Laser Beam Clipping for Wide Power Density Control in Evaporation

The patent divides the power adjustment function into two independent sections: a first adjusting section that handles coarse power level changes and a second adjusting section that handles fine power level changes. This segmentation allows continuous power adjustment without the thermal shock caused by pulse width modulation, as each section operates independently to provide smooth transitions. The clipping aperture further segments the beam path to enable precise control of the intermediate power level, eliminating the harmful time-varying signals that cause substrate failure.

The patent introduces a clipping aperture as an intermediary element between the two adjusting sections. This intermediary component creates an intermediate power level that serves as a bridge between high and low power states, allowing smooth transitions without abrupt changes. The clipping aperture mediates the power adjustment process by selectively blocking portions of the beam, thereby eliminating the thermal strain caused by direct pulse width modulation while maintaining continuous power control capability.

The patent divides the beam adjusting means into two independent adjusting sections, each capable of adjusting the beam cross section. This segmentation allows each section to operate within a specific power range and make targeted adjustments, thereby achieving a wide overall power density range without requiring a single complex adjusting mechanism. The first adjusting section handles coarse beam size changes for high power levels, while the second adjusting section handles fine beam size changes for low power levels, simplifying the control logic and reducing the complexity of any single adjusting component.

The patent implements dynamic switching between the two adjusting sections based on the current power level. The system automatically activates the appropriate adjusting section depending on whether the operating point is in the high-power or low-power regime, allowing the beam cross section to be dynamically adjusted across the full range. This dynamic operation enables wide power density control while keeping each individual adjusting section relatively simple, as each is only responsible for a specific portion of the overall adjustment range.