Space-time analogy and its application to design schemes borrowed from Fourier optics for processing ultrafast optical signals

TL;DR

This paper explores how space-time analogy and Fourier optics principles can be applied to generate and control ultrafast optical pulses with variable duty cycles using Talbot array illuminators and binary phase modulation.

Contribution

It introduces a novel application of space-time analogy to design optical pulse generation schemes based on Talbot effects and binary phase gratings, enhancing ultrafast signal processing capabilities.

Findings

Square-wave pulses with variable duty ratios can be generated using Talbot array ideas.

Maximum pulse intensities can double or triple relative to continuous wave signals.

Finite rise and drop times in phase modulation introduce additional features between pulses.

Abstract

Square-wave pulse generation with a variable duty ratio can be realized with the help of ideas of Talbot array illuminators formulated for binary phase gratings. A binary temporal phase modulation of CW laser field propagating through a group-delay-dispersion circuit of the fractional Talbot length $P/Q$ results in a well defined sequence of square-wave-form pulses. When $P=1$ a duty ratio of the pulses $D$ is $1/2$ for $Q=4$ and $1/3$ for $Q=3$ and 6. Maximum intensity of the pulses doubles and triples compared to the CW intensity for $D=1/2$ and $1/3$, respectively. These pulses can be used for return-to-zero laser field modulation in optical fiber communication. For $D=1/3$ extra features between the pulses are found originating from a finite rise and drop time of phase in a binary phase modulation. Similar effect as a benefit of the time-space analogy is predicted for binary phase gratings and interpreted as gleams produced by imperfect edges of the components of the rectangular phase gratings.