## Abstract

Silver–sodium ion exchange is a commonly used method for making waveguides in glass. This paper discusses two exchange media, KNO_{3}:AgNO_{3} and AgNO_{3} in NaNO_{3}:KNO_{3} which increase the flexibility of the process and decrease its cost. Exchange in the KNO_{3}:AgNO_{3} can be performed at temperatures as low as 150°C, which is particularly useful for field assisted exchange. When exchange is performed in a NaNO_{3}:KNO_{3} eutectic with small (≤5 mole %) added quantities of AgNO_{3}, it is possible to control the guide’s surface index within the range Δ*n* ≤ 0.01–0.09 and simultaneously allow the exchange to take place at temperatures as low as 220°C. Because the latter process requires very little of the relatively expensive AgNO_{3}, it can reduce the cost of the process.

© 1988 Optical Society of America

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### Equations (4)

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(1)
$$d={\left[4D\left(T\right)t\right]}^{1/2},$$
(2)
$${d}_{\text{thermal}}={\left(4kT{d}_{\text{field}}/eE\right)}^{1/2}.$$
(3)
$$D\left(T\right)={D}_{0}\phantom{\rule{0.2em}{0ex}}\text{exp}\left(-{T}_{0}/T\right),$$
(4)
$$\begin{array}{c}{D}_{0}=2.21\times {10}^{8}\phantom{\rule{0.2em}{0ex}}{\mu}^{2}/\mathrm{h}\phantom{\rule{0.2em}{0ex}}\text{and}\phantom{\rule{0.2em}{0ex}}{T}_{0}=9959\phantom{\rule{0.2em}{0ex}}\mathrm{K}\phantom{\rule{0.2em}{0ex}}\text{for}\phantom{\rule{0.2em}{0ex}}5\phantom{\rule{0.2em}{0ex}}\text{mole}\phantom{\rule{0.2em}{0ex}}\%\phantom{\rule{0.2em}{0ex}}{\text{AgNO}}_{3};\\ {D}_{0}=1.09\times {10}^{8}\phantom{\rule{0.2em}{0ex}}{\mu}^{2}/\mathrm{h}\phantom{\rule{0.2em}{0ex}}\text{and}\phantom{\rule{0.2em}{0ex}}{T}_{0}=9828\phantom{\rule{0.2em}{0ex}}\mathrm{K}\phantom{\rule{0.2em}{0ex}}\text{for}\phantom{\rule{0.2em}{0ex}}1\phantom{\rule{0.2em}{0ex}}\text{mole}\phantom{\rule{0.2em}{0ex}}\%\phantom{\rule{0.2em}{0ex}}{\text{AgNO}}_{3}.\end{array}$$