- The paper shows that exploiting EIT resonances in all-dielectric metasurfaces enhances high-harmonic signals by over two orders of magnitude.
- It employs a 225 nm silicon film patterned into dipolar bars and disk resonators to generate odd harmonics from the fifth to eleventh order with up to 150-fold improvement.
- The method provides tunability and robust damage thresholds, presenting a viable alternative to plasmonic structures for advancing nanoscale photonics.
This paper presents a paper on high-harmonic generation (HHG) utilizing an all-dielectric silicon metasurface, contributing significant advancements in nanophotonics and ultrafast optics. The research demonstrates a substantial enhancement of HHG by over two orders of magnitude through the employment of silicon (Si) metasurfaces with sharply defined Fano resonances, arising from a classical analogue of electromagnetically induced transparency (EIT).
The experimental setup comprises a metasurface fabricated from a 225 nm thick Si film on a sapphire substrate, with a periodic architecture of dipolar bars and disk resonators. When exposed to incident infrared radiation tuned to the EIT resonance, the metasurface yields a significantly enhanced HHG signal due to its resonant properties. This enhancement marks a technical leap forward when compared to conventional unpatterned Si films. Specifically, under excitation intensities of 0.071 TW/cm², odd harmonics from the fifth to the eleventh order are observed. Notably, the fifth harmonic shows an enhancement factor of 150 compared to unnanostructured Si, substantiating the field enhancement effect by the metasurface.
The theoretical implications of this work are profound. The metasurface with its EIT resonance furnishes an optimal platform for investigating non-linear light-matter interactions in the context of solid-state HHG. The findings suggest that the high field intensities achieved within the metasurface are congruent with those experienced at the atomic scale, even in solids. This positions all-dielectric metasurfaces as an auspicious alternative to metallic plasmonic structures, which often suffer from low damage thresholds and increased fabrication sensitivity.
The observed HHG enhancement is also subject to the excitation wavelength, illustrating a clear dependence on detuning from the EIT resonance. This tunability confers additional control over the HHG process, allowing greater manipulation in both the temporal and spectral domains. Moreover, this work demonstrates the potential of all-dielectric metasurfaces to supplant plasmonic counterparts, offering higher transparency and damage thresholds while facilitating precise control over the polarization and phase of the emitted harmonics.
Looking forward, the integration of larger bandgap dielectrics could extend the HHG to the XUV regime, increasing potential applications in attosecond pulse generation and nanoscale photonics. Furthermore, this robust field enhancement mechanism could trigger novel experimental setups to control emission properties through engineered nanoarchitectures. Future investigations might focus on the spatial arrangement of nanostructures to achieve diversified polarization states, including the generation of high harmonics with non-zero orbital angular momentum.
In conclusion, this paper enriches the understanding of HHG phenomena using all-dielectric metasurfaces, bridging the gap between nanophotonics and strong-field laser physics. By exploring resonant properties through EIT, the research outlines new opportunities for compact, efficient optical devices capable of operating at high intensities and short wavelengths, facilitating innovations across various photonic applications.