Optical pulse shaping based on discrete space-to-time mapping in cascaded co-directional couplers

Abstract

We propose and numerically validate a new design concept for on-chip optical pulse shaping based on discrete space-to-time mapping in cascaded co-directional couplers. We show that under weak-coupling conditions, the amplitude and phase of the discrete complex apodization profile of the device can be directly mapped into its temporal impulse response. In this scheme, the amplitude and phase of the apodization profile can be controlled by tuning the coupling strength and relative time delay between the couplers, respectively. The proposed concept enables direct synthesis of the target temporal waveforms over a very broad range of time-resolution, from the femtosecond to the sub-nanosecond regime, using readily feasible integrated waveguide technologies. Moreover, the device offers compactness and the potential for reconfigurability.

A Review of Photonic Generation of Arbitrary Microwave Waveforms

“…Another approach for arbitrary waveform generation is the Direct Space to Time Mapping (DSTM) [27]. This approach is recently proposed and its principle of operation is illustrated in Fig.…”

“…Under weak coupling approximations, it can be shown mathematically that the impulse response of the device is the summation of n impulses corresponding to the n stages shown as the inset impulse train (blue) of Fig. 7(a) [27]. Each of these impulses is weighted by the respective coupling coefficient and delayed by the accumulated time between the input and the considered stage itself [27].…”

“…7(a) [27]. Each of these impulses is weighted by the respective coupling coefficient and delayed by the accumulated time between the input and the considered stage itself [27]. By tailoring these stages (coupling coefficient and delay), any waveform profile can be generated as illustrated by the inset temporal waveform (red) of Fig.…”

“…Fig. 9(a) shows the values of the complex coefficients for the 24-stage design with the sampling time of 11.78 ps [27] and Fig. 9(b) presents the generated complex waveform.…”

“…This paper provides a tutorial on photonic arbitrary waveform generations and reviews the three major approaches for AWG including i) Fourier Transform Pulse Shaping following by Frequency to Time Mapping [22][23][24][25][26], ii) Discrete Space to Time Mapping [27] and iii) Microwave Photonic (MWP) Filtering [1,8,28]. For each of these approaches, we explain the operation principle and presents selected results from the literature and highlight salient features.…”