Laser Micromachining With Bessel Beams for Transparent Through-Holes
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Solution Overview
Problem
Current techniques for drilling through-holes in microelectronics and photovoltaics are limited by their slow speed and inflexibility, particularly for larger diameters, and are not well-suited for transparent materials like glass.
Innovation Solution
A device and method using a non-diffracting Bessel-Vortex beam focused according to a cylindrical profile, with multi-photonic absorption and time-domain conditioning of laser pulses to generate a plasma for high-speed micromachining, allowing for the creation of large diameter holes in transparent materials without hot spots or filamentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional drilling techniques (ebeam, photolithography, DRIE) are used, then holes can be drilled in semiconductor wafers, but the process is slow and not suitable for high-speed micromachining
Solution Approach 1:
The patent replaces conventional mechanical and chemical drilling processes (ebeam, photolithography, DRIE) with a laser-based micromachining system using Bessel-Gauss beams. This substitution enables high-speed processing by using photon-matter interaction (multi-photon absorption) instead of slow mechanical or chemical processes, directly addressing the productivity-speed contradiction.
Solution Approach 2:
The patent changes the spatial and temporal parameters of the laser beam by using Bessel-Gauss beam profiles with specific longitudinal and transverse characteristics. This parameter optimization allows the beam to maintain focus over extended depths while enabling high-speed processing, resolving the contradiction between machining speed and processing quality.
2Length of moving object
If simple annular diffracting beams are used, then large diameter holes can be drilled, but hot spots and multiple filamentation occur
Solution Approach 1:
The patent applies local quality by using Bessel-Gauss beam profiles that concentrate energy in a specific longitudinal region while maintaining a clean transverse profile. The beam's mathematical structure (J0 Bessel function in longitudinal direction, Gaussian in transverse) creates a localized energy deposition zone that avoids hot spots and filamentation, enabling large diameter drilling without harmful effects.
Solution Approach 2:
The patent uses the curved wavefront structure of Bessel-Gauss beams, which have a conical wavefront that focuses energy along a line rather than a point. This curved geometry allows the beam to maintain focus over an extended depth range while distributing energy uniformly, preventing hot spots and filamentation in large diameter holes.
3Manufacturing precision
If femtosecond Bessel beams are used for high aspect ratio nanochannels, then single shot machining is achieved, but the technique is limited to holes with diameters less than a few hundred nanometers
Solution Approach 1:
The patent creates a universal laser micromachining system that can handle both small nanoscale features and large micrometer-scale features by adjusting beam parameters. The Bessel-Gauss beam profile serves multiple functions: it maintains high aspect ratio capability for small features while also enabling large diameter drilling, making the system versatile across different length scales.
Solution Approach 2:
The patent dynamically adjusts the beam parameters (longitudinal and transverse profiles, pulse duration, wavelength) to optimize for different feature sizes. By making the beam characteristics adjustable rather than fixed, the system can transition from high aspect ratio nanochannel machining to large diameter hole drilling, resolving the contradiction between precision and size.
4Adaptability or versatility
If laser beams are used for micromachining transparent materials, then flexibility is improved, but linear absorption limits depth machining capability
Solution Approach 1:
The patent exploits non-linear optical effects (multi-photon absorption) that cause a phase transition in the material's response to laser energy. At low intensities, transparent materials do not absorb laser energy linearly. At the high intensities achieved by focused Bessel-Gauss beams, multi-photon absorption occurs, enabling deep machining in transparent materials by overcoming the linear absorption limitation.
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
Enables high-speed drilling of through-holes with diameters greater than a micron in transparent materials like glass, improving machining speed and flexibility while avoiding defects like hot spots and filamentation.
Implementation Method 1
a focusing module allowing the generation, starting from a given incident beam, of a non-diffracting beam focused according to a focusing cylinder
Implementation Method 2
the use of a femtosecond laser beam with a 'non-diffracting' spatial profile of the Bessel beam type
Implementation Method 3
means for emission of at least one first light pulse (I1) designed to generate, after focusing by said focusing module in the sample, a plasma of free charges by multi-photonic absorption
Implementation Method 4
This technology notably allows a micro-explosion to be created that is sufficiently intense and localized to evacuate the material to be ablated
Data Source
AI summary
The invention, according to an aspect thereof, relates to a device (60) for laser micromachining a sample made of a given material, which includes a focusing module enabling a nondiffracting beam to be generated from a given incident beam, said nondiffracting beam being focused along a focusing cylinder that is oriented generally along the optical axis of the focusing module, means (601) for transmitting at least one first light pulse (11) suitable for generating, after said focusing module focuses in the sample, a plasma of free charges by multiphotonic absorption in a volume of the sample located on the side surface of said focusing cylinder.