Uncoated Birefringent Prism for UV Separation
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Solution Overview
Problem
Existing devices for generating ultraviolet radiation through second-harmonic conversion suffer from damage and efficiency losses due to thin-film optical coatings, particularly for shorter-wavelength UV radiation, which reduces the useful lifetime and efficiency of resonators.
Innovation Solution
An optical apparatus with an uncoated birefringent prism is used in an optical resonator to separate and direct ultraviolet radiation from visible radiation, utilizing mutually-orthogonal linear polarizations and Brewster angles to minimize reflection losses without the need for thin-film coatings, ensuring efficient conversion and output coupling of second-harmonic radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thin-film dichroic filters are used to direct UV radiation out of the resonator, then UV radiation can be separated from visible radiation, but the thin-film coatings suffer from damage and efficiency losses due to UV radiation
Solution Approach 1:
The patent removes the thin-film dichroic filter from the optical resonator system and replaces it with an uncoated birefringent prism. This extraction eliminates the component (thin-film coating) that is vulnerable to UV radiation damage while preserving the wavelength separation function through the prism's birefringent properties and Brewster angle geometry.
Solution Approach 2:
The patent replaces the expensive, damage-prone thin-film coating with a simple uncoated birefringent prism made of bulk optical material. The prism, being a robust solid component without fragile coatings, can withstand UV radiation without degradation, effectively substituting a durable component for a vulnerable one.
2Reliability
If thin-film optical coatings are used for wavelength separation, then UV and visible radiation can be separated, but manufacturing variances in layer thickness and material absorption cause efficiency losses
Solution Approach 1:
The patent extracts the thin-film optical coating from the system and replaces it with an uncoated birefringent prism. This eliminates the source of manufacturing variances and material absorption losses associated with thin-film layers, achieving wavelength separation through the inherent birefringent properties of the bulk crystal material.
Solution Approach 2:
The patent changes the separation mechanism from relying on thin-film coating optical properties (which are sensitive to layer thickness and material composition) to utilizing the birefringent refractive index differences of a bulk crystal. The Brewster angle geometry further optimizes transmission by minimizing reflection losses for polarized light.
3Productivity
If thin-film coatings are used in the resonator, then wavelength separation is achieved, but the useful lifetime of the resonator is reduced due to coating degradation
Solution Approach 1:
The patent removes the thin-film coating from the resonator system and replaces it with an uncoated birefringent prism. This extraction eliminates the component that degrades over time under UV radiation, thereby extending the resonator's useful lifetime while maintaining wavelength separation functionality.
Solution Approach 2:
The patent substitutes a durable, maintenance-free uncoated birefringent prism for the vulnerable thin-film coating. The prism's robust construction without fragile coatings ensures long-term stability and resistance to UV-induced degradation, significantly extending the resonator operational lifetime.
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 significantly reduces reflection losses for fundamental radiation and enhances the efficiency of second-harmonic conversion, extending the lifetime and performance of resonators by avoiding coating degradation and manufacturing variances, while maintaining high-Q resonant enhancement.
Implementation Method 1
The fundamental radiation and second-harmonic radiation are incident on a first face of the prism at about an external Brewster angle for the fundamental radiation
Implementation Method 2
a portion of the second-harmonic radiation enters the prism through the first face thereof, is totally internally reflected by the second face thereof
Implementation Method 3
An optically nonlinear crystal is located in the optical resonator and arranged to convert circulating fundamental radiation to second-harmonic radiation
Implementation Method 4
The fundamental radiation is an extraordinary beam within the prism and the second-harmonic radiation is an ordinary beam within the prism
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
An optical ring-resonator (12) converts visible wavelength radiation to ultraviolet wavelength radiation by frequency-doubling the visible wavelength radiation in an optically nonlinear crystal (18). The resonator (12) includes an uncoated birefringent out-coupling prism (20). The visible wavelength radiation passes through faces of the prism (20) at a Brewster-angle. Ultraviolet wavelength radiation enters the prism (20), is totally internally reflected, directed out of the prism (20) at a Brewster- angle, and exits the ring-resonator (12) as output radiation.