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Using spectroscopic ellipsometry and rigorous coupled wave analysis, we studied the spin-coated resist coverage on 72.6 nm pitch line-and-space patterns of various depths (from ∼20 to ∼130 nm). Within the margin of measurement error, we find the tested nano-patterns have no apparent effect on the spin-coated resist thickness. The result suggests that, during the spinning, the resist ceased to flow at a critical thickness much larger than the pattern depth, and the resist thinning afterwards was dominated by solvent evaporation. The methods and results demonstrated in this work can improve the characterization and process control in a number of applications where spin coating on high-density nano-scale topographies is required. [ABSTRACT FROM AUTHOR]

Fast optical surface scanners are used in combination with high-resolution scanning electron microscopes to facilitate the identification and tracking of nanoimprint defects. We have confirmed that hard particles cause permanent template damages during imprint, resulting in repeating imprint defects. Since contaminants encountered during imprint are dominated by hard metal oxide particles capable of causing such damage, stringent pre-imprint substrate screening is a critical requirement in a manufacturing environment. [ABSTRACT FROM AUTHOR]

A metamaterial comprising an ordered array of four metallic L-shaped components designed to operate in the mid-IR frequency regime has been fabricated and characterized. The fourfold rotational symmetry of the unit cell should suppress the undesirable bianisotropy observed for split-ring resonators. Nanoimprint lithography was used to demonstrate scalability for mass production. A dipole plasmon resonance with a negative permittivity and a magnetic resonance with a negative permeability were observed at wavelengths of 3.7 and 5.25 μm, respectively, in agreement with theoretical predictions. [ABSTRACT FROM AUTHOR]

The authors have developed an approach to fabricate large area 50 nm period gratings (22 nm linewidth) with low cost. The method used a fabrication cycle twice, each combining nanoimprint lithography with a spatial frequency doubling based on electroless plating, lift-off, and reactive ion etching. Hence by frequency doubling twice, we started with a 200 nm period grating mold and finished with a 50 nm period grating with a uniform area of 3 cm2—the largest achieved today. This method is scalable for the fabrication of even smaller period gratings over a large area, and is a viable low-cost technique for making nanoimprint lithography molds for high-throughput fabrication of 50 nm period grating or grid devices. [ABSTRACT FROM AUTHOR]

We made uniform arrays of nanometer scale structures using nanoimprint lithography over large areas (100 mm wafers). The nanofluidic channels were further narrowed and sealed by techniques that are based on nonuniform deposition. The resulting sealed channels have a cross section as small as 10 nm by 50 nm, of great importance for confining biological molecules into ultrasmall spaces. These techniques can be valuable fabrication tools for Nanoelectromechanical Systems and Micro/ Nano Total Analysis Systems. [ABSTRACT FROM AUTHOR]

A reflective polarizer consisting of two layers of 190 nm period metal gratings was fabricated using nanoimprint lithography. Measurements with a He-Ne laser (wavelength=632.8 nm) showed that at normal incidence, this polarizer reflects light polarized perpendicular to the grating lines (transverse magnetic polarization) with a reflectance of 54%, but strongly absorbs parallel-polarized light (transverse electric polarization) with a reflectance of only 0.25%. The enhanced polarization extinction ratio of over 200 at this wavelength is possibly related to the resonance between the two layers of metal gratings. This polarizer is thin, compact, and is suited for integrated optical systems. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Optical limiters are nonlinear devices that feature decreasing transmittance with increasing incident optical intensity, and thus can protect sensitive components from high‐intensity illumination. The ideal optical limiter reflects rather than absorbs light in its active ("limiting") state, minimizing risk of damage to the limiter itself. Previous efforts to realize reflective (rather than absorbing) limiters were based on embedding nonlinear layers into relatively thick multilayer photonic structures, resulting in substantial fabrication complexity, reduced speed and, in some instances, limited working bandwidth. In this paper, these tradeoffs are overcome by using the insulator‐to‐metal transition (IMT) in vanadium dioxide (VO2) to achieve intensity‐dependent modulation of resonant transmission through aperture antennas. Due to the large change of optical properties across the IMT, low‐quality‐factor resonators are sufficient to achieve high on–off ratios in the transmittance of the limiter. As a result, our ultrathin reflective limiter (thickness ≈1/100 of the free‐space wavelength) is broadband in terms of operating wavelength (>2 µm at 10 µm) and angle of incidence (up to ≈50° away from the normal). Our analysis of the experimental results via opto‐thermal simulations provides insight into limiter performance and is a useful guidance for further engineering efforts. [ABSTRACT FROM AUTHOR]

We demonstrate a passive down-conversion imaging system that converts broadband ultraviolet light to narrow-band green light while preserving the directionality of rays, and thus enabling direct down-conversion imaging. At the same time our system has high transparency in the visible, enabling superimposed visible and ultraviolet imaging. The frequency conversion is performed by a subwavelength-thickness transparent downconverter based on highly efficient CsPbBr3 nanocrystals incorporated into the focal plane of a simple telescope or relay-lens geometry. The resulting imaging performance of this down-conversion system approaches the diffraction limit. This demonstration sets the stage for the incorporation of other high-efficiency perovskite nanocrystal materials to enable passive multi-frequency conversion imaging systems. [ABSTRACT FROM AUTHOR]

Thermal emission is the radiation of electromagnetic waves from hot objects. The promise of thermal‐emission engineering for applications in energy harvesting, radiative cooling, and thermal camouflage has recently led to renewed research interest in this topic. However, accurate and precise measurements of thermal emission in a laboratory setting can be challenging in part due to the presence of background emission from the surrounding environment and the measurement instrument itself. This problem is especially acute for thermal emitters that have unconventional temperature dependence, operate at low temperatures, or are out of equilibrium. In this paper, general procedures are described, recommended, and demonstrated for thermal‐emission measurements that can accommodate such unconventional thermal emitters. [ABSTRACT FROM AUTHOR]

We have studied the geometry dependency of fishnet-like negative refractive index meta-materials (NIMs), and developed a process to fabricate such NIMs using nanoimprint lithography (NIL) in a controlled way for it to achieve negative refractive index in the desired frequency range. As an example, we fabricated a fishnet structure with a minimum negative refractive index of −1.7 at 1560 nm, which was only 10 nm off the targeted wavelength of 1550 nm. [ABSTRACT FROM AUTHOR]

As demonstrated by Mikhail A. Kats and co-workers in article number 2100001, these devices have broadband transmittance for low-intensity illumination and high reflectance when the incident intensity increases, and thus help protect sensitive detectors from high-power illumination. The cover illustrates reflective optical limiters that incorporate phase-transition vanadium dioxide into arrays of metallic aperture antennas. The reflective high-intensity state minimizes absorption, and thus increases the damage threshold of the device. [Extracted from the article]

We demonstrate a smooth and low loss silver (Ag) optical superlens capable of resolving features at 1/12th of the illumination wavelength with high fidelity. This is made possible by utilizing state-of-the-art nanoimprint technology and intermediate wetting layer of germanium (Ge) for the growth of flat silver films with surface roughness at subnanometer scales. Our measurement of the resolved lines of 30 nm half-pitch shows a full-width at half-maximum better than 37 nm, in excellent agreement with theoretical predictions. The development of this unique optical superlens leads promise to parallel imaging and nanofabrication in a single snapshot. [ABSTRACT FROM AUTHOR]

Optical modulation of the effective refractive properties of a “fishnet” metamaterial with a Ag/Si/Ag heterostructure is demonstrated in the near-IR range and the associated fast dynamics of negative refractive index is studied by pump-probe method. Photoexcitation of the amorphous Si layer at visible wavelength and corresponding modification of its optical parameters is found to be responsible for the observed modulation of negative refractive index in near-IR. [ABSTRACT FROM AUTHOR]