110 Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B Volume 47 Number 2 April 2006 Paper presented at the American Ceramics Society Glass and Optical Ma- terials Division (GOMD) Fall Meeting and 14th International Symposium on Non-Oxide Glasses, Florida, USA. 7–12 November 2004. 1 Corresponding author. Email address: seppo@optics.arizona.edu 1. Introduction and review The process of ion exchange in glass has been known for well over a millennium. In large doses, ions intro- duced into a glass matrix will form metallic clusters. The type of ion and size distribution of the particles produces a spectral atenuation in the glass, giving it a characteristic colouring. The aesthetic properties of ion exchanged glass were known to Egyptians of the sixth century, who used the process to colour glazed earthenware, (1) and the technique is also known to have been applied to the staining of window glass in the middle ages. Ion exchange as an engineering process was originally used to improve the surface mechanical properties of structural glass. (2–4) As glass fails in tension, the introduction of a compressive stress at the surface will increase the modulus of rupture. This can be accomplished by exchanging sodium ions in the glass with ions of greater size, such as silver (the process is oten termed ‘ion stuf- ing’). Interestingly, this concept has recently found photonics applications, increasing the thermal shock resistance of laser glasses. (5) The fabrication of optical waveguides in glass by ion exchange was irst achieved in 1972 using a melt containing thallium ions. (6) The Tl + –Na + system was problematic due not only to the mild toxicity of Tl + , but also to the large index change (~0·1), which causes diiculty in repeatably producing single- mode waveguides. Subsequently, Giallorenzi et al (7) produced waveguides using a melt containing silver ions, which today is by far the most common process. Other dopant ions include Cs + , Rb + , K + , and Li + . (8) The creation of integrated optical devices (also referred to as ‘planar lightwave circuits’, due to the planar processing techniques used to fabricate them) in glass ofers several obvious beneits over other technologies. Intrinsic absorption is very low in the near infrared region of the spectrum. Coupling losses to optical ibre are minimised due to the similarity in refractive index. In addition, glasses are amorphous, meaning that they exhibit no intrinsic material bire- fringence, unlike crystalline semiconductors. This is not to say that birefringence is not an issue in glass waveguides – both the shape of the waveguide and the stresses that arise during fabrication contribute to birefringence, but with proper design, these can be balanced against each other to produce single-mode devices with very low polarisation dependence. (9) In addition to ion exchange, other processes exist through which glass waveguides have been fabri- cated. Most involve the deposition of thin glass ilms (e.g. chemical vapour deposition, lame hydrolysis deposition, sol-gel coating), followed by reactive ion etching to deine the device geometry, and subse- quent deposition of the overcladding. The multiple deposition steps and etching make these methods costly and time consuming. The benefits of ion exchange over competing glass based technologies Recent advances in ion exchanged glass waveguides and devices Seppo Honkanen, Brian R. West, Sanna Yliniemi, Pratheepan Madasamy, Michael Morrell, Jason Auxier, Axel Schülzgen, Nasser Peyghambarian, James Carriere, Jesse Frantz, Ray Kostuk Optical Sciences Center, University of Arizona, Tucson, AZ 85721, USA Jose Castro & David Geraghty Department of Electrical and Computer Engineering, University of Arizona, Tucson, AZ 85721, USA Ion exchange in glass is a well established method for fabrication of passive and active integrated photonic devices. For passive devices, the main advantages of ion exchanged waveguides are very low propagation losses, excellent mode match- ing to optical ibre and low waveguide birefringence that can all be achieved with a relatively simple fabrication process. For waveguide lasers and ampliiers, the ion exchange process is superior due to the compatibility with glass substrates having high rare earth ion concentrations. In this paper, we review the recent advances in the ield of ion exchange glass waveguide technology with the emphasis on the results of our research group. We describe an advanced design and modelling tool for ion exchanged glass waveguides and present results on various passive and active waveguides and devices. Invited paper Phys. Chem. Glasses: Eur. J. Glass Sci. Technol. B, April 2006, 47 (2), 110–120