Nonreciprocal transmission in a nonlinear photonic-crystal Fano structure with broken symmetry

Abstract

Nanostructures that feature nonreciprocal light transmission are highly desirable building blocks for realizing photonic integrated circuits. Here, a simple and ultracompact photonic‐crystal structure, where a waveguide is coupled to a single nanocavity, is proposed and experimentally demonstrated, showing very efficient optical diode functionality. The key novelty of the structure is the use of cavity‐enhanced material nonlinearities in combination with spatial symmetry breaking and a Fano resonance to realize nonreciprocal propagation effects at ultralow power and with good wavelength tunability. The nonlinearity of the device relies on ultrafast carrier dynamics, rather than the thermal effects usually considered, allowing the demonstration of nonreciprocal operation at a bit‐rate of 10 Gbit s−1 with a low energy consumption of 4.5 fJ bit−1.

Ultrafast low-energy all-optical switching using a photonic-crystal asymmetric Fano structure

“…This makes the coupling rate 1 γ between port 1 and cavity, differ from the rate 2 γ between port 2 and cavity. Recently, a similar structure with broken symmetry was shown to enable non-reciprocal light transmission when combined with an optical nonlinearity [19]. For the present design, FDTD simulations lead to B t =0.24 and 1 2 / γ γ =2.5.…”

Ultrafast all-optical modulation using a photonic-crystal Fano structure with broken symmetry

“…Figure 1(c) shows infrared images taken perpendicularly to the plane of the structure. The excitation of the cavity is larger when light is injected from the left since the coupling rate γ 1 is larger than γ 2 due to the interference effects [6,15].…”

“…This makes the coupling rate γ 1 between port 1 and cavity, differ from the rate γ 2 between port 2 and cavity. Recently, a similar structure with broken symmetry was shown to enable nonreciprocal light transmission when combined with an optical nonlinearity [15]. For the present design, FDTD simulations lead to t B 0.24 and γ 1 ∕γ 2 2.5, the latter being estimated from the ratio of the electromagnetic fluxes into ports 1 and 2, when exciting the corresponding eigenmode of the cavity.…”

“…Figure 1(c) shows infrared images taken perpendicularly to the plane of the structure. The excitation of the cavity is larger when light is injected from the left since the coupling rate γ 1 is larger than γ 2 due to the interference effects [6,15].We first analyze the dynamical properties of symmetric and asymmetric Fano structures using nonlinear temporal coupled-mode theory [14-16]. The dynamical May 15, 2015 / Vol.…”

Ultrafast Coherent Dynamics of a Photonic Crystal all-Optical Switch

“…The use of a small cavity with high-Q factor favors the use of TPA-based carrier generation [15] as does the use of shorter pulses. Although TPA-based switching usually requires higher switching energy than switching based on linear absorption, the energy consumption may be further reduced using waveguide-cavity designs exhibiting Fano resonances [16][17][18], where a nonlinear regeneration mechanism has been shown to improve the response [19].Despite a good understanding of the dynamics of PhC switches on the long time scale [5,20,21], the switching dynamics on short timescales as well as the possible role of coherent effects has so far received little attention. In addition to the resonance shift, caused by the FCD, the PhC cavity is also known to induce, during the first stage of its nonlinear evolution, an adiabatic frequency shift of the light [22][23][24] and to undergo rapid changes of its refractive index [25].…”