Novel active waveguide devices in direct-bonded structures

This thesis describes a series of experimental studies on the use of direct bonding for optical waveguide fabrication. The direct bonding technique involves contacting two ultra-clean polished surfaces to form an adhesive-free vacuum-tight bond. Optical materials bonded in this way can be formed into waveguide devices, and this work extends direct bonding to include periodically poled materials and a new solid-state ion-exchange process. <br/>The first result of this work describes the fabrication of a 5.5-mm-long, 12-µm-thick periodically poled LiNbO₃ planar waveguide buried in LiTaO₃. Frequency doubling experiments performed with this device demonstrate a conversion efficiency of 4.3 %W^-1, a value 40% greater than that calculated for an optimised bulk device of similar length.<br/>Also demonstrated is a photorefractive iron-doped LiNbO₃ waveguide buried in non-photorefractive magnesium-doped LiNbO₃. In optical limiting experiments this device demonstrates a change in optical density of 2 and photorefractive response time of 5 milliseconds, representing 20 times greater optical limiting and 60 times faster operational speed than the bulk material. <br/>K⁺-Na⁺ ion-exchange between direct-bonded glass layers is studied and used as a novel solid-state technique for waveguide fabrication. This process is also developed to incorporate direct-UV-written channel waveguides in an ion-exchanged buried photosensitive glass layer. Finally, operation of a single-mode channel waveguide laser in neodymium-doped photosensitive SGBN glass (based on a composition of silica, germania, boron, and sodium) is demonstrated, with propagation losses of &lt; 0.3 dB cm^-1 and milliwatt-order lasing thresholds. <br/>

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2002

Author dc:creator

• Gawith, C.B.E.

Advisor dc:contributor.advisor

• Smith, Peter