Nathaniel Kinsey

Virginia Commonwealth University | VCU · Department of Electrical and Computer Engineering

The discovery, design and development of materials are critically linked to advances in many areas of research, and optics is no exception. Recently, the spectral region in which the index of refraction of a material approaches zero has become a topic of interest owing to fascinating phenomena, such as static light, enhanced nonlinearities, light t...

For decades, nonlinear optics has been used to control the frequency and propagation of light in unique ways enabling a wide range of applications such as ultrafast lasing, sub-wavelength imaging, and novel sensing methods. Through this, a key thread of research in the field has always been the development of new and improved nonlinear materials to...

Major technological breakthroughs are often driven by advancements in materials research, and optics is no different. Over the last few years, near-zero-index (NZI) materials have triggered significant interest owing to their exceptional tunability of optical properties and enhanced light-matter interaction, leading to several demonstrations of com...

Novel materials, with enhanced light–matter interaction capabilities, play an essential role in achieving the lofty goals of nonlinear optics. Recently, epsilon‐near‐zero (ENZ) media have emerged as a promising candidate to enable the enhancement of several nonlinear processes including refractive index modulation and harmonic generation. Here, the...

The conversion of a photon’s frequency has long been a key application area of nonlinear optics. It has been discussed how a slow temporal variation of a material’s refractive index can lead to the adiabatic frequency shift (AFS) of a pulse spectrum. Such a rigid spectral change has relevant technological implications, for example, in ultrafast sig...

Plasmonic-based integrated nanophotonic modulators, despite their promising features, have one key limiting factor of large insertion loss (IL), which limits their practical potential. To combat this, we utilize a plasmon-assisted approach through the lens of surface-to-volume ratio to realize a 4-slot based EAM with an extinction ratio (ER) of 2.6...

Refractive index invariably describes the speed at which light passes through materials, and subsequently its perceived momentum. But what happens to these quantities as the index becomes zero? A new work explores this question, highlighting how momentum in near-zero-index materials affects linear optical processes.

In nonlinear optics, significant effort is concentrated on improving the strength and efficiency of interactions; however, experimentally investigating nonlinear materials is a complex, time-consuming, and costly investment. Moreover, it is often challenging to isolate, study, and optimize material parameters in an experiment due to complexities in...

Subwavelength epsilon-near-zero (ENZ) films with decorated nanoantennae are an emerging platform for coupling radiation into the ENZ mode: recent experiments have shown how strong coupling between the two systems underpins significant nonlinear effects. Field enhancement and the temporal dynamic of the radiation in ENZ films strongly coupled with p...

Electromagnetic radiation when coupled to collective oscillations of free electrons, dubbed as plasmonics, makes it possible to manipulate light at dimensions well below the diffraction limit and substantially enhances light–matter interaction. Plasmonics has already enabled many novel technologies with a wide variety of application in chemical and...

A mechanically robust metasurface exhibiting plasmonic colors across the visible and the near-IR spectrum is designed, fabricated, and characterized. Thin TiN layers (41 nm in thickness) prepared by plasma-enhanced atomic layer deposition (ALD) are patterned with sub-wavelength apertures (75 nm to 150 nm radii), arranged with hexagonal periodicity....

Titanium nitride (TiN) is a highly sought‐after material for plasmonics and nanophotonics applications owing to its gold‐like but tunable optical properties. Its prodigious potential in plasmonic devices has been demonstrated on sapphire or bulk MgO substrates. For a transformational impact, high optical quality TiN on Si is required instead, which...

Raw data from D. Fomra et al "Al:ZnO as a platform for near-zero-index photonics: enhancing the doping efficiency of atomic layer deposition" Opt. Mater. Express 10(12), 2020.

We report a plasmon-driven thermomechanical switch, which is actuated using the ohmic losses of plasmons as a highly concentrated and thermally isolated heat source. This device operates with sub-15ns switching time and sub-10mW power consumption.

We demonstrate an on-chip hybrid plasmonic-waveguide based trapping system to combine electro-thermo-plasmonic flow and negative thermophoretic force with optical gradient force in realizing stable (8 KBT) and fast (within seconds) trapping of sub-nm particles (10 nm).

Novel materials, with enhanced light-matter interaction capabilities, play an essential role in achieving the lofty goals of nonlinear optics. Recently, Epsilon-Near-Zero (ENZ) media have emerged as a promising candidate to enable the enhancement of several nonlinear processes including refractive index modulation and harmonic generation. Here, we...

Raw data from D. Fomra et al "Plasmonic titanium nitride via atomic layer deposition: a low-temperature route" J. Appl. Phys. 127(10), 2020.

For decades, nonlinear optics has been used to control the frequency and propagation of light in unique ways enabling a wide range of applications such as ultrafast lasing, sub-wavelength imaging, and novel sensing methods. Through this, a key thread of research in the field has always been the development of new and improved nonlinear materials to...

To integrate plasmonic devices into industry, it is essential to develop scalable and CMOS compatible plasmonic materials. In this work, we report high plasmonic quality titanium nitride (TiN) on c-plane sapphire grown by plasma-enhanced atomic layer deposition. TiN with low losses, high metallicity, and a plasma frequency below 500 nm was achieved...

To integrate plasmonic devices into industry, it is essential to develop scalable and CMOS compatible plasmonic materials. In this work, we report high plasmonic quality titanium nitride (TiN) on c-plane sapphire by plasma enhanced atomic layer deposition (PE-ALD). TiN with low losses and high metallicity was achieved at temperatures below 500{\deg...

Titanium nitride is widely used in plasmonic applications, due to its robustness and optical properties which resemble those of gold. Despite this interest, the nonlinear properties have only recently begun to be investigated. In this work, beam deflection and non-degenerate femtosecond pump-probe spectroscopy (800 nm pump and 650 nm probe) were us...

Epsilon-near-zero materials have recently come onto the scene as promising new nonlinear optical materials. However, this field is quite crowded and it is prudent to ask whether they possess any key features which will elevate them above other candidates. It is our opinion that they in fact possess two such features, a simultaneous intrinsic and ex...

We investigate adiabatic frequency conversion using epsilon near zero (ENZ) materials and show that while the maximum frequency conversion for a given change of permittivity does not exhibit increase in the vicinity of epsilon=0 condition. However, that change can be achieved in a shorter length, and if the pump is also in the ENZ vicinity, at a lo...

We investigate adiabatic frequency conversion using epsilon near zero (ENZ) materials and show that while the maximum frequency conversion for a given change of permittivity does not exhibit increase in the vicinity of {\epsilon}=0 condition. However, that change can be achieved in a shorter length, and if the pump is also in the ENZ vicinity, at a...

To optimize the excitation and predict behavior of nonlinear interactions in near-zero-index media, physically accurate models are needed. We describe a phenomenological model that can extract standard coefficients and optical excitation conditions.

We demonstrate high plasmonic quality TiN on Si (001) via PE-ALD. Employment of an MgO buffer improved the figure of merit (FoM) at 1550 nm from 2.0 to 2.5 and the peak FoM from 2.4 to 2.8.

Patterned titanium nitride films grown via PE-ALD exhibit plasmonic colors along with being scratch resistant and durable making them an attractive choice for applications that require robust materials such as security holograms and labels.

A solid-state hybrid photonic-plasmonic (HPP) waveguide geometry has been experimentally demonstrated with plasmonic titanium nitride. The configuration is made with robust fabrication techniques, CMOS-compatible materials, and features a straightforward design with dielectric cladding layers that exhibit a significant index mismatch with the subst...

A nearly monolayer, closely‐packed nanoparticle deposition is demonstrated by a dual‐droplet inkjet printing process. The colloidal nanoparticles in a wetting droplet spread on a supporting droplet and self‐assemble into a monolayer film at the interface. Upon solvent evaporation, the nearly monolayer deposition forms on the substrate, which exhibi...

For nearly two decades, researchers in the field of plasmonics 1 -which studies the coupling of electromagnetic waves to the motion of free electrons near the surface of a metal 2 -have sought to realize subwavelength optical devices for information technology3-6, sensing7,8, nonlinear optics9,10, optical nanotweezers 11 and biomedical applications...

The well‐known coffee‐ring effect causes colloidal particles to convectively transport toward the contact line of an inkjet droplet leading to a nonuniform deposition of the colloidal particles. In this work, the self‐assembly of colloidal particles in a dual‐droplet inkjet printing configuration to produce a nearly monolayer closely packed deposit...

We investigate the color of polystyrene metasurfaces printed via a novel dual-droplet ink-jet technique resulting in a closely-packed hexagonal formation through self-assembly. Simulations, Mie Theory, and Bragg Diffraction calculations are utilized for spectra validation.

Using the optical beam deflection method we measure the transient optical nonlinearity of titanium nitride thin films deposited at 350° and 800° C around their respective epsilon near-zero wavelengths.

We show that Ohmic losses in plasmonic modulators can be bypassed by using a resonant scheme. This enables the first modulator that unites low-loss, high-speed, compact footprint and low-electrical energy consumption.

We investigate the quality of atomic layer deposited Titanium nitride thin films and find metallicity close to high quality sputtered films on both sapphire and silicon for a deposition temperature of 375°C.

We investigate and find that the quality of titanium nitride grown at 350°C and 375°C using atomic layer deposition on silicon and sapphire substrates respectively are approaching the metallicity of sputtered films.

By combining first principles theoretical calculations and experimental optical and structural characterization such as spectroscopic ellipsometry, X-ray spectroscopy, and electron microscopy, we study the dielectric permittivity and plasmonic properties of ultrathin TiN films at an atomistic level. Our results indicate a remarkably persistent meta...

Plasmonics is a rapidly developing field at the boundary of physical optics and condensed matter physics. It studies phenomena induced by and associated with surface plasmons—elementary polar excitations bound to surfaces and interfaces of good nanostructured metals. This Roadmap is written collectively by prominent researchers in the field of plas...

This corrects the article DOI: 10.1038/ncomms15829.

Nanophotonics and metamaterials have revolutionized the way we think about optical space (ɛ,μ), enabling us to engineer the refractive index almost at will, to confine light to the smallest of the volumes, and to manipulate optical signals with extremely small footprints and energy requirements. Significant efforts are now devoted to finding suitab...

Supplementary Notes, Supplementary Figures, Supplementary Discussion and Supplementary References

Overcoming the challenge of growing ultrathin metallic films is of great importance for practical applications of nanoplasmonic structures. In the present work, epitaxial, ultrathin (<10 nm) films of plasmonic TiN are grown on MgO using DC reactive magnetron sputtering. The optical properties of the films are studied through variable angle spectros...

The field of nanophotonics has ushered in a new paradigm of light manipulation by enabling deep subdiffraction confinement assisted by metallic nanostructures. However, a key limitation which has stunted a full development of high-performance nanophotonic devices is the typical large losses associated with the constituent metals. Although silver ha...

The field of integrated plasmonics is multifaceted in a way that few other disciplines in applied science are, mainly due to its intrinsic "hybrid" nature of combining materials and strategies borrowed from electronics and photonics. Because of the multitude of angles under which the plasmonic world could be analyzed, and also because of the intrin...

Towards the fabrication of all-dielectric nanophotonic devices with tunable capabilities, we combined interband and intraband nonlinearities in aluminum-doped zinc oxide thin films thus enlarging the material bandwidth and gaining ultra-fast control over the transmitted spectrum.

The development of optical metamaterials enabled new light?matter interaction effects based on nano-structural engineering rather than the natural properties of the constituent materials. This facilitated applications unachievable with natural materials; however, practical applications of the proposed three-dimensional devices are limited by costly...