power at any single point and thereby protecting against laser-induced damage while maintaining efficient coupling
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 solution achieves a uniform and monochromatic extended light source with reduced speckle and low light losses, suitable for applications requiring continuous and uniform illumination, such as Koehler illumination microscopy.
Implementation Method 1
one or more deflection mirrors to deflect a laser beam at varying angles
Implementation Method 2
diffractive optics to diffract the deflected laser beam
Implementation Method 3
a multi-mode fiber to transmit the diffracted laser beam
Data Source
AI summary
A light source includes one or more deflection mirrors to deflect a laser beam at varying angles and diffractive optics to diffract the deflected laser beam. The light source also includes a multi-mode fiber to transmit the diffracted laser beam and a plurality of lenses, disposed between the diffractive optics and the multi-mode fiber, to provide the diffracted laser beam to the multi-mode fiber.