We present a novel approach to designing high-quality bound states in the continuum (BIC) in dielectric metasurfaces using magnetic dipole resonances coupled to a mirror, enabling strong light–matter interaction without the need for asymmetric geometry or polarization dependence. This simplifies fabrication and enhances practical applications, demonstrated by a record-breaking third harmonic generation efficiency. Additionally, we showcase superior modulation characteristics with a pulsewidth-limited switching time of 100 fs and a remarkably low energy consumption, facilitated by the narrow photonic resonance of our metasurface. Our findings offer significant potential for optical sensing, quantum photonics, and nonlinear devices.
Epsilon-near-zero (ENZ) materials such as indium tin oxide (ITO), have recently emerged as a new platform to enhance optical nonlinearities. In this talk I will report on our recent theoretical and experimental results on the origin of ultrafast nonlinearities in ITO films that are dominated by intraband and interband transitions. We show that there are two competing factors that jointly contribute to a spectrally-invertible nonlinearity of ITO near its ENZ region i.e. the nonparabolicity of the bands that results in a larger effective mass and the Fermi energy shift, which determines the free carrier density. Our work reveals the relationship between the large nonlinearity and the intrinsic material properties of the ITO films which will enable design and development of photonic materials and nonlinear devices made of transparent conductive oxides.
Bound states in the continuum (BIC) to achieve highly efficient frequency conversion using high quality-factor (high-Q) metasurfaces have been demonstrated using symmetry-broken structures with high robustness; however, the breaking-symmetry tactics are typically limited to one of the dimensions of the structures, which restricts the nonlinearity with BIC. In this work, we present a new metasurface structure in the form of an array of unit cells composed of two identical nano-bars with two mirror-symmetric corners cut into each nano-bar to break this limit. By using the high refractive index and large third-order nonlinearity of amorphous silicon (a-Si), we demonstrate ultra-high theoretical Qs up to ~ 2×10^5. Owing to the large nearfield enhancement in the meta-atoms, we observe optical Kerr effect in efficient third harmonic generation from the a-Si BIC metasurfaces via different levels of pump power, which paves the way for variational quasi-BIC for switchable nonlinear generation.
Subwavelength nonlinear optical sources with high efficiency have received extensive attention although
strong dynamic tunability of these sources is still elusive. Germanium antimony telluride (GST) as a well-established phase-change chalcogenide is a promising candidate for the reconfiguration of subwavelength
nanostructures. Here, we design an electromagnetically induced transparency (EIT)-based high-quality-factor (high-Q) silicon metasurface that is actively controlled with a quarter-wave asymmetric Fabry-Perot cavity incorporating GST to modulate the relative phase of incident and reflected pump waves. We demonstrate a multi-level third-harmonic generation (THG) switch with a theoretical modulation depth as high as ~ 70 dB for the fundamental C-band crossing through multiple intermediate states of GST. This study shows the high potential of GST-based dynamic nonlinear photonic switches for a wide range of applications ranging from communications to optical computing.
Monolayer transition metal dichalcogenides, coupled to metal plasmonic nanocavities, have recently emerged as new platforms for strong light–matter interactions. These systems are expected to have nonlinear-optical properties that will enable them to be used as entangled photon sources, compact wave-mixing devices, and other elements for classical and quantum photonic technologies. Here, we report the first experimental investigation of the nonlinear properties of these strongly coupled systems, by observing second harmonic generation from a WSe2 monolayer strongly coupled to a single gold nanorod. The pump-frequency dependence of the second-harmonic signal displays a pronounced splitting that can be explained by a coupled-oscillator model with second-order nonlinearities. Rigorous numerical simulations utilizing a nonperturbative nonlinear hydrodynamic model of conduction electrons support this interpretation and reproduce experimental results. Our study thus lays the groundwork for understanding the nonlinear properties of strongly coupled nanoscale systems.
Since its discovery in the 1960s, nonlinear optics has revolutionized optical technologies and laser industry. Development of efficient nanoscale nonlinear sources will pave the way for new applications in photonic circuitry, quantum optics and bio-sensing. However, nonlinear signal generation at dimensions smaller than the wavelength of light brings new challenges. These include the reduced light-matter interaction volume, mode overlap and increased losses. Here, we develop hybrid plasmonic – dielectric metamaterials that overcome these limitations and show a dramatic increase of the efficiency of nonlinear optical response at the nanoscale.
In the first part of my talk I will introduce a new type of 3-dimensional, non-planar plasmonic metasurface and demonstrate 4 orders of magnitude enhancement of second harmonic generation (SHG) compared to doubly-resonant plasmonic systems. The geometry of the metamaterial design minimizes the destructive interference of nonlinear emission into the far-field, provides independently tunable resonances both for fundamental and harmonic frequencies, a good mutual overlap of the modes and a strong interaction with the nonlinear material. In the second part of my talk I will describe our recent efforts to combine localized plasmon modes with propagating photonic waveguide modes. The hybridized mode that is formed as a result of such coupling can exhibit the desirable features of plasmonic modes such as high Purcell factors and large field enhancement but with significantly reduced losses.
Our findings can enable the development of efficient nanoscale single photon sources, integrated frequency converters and other nonlinear devices.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.