Ultrashort Laser Separation of High-Index Transparent Workpieces

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Solution Overview

Problem

The separation of materials with high refractive indices using ultrashort pulse lasers is challenging due to significant aberration of the laser beam and weak coupling into the material, leading to inefficient energy deposition and material removal.

Innovation Solution

A method employing ultrashort laser pulses to create a notch in materials with refractive indices between 2.0 and 3.5, utilizing nonlinear absorption and micro-explosions to remove material along a separation line, followed by mechanical, thermal, or chemical separation techniques to achieve precise and efficient separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If perpendicular incidence is used to minimize reflection losses, then reflection losses are reduced, but significant aberration of the laser beam arises due to large refractive index difference

Engineering Contradiction:

Improvereflection lossesVSAvoidtargeted energy deposition

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

An immersion medium with refractive index between 1.5 and 2.5 is introduced between the laser beam and the workpiece material. This intermediary reduces the refractive index mismatch, minimizing beam aberration while allowing effective energy coupling into the high refractive index material (n=2.0-3.5) for precise targeted processing

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If high pulse peak power is used to achieve nonlinear absorption in transparent materials, then material removal is enabled, but coupling efficiency into high refractive index materials remains poor

Engineering Contradiction:

Improvematerial removal capabilityVSAvoidcoupling efficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The refractive index parameter of the surrounding medium is changed by using an immersion medium (n=1.5-2.5) instead of air (n=1.0). This parameter change optimizes the impedance matching between the laser beam and the workpiece material, significantly improving coupling efficiency and energy transfer to enable reliable nonlinear absorption and material removal in high refractive index materials

Inventive Principle:

Principle #35Parameter changes

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 enables effective material removal and separation with high-quality edges, overcoming the limitations of traditional methods by leveraging nonlinear absorption and controlled material modification to create a predetermined breaking point.

Implementation Method 1

The short pulse length and high pulse peak power, or the high pulse energy of the few 100 μJ, may lead to nonlinear absorption of the pulse energy within the material of a workpiece

Methodology Applied

Scientific EffectNonlinear absorption: Absorption (EM radiation)

Implementation Method 2

removing material of the workpiece along a separation line by using a laser beam comprising ultrashort laser pulses

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS20230373034A1Method for separating a workpiece

Publication Date: 2023.11.23 TRUMPF LASER & SYSTEMTECHNIK GMBH

AI summary

A method for separating a workpiece includes removing material of the workpiece along a separation line by using a laser beam comprising ultrashort laser pulses of an ultrashort pulse laser. The material of the workpiece is transparent to a wavelength of the laser beam, and has a refractive index between 2.0 and 3.5. The method further includes separating the workpiece along a notch formed by the removal of the material.