Highly-nonlinear Chalcogenide Glass Devices for High-speed Signal Processing and Characterization M.D. Pelusi 1 , T.D. Vo 1 , F. Luan 1 , S.J. Madden 2 , D.-Y. Choi 2 , D.A.P. Bulla 2 , B. Luther-Davies 2 , and B.J. Eggleton 1 1, 2 ARC Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS) Phone: +61-2-9351-7697, Fax: +61-2-9351-7726, Email: m.pelusi@physics.usyd.edu.au ( 1 School of Physics, University of Sydney, New South Wales 2006, Australia) ( 2 Laser Physics Centre, Australian National University, Canberra ACT 0200, Australia) Abstract We review the latest advances in dispersion-shifted Chalcogenide waveguides enabling highly nonlinear and low dispersion planar rib circuits of centimetre length. Its performance advantages for more broadband and higher speed nonlinear signal processing are shown. Introduction All-optical signal processing is a key technology for enabling various functions applicable to future high- speed optical communications such as optical switching, wavelength conversion [1], and performance monitoring [2]. These can be performed on an ultra-fast timescale by harnessing the optical Kerr effect of an optical waveguide exhibiting a χ (3) nonlinearity, whereby its refractive index changes in proportional to the instantaneous optical intensity, and the nonlinear refractive index, n 2 . This gives rise to the nonlinear effects of cross-phase modulation (XPM) and four-wave mixing (FWM), which can underpin many all-optical signal processing functions [1]. The efficiency however, depends on the waveguide nonlinearity coefficient determined by γ = (2π∕ λ)⋅(n 2 /A eff ), where A eff is the effective mode area at the signal wavelength, λ. The nonlinear phase shift also scales with waveguide length which dictates the need for kilometers of standard single mode fiber (SMF), whose γ is low, or hundreds of meters for silica based highly nonlinear fiber (HNF) [3]. Recent advances in fabricating planar rib waveguides from high index glasses such as silicon [4] and Chalcogenide (ChG) [1] have shown the capability for reaching much higher γ through their combined high n 2 and small A eff allowing much shorter circuits on the order of centimeters. This translates to reduced dispersion effects, which otherwise degrades the FWM and XPM efficiency through the phase and group velocity mismatch respectively between co-propagating waves. In this paper, we review the development of a dispersion-shifted planar rib waveguide based on the ChG glass, As 2 S 3 whose n 2 = 3×10 -18 m 2 /W (i.e. ≈100 times of silica). Its design for a smaller A eff produces both an increased γ and tailoring of the net dispersion parameter, D, to near zero at the 1550 nm wavelength. Its performance advantage for both wavelength conversion of 40 Gb/s signals across the S-C-L optical bands of the optical communication spectrum, and high- speed time-division demultiplexing of 320 Gb/s signals are shown. The photonic chip is also applied to an RF spectrum analyzer system enabling characterization and dispersion monitoring of 320 Gb/s data signals. Waveguide characteristics The primary advance over previously reported As 2 S 3 planar rib waveguides is its design for higher γ and tailoring of D toward zero at the 1550 nm wavelength. This was realized by thinning the As 2 S 3 film during deposition [5], by nearly a factor of 3 to 0.85 μm. Photolithography and dry-etching [5] produced ribs as narrow as 2 μm with a reduced A eff approaching 1 μm 2 . This increased both γ and waveguiding dispersion which has a sign countering the large material component of As 2 S 3 (= -364 ps/nm/km at 1550 nm wavelength). A typical device schematic is shown in Fig. 1. Waveguides (a) (b) Fig. 1. a) Device illustration of a 6 cm length planar rib As 2 S 3 waveguide and (b) calculated group velocity dispersion of fundamental TM and TE modes compared to material dispersion of As 2 S 3 highlighting the dispersion-shifted design enabled by the thinner As 2 S 3 film thickness, as reported in [6].