Proposal and analysis of a reconfigurable pulse shaping technique based on multi-arm optical differentiators

We propose and numerically investigate an optical pulse re-shaping method based on multi-arm ultrafast optical differentiators. In this approach, the desired (arbitrary) optical pulse shape is synthesized by coherently overlapping different successive time derivatives of an input optical pulse (not necessarily a Gaussian-shape pulse), including the input pulse itself, with suitable relative weights. Time derivatives of (sub-)picosecond pulses can be obtained using first and higher-order ultrafast optical differentiators practically implemented with integrated waveguide or fiber-based linear filtering technologies. Different output pulse shapes can be generated from the same platform by properly programming the relative weights among the different pulse derivatives. The effective bandwidth of the output waveform is not necessarily limited by the input pulse bandwidth but rather it depends on the highest derivative order used for the pulse synthesis. Our results reveal that interesting transform-limited pulse shapes (including flat-top and parabolic waveforms) can be synthesized from Gaussian-like (e.g. Gaussian, sech) pulses using a simple and practical three-arm ultrafast differentiation system with amplitude-only relative weights. (C) 2008 Elsevier B.V. All rights reserved.