Prism-Coupling Systems for Large Depth-of-Layer Waveguide Characterization
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Solution Overview
Problem
Conventional prism-coupling systems face limitations in measuring the depth-of-layer (DOL) of ion-exchanged glasses with large DOL values, leading to under-sampling of high-order modes and reduced measurement accuracy, especially beyond 100 μm, due to the assumption of a linear refractive index profile and the need for larger, more complex photodetectors and optical systems.
Innovation Solution
The system optimizes prism-coupling for high-resolution measurements by using light-blocking features to improve contrast for low-order modes while reducing resolution for higher-order modes, employing a combination of optics and photodetectors with high pixel density and a near-IR light source to measure the refractive index profile in two distinct regions, allowing for independent control of deep and shallow regions, and utilizing a chuck assembly for shape control to minimize measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional prism-coupling systems are used to measure waveguides with large depth-of-layer, then the measurement system becomes more complex and costly with larger photodetectors and larger-aperture optical systems, but the measurement precision of high-order modes deteriorates due to under-sampling
Solution Approach 1:
The patent divides the measurement process into two distinct measurement modes: a first measurement mode for shallow waveguides using conventional optics, and a second measurement mode for deep waveguides using optimized optics with smaller aperture and lower pixel density. This segmentation allows each mode to be optimized independently, avoiding the need for a single complex system that must handle both cases.
Solution Approach 2:
The patent changes key optical parameters based on the waveguide depth being measured. For deep waveguides, it uses a smaller aperture size and lower pixel density photodetector, which reduces system complexity and cost while maintaining adequate measurement precision for the specific application.
2Measurement precision
If larger photodetectors with more pixels are used to improve resolution for deep DOL measurements, then measurement precision improves, but system cost and complexity increase substantially
Solution Approach 1:
The patent changes the pixel density parameter of the photodetector based on the measurement requirements. For deep waveguide measurements, it uses lower pixel density photodetectors with smaller aperture sizes, which significantly reduces system cost while providing adequate resolution for the specific measurement needs.
3Measurement precision
If larger aperture optical systems are used to improve measurement resolution for large DOL, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent applies local quality by optimizing the optical system parameters specifically for deep waveguide measurements rather than designing a universally high-performance system. The smaller aperture and lower pixel density are sufficient for the specific measurement requirements of deep waveguides, avoiding unnecessary 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
This approach enables precise measurement of DOL and compressive stress in chemically strengthened glasses with large DOL values, improving measurement accuracy and reducing costs and complexity, while maintaining control over product quality and frangibility.
Implementation Method 1
Prism-coupling techniques can be used to measure the spectrum of guided modes of a planar optical waveguide
Implementation Method 2
Certain types of IOX glasses are actual dual IOX (DIOX) glasses formed by first and second diffusions
Data Source
AI summary
Prism-coupling systems and methods for characterizing large depth-of-layer waveguides formed in glass substrates are disclosed. One method includes making a first measurement after a first ion-exchange process that forms a deep region and then performing a second measurement after a second ion-exchange process that forms a shallow region. Light-blocking features are arranged relative to the prism to produce a mode spectrum where the contrast of the mode lines for the strongly coupled low-order modes is improved at the expense of loss of resolution for measuring characteristics of the shallow region. Standard techniques for determining the compressive stress, the depth of layer or the tensile strength of the shallow region are then employed. A second measurement can be made using a near-IR wavelength to measure characteristics of the deeper, first ion-exchange process. Systems and methods of measuring ion-exchanged samples using shape control are also disclosed.