UV-Nanoimprint Lithography for Predefined SERS Nanopatterns Which Are Reproducible at Low Cost and High Throughput.

A controlled and reliable nanostructured metallic substrate is a prerequisite for developing effective surface-enhanced Raman scattering (SERS) spectroscopy techniques. In this study, we present a novel SERS platform fabricated using ultra-violet nanoimprint lithography (UV-NIL) to produce large-area, ordered nanostructured arrays. By using UV-NIL imprinted patterns in resist, we were able to overcome the main limitations present in most common SERS platforms, such as nonuniformity, nonreproducibility, low throughput, and high cost.

Tuning the infrared resonance of thermal emission from metasurfaces working in near-infrared.

We simulated numerically and demonstrated experimentally that the thermal emittance of a metasurface consisting of an array of rectangular metallic meta-atoms patterned on a layered periodic dielectric structure grown on top of a metallic layer can be tuned by changing several parameters. The resonance frequency, designed to be in the near-infrared spectral region, can be tuned by modifying the number of dielectric periods, and the polarization and incidence angle of the incoming radiation. In addition, the absorbance/emittance value at the resonant wavelength can be tuned by modifying the orientation of meta-atoms with respect to the illumination direction.

UV-Nanoimprint and Deep Reactive Ion Etching of High Efficiency Silicon Metalenses: High Throughput at Low Cost with Excellent Resolution and Repeatability.

As metasurfaces begin to find industrial applications there is a need to develop scalable and cost-effective fabrication techniques which offer sub-100 nm resolution while providing high throughput and large area patterning. Here we demonstrate the use of UV-Nanoimprint Lithography and Deep Reactive Ion Etching (Bosch and Cryogenic) towards this goal. Robust processes are described for the fabrication of silicon rectangular pillars of high pattern fidelity.

MEMS-tunable dielectric metasurface lens using thin-film PZT for large displacements at low voltages.

Tunable focusing is a desired property in a wide range of optical imaging and sensing technologies but has tended to require bulky components that cannot be integrated on-chip and have slow actuation speeds. Recently, integration of metasurfaces into electrostatic micro-electromechanical system (MEMS) architectures has shown potential to overcome these challenges but has offered limited out-of-plane displacement range while requiring large voltages. We demonstrate for the first time, to the best of our knowledge, a movable metasurface lens actuated by integrated thin-film PZT MEMS, which has the advantage of offering large displacements at low voltages.

Silicon Metalens Fabrication from Electron Beam to UV-Nanoimprint Lithography.

This study presents the design and manufacture of metasurface lenses optimized for focusing light with 1.55 µm wavelength. The lenses are fabricated on silicon substrates using electron beam lithography, ultraviolet-nanoimprint lithography and cryogenic deep reactive-ion etching techniques.

Metasurface Fabrication by Cryogenic and Bosch Deep Reactive Ion Etching.

The research field of metasurfaces has attracted considerable attention in recent years due to its high potential to achieve flat, ultrathin optical devices of high performance. Metasurfaces, consisting of artificial patterns of subwavelength dimensions, often require fabrication techniques with high aspect ratios (HARs). Bosch and Cryogenic methods are the best etching candidates of industrial relevance towards the fabrication of these nanostructures.

Low-loss ultrasound transmission through glass assisted by resonance.

We have investigated transmission of ultrasound signals from a speaker in air through a 400 µm thick borosilicate glass plate, similar to those found in consumer electronics products such as mobile phones and tablets. In order to enhance transmission, we took advantage of resonances in the glass plate and a cavity, which is placed between the glass and the microphone. The results show that it is possible to achieve transmission of a signal with bandwidth of approximately 5 kHz with less than -10 dB attenuation, and only -2 dB attenuation at the resonance peak frequency.