Ramin Yazdaanpanah

Optical metasurfaces have transformed nanoscale light control, but conventional platforms remain predominantly rigid and fabrication intensive. Polymer-based metasurfaces offer a complementary design space combining scalable manufacturing, mechanical compliance, chemical tunability, three-dimensional structuring, and functional molecular and nanoparticle incorporation. This Review examines polymer materials, fabrication strategies, and emerging applications in sensing, imaging, reconfigurable optics, light emission, and inverse-designed photonics, highlighting opportunities and challenges for scalable, adaptive, and multifunctional nanophotonic systems.

Borophene is a monoelemental two‐dimensional (2D) material whose electron‐deficient bonding renders free‐standing monolayers intrinsically unstable, raising the question of how borophene can be converted into stable boron nanostructures. Borophene's structural stability and electronic properties are strongly influenced by vacancy configurations and defect engineering, while hydrogenation offers an additional pathway for stabilization and property tuning. Here, we introduce a solvent‐free solid‐state route that transforms hydrogenated borophene (HB) into either B ₂ O ₃ nanoplatelets or boron quantum dots (BQDs) via thermal dehydrogenation. Cleavage of B─H bonds releases hydrogen gas, whose escape under flowing N ₂ facilitates structural reconstruction and leads to the formation of B ₂ O ₃ nanoplatelets. In sealed conditions, hydrogen accumulation generates internal pressure that drives fragmentation of the boron framework into BQDs. The resulting materials exhibit distinct photoluminescence (PL) behavior that correlates with their structural evolution, in agreement with first‐principles calculations of band‐gap changes. This work establishes solvent‐free, pressure‐assisted dimensional engineering of boron nanostructures and provides a new strategy for controlling the structural and optoelectronic properties of boron‐based materials.

Metasurfaces offer control over light–matter interactions, but their material scope is often constrained by top‐down fabrication techniques, limiting compositional flexibility in meta‐atoms and the accessible optical properties. Herein, a bottom‐up approach integrates colloidal crystal engineering with DNA with lithographically defined microwell templates to create meta‐structures composed of nanoparticle superlattices that function as programmable meta‐atoms. The microwell environment stabilizes non‐equilibrium superlattice habits inaccessible with homogeneous crystallization, decoupling habit formation from lattice symmetry. This approach enables tuning of optical response through hierarchical parameters: 1) nanoparticle composition and size, DNA length, and lattice symmetry define superlattice optical characteristics; 2) superlattice size and habit determine resonator supported modes; and 3) inter‐superlattice spacing and arrangement govern collective lattice effects. This multiscale modularity enables access to a vast combinatorial design space for optical engineering. As proof‐of‐concept, a meta‐structure comprised of periodic cylindrical superlattices exhibiting a near‐infrared Mie‐ resonance is fabricated. Despite being composed of metallic gold nanoparticles, the superlattices exhibit an emergent dielectric‐like response with low effective extinction in the NIR/mid‐IR regime, enabling volumetric electromagnetic field penetration. Field maps show resonant behavior characteristic of magnetic dipole Mie modes. By integrating colloidal assembly with system‐level optical functionality, this work establishes a bottom‐up framework for designing photonic meta‐structures.

Heteroepitaxial growth is a powerful strategy for constructing hierarchical systems by integrating materials with different structures across the angstrom to nanometer length scale. However, lattice mismatches between different phases often impact the resulting crystal stability. This is especially true for colloidal crystal systems. Here, colloidal crystal engineering with DNA is used to assemble multi‐phase colloidal crystals, with extreme tolerance for lattice strain. Most notably, the structural flexibility of DNA can accommodate lattice mismatch up to 18%, allowing one to grow, for the first time, face‐centered cubic (fcc) lattices with (111) facets on body‐centered cubic (bcc) crystals with (110) facets (a 13% bcc‐fcc phase misfit for the particles studied; 2%–4% in an atomic system). By adjusting particle size, more or less strain can be induced, allowing one to determine the upper limit for bcc‐fcc phase misfit (34%). Finite‐difference time‐domain (FDTD) optical simulations reveal that these multi‐phase heteroepitaxial structures can function as waveguides, making them attractive targets for those interested in optics. The lattice mismatches accommodated through DNA bonding exceed those typical in atomic heteroepitaxy (a few percent without a buffer layer), highlighting the versatility of this technique for designing and preparing hierarchical materials with tailored structure‐function relationships.

We present a theoretical analysis aimed at comprehending and mitigating the focal shift phenomenon in planar dielectric metalenses. To conduct this analysis, we introduce metalens designs consisting of silicon and germanium nanoblocks on a calcium fluoride substrate, operating in the mid-IR frequency range. The lensing performance of these metalenses is investigated using the finite-difference time-domain method, and they operate at wavelengths of 3 and 4 µm with a polarization conversion efficiency close to unity. Our findings indicate a strong correlation between the focal shift phenomena on dielectric metalenses and the numerical aperture (NA), revealing that increasing the Fresnel number is not always an effective approach to minimizing the focal shift. In contrast to previous studies, we define a critical NA, independent of the lens size, where the focal shift reaches a minimum, resulting in a symmetric focal intensity distribution and ultimately yielding a better-performing metalens. We demonstrate that for NAs greater than the determined critical value, a positive focal shift is observed on planar metalenses, diverging from the conventional negative shift predicted by existing models. Additionally, we show that by selecting a metalens within a specific NA range and with smaller diameters, high focusing efficiencies can be achieved. The focusing efficiency of the studied metalenses is measured as high as 70%, marking one of the best values reported for the IR range to date. These results serve as a guide for improving the agreement between experimental and designed metalens features, enhancing their practical applications.

We present a metamaterial-based perfect absorber (PA) that strongly supports four resonances covering a wide spectral range from 1.8 µm to 10 µm of the electromagnetic spectrum. The designed perfect absorber has metal–dielectric–metal layers where a MgF₂ spacer is sandwiched between an optically thick gold film and patterned gold nanoantennas. The spectral tuning of PA is achieved by calibrating the geometrical parameters numerically and experimentally. The manufactured quad-band plasmonic PA absorbs light close to the unity. Moreover, the biosensing capacity of the PA is tested using a 14 kDa S100A9 antibody, which is a clinically relevant biomarker for brain metastatic cancer cells. We utilize a UV-based photochemical immobilization technique for patterning of the antibody monolayer on a gold surface. Our results reveal that the presented PA is eligible for ultrasensitive detection of such small biomarkers in a point-of-care device to potentially personalize radiotherapy for patients with brain metastases.