Bonded SHG Crystal Assembly for UV-Visible Beam Separation
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Solution Overview
Problem
Existing laser devices face challenges in generating UV radiation while effectively separating it from residual visible radiation, leading to damage of thin-film dielectric coatings and increased complexity and cost due to the need for additional optical elements and precise alignment.
Innovation Solution
A laser apparatus utilizing two or three optically-nonlinear crystals bonded together with matched thermal expansion coefficients and oriented to achieve phase matching and reflection symmetry, allowing for spatial separation of UV and visible radiation without additional coatings, minimizing reflection losses, and enabling translation to extend the device's lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dichroic mirror with thin-film dielectric coating is used to separate UV radiation from visible radiation, then spatial separation is achieved, but the coating suffers from UV radiation damage and manufacturing losses
Solution Approach 1:
The harmful thin-film dielectric coating is extracted and removed from the system. Instead of using a coated dichroic mirror, the patent employs an uncoated birefringent prism that separates UV and visible radiation through natural birefringence and total internal reflection, eliminating the coating that is vulnerable to UV damage
Solution Approach 2:
An uncoated birefringent prism is introduced as an intermediary element to perform the separation function. The prism uses the intrinsic optical properties of birefringent material to achieve wavelength-dependent separation without requiring any protective coatings that would be damaged by UV radiation
2Duration of action of stationary object
If intra-cavity elements are translated to shift damaged areas out of radiation, then coating damage is mitigated, but device complexity and cost increase significantly
Solution Approach 1:
The vulnerable coated element is extracted and replaced with an uncoated birefringent prism. Since the prism has no coating to damage, there is no need for translation mechanisms to move damaged areas out of the radiation path, thereby eliminating the complexity while extending the useful lifetime
Solution Approach 2:
The uncoated birefringent prism is inherently resistant to UV damage, making it self-sufficient and eliminating the need for additional translation mechanisms or maintenance interventions to extend its operational lifetime
3Reliability
If thin-film dielectric coatings are used for wavelength separation, then spatial separation is achieved, but manufacturing variances and absorption cause efficiency losses
Solution Approach 1:
The lossy thin-film dielectric coating is extracted and replaced with an uncoated birefringent prism. The prism achieves wavelength separation through natural birefringence and total internal reflection, eliminating manufacturing variances and absorption losses associated with thin-film coatings
Solution Approach 2:
The separation mechanism changes from relying on thin-film interference (which is sensitive to manufacturing tolerances) to relying on birefringence and total internal reflection. This parameter change eliminates the source of manufacturing-related efficiency losses while maintaining effective wavelength separation
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 solution efficiently generates and separates UV radiation from visible radiation, reducing optical damage and complexity, while maintaining high conversion efficiency and extending the useful lifetime of the laser device.
Implementation Method 1
An optically-nonlinear crystal within the resonant cavity then converts the visible radiation to UV radiation by type-I second-harmonic conversion
Implementation Method 2
The birefringent crystal has an internal surface oriented at Brewster angle for the visible radiation and oriented for total internal reflection of the UV radiation
Implementation Method 3
The birefringent crystal has an internal surface oriented at Brewster angle for the visible radiation
Implementation Method 4
The coefficients of thermal expansion of the first and second crystals are thereby matched along the first planar interface
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3
AI summary
An optic (10) produces a beam of ultraviolet laser radiation from a beam of visible laser radiation and spatially separates the ultraviolet laser beam from the visible laser beam. The optic (10) includes two crystals (12,14) made of the same optically- nonlinear material that are contact bonded along a planar interface (16). One crystal (12) has principle crystal axes that are oriented for type-I second-harmonic generation. The ultraviolet laser beam exits the optic (10) through an uncoated surface (26) of the other crystal (14). The principle crystal axes of the two crystals (12,14) have different orientations and have reflection symmetry about the planar interface (16).