Gain through losses in nonlinear optics

Abstract

Instabilities of uniform states are ubiquitous processes occurring in a variety of spatially extended nonlinear systems. These instabilities are at the heart of symmetry breaking, condensate dynamics, self-organisation, pattern formation, and noise amplification across diverse disciplines, including physics, chemistry, engineering, and biology. In nonlinear optics, modulation instabilities are generally linked to the so-called parametric amplification process, which occurs when certain phase-matching or quasi-phase-matching conditions are satisfied.In the present review article, we summarise the principle results on modulation instabilities and parametric amplification in nonlinear optics, with special emphasis on optical fibres. We then review state-of-the-art research about a peculiar class of modulation instabilities (MIs) and signal amplification processes induced by dissipation in nonlinear optical systems. Losses applied to certain parts of the spectrum counterintuitively lead to the exponential growth of the damped mode themselves, causing gain through losses. We discuss the concept of imaging of losses into gain, showing how to map a given spectral loss profile into a gain spectrum. We demonstrate with concrete examples that dissipation-induced MI, apart from being of fundamental theoretical interest, may pave the way towards the design of a new class of tuneable fibre-based optical amplifiers, optical parametric oscillators, frequency comb sources, and pulsed lasers.

Lumped Dissipation Induced Quasi-Phase Matching for Broad and Flat Optical Parametric Processes

“…The idea of harvesting gain through dissipation in optical parametric processes has attracted renewed interests recently [1]- [6] due to its rich physics including modulation instability in normal dispersion regime [1], optical parametric amplification (OPA) enabled by non-hermitian phase matching [2], high conversion efficiency in chirped pulse amplification [3], related applications to optical parametric oscillation [7] and optical frequency comb generation [4] etc. However, distributed losses are in general difficult to implement and have been so far demonstrated using stimulated Brillouin scattering (SBS) [1] or appropriate material with required loss dispersion [3].…”

Theory of filter-induced modulation instability in driven passive optical resonators

“…Homogeneously distributed frequency-dependent losses can result in counterintuitive amplification of damped modes themselves. This happens if losses act in an unbalanced fashion on two sideband waves whose frequencies are symmetrically located with respect to a powerful input one, which in the absence of losses would be stable [25] (a fortiori for symmetric losses [26]). This case has been analyzed by Tanemura et al in an optical fiber [27] and also subsequently described by other authors using coupled mode theory (non-Hermitian phase matching) [28,29].…”

Turning losses into gain in nonlinear optics

“…This sentence describes well the “identity of the opposites”, one of the most fruitful principles of dialectic thinking from ancient Greece to Hegel and beyond. These thoughts came to my mind when I read a recent paper by Perego and coworkers 2 , in which they show how in nonlinear optical systems, spectrally asymmetric losses can generate gain in the very same beam that is affected by losses. The death of losses is to become gain.…”