Joseph S T Smalley

University of California, Berkeley | UCB

The demand for essential pixel components with ever-decreasing size and enhanced performance is central to current optoelectronic applications, including imaging, sensing, photovoltaics and communications. The size of the pixels, however, are severely limited by the fundamental constraints of lightwave diffraction. Current development using transmi...

A special class of anisotropic media, hyperbolic metamaterials and metasurfaces (HMMs), has attracted much attention in recent years due to its unique abilities to manipulate and engineer electromagnetic waves on the subwavelength scale. Because all HMM designs require metal dielectric composites, the unavoidable metal loss at optical frequencies i...

Acoustic communication is crucial in underwater exploration, where sound is the dominant information carrier, with significantly less loss and scattering than that of electromagnetic waves. However, the capacity of acoustic communication channels is limited due to the intrinsically low speed of sound relative to that of electromagnetic waves and be...

We experimentally demonstrate a type II hyperbolic metamaterials (HMMs) using the recently emerged perovskite gain material and Au. The hyperbolic dispersion of the fabricated device is investigated by measuring its polarization anisotropy.

We survey expressions of the effective modal volume, Veff, commonly used in the literature for nanoscale photonic and plasmonic cavities. We apply different expressions of Veff to several canonical cavities designed for nanoscale near-infrared light sources, including metallo-dielectric and coaxial geometries. We develop a metric for quantifying th...

We design, fabricate and analyze a nanostructured plasmonic light emitting diode (LED) that simultaneously increases the modulation speed and radiative efficiency, compared to conventional LEDs and unpatterned plasmonic LEDs respectively. Our structure, optimized to ensure its integrability with electrical contacts, couples an InGaN/GaN blue LED wi...

The first generation of hyperbolic metamaterials, metasurfaces, and naturally hyperbolic materials (HMMs) utilized the static and passive properties of their constituent metallic and dielectric components to achieve intriguing macroscopic behavior, such as imaging and focusing of light below the diffraction limit and the broadband modification to t...

We present an analytical technique for designing integrated polarized light-emitting diodes (LEDs) and polarization-sensitive photodiodes (PD) based on hyperbolic metasurfaces (HMS) for the detection of optical activity. Leveraging effective medium theory and the scattering matrix method, we first derive the conditions for optimizing the transmissi...

A novel method is presented to outcouple high spatial frequency (large-k) waves from hyperbolic metamaterials (HMMs) without the use of a grating. This approach relies exclusively on dispersion engineering, and enables preferential power extraction from the top or from the side of a HMM. Multilayer (ML) HMMs are shown to be better suited for latera...

Extremely compact nanoscale devices such as electrically pumped nanolasers are difficult to operate at room temperature due to the high electrical resistance inherent to small cavities. As a consequence, large voltages are necessary to reach the lasing threshold, which generates heat and reduces device efficiency. The poor heat sinking of small dev...

Significance The ability to perfectly absorb light with optically thin materials poses a significant challenge for many applications such as camouflage, light detection, and energy harvesting. Current designs require planar reflectors that crack and delaminate after heating or flexing. Moreover, they cannot be transferred to more desirable substrat...

When engineered on scales much smaller than the operating wavelength, metal-semiconductor nanostructures exhibit properties unobtainable in nature. Namely, a uniaxial optical metamaterial described by a hyperbolic dispersion relation can simultaneously behave as a reflective metal and an absorptive or emissive semiconductor for electromagnetic wave...

Supplementary Figures, Supplementary Notes and Supplementary References.

We review the current applications of photonic technologies to Smart Cities. Inspired by the future needs of Smart Cities, we then propose potential applications of advanced photonic technologies. We find that photonics already has a major impact on Smart Cities, in terms of smart lighting, sensing, and communication technologies. We further find t...

Plasmonic modes provide the potential for routing information with optical speeds and bandwidth at the nanoscale. The inherent tradeoff between modal energy confinement and energy dissipation, however, makes realizing this potential an extreme challenge. For decades, researchers have investigated compensating losses in plasmonic systems with active...

The integration of a photonic information processing system onto a single chip requires great research effort toward engineering metamaterials for miniaturization of the optical devices and circuits. We discuss nanoscale engineered optical nonlinearities for modulation and wave mixing of optical fields, and metal-dielectric-semiconductor nanostruct...

We fabricate and characterize a luminescent hyperbolic metamaterial consisting of InGaAsP/Ag multilayers. For the first time, one of the metamaterial constituents is a gain media. The hyperbolic dispersion is confirmed through the anisotropic photoluminescence, with emission strongly dependent on pump polarization.

Hyperbolic metasurfaces (HMS) combine the potential for chip-scale integration of optical metasurfaces with the properties of hyperbolic dispersion. In the ideal, lossless effective medium limit, HMS have an unbound optical density of states (DOS). The unbound DOS enables infinite mode densities in waveguides and cavities, and, in principal, an inf...

We demonstrate light-emitting hyperbolic metasurfaces in the 1200-1600nm spectral range. The multilayer configuration, ideal for planar integration, enables characterization of hyperbolic dispersion by polarization anisotropy of photoluminescence. OCIS codes: (160.3918) Metamaterials; (250.5230) Photoluminescence; (160.1190) Anisotropic optical mat...

Aluminum-doped zinc oxide (AZO) is a tunable low-loss plasmonic material capable of supporting dopant concentrations high enough to operate at telecommunication wavelengths. Due to its ultrahigh conformality and compatibility with semiconductor processing, atomic layer deposition (ALD) is a powerful tool for many plasmonic applications. However, de...

Using effective medium theory (EMT), Bloch’s theorem (BT), and the transfer matrix method (TMM), we analyze the possibility of gain-enhanced transmission in metamaterials with hyperbolic dispersion at telecommunication frequencies. We compare different combinations of dissipative metals and active dielectrics, including noble metals, transparent co...

Using established nanofabrication techniques, we realize deeply subwavelength multilayer metal-dielectric nanostructures composed of silver and indium gallium arsenide phosphide (InGaAsP). In contrast to most, if not all, subwavelength multilayer metal-dielectric systems to date, the Bloch vector of the fabricated structure is parallel to the plane...

We analyze the steady-state transmission of high-momentum (high-k) electromagnetic waves through metal-semiconductor multilayer systems with loss and gain in the near-infrared (NIR). Using a semi-classical optical gain model in conjunction with the scattering matrix method (SMM), we study indium gallium arsenide phosphide (InGaAsP) quantum wells as...

We analyze the steady-state transmission of high-momentum (high-$k$) electromagnetic waves through metal-semiconductor multilayer systems with loss and gain in the near-infrared (NIR). Using a semi-classical optical gain model in conjunction with the scattering matrix method (SMM), we study indium gallium arsenide phosphide (InGaAsP) quantum wells...

We present general conditions for lossless propagation in near-infrared hyperbolic metamaterial (HMM) waveguides with lateral confinement. We conclude that HMMs based on noble metals, rather than transparent conducting oxides, offer greatest promise for low-loss propagation.

In this manuscript we discuss state of the art hybrid integration techniques and III-V/Si active components with an emphasis on hybrid distributed feedback (DFB) lasers for telecom applications. We review our work on ultra-compact III-V/Si DFB lasers and further describe design considerations and challenges associated with electrically pumped hybri...

As the field of semiconductor nanolasers becomes mature in terms of both the miniaturization to the true sub-wavelength scale, and the realization of room temperature devices, the integrated treatment of multiple design aspects beyond pure electromagnetic consideration becomes necessary to further advance the field. In this review, we focus on one...

We implement amorphous-Al2O3 as thermally-conductive shield in metallo-dielectric nanolasers, and demonstrate an electrically pumped device. Joint consideration of various design parameters reveals that this design allows the laser to dissipate heat through its shield, aiding thermal management in nanoscale devices.

Dense photonic integration requires miniaturization of materials, devices and subsystems, including passive components (e.g., engineered composite metamaterials, filters, etc.) and active components (e.g., lasers, modulators, detectors). This paper discusses passive and active devices that recently have been demonstrated in our laboratory and desig...

Currently there is a strong interest in plasmonic materials operating in the near-infrared (NIR), however, conventional metals such as gold and silver possess high optical losses in this region. In this work we demonstrate localized surface plasmon resonances (LSPRs) with low loss in the NIR region by utilizing atomic layer deposition to deposit th...

We present a method for studying amplification of electromagnetic modes in active, circularly symmetric waveguides with hyperbolic dispersion. Using this method, we obtain a closed-form expression for the modal threshold condition. We find that modal amplification is possible in a region of the radius-wavelength phase-space with small enough radius...

We analyze amorphous Al2O3 ( (alpha ) -Al2O3) for use as a thick thermally conductive shield in metallo-dielectric semiconductor nanolasers, and show that the use of (alpha ) -Al2O3 allows a laser to efficiently dissipate heat through its shield. This new mechanism for thermal management leads to a significantly lower operating temperature within t...

We present several improvements to the understanding of strained silicon’s second-order optical nonlinearity. In addition to incorporating the material into electro-optic modulators and wave-mixers, we analyze the nature of the optical nonlinearity on the nanoscale.

We theoretically consider the existence of multiple nonzero components of the second-order nonlinear susceptibility tensor, χ ( 2 ) , generated via strain-induced symmetry breaking in crystalline silicon. We determine that, in addition to the previously reported χ x x y ( 2 ) component, the χ y y y ( 2 ) component also becomes nonzero based on the...

Metal-clad subwavelength lasers have recently become excellent candidates for light sources in densely packed chip-scale photonic circuits. In this review, we summarize recent research efforts in the theory, design, fabrication, and characterization of such lasers. We detail advancements of both the metallo-dielectric and the coaxial type lasers: f...

We perform two analyses on temperature effects in Metal-Clad Subwavelength Semiconductor Lasers (MCSELs). Firstly, we analyze the temperature dependence of the threshold gain in the infinite waveguide approximation. We show that the dielectric layer of the semiconductor-dielectric-metal composite waveguide (CWG) becomes increasingly important as te...

Metal nanocavity-based lasers show promise for dense integration in nanophotonic devices, thanks to their compact size and lack of crosstalk. Thermal considerations in these devices have been largely overlooked in design, despite the importance of self-heating and heat dissipation to device performance. We discuss the sources of self-heating in ele...

We carry out a theoretical analysis of strained silicon's nonlinear optical properties, and present experimental validations of our predictions. Additionally, we discuss strained silicon's applicability to electro-optic modulators and wave-mixers.

We implement α-Al2O3 as the shield in metallo-dielectric nanolasers, and demonstrate an electrically pumped device. Joint consideration of various design parameters reveals that this design allows the laser to dissipate heat through its shield.

Accounting for the temperature dependence of the cavity resonances and gain medium, we investigate a metal-clad subwavelength semiconductor laser with a spontaneous emission factor, β, approaching unity for all temperatures.

We optimize the threshold gain for cylindrical composite (semiconductor–dielectric–metal) waveguides (WGs) with various metal claddings. We show that the optimal dielectric width is invariant with respect to the imaginary part of the permittivity of the metal, ε M ′ ′ , and weakly dependent on the real part, ε M ′ . To explain this behavior, we com...

We present a formal treatment of the modification of spontaneous emission rate by a cavity (Purcell effect) in sub-wavelength semiconductor lasers. To explicitly express the assumptions upon which our formalism builds, we summarize the results of non-relativistic quantum electrodynamics (QED) and the emitter-field-reservoir model in the quantum the...

We have designed and simulated a dual-frequency liquid crystal (DFLC) based plasmonic signal modulator capable of achieving over 15 dB modulation depth. The voltage-controlled DFLC is combined with a groove and slit configuration and its operation is discussed. Using the finite-difference time domain (FDTD) method, simulations were conducted to dis...

A frequency-addressed plasmonic switch was demonstrated by embedding a uniform gold nanodisk array into dual-frequency liquid crystals (DFLCs). The optical properties of the hybrid system were characterized by extinction spectra of localized surface plasmon resonances (LSPRs). The LSPR peak was tuned using a frequency-dependent electric field. A ∼...