Glass waveguides made using low melting point nitrate mixtures.

Area of Science:

• Materials Science
• Optoelectronics
• Glass Chemistry

Background:

• Silver-sodium ion exchange is a standard technique for fabricating optical waveguides in glass.
• Existing methods can be costly and lack process flexibility.

Purpose of the Study:

• To explore alternative molten salt media for silver-sodium ion exchange.
• To reduce the cost and increase the flexibility of waveguide fabrication.
• To investigate the control over refractive index profiles.

Main Methods:

• Utilized two distinct molten salt exchange media: potassium nitrate:silver nitrate (KNO(3):AgNO(3)) and a sodium nitrate:potassium nitrate (NaNO(3):KNO(3)) eutectic with added silver nitrate (AgNO(3)).
• Investigated ion exchange at reduced temperatures, as low as 150°C for KNO(3):AgNO(3) and 220°C for the eutectic mixture.
• Analyzed the control over the surface refractive index change (deltan).

Main Results:

• The KNO(3):AgNO(3) medium allows ion exchange at temperatures as low as 150°C, suitable for field-assisted processes.
• The NaNO(3):KNO(3) eutectic with low AgNO(3) concentrations (≤5 mole %) enables control of deltan between 0.01-0.09 at 220°C.
• The eutectic method significantly reduces the consumption of expensive AgNO(3), thereby lowering fabrication costs.

Conclusions:

• The developed molten salt media offer enhanced flexibility and cost-effectiveness for fabricating glass waveguides.
• Low-concentration silver nitrate in a NaNO(3):KNO(3) eutectic provides a viable method for controlled surface index modification.
• These advancements make waveguide fabrication more accessible and economical.