Aspherical Phase Plate for Uniform Laser Beam Shaping
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Solution Overview
Problem
Conventional beam shaping methods for focused laser beams suffer from high energy losses and inability to achieve uniform or ring-shaped intensity distributions in the focal plane, due to diffraction effects and the use of complex, expensive optical elements, which limits their applicability in industrial and scientific applications.
Innovation Solution
A phase transforming optical system introduces a smooth phase shift in the central region of the laser beam, while maintaining an unchanged wavefront in the peripheral region, allowing for efficient beam shaping that approximates the Airy disk intensity distribution, reducing sidelobes and enhancing energy utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional beam shaping methods using arrays of microlenses, micromirrors, and prisms are used to transform intensity distribution, then uniform or ring-shaped intensity profiles can be achieved, but the device complexity increases and energy losses occur due to speckle effects and destruction of beam structure
Solution Approach 1:
The invention extracts only the essential function of beam shaping by using a single aspherical optical surface that introduces the required phase shift, eliminating the need for complex arrays of microlenses, micromirrors, and prisms. This single element performs the entire beam shaping function that previously required multiple components working together.
Solution Approach 2:
The invention combines the beam shaping function and focusing function into a single aspherical optical element. The optical surface is designed with a specific aspherical profile that simultaneously performs phase modulation for intensity distribution control and focusing of the laser beam, merging multiple functions into one component.
2Illumination intensity
If diffractive optical elements (DOE) are used to create uniform intensity distribution, then beam shaping is achieved, but diffraction losses increase and resistance to high power laser beams decreases
Solution Approach 1:
The invention changes the fundamental approach from diffractive optics to refractive optics by using an aspherical surface profile. Instead of relying on diffraction patterns created by periodic structures, the aspherical surface uses continuous refraction with a specifically designed profile to achieve the desired phase distribution, thereby eliminating diffraction losses associated with DOE elements.
3Illumination intensity
If binary phase plates are used to create Airy disk intensity distribution, then uniform intensity in focal plane can be achieved, but sharp edges cause overheating and destruction under high peak power lasers
Solution Approach 1:
The invention uses a smooth aspherical surface profile with continuous curvature variations instead of binary phase plates with sharp edges. The aspherical profile is defined by a mathematical function that provides gradual phase transitions, eliminating the abrupt phase jumps at edges that cause stress concentration and overheating in binary phase plates under high peak power laser illumination.
4Power
If Gaussian laser beam is focused by a lens, then high energy concentration is achieved, but non-uniform intensity distribution results which is not optimum for many applications
Solution Approach 1:
The aspherical optical surface introduces different phase shifts at different radial positions of the laser beam. The phase shift varies continuously from the center to the periphery according to the aspherical profile, creating a non-uniform phase distribution that transforms the Gaussian intensity profile into a uniform or ring-shaped profile in the focal plane, while maintaining high energy concentration.
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
This approach effectively suppresses energy losses and provides flexible intensity profiles, including uniform, ring-shaped, and donut distributions, improving the performance of laser technologies by optimizing energy distribution and increasing the resistance to high peak power lasers.
Implementation Method 1
at least one optical surface with a shape such that a part of the surface protrudes above the remaining part of the surface... introducing a phase shift to a region of a laser beam
Implementation Method 2
a focusing optical system with positive dioptric power... focusing the beam with using a focusing optical system... provides uniform, ring-shaped or other required intensity profiles
Data Source
AI summary
Beam shaping methods, systems, devices and apparatus to provide transformation of a TEM00 beam which intensity distribution is described by the Gaussian or similar functions to a focused spot of round or square shape with uniform intensity distribution achieved through introducing in the TEM00 beam a phase shift function with smooth phase transition and further focusing of the transformed beam; the resulting intensity distributions are created around the focal plane of a focusing optical system. The phase shift function is introduced by a phase transforming optical system implemented in apparatuses of the invention in form of a plate, or a telescope, or a collimator, or integrated to the focusing optical system: the phase transforming optical system including an aspheric optical surface providing the phase shift function with smooth phase transition. As a focusing optical system any diffraction limited optics with positive dioptric power can be applied.