There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

This Colloquium describes a new paradigm for creating strong quantum interactions of light and matter by way of single atoms and photons in nanoscopic lattices. Beyond the possibilities for quantitative improvements for familiar phenomena in atomic physics and quantum optics, there is a growing research community that is exploring novel quantum phases and phenomena that arise from atom-photon interactions in one- and two-dimensional nanophotonic lattices. Nanophotonic structures offer the intriguing possibility to control atom-photon interactions by engineering the medium properties through which they interact. An important aspect of these new research lines is that they have become possible only by pushing the state-of-the-art capabilities in nanophotonic device fabrication and by the integration of these capabilities into the realm of ultracold atoms. This Colloquium attempts to inform a broad physics community of the emerging opportunities in this new field on both theoretical and experimental fronts. The research is inherently multidisciplinary, spanning the fields of nanophotonics, atomic physics, quantum optics, and condensed matter physics.

https://link.aps.org/accepted/10.1103/RevModPhys.90.031002

Colloquium: Quantum matter built from nanoscopic lattices of atoms and photons

We demonstrate all-optical modulation based on ultrafast optical carrier injection in a GaAs photonic crystal cavity using a degenerate pump-probe technique. The observations agree well with a coupled-mode model incorporating all relevant nonlinearities. The low switching energy (∼120 fJ), small energy absorption (∼10 fJ), fast on-off response (∼15 ps), limited only by carrier lifetime, and a minimum 10 dB modulation depth suggest practical all-optical switching applications at high repetition rates.

Ultrafast all-optical modulation in GaAs photonic crystal cavities

Solitons are nonlinear waves that exhibit invariant or recurrent behaviour as they propagate. Precise control of dispersion and nonlinear effects governs soliton propagation and, through the formation of higher-order solitons, permits pulse compression. In recent years the development of photonic crystals—highly dispersive periodic dielectric media—has attracted a great deal of attention due to the facility to engineer and enhance both their nonlinear and dispersive effects. In this Article, we demonstrate the first experimental observations of optical solitons and pulse compression in ∼1-mm-long photonic crystal waveguides. Suppression of two-photon absorption in the GaInP material is crucial to these observations. Compression of 3-ps pulses to a minimum duration of 580 fs with a simultaneously low pulse energy of ∼20 pJ is achieved. These small-footprint devices open up the possibility of transferring soliton applications into integrated photonic chips. Using ∼1-mm-long photonic crystal waveguides, scientists experimentally demonstrate the compression of 3 ps pulses to a minimum duration of 580 fs at a low pulse energy of ∼20 pJ. The approach may pave the way for soliton applications in integrated photonic chips.

/pdf/temporal-solitons-and-pulse-compression-in-photonic-crystal-4xzka0o0rj.pdf

Temporal solitons and pulse compression in photonic crystal waveguides

The flexibility of microwave photonics provides advantages over electronic circuitry, yet the lack of integrated chip-scale devices limits its practical application. This study presents microwave filters based on photonic crystal waveguides with controllable delays as a step towards intregable circuits.

/pdf/integrable-microwave-filter-based-on-a-photonic-crystal-22603ilmg2.pdf

Integrable microwave filter based on a photonic crystal delay line

Light transmission measurements and frequency-delay reflectometry maps for GaAs photonic crystal membranes are presented and analyzed, showing the transition from propagation with a well-defined group velocity to a regime completely dominated by disorder-induced coherent scattering. Employing a self-consistent optical scattering theory, with only statistical functions to describe the structural disorder, we obtain excellent agreement with the experiments using no fitting parameters. Our experiments and theory together provide clear physical insight into naturally occurring light localization and multiple coherent-scattering phenomena in slow-light waveguides.

Disorder-induced coherent scattering in slow-light photonic crystal waveguides.

The equations for Four-Wave-Mixing in a photonic crystal waveguide are derived accurately in the hypotesis of negligible nonlinear absorption. The dispersive nature of slow-light enhancement, the impact of Bloch mode reshaping in the nonlinear overlap integrals and the tensor nature of the third order polarization are therefore taken into account. Numerical calculations reveal substantial differences from simpler models, which increase with decreasing group velocity. We predict that the gain for a 1.3 mm long, un-optimized GaInP waveguide will exceed 10 dB if the pump power exceeds 1 W.

Theory of slow light enhanced four-wave mixing in photonic crystal waveguides.

The equations for Four-Wave-Mixing in a Photonic Crystal waveguide are derived accurately. The dispersive nature of slow-light enhancement, the impact of Bloch mode reshaping in the nonlinear overlap integrals and the tensor nature of the third order polarization are therefore taken into account. Numerical calculations reveal substantial differences with simpler models, which increase with decreasing group velocity. We predict that the gain for a 1.3 mm long, unoptimized GaInP waveguide will exceed 10 dB if the pump power exceeds 1 W.

Theory of Slow Light Enhanced Four-Wave Mixing in Photonic Crystal Waveguides

We investigate experimentally resonant radiation processes driven by slow solitons in a dispersion-engineered photonic crystal waveguide in a regime virtually free of dissipative nonlinear processes (two-photon absorption and Raman scattering). Strong (30% energy conversion) Cherenkov-like radiation accompanied by the blue self-frequency shift of the soliton is observed close to the zero dispersion point, and is explained in terms of the soliton-radiation locking of the velocity.

Blue self-frequency shift of slow solitons and radiation locking in a line-defect waveguide

A new scattering theory for describing disorder-induced multiple scattering events in photonic crystal waveguides is presented with matching experiments on GaAs samples. Our self-consistent 3D model successfully reproduces the rich experimental features including band-edge resonances.

/pdf/disorder-induced-coherent-scattering-in-slow-light-photonic-5uofadz71d.pdf

A. De Rossi

Papers

Disorder-induced coherent scattering in slow-light photonic crystal waveguides.

Theory of slow light enhanced four-wave mixing in photonic crystal waveguides.

Theory of Slow Light Enhanced Four-Wave Mixing in Photonic Crystal Waveguides

Blue self-frequency shift of slow solitons and radiation locking in a line-defect waveguide

Disorder-induced coherent scattering in slow-light photonic crystal waveguides