arXiv subjects

Daniel Wasserman

Publications and source records attributed to Daniel Wasserman.

14 recordsLinked to original sources

arXiv2026

Surface Modification for III-V Selective Area Molecular Beam Epitaxy of Non-Selective Mask Materials

Selective-area embedded regrowth of III-V semiconductors by molecular beam epitaxy enables the seamless integration of metals and dielectrics into crystalline material for novel design of optoelectronic devices. However, traditional masks like $SiO_2$ and $Si_{3}N_{4}$ limit the design of high-contrast photonics in the infrared due to their high extinction coefficients at technologically relevant wavelengths. Consequently, there is a need to explore alternative mask materials to expand the selective area molecular beam epitaxy capabilities beyond those traditionally used. This study evaluates the deposition selectivity of the alternative materials $Al_{2}O_{3}$, $TiO_2$, and $HfO_2$, films with preferable spectral responses but higher surface reactivity. It was found that $Al_{2}O_{3}$ exhibits promising selective growth characteristics within typical GaAs growth temperatures, $HfO_2$ demonstrated a high non-selectivity dominated by Ga adsorption on the mask at temperatures up to 650 $^\circ$C, and $TiO_2$ proved reactive during deposition. To achieve selective growth of highly non-selective and even reactive mask materials, a surface modification technique was employed to improve the selective growth characteristics of any given film. Selective growth of $Si_{3}N_{4}$ and $TiO_2$ films was achieved with the application of a thin $SiO_2$ capping layer utilizing growth conditions typical of the GaAs/$SiO_2$ system. The relationship between the thickness of $SiO_2$ caps and growth selectivity was examined, revealing that sub-1 nm capping layers can significantly influence the mask surface chemistry, indicating that by depositing a thin layer of $SiO_2$, $SiO_2$-like selectivity for any mask material can be realized without degrading its optical response.

cond-mat.mtrl-sci↗

arXiv2026

Thin Film AlN Microbolometer for Very Long-Wave Infrared Detection

We demonstrate a suspended thin-film aluminum nitride (AlN) microbolometer for narrowband very long-wave infrared detection. The device uses a 100-nm-thick AlN membrane suspended above a Pt back reflector by a 1-um air gap. Resonant absorption is set by the AlN transverse optical phonon near 15.4 um and is strengthened by suspension above the reflector. A periodic perforation pattern reduces membrane thermal mass and enhances absorption without further thinning the film. DC resistance measurements under tunable infrared illumination verify bolometric operation, and the measured spectral response follows the absorption profile expected from spectroscopic measurement of passive devices. Narrowband response is observed in the 14--18 um range, with peak responsivity of 920.8 ppm/mW at 15.48 um. This platform can enable compact wavelength-selective thermal detectors for multispectral imaging, on-chip infrared spectroscopy, and chemical sensing.

physics.optics↗

arXiv2026

Enhanced Interband Optical Nonlinearities from Coupled Quantum Wells

The recent, rapid advances in nonlinear chipscale nanophotonics in the visible and near-infrared have been largely driven by manipulating the local dielectric environment proximate to decades-old workhorse bulk nonlinear optical materials, rather than increasing the inherent strength of their nonlinear response. While proposed decades ago, we demonstrate the first experimental realization of a new class of designer nonlinear materials that leverage the interband optical transition in asymmetric structures to provide strong second order susceptibility, $\chi^{(2)}$. Using simple AlGaAs/GaAs coupled quantum wells operating in the near-infrared as a prototype, we observed strong second harmonic generation enhancement of 1550 nm to 775 nm over bulk controls. Extracted $\chi^{(2)}$ values were as high as 2750 pm/V, which is $>$7x that of bulk GaAs. Furthermore, measured susceptibilities agreed well with quantum mechanical calculations of $\chi^{(2)}$ using layer profiles extracted from electron microscopy. Growth interruptions were employed to improve interfacial abruptness in response to electron microscopy characterization, resulting in increased $\chi^{(2)}$ toward the simulation predictions for ideal heterointerfaces. More complex layer designs showed predicted $\chi^{(2)}$ up to 7 nm/V. Such materials are anticipated to find myriad applications, including entangled photon generation at telecommunications wavelengths for chipscale quantum information processing.

physics.optics↗

arXiv2025

Lateral Cavity-Enhanced Guided Mode Resonance Structures for Mid-wave Infrared Photodetector Pixels

We present the design, fabrication, and optical characterization of ultra-compact mid-wave infrared photodetector pixels. Our design relies on a guided mode resonance structure to confine incident mid-infrared light to the 250 nm-thick absorber region of all-epitaxially-grown material stack, and a hybrid cavity-guided mode resonance to confine the mode in the lateral direction. The resulting pixel, with deep subwavelength thickness and lateral dimensions on the order of almost two times free space operating wavelength is predicted to achieve external quantum efficiency of the order of 50%. Our work opens the door for truly compact mid-wave infrared pixels that offer the combined benefits of low dark current, room temperature operation, and small lateral size.

physics.optics↗

arXiv2025

Infrared Metaplasmonics

Plasmonic response in metals, defined as the ability to support subwavelength confinement of surface plasmon modes, is typically limited to a narrow frequency range below the metals' plasma frequency. This places severe limitations on the operational wavelengths of plasmonic materials and devices. However, when the volume of a metal film is massively decreased, highly confined quasi-two-dimensional surface plasmon modes can be supported out to wavelengths well beyond the plasma wavelength. While this has, thus far, been achieved using ultra-thin (nm-scale) metals, such films are quite difficult to realize, and suffer from even higher losses than bulk plasmonic films. To extend the plasmonic response to the infrared, here we introduce the concept of metaplasmonics, representing a novel plasmonic modality with a host of appealing properties. By fabricating and characterizing a series of metaplasmonic nanoribbons, we demonstrate large confinement, high quality factors, and large near-field enhancements across a broad wavelength range, extending well beyond the limited bandwidth of traditional plasmonic materials. We demonstrate $35\times$ plasmon wavelength reduction, and our numerical simulations suggest that further wavelength reduction, up to a factor of 150, is achievable using our approach. The demonstration of the metaplasmonics paradigm offers a promising path to fill the near- and mid-infrared technological gap for high quality plasmonic materials, and provides a new material system to study the effects of extreme plasmonic confinement for applications in nonlinear and quantum plasmonics.

physics.optics↗

arXiv2024

Plasmonic Metal Oxide Nanocrystals as Building Blocks for Infrared Metasurfaces

Based on experimental and simulation methods we helped develop, we are advancing mechanistic understanding of how self-assembled NC metamaterials can produce distinctive near- and far-field optical properties not readily achievable in lithographically patterned structures. First, the impacts of the inevitable defects and disorder associated with self-assembly can be rationalized and, in some cases, recognized as advantageous. Second, self-assembly enables intimate nanoscale intermixing of different NC and molecular components. By incorporating probe molecules within the gaps between NCs where the electric field enhancement is strongest, we show enhanced detection of molecular vibrations that can be optimized by tuning the size and resonance frequency of the NCs. We show how metasurfaces incorporating mixtures of NCs with different doping concentrations can achieve epsilon-near-zero dielectric response over a broad frequency range. Finally, considering the NC metasurface itself as a building block, we show how photonic structures incorporating these assemblies can harness and amplify their distinctive properties. Through modeling the NC monolayer as a slab with an effective permittivity response, we designed a frequency-tunable IR perfect absorber by layering the NCs on a simple open cavity structure. Since the perfect absorption architecture further enhances the IR electric field localization strength, we expect that this integration strategy can enhance molecular vibration coupling or non-linear optical response. The versatility of the NC assembly and integration approach suggests opportunities for various metal oxide NC superstructures, including mixing and stacking of NCs beyond a single monolayer, representing a vast parameter space for design of linear and nonlinear IR optical components.

physics.optics↗

arXiv2023

Perfect Absorption at the Ultimate Thickness Limit in Planar Films

Reducing device volume is one of the key requirements for advanced nanophotonic technologies, however this demand is often at odds with designing highly absorbing elements which usually require sizeable thicknesses, such as for detector and sensor applications. Here we theoretically explore the thickness limitations of perfectly absorbing resonant systems and show surprisingly low bounds on minimal required thicknesses for total light absorption in thin planar films. We present a framework for understanding, predicting, and engineering topologically protected perfect absorption in a wide range of resonantly absorbing materials. The proposed analytical approach leads to a simple relation between a perfect absorbers thickness and dielectric function loss, which also serves as a guide for determining the absorption potential of existing and emerging materials at the ultimate thickness limit. The presented results offer new insights into the extremes of light-matter interaction and can facilitate the design of ultra-sensitive light absorbers for detector and sensor systems.

physics.optics↗

arXiv2021

Low-threshold InP quantum dot and InGaP quantum well visible lasers on silicon (001)

Monolithically combining silicon nitride (SiNx) photonics technology with III-V active devices could open a broad range of on-chip applications spanning a wide wavelength range of ~400-4000 nm. With the development of nitride, arsenide, and antimonide lasers based on quantum well (QW) and quantum dot (QD) active regions, the wavelength palette of integrated III-V lasers on Si currently spans from 400 nm to 11 {\mu}m with a crucial gap in the red-wavelength regime of 630-750 nm. Here, we demonstrate the first red InGaP QW and far-red InP QD lasers monolithically grown on CMOS compatible Si (001) substrates with continuous-wave operation at room temperature. A low-threshold current density of 550 A/cm2 and 690 A/cm2 with emission at 680-730 nm was achieved for QW and QD lasers on Si, respectively. This work takes the first vital step towards integration of visible red lasers on Si allowing the utilization of integrated photonics for applications including biophotonic sensing, quantum computing, and near-eye displays.

physics.optics↗

arXiv2021

Bright mid-infrared photoluminescence from high dislocation density epitaxial PbSe films on GaAs

We report on photoluminescence in the 3-7 $\mu$m mid-wave infrared (MWIR) range from sub-100 nm strained thin films of rocksalt PbSe(001) grown on GaAs(001) substrates by molecular beam epitaxy. These bare films, grown epitaxially at temperatures below 400 {\deg}C, luminesce brightly at room temperature and have minority carrier lifetimes as long as 172 ns. The relatively long lifetimes in PbSe thin films are achievable despite threading dislocation densities exceeding $10^9$ $cm^{-2}$ arising from island growth on the nearly 8% lattice- and crystal-structure-mismatched GaAs substrate. Using quasi-continuous-wave and time-resolved photoluminescence, we show Shockley-Read-Hall recombination is slow in our high dislocation density PbSe films at room temperature, a hallmark of defect tolerance. Power-dependent photoluminescence and high injection excess carrier lifetimes at room temperature suggest that degenerate Auger recombination limits the efficiency of our films, though the Auger recombination rates are significantly lower than equivalent, III-V bulk materials and even a bit slower than expectations for bulk PbSe. Consequently, the combined effects of defect tolerance and low Auger recombination rates yield an estimated peak internal quantum efficiency of roughly 30% at room temperature, unparalleled in the MWIR for a severely lattice-mismatched thin film. We anticipate substantial opportunities for improving performance by optimizing crystal growth as well as understanding Auger processes in thin films. These results highlight the unique opportunity to harness the unusual chemical bonding in PbSe and related IV-VI semiconductors for heterogeneously integrated mid-infrared light sources constrained by tight thermal budgets in new device designs.

cond-mat.mtrl-sci↗

arXiv2021

Ultra-Thin All-Epitaxial Plasmonic Detectors

We present an infrared photodetector leveraging an all-epitaxial device architecture consisting of a 'designer' plasmonic metal integrated with a quantum-engineered detector structure, all in a mature III-V semiconductor material system. Incident light is coupled into surface plasmon-polariton modes at the detector/'designer' metal interface, and the strong confinement of these modes allows for a sub-diffractive ($\sim \lambda_0 / 33$) detector absorber layer thickness, effectively decoupling the detector's absorption efficiency and dark current. We demonstrate high-performance detectors operating at non-cryogenic temperatures (T = 195 K), without sacrificing external quantum efficiency, and superior to well established and commercially-available detectors. This work provides a practical and scalable plasmonic optoelectronic device architecture with real world mid-infrared applications.

physics.optics↗

arXiv2020

Enhanced Room Temperature Infrared LEDs using Monolithically Integrated Plasmonic Materials

Remarkable systems have been reported recently using the polylithic integration of semiconductor optoelectronic devices and plasmonic materials exhibiting epsilon-near-zero (ENZ) and negative permittivity. In traditional noble metals, the ENZ and plasmonic response is achieved near their plasma frequencies, limiting plasmonic optoelectronic device design flexibility. Here, we leverage an all-epitaxial approach to monolithically and seamlessly integrate designer plasmonic materials into a quantum dot light emitting diode (LED), leading to a ~5.6 x enhancement over an otherwise identical non-plasmonic control sample. Devices exhibited optical powers comparable, and temperature performance far superior, to commercially-available devices.

physics.app-ph↗

arXiv2019

Ballistic Metamaterials

The interaction of free electrons with electromagnetic excitation is the fundamental mechanism responsible for ultra-strong confinement of light that, in turn, enables biosensing, near-field microscopy, optical cloaking, sub-wavelength focusing, and super-resolution imaging. These unique phenomena and functionalities critically rely on the negative permittivity of optical elements resulting from the free electrons. As result, progress in nanophotonics and nano-optics is often related to the development of new negative permittivity (plasmonic) media at the optical frequency of interest. Here we show that the essential mobility of free charge carriers in such conducting media dramatically alters the well-known optical response of free electron gases. We demonstrate that a ballistic resonance associated with the interplay of the time-periodic motion of the free electrons in the confines of a sub-wavelength scale nanostructure and the time periodic electromagnetic field leads to a dramatic enhancement of the electric polarization of the medium - to the point where a plasmonic response can be achieved in a composite material using only positive bulk permittivity components. This ballistic resonance opens the fields of plasmonics, nanophotonics, and metamaterials to many new constituent materials that until now were considered unsuitable for such applications, and extends the operational frequency range of existing materials to substantially shorter wavelengths. As a proof of concept, we experimentally demonstrate that ballistic resonance in all-semiconductor metamaterials results in strongly anisotropic (hyperbolic) response well above the plasma frequencies of the metamaterial components.

physics.optics↗

arXiv2016

Epsilon-Near-Zero Photonics Wires for Mid-Infrared Optical Lumped Circuitry

There has been recent interest in the development of optical analogues of lumped element circuitry, where optical elements act as effective optical inductors, capacitors, and resistors. Such optical circuitry requires the photonic equivalent of electrical wires, structures able carry optical frequency signals to and from the lumped circuit elements while simultaneously maintaining signal carrier wavelengths much larger than the size of the lumped elements. Here we demonstrate the design, fabrication, and characterization of hybrid metal/doped-semiconductor 'photonic wires' operating at optical frequencies with effective indices of propagation near-zero. Our samples are characterized by polarization and angle-dependent FTIR spectroscopy and modeled by finite element methods and rigorous coupled wave analysis. We demonstrate coupling to such photonic wires from free space, and show the effective wavelength of the excited mode to be approximately an order of magnitude larger than the free-space wavelength of our light. The operational length of the photonic wires approaches twice the free space wavelength, significantly longer than what is achievable with bulk epsilon near zero materials. The novel architecture utilized in our hybrid waveguides allows for significant design flexibility by control of the semiconductor material's optical properties and the sample geometry. In addition, by utilizing a semiconductor-based architecture, our photonic wires can be designed to monolithically integrate the optical equivalents of capacitive, inductive, and resistive lumped circuit elements, as well optoelectronic sources and detectors. As such, the demonstrated photonic wires have the potential to provide a key component, and a realistic framework, for the development of optical circuitry.

physics.optics↗

arXiv2011

Funneling Light Through a Subwavelength Aperture with Epsilon-Near-Zero Materials

Integration of the next generation of photonic structures with electronic and optical on-chip components requires the development of effective methods for confining and controlling light in subwavelength volumes. Several techniques enabling light coupling to sub-wavelength objects have recently been proposed, including grating-, and composite-based solutions. However, experi-mental realization of these couplers involves complex fabrication with \sim 10nm resolution in three dimensions. One promising alternative to complex coupling structures involves materials with vanishingly small dielectric permittivity, also known as epsilon-near-zero (ENZ) materials. In contrast to the previously referenced approaches, a single at layer of ENZ-material is expected to provide effcient coupling between free-space radiation and sub-wavelength guiding structures. Here we report the first direct observation of bulk-ENZ-enhanced transmission through a subwavelength slit, accompanied by a theoretical study of this phenomenon. Our study opens the door to multiple practical applications of ENZ materials and ENZ-based photonic systems.

physics.optics↗