Wavelength Converting Optical System for Eighth Harmonic Generation
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Solution Overview
Problem
Conventional wavelength converting optical systems for generating an eighth harmonic wave are complex and require the superimposition of fundamental and seventh harmonic waves, which is difficult to adjust and results in poor durability for deep ultraviolet light, especially with dichroic mirrors.
Innovation Solution
A simplified wavelength converting optical system that forms an eighth harmonic wave without the need for superimposing fundamental and seventh harmonic waves, using a series of wavelength converting optical elements and optical members to combine and convert waves efficiently, with a focus on high conversion efficiency and reduced complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional wavelength converting optical system is used to generate an eighth harmonic wave, then the conversion can be achieved, but the system becomes complex and requires superimposition of fundamental and seventh harmonic waves which is difficult to adjust
Solution Approach 1:
The invention extracts and eliminates the need for superimposing fundamental and seventh harmonic waves from the optical system. By using a simplified configuration where only the seventh harmonic wave is generated and then combined with the fundamental wave in a single non-linear optical crystal to produce the eighth harmonic, the complex dichroic mirror superimposition system is removed entirely.
Solution Approach 2:
The invention merges the generation of the eighth harmonic wave into a single non-linear optical crystal process, combining the seventh harmonic wave and fundamental wave simultaneously within one crystal element. This eliminates the need for separate superimposition steps and reduces the number of optical components required.
2Reliability
If dichroic mirrors are used for superimposition of fundamental and seventh harmonic waves, then wavelength conversion can proceed, but the durability deteriorates due to poor durability for deep ultraviolet light
Solution Approach 1:
The invention extracts and removes the dichroic mirrors from the optical system entirely. By redesigning the wavelength conversion process to eliminate the superimposition step that requires dichroic mirrors, the durability issue with deep ultraviolet light exposure is completely avoided.
Solution Approach 2:
The invention introduces a single non-linear optical crystal as an intermediary element that directly converts the seventh harmonic wave and fundamental wave into the eighth harmonic wave without requiring dichroic mirrors for superimposition. This intermediary crystal performs the wavelength conversion function that previously required multiple components including durable dichroic mirrors.
3Device complexity
If a simplified optical system is used, then the complexity is reduced, but the conversion efficiency may be compromised
Solution Approach 1:
The invention optimizes parameters within the simplified optical system, including selecting appropriate non-linear optical crystal materials with high conversion efficiency for the specific wavelength transition, adjusting crystal orientation and temperature, and optimizing the input beam parameters to maximize the eighth harmonic generation efficiency despite the reduced system complexity.
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 system achieves high conversion efficiency for generating an eighth harmonic wave with improved durability and reduced complexity, enabling effective use in applications such as exposure apparatus and polymer crystal working without the need for complex dichroic mirror adjustments.
Implementation Method 1
a wavelength converting optical system which forms an eighth harmonic wave from semiconductor laser light mainly having long wavelength (light having a frequency that is n times that of the fundamental wave is referred to as an n-th harmonic wave)
Implementation Method 2
a first optical member which combines a third fundamental wave and the second harmonic wave emitted from the second harmonic wave forming optical element on the same optical path, a second optical member which combines the third fundamental wave, the second harmonic wave emitted from the second harmonic wave forming optical element, and the fifth harmonic wave emitted from the first wavelength converting optical system on the same optical path
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3(a)~3(b)
AI summary
A fifth harmonic wave is formed from a fundamental wave of P polarization via a second harmonic wave forming optical element 3, a third harmonic wave forming optical element 4, and a fifth harmonic wave forming optical element 6, and a second harmonic wave of P polarization is formed from a fundamental wave of P polarization via a second harmonic wave forming optical element 9. A fundamental wave of S polarization is combined with the second harmonic wave of P polarization described above by a dichroic mirror 13; furthermore, the fifth harmonic wave of P polarization, the fundamental wave of S polarization described above and the second harmonic wave of P polarization are combined by a dichroic mirror 10, and are incident on a seventh harmonic wave forming optical element 11. A seventh harmonic wave of S polarization is formed from the fifth harmonic wave and second harmonic wave of P polarization, and is combined with the fundamental wave of S polarization by being incident on an eighth harmonic wave forming optical element 12, so that an eighth harmonic wave of P polarization is formed.