> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract—We demonstrate all-optical ultra-broadband tunable wavelength conversion of one-picosecond pulses based on four-wave mixing in a 3-millimeter long dispersion engineered silicon waveguide. In the waveguide, an input pulse with center wavelength at 1600 nm is down-converted by 135 nm (17.3 THz) to 1465 nm. A tuning range of 115 nm (15 THz, from 1465 nm to 1580 nm) of the converted wavelength is demonstrated, while keeping conversion efficiency, pulse shape and pulse width almost unchanged. Index Terms—All-optical wavelength conversion, four-wave mixing, integrated optics, nonlinear optics, silicon waveguide. I. INTRODUCTION avelength conversion (WC) in wavelength division multiplexed (WDM) and time division multiplexed (TDM) optical networks is a key technology for future high-bit-rate transport systems because it offers a higher flexibility in traffic management and a dynamic reconfiguration of the optical network [1]. It is desirable that the WC is tunable over a broad wavelength range for wavelength routing and switching. Several all-optical wavelength conversion (AOWC) techniques have been demonstrated using different components including highly nonlinear fibers (HNLFs) [2], photonic crystal fibers (PCFs), LiNbO 3 waveguides [3], and semiconductor optical amplifiers (SOAs). Recently, WC in silicon waveguides has also attracted considerable research interest due to compactness, broad bandwidth, and complementary metal-oxide-semiconductor (CMOS) compatibility [4]. As the dispersion of a silicon waveguide can be engineered by the control of the waveguide geometry or shape, broadband conversion bandwidths have been demonstrated in [5], [6]. Previously, silicon waveguides have been utilized to demonstrate WC for data rates from 10 Gb/s to 160 Gb/s [7], [8]. However, in those reports, all the WCs have a fixed pump Manuscript received March 15th, 2011. This work was supported by the Danish Strategic Research Council and the EU FP7 via the projects Nano·COM and GOSPEL, respectively. M. Pu, H. Hu, M. Galili, H. Ji, C. Peucheret, L.K. Oxenløwe, K. Yvind, P. Jeppensen, and J.M. Hvam are with the DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark (e-mail: mipu@fotonik.dtu.dk). Copyright (c) 2011 IEEE. Personal use of this material is permitted. However, permission to use this material for any other purposes must be obtained from the IEEE by sending a request to pubs-permissions@ieee.org . wavelength, and a tunable wavelength conversion (TWC) was not demonstrated. Very recently, TWC has been demonstrated in a silicon waveguide based on two-pump non-degenerate four-wave mixing (FWM) [9]. In this paper, based on degenerate FWM, we demonstrate TWC of one-picosecond pulses in a dispersion engineered silicon waveguide, which offers a large conversion bandwidth by varying the pump wavelength. A 115-nm tuning range of the converted wavelength within the S-, C- and L- bands is demonstrated. II. DEVICE DESIGN AND CHARACTERIZATION In parametric WC, the group velocity dispersion (GVD) of a silicon waveguide is of crucial importance since it controls the phase-matching of parametric processes. Due to the strong light confinement in silicon waveguides, the GVD can be tuned by changing the waveguide dimensions [10], [11]. Fig. 1 shows the simulated GVD for silicon waveguides with different dimensions for the transverse-electric (TE) mode. The schematic of the waveguide cross section is shown in the inset of Fig. 1. It is seen that a small difference in waveguide dimensions leads to a shift of the zero-GVD (ZGVD) wavelength. Therefore, the waveguide dimensions should be carefully controlled to get a desired ZGVD wavelength. For TWC with varying pump wavelengths, a broadband phase-matching is necessary to keep the conversion efficiency constant for a fixed signal wavelength. In the low-gain limit, the phase mismatch is dominated by the linear phase mismatch between the signal, pump, and idler waves. And the linear phase mismatch is highly dependent on  2  2 , where  2 =-2πcD/λ 2 is the GVD parameter at the pump wavelength and  the frequency spacing between the signal and pump waves. The influence of the fourth-order dispersion (FOD) can be neglected in the wavelength range of interest. Then, if the 15-THz Tunable Wavelength Conversion of Picosecond Pulses in a Silicon Waveguide Minhao Pu, Hao Hu, Michael Galili, Hua Ji, Christophe Peucheret, Leif K. Oxenløwe, Kresten Yvind, Palle Jeppesen, and Jørn M. Hvam W 1500 1520 1540 1560 1580 1600 -750 -500 -250 0 250 500 220x465 nm 2 230x450 nm 2 240x435 nm 2 250x420 nm 2 SiO2 SU-8 Si D [ps/(km*nm)] Wavelength (nm) Fig. 1. Simulated group-velocity dispersion D for waveguides with different dimensions for the TE mode. Inset: cross-section of a silicon waveguide.