Prism coupling methods of characterizing stress in glass-based ion-exchanged articles having problematic refractive index profiles

Abstract

Prism coupling methods disclosed herein are directed to determining a stress characteristic of an original IOX article having a buried IOX region with a buried refractive index profile that is problematic in the sense that it prevents the original IOX article from being measured using a prism coupler system. The methods include modifying the buried IOX region of the original IOX article in a surface portion of the buried IOX region to form a modified IOX article having an unburied refractive index profile that allows the modified IOX article to be measured using a prism coupler. The methods also include measuring a mode spectrum of the modified IOX article using the prism coupler system. The methods further include determining one or more stress characteristic of the original IOX article from the mode spectrum of the modified IOX article.

Description

[0001] Cross References to Related Applications [0002] This application claims the benefit of priority under 35 U.S.C. §119 to U.S. Provisional Application Serial No. 62 / 637,679, filed March 2, 2018, the contents of which are based upon and incorporated by reference in its entirety. technical field [0003] This disclosure relates to glass-based ion exchange (IOX) articles, and more particularly to a prism coupling method for characterizing stress in glass-based IOX articles where the refractive index profile is problematic because it prevents prism coupling for characterizing stress Routine application of measurement methods. Background technique [0004] Chemically strengthened glass-based articles are formed by subjecting a glass-based substrate to chemical modifications to enhance at least one strength-related characteristic (eg, hardness, fracture resistance, etc.). Chemically strengthened glass-based articles have found particular use as cover glasses for display-ba...

AI Technical Summary

Problems solved by technology

[0007] While prism coupling methods can be used for many types of conventional glass-based IOX articles, these methods are not always effective, and sometimes not effective at all, for some glass-based IOX articles that, for example, have buried refractive index profiles such that Those articles where optical coupling to IOX waveguides is problematic

In one case, buried refractive index profiles with large layer depths support waveguide modes with a large number m (e.g., m > 100), which can obscure the resolution of prism coupler measurement systems

At the same time, even the relatively small refractive index difference Δn in the near-surface part of the IOX region s =n 1 –n s (where n 1 is the maximum refractive index n 1 and n s is the surface refractive index, and where n 1 s ) can limit the ability of the prism coupling system to couple light into deep portions of the IOX region, which in turn prevents the measurement of one or more selected stress-related properties over the entire IOX region

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