All-optical temporal differentiation of ultra-high-speed picosecond pulses based on compact silicon microring resonator

Introduction: Recent years have witnessed intensive interest in and the rapid development of implementations of basic operations with optics thanks to the high potential to increase signal processing speed that is several orders of magnitude higher than that of digital electronics [1]. CMOS-compatible silicon based all-optical signal processing devices could be important basic building blocks, e.g. for mathematical and logical operations [2–5]. The optical processing could overcome the speed and bandwidth limitations of conventional electronic circuits. One of these signal processing devices is the temporal differentiator which has a wide range of applications, including ultrafast all-optical information processing and computing, optical pulse shaping and coding, ultra-wideband microwave signal generation, higher-order Hermite-Gaussian waveforms generation and processing, and direct phase reconstruction of arbitrary optical signals [2]. As a result, it is highly desirable to develop a high-speed silicon based all-optical differentiator. Reference [2] experimentally demonstrated a high-order temporal differentiator based on a long-period fibre grating with a pulse train of 16.7 Mbit/s. Reference [3] proposed a temporal differentiator with a pulse train of 8 Gbit/s employing a LiNbO3 phase modulator. An optical differentiator with a data rate of 10 Gbit/s was experimentally proposed using a long-period fibre grating interferometer [4]. An alloptical temporal differentiator of a single sub-picosecond pulse utilising silicon-on-insulator (SOI) Bragg gratings was proposed in [5]. Experimental realisation of a 13.6 Gbit/s temporal differentiator was reported based on a fibre Bragg grating [1]. In [6], we demonstrated an all-optical temporal differentiator based on a compact silicon microring resonator, which was used for 10 Gbit/s signal differentiation. The speed is mainly limited by the bandwidth of the ring resonator, which is 0.34 nm in [6]. In this Letter, using a silicon ring resonator with bandwidth of 2.5 nm and radius of 20 mm, we experimentally demonstrate an optical temporal differentiator for an 80 Gbit/s OTDM picosecond pulsed signal. To the best of our knowledge, it is the most compact silicon based all-optical differentiator for a signal with a data rate of up to 80 Gbit/s.