Passive, Noiseless, Intensity Amplification of Repetitive Signals

TL;DR

This paper introduces a passive, noiseless method for amplifying repetitive optical signals by recycling their energy through dispersion effects, reducing noise and distortion without external power or active gain.

Contribution

The authors demonstrate a novel passive amplification technique using dispersion-induced self-imaging to amplify repetitive signals without noise, applicable across various wave systems.

Findings

Achieved noiseless amplification with gain from 2 to 20

Reduced noise fluctuations and improved pulse extinction ratio

Applicable to optical, acoustic, mechanical, and quantum waveforms

Abstract

Amplification of signal intensity is essential for initiating physical processes, diagnostics, sensing, communications, and scientific measurement. During traditional amplification, the signal is amplified by multiplying the signal carriers through an active gain process using an external power source. However, for repetitive waveforms, sufficient energy for amplification often resides in the signal itself. In such cases, the unneeded external power is wasted, and the signal is additionally degraded by noise and distortions that accompany active gain processes. We show noiseless, intensity amplification of repetitive optical pulse waveforms with a gain from 2 to ~20 without using active gain, by recycling energy already stored in the input repetitive signal. This "green" method uses dispersion-induced self-imaging (Talbot) effects to precisely re-distribute the original signal energy into fewer replica waveforms. This approach simply requires a suitable manipulation of the input signal's phase profile along the temporal and spectral domains. In addition, we show experimentally how our passive amplifier performs a real-time average of the wave train to reduce noise fluctuation present on the input pulse train, as well as enhances the extinction ratio of pulses to stand above the noise floor by approximately the passive gain factor. Finally, our technique is applicable to repetitive waveforms in any spectral region or wave system, including acoustic, mechanical, and quantum probability waveforms, for which active amplification methods are challenging to implement or nonexistent.