Gigahertz free-space electro-optic modulators based on Mie resonances

Abstract

Electro-optic modulators are essential for sensing, metrology and telecommunications. Most target fiber applications. Instead, metasurface-based architectures that modulate free-space light at gigahertz (GHz) speeds can boost flat optics technology by microwave electronics for active optics, diffractive computing or optoelectronic control. Current realizations are bulky or have low modulation efficiencies. Here, we demonstrate a hybrid silicon-organic metasurface platform that leverages Mie resonances for efficient electro-optic modulation at GHz speeds. We exploit quasi bound states in the continuum (BIC) that provide narrow linewidth (Q = 550 at $${\lambda }_{{{{{{{{\rm{res}}}}}}}}}=1594$$ λ res = 1594 nm), light confinement to the non-linear material, tunability by design and voltage and GHz-speed electrodes. Key to the achieved modulation of $$\frac{{{\Delta }}T}{{T}_{\max }}=67 \%$$ Δ T T max = 67 % are molecules with r33 = 100 pm/V and optical field optimization for low-loss. We demonstrate DC tuning of the resonant frequency of quasi-BIC by $${{\Delta }}{\lambda }_{{{{{{{{\rm{res}}}}}}}}}=$$ Δ λ res = 11 nm, surpassing its linewidth, and modulation up to 5 GHz (fEO,−3dB = 3 GHz). Guided mode resonances tune by $${{\Delta }}{\lambda }_{{{{{{{{\rm{res}}}}}}}}}=$$ Δ λ res = 20 nm. Our hybrid platform may incorporate free-space nanostructures of any geometry or material, by application of the active layer post-fabrication.

Manipulating Dual Bound States in the Continuum for Efficient Spatial Light Modulator

“…At f mod = 75 MHz, the maximal modulation is about 62% of its maximal value (realized by 1 MHz), which further confirms the f 3 dB of the device. It is worth noting that compared to most of the previous work based on electrically driven SLMs with various active materials, − ,,− our BP-array based SLM shows a superior modulation depth and speed in the telecommunicate wavelength regime (Figure h and Supplementary Table 1).…”

“…Among the existing SLM architectures, recently, nonlinear χ (2) materials integrated with metasurfaces have been proven to be a promising candidate to produce electric-optic modulation performance with a high-speed and compact footprint. − For example, a device combining a plasmonic metasurface with lithium niobate has shown a modulation speed of around hundreds of kilohertz in an ultrathin dimension . Organic electro-optical (EO) polymer based devices leveraging various metal-dielectric hybrid metasurface architectures have been reported to reach high modulation speeds to gigahertz or multiplex pixels, , revealing the great potential for active photonic devices. However, there remain challenges, including the nonnegligible leakage of the optical field outside the active material, as well as inevitable disturbance and loss due to the metal electrode. , Thus, a metasurface-based SLM with a tight-confined optical field and low radiative loss is keenly demanded for their practical application.…”

Lithium Niobate Meta-Optics

“…186 Recently, EO silicon metasurfaces were realized by infiltrating them with JRD1:PMMA that exhibits r 33 ∼ 100 pm/V. 187 Despite such large Pockels coefficients, organic polymers are typically affected by temperature and chemical instabilities. Finally, strained silicon was also suggested as an innovative route to attain a large Pockels effect.…”

“…The challenges of top-down nanofabrication listed in detail in Section , along with the advancements in bottom-up nanofabrication, fostered the investigation of metasurfaces composed of BaTiO 3 nanoparticle films for EO applications. , However, sizable drops in the values of the Pockels coefficient as well as the χ (2) have been reported for nanoparticles of small size (e.g., r 33 ∼ 37 pm/V for 50 nm nanoparticle diameter). , Other materials, like organic polymers, can also show large EO coefficients . Recently, EO silicon metasurfaces were realized by infiltrating them with JRD1:PMMA that exhibits r 33 ∼ 100 pm/V . Despite such large Pockels coefficients, organic polymers are typically affected by temperature and chemical instabilities.…”

Efficient Excitation and Tuning of Multi-Fano Resonances with High Q-Factor in All-Dielectric Metasurfaces

“…It is an effective method to obtain a high Q-factor in all-dielectric metasurfaces [17][18][19][20]. Mie resonance means that when electromagnetic waves are irradiated on dielectric particles, they will interact with each other to realize scattering in response to electric or magnetic fields [21,22]. This can not only generate electric resonance modes but also generate magnetic and toroidal resonance modes [23,24], thereby significantly reducing radiation loss.…”