On-chip arbitrary waveform generator and differentiator

Optical arbitrary waveform generation (OAWG) plays a critical role in many applications, such as generating optical ultra-wide band (UWB) signal, optical pulse radar, all-optical temporal differentiator, and test of optical communication system. Although lots of OAWG schemes were reported using mature fiber grating techniques, one of the most promising solutions is prone to be the miniaturization and integration with photonic integrated circuits, such as using indium phosphide (InP) platform, silica on silicon, silicon nitride or silicon platform. In this talk, we review our recent progress on some OAWG schemes using silicon platform and their applications in photonic computing. First, we report an OAWG and high-order photonic differentiator based on a four-tap FIR silicon integrated circuit. By thermally controlling the amplitude and phase of each tap, we obtain several typical waveforms such as triangular waveform, sawtooth waveform, square waveform and Gaussian waveform, etc. Furthermore, we demonstrate first-, second- and third-order differentiation based on the optical pulse shaper, whose spectra were tailored to the transfer functions of temporal differentiators. Especially, our scheme can switch the differentiator patterns from first- to third-order freely on a fixed photonic chip, and this is unable in our previous works such as cascaded microrings or cascaded Mach-Zehnder interferometers (MZIs). Second, we demonstrate radio-frequency arbitrary waveform generation using temporal synthesis. We compare two schemes of cascaded microring resonators and finite impulse response. There functional photnic chip has only millmeter size, low power consumption, and high frequency response. Third, we will demonstrate an OAWG scheme based on superposition of differentiated waveforms. Compared to the first two schemes, this one shows a more compact size and a more flexible operation.