Hollow-Core Fiber End Facet Shield for Metrology Light Sources
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Solution Overview
Problem
Broadband light sources using hollow-core photonic crystal fibers face challenges with contamination growth and reduced operational lifetime due to plasma-induced degradation and turbulent gas flows, leading to decreased performance and frequent re-calibrations in lithographic and metrology applications.
Innovation Solution
A light source design with a gas cell and hollow-core photonic crystal fiber that minimizes gas volume and turbulence, using a shield or surface to restrict gas exchange and reduce contamination growth, thereby extending the operational lifetime and maintaining spectral and power output quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a gas-filled hollow-core photonic crystal fiber is used to generate broadband light, then spectral broadening and high power output are achieved, but contamination growth and plasma-induced degradation occur, reducing operational lifetime
Solution Approach 1:
The gas cell is divided into two distinct regions: a first region containing the hollow-core photonic crystal fiber for light generation, and a second region serving as a contamination sink to trap and remove contaminant material. This spatial segmentation prevents contaminants generated in the fiber region from accumulating and degrading the fiber, thereby extending operational lifetime while maintaining high power output.
Solution Approach 2:
A shield or surface structure is introduced as an intermediary element between the fiber and the contamination environment. This shield redirects gas flows and traps contaminants before they can reach and deposit on the fiber end facets, acting as a protective mediator that allows the fiber to operate at high power without immediate contamination damage.
2Object-generated harmful factors
If gas flow is increased to remove contaminants, then contamination growth is reduced, but turbulent gas flows increase, causing further contamination and performance degradation
Solution Approach 1:
Different regions of the gas cell are assigned different gas flow characteristics: the first region around the fiber maintains laminar, low-velocity flow to prevent turbulence-induced contamination, while the second region employs higher velocity flows to actively transport and remove contaminants. This local differentiation allows simultaneous contamination removal and flow stability.
Solution Approach 2:
The contamination removal function is extracted from the primary light generation region and placed in a separate second region. Contaminants are transported out of the fiber region and trapped in the second region, separating the contamination management function from the light generation function and preventing turbulence in the critical fiber region.
3Stability of the object's composition
If the gas cell volume is increased to reduce turbulence, then gas flow stability improves, but the device complexity and gas consumption increase
Solution Approach 1:
Instead of increasing the overall gas cell volume to reduce turbulence, the design uses a directional approach by introducing a second region downstream where contaminants are trapped. This dimensional organization of gas flow (separating clean generation region from contamination trapping region) achieves flow stability without requiring a proportionally larger cell volume, reducing device 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 design effectively reduces contamination growth and turbulence, enhancing the operational stability and longevity of the broadband light source, ensuring consistent performance and reducing downtime in industrial applications.
Implementation Method 1
A laser source may be coupled to the input of the optical fiber of the light source, and be spectrally broadened in the optical fiber
Implementation Method 2
hollow-core photonic crystal fibres provide pressure-adjustable normal or anomalous dispersion, which also permit low-loss guidance in a hollow channel that is about ten times narrower and has a 100-fold-higher effective nonlinearity than capillary-based systems
Implementation Method 3
spectrally broadening the light pulses propagating along the pulse guiding medium by subjecting them to the Raman nonlinearity via excitation of a Raman polarization
Implementation Method 4
coupling the laser pulses into a pulse guiding medium having an anomalous group-velocity dispersion and a Kerr nonlinearity
Implementation Method 5
the pulse guiding medium having an anomalous group-velocity dispersion
Implementation Method 6
the light pulses are subjected to anomalous group velocity dispersion which combines with the spectral broadening of the light pulses to result in a Raman-enhanced self-compression of the light pulses
Implementation Method 7
A light source design with a gas cell and hollow-core photonic crystal fiber that minimizes gas volume and turbulence, using a shield or surface to restrict gas exchange
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
A system and method for providing a light source is disclosed. In one arrangement, the light source comprises a gas cell having a window, an optical fiber that is hollow and has an axial direction, an end thereof being enclosed within the gas cell and optically coupled to the window via an optical path, and a surface, disposed around the end of the optical fiber, and extending past the end of the optical fiber in the axial direction towards the window so as to limit one or more of: the exchange of gas between the optical path and the remainder of the gas cell; ingress of plasma towards or into the optical fiber; and radical flux towards etch-susceptible surfaces.