Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2606.11567

Nonlinearity Reversal in Epsilon-Near-Zero Indium Tin Oxide Driven by Few-Cycle Light Pulse

Mustafa Goksu Ozlu·Colton Fruhling·Ian Hoffman·Jae Ik Choi·Marcello Ferrera·Alexandra Boltasseva·Vladimir M. Shalaev
View original source ↗Read source document ↗Export metadata ↓

Abstract

Recent breakthrough studies of nonlinearities at extreme pump intensities ($\sim$1 $\text{TW/cm}^2$) in transparent conducting oxides (TCOs) have rewritten our understanding of the dynamics in these materials. However, exploring TCO dynamics beyond these intensities is prohibited by the damage threshold of the material. In this work, we overcome this problem by using a few-cycle pump laser pulse (sub-8\,fs) to maximize the intensity while keeping the optical fluence below the damage threshold. We observe a reversal in the optical response trend starting at optical pump laser intensities of $\sim$5 $\text{TW/cm}^2$ similar to Segal et al. At the highest pump pulse intensities, we obtain a complete change in the sign of the modulation for both transmission and reflection, producing a full-cycle oscillation of the refractive index modulation within 300\,fs. The amplitude of the sign reversal scales quadratically with the intensity. We therefore propose a simple two-photon absorption (TPA) model to explain the observed behaviour. The TPA, which is normally forbidden by the Pauli blocking, is enabled here by intraband excitations from the lower to the upper non-equilibrium states of the conduction band (CB). Such excitations vacate the states at the bottom of the CB, lifting up the blocking and thus making interband TPA possible. The model is in good agreement with experimental results, capturing the essential trends in the observed data and revealing the dynamics of competing channels caused by the interplay between interband and intraband transitions. This intensity-controlled mechanism could be the key to unlocking new applications of TCOs for time-varying photonics such as photonic time crystals.

Explore related subjects

physics.optics

Keep this discovery

BibTeXRIS

Mustafa Goksu Ozlu, Colton Fruhling, Ian Hoffman, Jae Ik Choi, Marcello Ferrera, Alexandra Boltasseva, Vladimir M. Shalaev. 2026-06-10. Nonlinearity Reversal in Epsilon-Near-Zero Indium Tin Oxide Driven by Few-Cycle Light Pulse. https://arxiv.org/abs/2606.11567

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Two-step high-accuracy microwave frequency measurement and time-frequency analysis based on optical frequency combs

Broadband microwave frequency measurement and time-frequency analysis are crucial for applications such as electronic warfare. However, when it comes to ultra wideband signal analysis, traditional electronic methods have high analysis accuracy, but intrinsic electronic bottlenecks limit their real-time analysis. Here, we propose and experimentally demonstrate a two-step microwave frequency measurement and time-frequency analysis method based on optical frequency combs. The system first performs coarse frequency localization over the 0-40 GHz range using stimulated-Brillouin-scattering-assisted frequency-to-time mapping (FTTM) and dual-comb channelized reception. The dual-comb is then reapplied for downconverting the signal under test, followed by digital signal processing to achieve high-accuracy unambiguous frequency extraction. Experimental results show that the system achieves mean single-tone frequency measurement errors of less than 10 kHz over 0-40 GHz. We further experimentally measure multi-tone, linearly frequency-modulated, and V-shaped frequency-modulated signals, demonstrating the proposed method's capability for analyzing complex signals.

physics.optics↗
arXiv2026

A Two-Mirror Faceted Projection System for EUV Lithography

We propose an all-reflective two-mirror projection system for extreme ultraviolet (EUV) lithography operating at exposure wavelengths of $13.5$~nm (Mo/Si) and $11.2$~nm (Ru/Be), delivering a fourfold ($4\times$) demagnification of the periodic mask pattern at a numerical aperture approaching unity ($\mathrm{NA}_{\max} \approx 0.993$). In contrast to conventional EUV projection objectives that incorporate 6--10 aspheric mirrors with an overall optical throughput of less than $15\%$, the proposed design redirects each accepted discrete spatial diffraction order scattered by the mask onto the wafer via a dedicated pair of planar mirror facets. The number of reflections is strictly fixed at two for all accepted orders, retaining $50$--$60\%$ of the power leaving the mask in each accepted order. We derive a spatial geometry providing rigorous optical path length equalization across all diffraction orders, thereby removing order-dependent propagation phase shifts. Individually optimized 30-bilayer Bragg multilayer coatings are designed for each facet using the transfer matrix method combined with global evolutionary optimization algorithms. The architecture is generalized to a three-dimensional vector formulation with a two-dimensionally periodic mask. Utilizing inverse lithography technology, Fourier parameterization, and a differentiable electromagnetic modal waveguide solver, we solve the synthesis problem for binary absorber masks (La absorber on a Ru/Be/Sr multilayer mirror). We demonstrate simulated aerial images of sub-10-nm features on the wafer (isolated peaks with a full width at half maximum (FWHM) of approximately $5.4$~nm and line pairs with a critical dimension of $6$~nm) and find that the two peaks remain resolved for the tested wafer defocus values from $0$ to $5$~nm along the $z$-axis.

physics.optics↗
arXiv2026

Antimony for broadband nanophotonics across the ultraviolet, visible and infrared

Semimetal elemental antimony (Sb) nanostructures show great potential for applications where nanophotonic properties play a key role, such as phase-change optical memories, non-linear optical elements, photothermal therapy agents, photodetectors and photocatalysts. However, designing advanced Sb-based photonic devices critically requires an accurate and reliable knowledge of the optical response of bulk and nanoscale Sb. Herein, we report for the first time a fully consistent and accurately measured dielectric function for Sb nanoscale films in a wide spectral range from the ultraviolet to the far infrared (4 - 0.04 eV, i.e. ~ 0.3 - 30 $\mu$m), surpassing previous reports that explored a limited spectral range. It is found that the Sb spectral response is driven exclusively by giant interband transitions in the visible up to mid infrared (4 - 0.4 eV, i.e. ~ 0.3 - 3 $\mu$m), and that their contribution dominates over that of free carriers down to 0.12 eV (i.e. ~ 10 $\mu$m). Such spectral response enables Sb nanostructures to display spectrally selective and tunable nanophotonic resonances. First, we showcase interband plasmonic resonances in the visible-to-near infrared for Sb nanogratings. Second, we report giant refractive index dielectric resonances in the mid infrared for nanostructured Sb/dielectric/metal resonant cavities. These findings open a pathway to optimized planar Sb nanoscale designs enabling a tailored light-matter interaction, which will be useful for integrated data, telecom, medical, optoelectronic and energy conversion devices operating in a broad spectral range.

physics.optics↗