Two-dimensional beam steering with tunable metasurface in infrared regime.

Tunable metasurfaces can change the optical properties of incident light at will such as amplitude, phase, and polarization in a time-dependent fashion. Ultrafast switching speed and the ability for the pixel size reduction of the tunable metasurface can allow various applications such as light detection and ranging, interferometric sensors, and free space optical communications, to name a few. Although there have been successful demonstrations of the wavefront shaping using the tunable metasurface, the implementation of the two-dimensional metasurface pixel array that can be individually addressed in the optical frequency regime still remains challenging.

All-solid-state spatial light modulator with independent phase and amplitude control for three-dimensional LiDAR applications.

Spatial light modulators are essential optical elements in applications that require the ability to regulate the amplitude, phase and polarization of light, such as digital holography, optical communications and biomedical imaging. With the push towards miniaturization of optical components, static metasurfaces are used as competent alternatives. These evolved to active metasurfaces in which light-wavefront manipulation can be done in a time-dependent fashion.

Time-asymmetric loop around an exceptional point over the full optical communications band.

Topological operations around exceptional points-time-varying system configurations associated with non-Hermitian singularities-have been proposed as a robust approach to achieving far-reaching open-system dynamics, as demonstrated in highly dissipative microwave transmission and cryogenic optomechanical oscillator experiments. In stark contrast to conventional systems based on closed-system Hermitian dynamics, environmental interferences at exceptional points are dynamically engaged with their internal coupling properties to create rotational stimuli in fictitious-parameter domains, resulting in chiral systems that exhibit various anomalous physical phenomena. To achieve new wave properties and concomitant device architectures to control them, realizations of such systems in application-abundant technological areas, including communications and signal processing systems, are the next step.

Fabrication of a polyurethane acrylate/polyimide-based polymer mold for a hot embossing process.

A high-thermal-resistance polymer-based flexible imprint mold was developed to be used in a hot embossing process. This mold was readily replicated in a UV curing imprint process and can be used as a mold for hot embossing and thermally curing imprint processes. The nano-sized pattern of this mold was not degraded by soaking at 350 degrees C for 10 min and the pattern fidelity was maintained after 10 separate cyclic heating tests between 0 degrees C and 350 degrees C.

Sub 50 nm nano-patterns with carbon based spin-on organic hardmask.

Carbon based spin-on organic hardmask (C-SOH) was used as an imprint resin to fabricate sub 50 nm sized patterns. Imprinting of C-SOH was done with a polyurethaneacrylate (PUA) stamp. Patternability and etch resistance of the C-SOH resin was compared to poly(methyl methacrylate) (PMMA).

The fabrication of a patterned ZnO nanorod array for high brightness LEDs.

In this study, a patterned ZnO nanorod array was formed on the ITO layer of GaN-based light-emitting diodes (LEDs), to increase the light extraction efficiency of the LED. The bi-layer imprinted resin pattern was used for selective growth of the ZnO nanorod array on the ITO layer. Compared to conventional LEDs grown on patterned sapphire substrate (PSS), the deposition of the blanket ZnO layer on the ITO layer increased the light extraction efficiency of the LED by about 10%.

Fabrication of 70 nm-sized zero residual polymer patterns by thermal nanoimprint lithography.

The formation of a residual layer under the imprinted patterns is commonly observed after the imprinting process. In order to utilize the imprinted patterns into the top-down process, the removal process of the residual layer using oxygen plasma is inevitable. However, the critical dimension of the imprinted patterns can be degraded during the residual layer removal process and this degradation becomes severer for smaller sized patterns.

Thermal imprinting of nano-patterns using thiol-based self-assembled monolayer-treated nickel template.

A highly durable imprint template is essential for the industrialization of nanoimprint lithography (NIL). Conventionally, Si-based materials were used for the fabrication of imprint templates. However, their fabrication is very expensive and they can be easily damaged during repeated imprint processes due to their brittleness and poor mechanical properties.