arXiv subjects

Samir Rosas

Publications and source records attributed to Samir Rosas.

7 recordsLinked to original sources

arXiv2026

Scalable Fabrication of Thermally Reconfigurable Ge Metasurfaces Using Stencil Lithography for Mid-Infrared Molecular Sensing

Mid-infrared (mid-IR) spectroscopy enables label-free molecular detection and is widely employed in biomedical, environmental, and chemical sensing; however, its broader deployment remains limited by bulky instrumentation and insufficient analytical sensitivity. Photonic metasurfaces supporting strong mid-IR resonances provide a promising route toward compact on-chip spectrometers and enhanced molecular sensing, yet their practical implementation is often constrained by limited spectral coverage and fabrication complexity. Here, we present a scalable, resist-free stencil lithography approach for fabricating arrays of Ge pillar metasurfaces on CaF2 substrates that support polarization-insensitive Mie resonances dominated by electric dipole modes. By varying the geometric design parameters during fabrication, we engineered metasurface arrays with discrete resonances spanning the 950-1700 cm^-1 molecular fingerprint region. Furthermore, leveraging the thermo-optic response of Ge, we achieved dynamic tuning of these discrete resonances, demonstrating continuous and reversible resonance shifts of approximately 36 cm^-1 per metasurface over 300-500 K, corresponding to a tuning rate of 0.18 cm^-1/K. The thermally induced spectral sweeping enables multiplexed detection of poly(methyl methacrylate) vibrational modes and continuous reconstruction of its absorbance spectrum across 1100-1215 cm^-1. These results establish a scalable dielectric metasurface platform with spectrally reconfigurable mid - IR modes for molecular sensing across the fingerprint region and compact infrared sensor technologies.

physics.optics↗

arXiv2025

Wafer-Scale All-Dielectric quasi-BIC Metasurfaces: Bridging High-throughput Deep-UV Lithography with Nanophotonic Applications

High quality-factor (Q) dielectric metasurfaces operating in the visible to near-infrared range usually require sub-200 nm features, limiting their fabrication to expensive, low-throughput electron beam lithography. Here, we demonstrate wafer-scale metasurfaces fabricated using deep ultraviolet lithography (DUVL), a workhorse technology in the semiconductor industry. Using a radius and depth perturbation technique in a hole array patterned into a silicon nitride slab, we achieve quasi-bound states in the continuum (qBIC) resonances with measured Q-factors of 150. Critically, we introduce DUV exposure dose as a Q-factor engineering parameter and demonstrate how hole depth control circumvents DUVL resolution limits. Despite stochastic nanoscale variations, the fabricated metasurfaces exhibit spatial uniformity, a consequence of the nonlocal nature of the qBIC resonances. Proof of concept refractive index sensing demonstrates 129 nm/RIU sensitivity while maintaining simple CMOS camera-based resonance shift interrogation. This work bridges scalable semiconductor manufacturing with high-performance nanophotonics, establishing a practical pathway for commercializing metasurface-based sensors, on-chip spectrometers, and integrated photonic systems.

physics.optics↗

arXiv2025

Dynamically Tunable Membrane Metasurfaces for Infrared Spectroscopy

Mid-infrared spectroscopy enables biochemical sensing by identifying vibrational molecular fingerprints, but it faces limitations in instrumentation portability and analytical sensitivity. Optical metasurfaces with strong mid-IR photonic resonances provide an attractive solution towards on-chip spectrometry and sensitive molecular detection, yet their static nature hinders their anticipated impact. Here, we introduce and demonstrate dynamically tunable silicon membrane metasurfaces exhibiting high-Q transmissive resonances in the fingerprint region. By harnessing silicon's thermo-optical properties, we achieve continuous modulation of electromagnetically induced transparency (EIT)-like modes that emerge upon the interference of quasi-bound states in the continuum (q-BICs) and surface lattice modes. We measure a spectral tuning rate of 0.06 $cm^{-1}/K$ by continuously sweeping the sharp EIT resonances over a 23.5 $cm^{-1}$ spectral range across a temperature range of 300-700 K. This dynamic transmission control enables non-contact chemical analysis of polymer films by detecting characteristic absorption bands of polystyrene (1450 and 1492 $cm^{-1}$) and Poly(methyl methacrylate) (1730 $cm^{-1}$) without bulky spectrometers. When analyte molecules fill the metasurface-generated photonic cavities, we demonstrate vibrational strong coupling between the Poly(methyl methacrylate)'s carbonyl band and the EIT mode, manifested in the Rabi splitting of $\sim$ 43 $cm^{-1}$. Our results establish a new photonic platform that unites spectral precision, strong field enhancement, and reconfigurability, offering diverse potential for compact mid-IR spectroscopy, molecular sensing, and programmable polaritonic photonics.

physics.app-ph↗

arXiv2025

Mass-manufactured Gradient Plasmonic Metasurfaces for Enhanced Mid-IR Spectrochemical Analysis of Complex Biofluids

Mid-infrared spectroscopy offers powerful label-free molecular analysis capabilities but faces significant challenges when analyzing complex biological samples. Here, we present a transformative surface-enhanced infrared absorption spectroscopy (SEIRAS) platform that overcomes fundamental limitations through key innovations. First, we demonstrate high-throughput wafer-scale fabrication of mid-IR plasmonic micro-hole-array (MHA) metasurfaces on free-standing silicon nitride membranes, yielding approximately 400 sensor chips per 6-inch wafer. Second, our gradient MHA metasurface design supports spectrally cascaded plasmonic modes, generating over 400 sharp resonance peaks across the 1200-2000 cm-1 fingerprint region. This approach enables comprehensive molecular fingerprinting using simple imaging optics in transmission mode. Third, we validate our SEIRAS platform using a model polymer system and clinical peritoneal fluid samples from ovarian cancer patients, demonstrating its capability to resolve complex molecular signatures in real biological specimens. The platform's dense spectral coverage ensures optimal on-resonance enhancement across the broad fingerprint region, revealing previously obscured vibrational bands that conventional IR spectroscopy cannot distinguish. By combining high-throughput fabrication with simplified optical readout and the capability to analyze complex biological samples, our work establishes a foundation for translating SEIRAS technology into practical biomedical applications.

physics.optics↗

arXiv2024

Enhanced biochemical sensing with high-Q transmission resonances in free-standing membrane metasurfaces

Optical metasurfaces provide novel solutions to label-free biochemical sensing by localizing light resonantly beyond the diffraction limit, thereby selectively enhancing light-matter interactions for improved analytical performance. However, high-Q resonances in metasurfaces are usually achieved in the reflection mode, which impedes metasurface integration into compact imaging systems. Here, we demonstrate a novel metasurface platform for advanced biochemical sensing based on the physics of the bound states in the continuum (BIC) and electromagnetically induced transparency (EIT) modes, which arise when two interfering resonances from a periodic pattern of tilted elliptic holes overlap both spectrally and spatially, creating a narrow transparency window in the mid-infrared spectrum. We experimentally measure these resonant peaks observed in transmission mode (Q~734 at ~8.8 um) in free-standing silicon membranes and confirm their tunability through geometric scaling. We also demonstrate the strong coupling of the BIC-EIT modes with a thinly coated PMMA film on the metasurface, characterized by a large Rabi splitting (32 cm-1) and biosensing of protein monolayers in transmission mode. Our new photonic platform can facilitate the integration of metasurface biochemical sensors into compact and monolithic optical systems while being compatible with scalable manufacturing, thereby clearing the way for on-site biochemical sensing in everyday applications.

physics.optics↗

arXiv2024

Trapping light in air with membrane metasurfaces for vibrational strong coupling

Optical metasurfaces can manipulate electromagnetic waves in unprecedented ways at ultra-thin engineered interfaces. Specifically, in the mid-infrared (mid-IR) region, metasurfaces have enabled numerous biochemical sensing, spectroscopy, and vibrational strong coupling (VSC) applications via enhanced light-matter interactions in resonant cavities. However, mid-IR metasurfaces are usually fabricated on solid supporting substrates, which degrade resonance quality factors (Q) and hinder efficient sample access to the near-field electromagnetic hotspots. Besides, typical IR-transparent substrate materials with low refractive indices, such as CaF2, NaCl, KBr, and ZnSe, are usually either water-soluble, expensive, or not compatible with low-cost mass manufacturing processes. Here, we present novel free-standing Si-membrane mid-IR metasurfaces with strong light-trapping capabilities in accessible air voids. We employ the Brillouin zone folding technique to excite tunable, high-Q quasi-bound states in the continuum (q-BIC) resonances with our highest measured Q-factor of 722. Leveraging the strong field localizations in accessible air cavities, we demonstrate VSC with multiple quantities of PMMA molecules and the q-BIC modes at various detuning frequencies. Our new approach of fabricating mid-IR metasurfaces into semiconductor membranes enables scalable manufacturing of mid-IR photonic devices and provides exciting opportunities for quantum-coherent light-matter interactions, biochemical sensing, and polaritonic chemistry.

physics.optics↗

arXiv2023

From Weak to Strong Coupling: Quasi-BIC Metasurfaces for Mid-infrared Light-Matter Interactions

Resonant metasurfaces present extraordinary subwavelength light trapping capabilities, which have been critical to the development of high-performance biochemical sensors and surface-enhanced spectroscopy techniques. To date, metasurface-enhanced light-matter interactions in the mid-infrared region have been primarily leveraged in the weak coupling regime. Nevertheless, the strong coupling regime, characterized by the hybrid light-matter states - polaritons, has not been fully explored. Specifically, metasurfaces made from low-loss dielectric resonators underpinned by the bound states in the continuum (BIC) are well suited for quantum coherent energy exchange between their high-Q open cavities and molecules' resonant transitions. This paper delves into the light-matter interactions in metasurface cavities generated by quasi-BIC resonances at mid-infrared frequencies. We thoroughly investigate the material and cavity parameters that define the boundaries between weak and strong coupling. Our findings underscore the transformative potential of dielectric metasurfaces to harness vibrational strong coupling for applications such as cavity polaritonic chemistry, modulation of chemical reactivity with light, and highly sensitive molecular spectroscopy.

physics.optics↗