Beam Mixer Spatial Inversion for Laser Intensity Symmetry
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Solution Overview
Problem
High power Excimer gas discharge laser beams often exhibit non-symmetrical intensity profiles along the long axis, leading to non-uniform crystallization of silicon films during laser processing, which can result in regions of unevenly crystallized material due to the instability of pulse shape and symmetry.
Innovation Solution
A beam mixer is introduced, utilizing a spatially inverting path and a beam splitter to redirect and recombine parts of the beam, ensuring increased intensity symmetry along a selected axis by using a series of flat mirrors and an optic to create a combined beam path, thereby stabilizing the intensity profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high power Excimer gas discharge laser is used to process silicon films, then high energy pulses are achieved, but the intensity profile becomes non-symmetrical and unstable along the long axis
Solution Approach 1:
The patent applies spatial inversion by redirecting the beam through a sequence of mirrors that flip the beam profile 180 degrees around the long axis. This inversion process transforms the non-symmetrical intensity profile into a symmetrical one by reversing the spatial distribution of intensity variations, effectively canceling out asymmetries when the inverted beam is recombined with the original beam path.
2Power
If the laser beam intensity profile is non-symmetrical, then high power pulses are maintained, but uniform crystallization of silicon film cannot be achieved
Solution Approach 1:
By inverting the beam spatially through the mirror system, the patent transforms regions of high intensity to low intensity and vice versa in a controlled manner. When this inverted beam is recombined with the original beam path, the intensity variations are averaged out, producing a uniform intensity profile that enables uniform silicon film crystallization while preserving the high power characteristics.
3Stability of the object's composition
If beam homogenizers are used downstream, then beam uniformity is improved, but the effectiveness is degraded by non-symmetrical input beam profiles
Solution Approach 1:
The patent performs the symmetry correction action upstream of the homogenizer by inverting the beam profile before it enters the homogenization stage. This preliminary inversion prepares the beam by creating a symmetrical intensity distribution, which allows the downstream homogenizer to operate at optimal effectiveness and achieve the desired beam uniformity for uniform silicon film crystallization.
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 beam mixer effectively enhances the symmetry of the laser beam's intensity, improving the uniformity of the crystallization process and reducing undesirable intensity variations, resulting in more consistent material processing outcomes.
Implementation Method 1
an optic dividing the beam into first and second beam portions
Implementation Method 2
a plurality of mirrors establishing a spatially inverting path
Implementation Method 3
recombining the first and second portions onto a common path after the first portion has traveled along the inverting path thereby mixing the beam
Data Source
AI summary
A beam mixer for increasing intensity symmetry along a selected axis of a beam (wherein the beam extends from a first edge to a second edge along the axis) is disclosed and may include a plurality of mirrors establishing a spatially inverting path. For the beam mixer, the inverting path may have a beginning and an end and may be characterized in that a part of the beam near the first beam edge at the beginning of the path translates to the second beam edge at the end of the path. For this aspect, the beam mixer may further include an optic dividing the beam into first and second beam portions, the optic placing the first portion onto the inverting path and recombining the first and second portions onto a common path after the first portion has traveled along the inverting path thereby mixing the beam.