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

The potential of GaAs‐based photonic crystals for fast all‐optical switching in the telecom spectral range is exploited by controlling the surface recombination and, thereby, the carrier relaxation dynamics. The structure is entirely coated with a layer of aluminium oxide using atomic layer deposition. This results in a carrier lifetime of about 10 ps, as determined by spectrally resolved pump–probe measurements. We show that the nonlinear response of the resonator is optimized when it is excited with a few‐picoseconds pulse. This dynamics is perfectly captured by our model accounting for the carrier diffusion with an impulse response function. Moreover, the suppression of photo‐induced oxidation is revealed to be crucial to demonstrate all‐optical operation at GHz rates with average coupled pump power of 0.5 mW (hence 100 fJ/bit). The switching window is 12 ps wide (1/e), as resolved by homodyne pump–probe measurements. The devices respond to a sequence of closely spaced pump pulses demonstrating a gating window close to 10 ps, with a contrast as high as 7 dB.

Section: Introductionmentioning

confidence: 99%

Integrated all‐optical switch with 10 ps time resolution enabled by ALD

Moille

Combrié

Morgenroth

et al. 2016

“…The realization of ultra‐compact lasers that generate short optical pulses are of interest for applications, e.g., in on‐chip optical signal processing. Fano resonances in photonic crystal membrane structures have previously been used to demonstrate improved optical switching characteristics and non‐reciprocal transmission and the use of narrow‐band mirrors for lasers was also demonstrated in hybrid platforms . In this paper we develop a theory for the photonic crystal Fano laser, which successfully accounts for the self‐pulsations observed experimentally and clarifies the physics of the self‐pulsing dynamics.…”

Section: Introductionmentioning

confidence: 85%

Theory of Self‐pulsing in Photonic Crystal Fano Lasers

Rasmussen

Mørk

2017

Self Cite

Laser self‐pulsing was a phenomenon exclusive to macroscopic lasers until recently, where self‐starting laser pulsation in a microscopic photonic crystal Fano laser was reported. In this paper a theoretical model is developed to describe the Fano laser, including descriptions of the highly‐dispersive Fano mirror, the laser frequency and the threshold gain. The model is based upon a combination of conventional laser rate equations and coupled‐mode theory. The dynamical model is used to demonstrate how the laser has two regimes of operation, continuous‐wave output and self‐pulsing, and these regimes are characterised using phase diagrams, establishing the regime of self‐pulsing numerically. Furthermore, the physics behind the self‐pulsing mechanism are explained in detail and it is demonstrated how cavity absorption makes the Fano mirror function as a saturable absorber, leading to Q‐switched pulse generation. A stability analysis is used to demonstrate how the dominant mechanism of instability is relaxation oscillations becoming un‐damped. Finally the effect of varying key self‐pulsing parameters is investigated by characterisation of the change in self‐pulsing regions.

“…The H0 type is formed by shifting the airholes around the cavity away from the cavity center. The line‐defect waveguides are of W1‐type formed by removing one row of airholes and shifting the inner most row of airholes toward the waveguide center . Assuming the same Q ‐factor and cavity mode symmetry, the choice of quasi‐H1 or H0 does not affect the lineshapes.…”

Section: Introductionmentioning

confidence: 99%

In‐Plane Photonic Crystal Devices using Fano Resonances

Bekele

Yvind

et al. 2019

Self Cite

Nanocavity devices enabling concentration of light in a very small volume have resulted in several interesting applications over the past years. Of particular interest are the asymmetric resonance lineshapes known as Fano resonances, which result from the interference between a discrete mode of the nanocavity and a continuum of background modes. Compared to the conventional symmetric Lorentzian lineshape, asymmetric Fano lineshapes enable novel or improved device structures for use in optical switches, sensors, lasers, and narrow band filters. Herein, the use of Fano lineshapes in photonic crystal membranes for realizing various optical signal processing functionalities is reviewed. The basic theory of Fano resonances is presented, different photonic crystal Fano device geometries are discussed, the nonlinear processes empowering the devices are explained, and an overview of all‐optical signal processing demonstrations based on Fano resonances is given.