Ultralow-energy and high-contrast all-optical switch involving Fano resonance based on coupled photonic crystal nanocavities

Abstract

We experimentally and theoretically clarified that a Fano resonant system based on a coupled optical cavity has better performance when used as an all-optical switch than a single cavity in terms of switching energy, contrast, and operation bandwidth. We successfully fabricated a Fano system consisting of doubly coupled photonic-crystal (PhC) nanocavities, and demonstrated all-optical switching for the first time. A steep asymmetric transmission spectrum was clearly observed, thereby enabling a low-energy and high-contrast switching operation. We achieved the switching with a pump energy of a few fJ, a contrast of more than 10 dB, and an 18 ps switching time window. These levels of performance are actually better than those for Lorentzian resonance in a single cavity. We also theoretically investigated the achievable performance in a well-designed Fano system, which suggested a high contrast for the switching of more than 20 dB in a fJ energy regime.

Polarization-Tailored Fano Interference in Plasmonic Crystals: A Mueller Matrix Model of Anisotropic Fano Resonance

“…[3][4][5][6][7][8][9][10][11][12][13][14][15]. Fano resonances in such micro and nano optical systems have been the subject of intensive investigations due to their numerous potential applications like in sensing, switching, lasing, filters and robust color display, nonlinear and slow-light devices, invisibility cloaking, and so forth [2,4,5,[18][19][20][21]. Most of the aforementioned applications are known to critically depend upon the ability to control or modulate the asymmetry of the line shape by external means [4].…”

Fano resonances and all-optical switching in a resonantly coupled plasmonic–atomic system

“…Systems supporting such coupling are of major importance in science and technology, as their properties can vary drastically depending on the coupling conditions. Two universal effects that may arise by the resonant coupling of atoms and plasmons are the Fano spectral lineshape [4][5][6][7][8][9][10][11][12][13][14] and the resonance splitting [15][16][17][18][19] , the latter being attributed to strong coupling. While the original work of Fano 4 describes the coupling between an atomic resonance and the continuum, nowadays it is common to use a broader definition in which a narrow resonant line width system is coupled to a system with a broader resonance.…”

“…For example, the same system can provide symmetric, antisymmetric and asymmetric lineshape, depending not only on the inherent properties of each resonance, but primarily on their relative frequency separation. Over the years, Fano resonances have been studied theoretically and experimentally in a variety of photonic systems [5][6][7] . Due to the high sensitivity to variations in refractive index, devices exploiting Fano resonances are excellent candidates to mitigate applications such as sensing and switching 7,8 .…”

“…Over the years, Fano resonances have been studied theoretically and experimentally in a variety of photonic systems [5][6][7] . Due to the high sensitivity to variations in refractive index, devices exploiting Fano resonances are excellent candidates to mitigate applications such as sensing and switching 7,8 . More recently, Fano resonances were also observed in several plasmonic systems initiating a flourishing research in the field [9][10][11][12][13][14] .…”

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

“…1(a), the extended tails of a Lorentzian spectrum imply large switching energies, since the resonance needs to be shifted significantly to properly switch the signal. In contrast, a Fano resonance [6], [7] has an asymmetric spectrum, featuring a large transmission change within a narrow wavelength range, determined by the transition from constructive to destructive interference between the discrete resonance and the continuum, thus enabling low-energy switching. The advantage of a Fano resonance was recently demonstrated using a symmetric photonic-crystal (PhC) structure employing an H1-type cavity [8].…”