Thermal annealing of arsenic tri-sulphide thin film and its influence on device performance
Date
2010-03-04
Authors
Madden, Steve
Bulla, Douglas
Wang, Rongping
Rode, Andrei
Luther-Davies, Barry
Choi, Duk-Yong
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American Institute of Physics (AIP)
Abstract
Arsenic tri-sulphide (As₂S₃)thin filmwaveguides have been used successfully as nonlinear optical devices for all-optical signal processors. For such devices, low propagation loss is vital if high performance is to be obtained. In this study, thermal annealing was employed not only to stabilize the physical properties of the films, but also to reduce the sources of light attenuation in the as-deposited material. Here we investigated heat-induced changes to the microstructure and optical properties of As₂S₃thin films and, based on this information, determined the best annealing conditions. The refractive index of the films rises with annealing due to thermal densification and increased heteropolar bond density. The growth of surface roughness and thermal stress in the film, however, limits the annealing temperature to ∼130 °C. We fabricated and analyzed waveguides produced from as-deposited and annealedfilms and found that the propagation loss of the guides dropped by ∼0.2 dB/cm as a result of appropriate annealing.Rayleigh scattering and absorption from defects associated with phase separation, homopolar bonds, voids, and dangling bonds in the as-deposited film are shown to contribute to the higher light attenuation in unannealed films.
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Keywords: All-optical; Annealed films; Annealing condition; Annealing temperatures; As-deposited films; Deposited materials; Device performance; Heteropolar bonds; Homopolar bonds; Light attenuation; Low propagation loss; Nonlinear optical devices; Propagation loss
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Journal of Applied Physics
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