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Electricity from thermal sources It is desirable to harvest as much energy as possible from processes that produce useful amounts of heat and convert it from waste into electrical power. Thermoelectrics and thermophotovoltaics can harness and convert heat waste but tend to operate at high temperatures. Davids et al. designed and fabricated a complementary metal-oxide semiconductor infrared photonic device that can harvest and recover energy from low-temperature thermal sources (see the Perspective by Raman). Using a new conversion mechanism, they experimentally demonstrate large thermal-to-electrical power generation in a bipolar grating-coupled tunneling device, rivaling the best thermoelectric devices. The device design could be used for energy harvesting of waste heat and the development of compact thermal batteries. Science , this issue p. 1341 ; see also p. 1301

Energy harvesting from relatively low-temperature heat sources is important in applications where long-term power sources are needed such as deep space radioisotope thermoelectric generators (RTGs). Current solutions exhibit low efficiency, require exotic materials and structures, and direct contact to the heat source. While the infrared rectenna is currently low efficiency, the path exists for high-efficiency solid state devices. We have made a scalable design using standard CMOS processes, allowing for large-area fabrication. This would allow devices to be made on the wafer scale using existing fabrication technology. The rectenna has the advantage of using radiated power, thus it does not require direct contact to the hot source, but instead must only view the source. This will simplify packaging requirements and make a more robust system. The devices are monolithic and thus robust to adverse operating environments. Here we will discuss the rectenna's physics of operation, particularly light coupling into the structure. Incoming light is coupled to a metal-oxide-semiconductor (MOS) tunnel diode via a broad-area nanoantenna. The nanoantenna consists of a subwavelength metal patterning that concentrates the light into the tunnel diode where the optical signal is rectified. Both the nanoantenna and tunnel diode are distributed devices utilizing the entire area of the surface. The nanoantenna also serves as one contact of the tunnel diode. This direct integration of the nanoantenna and diode overcomes the resistive loss limitations found in prior IR rectenna concepts that resembled microwave rectenna designs scaled down to infrared sizes. We will show simulation and experimental results of fabricated devices. Simulations of the optical fields in the tunnel gap are illustrative of device operation and will be discussed. The measured infrared photocurrent is compared to simulated expectations. Far-field radiation power conversion is demonstrated using standard radiometric techniques and correlated with the rectified current response. We discuss thermal modelling of the localized heat generation within the rectenna structure to demonstrate the lack of a thermoelectric response. Lastly, we discuss future directions of work to improve power conversion efficiency.

We demonstrate thinned resonant longwave infrared detectors with quantum efficiencies of over 60% in the longwave infrared. This improvement over unthinned detectors is made possible by a nanoantenna that confines the incident optical energy in a reduced volume compared to traditional detector architectures.

Direct rectification of electromagnetic radiation is a well-established method for wireless power conversion in the microwave region of the spectrum, for which conversion efficiencies in excess of 84% have been demonstrated. Scaling to the infrared or optical part of the spectrum requires ultrafast rectification that can only be obtained by direct tunnelling. Many research groups have looked to plasmonics to overcome antenna-scaling limits and to increase the confinement. Recently, surface plasmons on heavily doped Si surfaces were investigated as a way of extending surface-mode confinement to the thermal infrared region. Here we combine a nanostructured metallic surface with a heavily doped Si infrared-reflective ground plane designed to confine infrared radiation in an active electronic direct-conversion device. The interplay of strong infrared photon-phonon coupling and electromagnetic confinement in nanoscale devices is demonstrated to have a large impact on ultrafast electronic tunnelling in metal-oxide-semiconductor (MOS) structures. Infrared dispersion of SiO2 near a longitudinal optical (LO) phonon mode gives large transverse-field confinement in a nanometre-scale oxide-tunnel gap as the wavelength-dependent permittivity changes from 1 to 0, which leads to enhanced electromagnetic fields at material interfaces and a rectified displacement current that provides a direct conversion of infrared radiation into electric current. The spectral and electrical signatures of the nanoantenna-coupled tunnel diodes are examined under broadband blackbody and quantum-cascade laser (QCL) illumination. In the region near the LO phonon resonance, we obtained a measured photoresponsivity of 2.7 mA W(-1) cm(-2) at -0.1 V.

A sensitive optical detector is presented based on a deeply depleted graphene-insulator-semiconducting (D2GIS) junction, which offers the possibility of simultaneously leveraging the advantages of both charge integration and localized amplification. Direct read-out and built-in amplification are accomplished via photogating of a graphene field-effect transistor (GFET) by carriers generated within a deeply depleted low-doped silicon substrate. Analogous to a depleted metal-oxide-semiconducting junction, photo-generated charge collects in the potential well that forms at the semiconductor/insulator interface and induces charges of opposite polarity within the graphene film modifying its conductivity. This device enables simultaneous photo-induced charge integration with continuous “on detector” readout through use of graphene. The resulting devices exhibit responsivities as high as 2,500 A/W (25,000 S/W) for visible wavelengths and a dynamic range of 30 dB. As both the graphene and device principles are transferrable to arbitrary semiconductor absorbers, D2GIS devices offer a high-performance paradigm for imaging across the electromagnetic spectrum.

We examine integration of a patterned metal nanoantenna (or metasurface) directly onto long-wave infrared detectors. These structures show significantly improved external quantum efficiency compared to their traditional counterparts. We will show simulation and experimental results.

We examine the vacuum infrared photoresponse of a large-area nanoantenna-coupled tunnel diode rectenna resulting from thermal radiation from a temperature controlled heater. The measured infrared photocurrent is obtained as a function of the source temperature, sample distance and view factor. Far-field radiation power conversion is examined using standard radiometric techniques and correlated with the rectified current response.

High-quality infrared focal plane arrays (FPAs) are used in many satellite, astronomical, and terrestrial applications. These applications require highly-sensitive, low-noise FPAs, and therefore do not benefit from advances made in low-cost thermal imagers where reducing cost and enabling high-temperature operation drive device development. Infrared detectors used in FPAs have been made for decades from alloys of mercury cadmium telluride (MCT). These infrared detectors are nearing the believed limit of their performance. This limit, known in the infrared detector community as Rule 07, dictates the dark current floor for MCT detectors, in their traditional architecture, for a given temperature and cutoff wavelength. To overcome the bounds imposed by Rule 07, many groups are working on detector compounds other than MCT. We focus on detectors employing III-V-based gallium-free In As Sb superlattice active regions while also changing the basic architecture of the pixel to improve signal-to-noise. Our architecture relies on a resonant, metallic, subwavelength nanoantenna patterned on the absorber surface, in combination with a Fabry-Perot cavity, to couple the incoming radiation into tightly confined modes near the nanoantenna. This confinement of the incident energy in a thin layer allows us to greatly reduce the volume of the absorbing layer to a fraction of the free-space wavelength, yielding a corresponding reduction in dark current from spontaneously generated electron-hole pairs in the absorber material. This architecture is detector material agnostic and could be applied to MCT detector structures as well, although we focus on using superlattice antimonide-based detector materials. This detector concept has been applied to both mid-wave (3–5 μm) and longwave (8–12 μm) infrared detectors and absorbers. Here we examine long-wave devices, as these detectors currently have a larger gap between desired device performance and that of currently existing detectors. The measured structures show an external quantum efficiency exceeding 50%. We present a comparison of the modeled and measured photoresponse of these detectors and compare these detectors to currently available commercial detectors using relevant metrics such as external quantum efficiency. We also discuss modeling of crosstalk between adjacent pixels and its influence on the potential for a dual-wavelength detector. Finally, we evaluate potential advances in these detectors that may occur in the near future.

We demonstrate a silicon photonic transceiver circuit to implement polarization encoding/decoding for DV-QKD. The circuit is capable of encoding BB84 states with >30 dB PER and decoding with >20 dB ER.

We present experimental results for a selective epitaxially grown Ge-on-Si separate absorption and charge multiplication (SACM) integrated waveguide coupled avalanche photodiode (APD) compatible with our silicon photonics platform. Epitaxially grown Ge-on-Si waveguide-coupled linear mode avalanche photodiodes with varying lateral multiplication regions and different charge implant dimensions are fabricated and their illuminated device characteristics and high-speed performance is measured. We report a record gain-bandwidth product of 432 GHz for our highest performing waveguide-coupled avalanche photodiode operating at 1510nm. Bit error rate measurements show operation with BER< 10-12, in the range from -18.3 dBm to -12 dBm received optical power into a 50 Ω load and open eye diagrams with 13 Gbps pseudo-random data at 1550 nm.

Si-Ge lateral avalanche photodiodes (Si-Ge LAPDs) are promising devices for single photon detection, but they also have technology challenges. Si-Ge LAPDs are CMOS compatible and capable of detecting photons near the 1550 nm telecommunications bands. However, the Si-Ge LAPD exhibits a unique avalanche multiplication process in silicon, where the electrons and holes follow curved paths in three-dimensional space. Traditional models for the analysis of the avalanche multiplication process assume one-dimensional paths for the carriers that undergo the chains of impact ionizations; therefore, they are not suitable for analyzing the avalanche properties of Si-Ge LAPDs. In this paper, the statistics of the avalanche process in the Si-Ge LAPD are modeled analytically using a method that was recently developed by our group for understanding the avalanche multiplication in nanopillar, core-shell GaAs avalanche photodiodes, for which the electric field is non-uniform in magnitude and direction. Specifically, the calculated mean avalanche gain and the excess noise are presented for the Si-Ge LAPD device. It is also shown that the avalanche characteristics depend upon the specific avalanche path taken by the carrier, which depends, in turn, on the lateral location where each photon is absorbed in the Ge absorber. This property can be exploited to achieve reduced excess noise as well as wavelength-sensitive single-photon detection.

We present experimental results for a Ge on Si separate absorption and charge multiplication (SACM) integrated waveguide coupled avalanche photodiode (APD) compatible with our silicon photonics platform. Our linear mode APD has a gain-bandwidth product in excess of 200 GHz. Furthermore, we demonstrate error free operation (BER< 10−12) with our waveguide coupled linear mode APD using pseudo-random bit sequence (PBRS) data at 10 Gb/s.

Conversion of plane waves to surface waves prior to detection allows key advantages in changes to the architecture of the detector pixels in a focal plane array. We have integrated subwavelength patterned metal nanoantennas with various detector materials to incorporate these advantages: midwave infrared indium gallium arsenide antimonide detectors and longwave infrared graphene detectors. Nanoantennas offer a means to make infrared detectors much thinner by converting incoming plane waves to more tightly bound and concentrated surface waves. Thinner architectures reduce both dark current and crosstalk for improved performance. For graphene detectors, which are only one or two atomic layers thick, such field concentration is a necessity for usable device performance, as single pass plane wave absorption is insufficient. Using III-V detector material, we reduced thickness by over an order of magnitude compared to traditional devices. We will discuss Sandia’s motivation for these devices, which go beyond simple improvement in traditional performance metrics. The simulation methodology and design rules will be discussed in detail. We will also offer an overview of the fabrication processes required to make these subwavelength structures on at times complex underlying devices based on III-V detector material or graphene on silicon or silicon carbide. Finally, we will present our latest infrared detector characterization results for both III-V and graphene structures.

We examine gated-Geiger mode operation of an integrated waveguide-coupled Ge-on-Si lateral avalanche photodiode (APD) and demonstrate single photon detection at low dark count for this mode of operation. Our integrated waveguide-coupled APD is fabricated using a selective epitaxial Ge-on-Si growth process resulting in a separate absorption and charge multiplication (SACM) design compatible with our silicon photonics platform. Single photon detection efficiency and dark count rate is measured as a function of temperature in order to understand and optimize performance characteristics in this device. We report single photon detection of 5.27% at 1310 nm and a dark count rate of 534 kHz at 80 K for a Ge-on-Si single photon avalanche diode. Dark count rate is the lowest for a Ge-on-Si single photon detector in this range of temperatures while maintaining competitive detection efficiency. A jitter of 105 ps was measured for this device.

We have examined graphene absorption in a range of graphene-based infrared devices that combine either monolayer or bilayer graphene with three different gate dielectrics. Electromagnetic simulations show that the optical absorption in graphene in these devices, an important factor in a functional graphene-based detector, is strongly dielectric-dependent. These simulations reveal that plasmonic excitation in graphene can significantly influence the percentage of light absorbed in the entire device, as well as the graphene layer itself, with graphene absorption exceeding 25% in regions where plasmonic excitation occurs. Notably, the dielectric environment of graphene has a dramatic influence on the strength and wavelength range over which the plasmons can be excited, making dielectric choice paramount to final detector tunability and sensitivity.

We examined the spectral responsivity of a 1.77 μm thick type-II superlattice based long-wave infrared detector in combination with metallic nanoantennas. Coupling between the Fabry-Perot cavity formed by the semiconductor layer and the resonant nanoantennas on its surface enables spectral selectivity, while also increasing peak quantum efficiency to over 50%. Electromagnetic simulations reveal that this high responsivity is a direct result of field-enhancement in the absorber layer, enabling significant absorption in spite of the absorber's subwavelength thickness. Notably, thinning of the absorbing material could ultimately yield lower photodetector noise through a reduction in dark current while improving photocarrier collection efficiency. The temperature- and incident-angle-independent spectral response observed in these devices allows for operation over a wide range of temperatures and optical systems. This detector paradigm demonstrates potential benefits to device performance with applications throughout the infrared.

Organic materials that have desirable luminescence properties, such as a favorable emission spectrum and high luminescence efficiency, are not necessarily suitable for single layer organic light-emitting diodes (LEDs) because the material may have unequal carrier mobilities or contact limited injection properties. As a result, single layer LEDs made from such organic materials are inefficient. In this article, we present device model calculations of single layer and bilayer organic LED characteristics that demonstrate the improvements in device performance that can occur in bilayer devices. We first consider an organic material where the mobilities of the electrons and holes are significantly different. The role of the bilayer structure in this case is to move the recombination away from the electrode that injects the low mobility carrier. We then consider an organic material with equal electron and hole mobilities but where it is not possible to make a good contact for one carrier type, say electrons. Th...

We present calculations of single layer organic light emitting diode (LED) characteristics using a device model which includes charge injection, transport, recombination, and space charge effects in the organic material. Contact limited and ohmic contacts, high and low carrier mobilities, and device thicknesses from 5 to 200 nm are considered. The scaling of device current with applied voltage bias and organic film thickness is described for contact limited and ohmic contacts. Calculated device current, light output, and quantum and power efficiency are presented for representative cases of material and device parameters. These results are interpreted using the calculated spatial variation of the electric field, charge density, and recombination rate density in the devices. We find that efficient single layer organic LEDs are possible for a wide range of organic material and contact parameters.

We present a unified device model for single layer organic light emitting diodes (LEDs) which includes charge injection, transport, and space charge effects in the organic material. The model can describe both injection limited and space charge limited current flow and the transition between them. We specifically considered cases in which the energy barrier to injection of electrons is much larger than that for holes so that holes dominate the current flow in the device. Charge injection into the organic material occurs by thermionic emission and by tunneling. For Schottky energy barriers less than about 0.3–0.4 eV, for typical organic LED device parameters, the current flow is space charge limited and the electric field in the structure is highly nonuniform. For larger energy barriers the current flow is injection limited. In the injection limited regime, the net injected charge is relatively small, the electric field is nearly uniform, and space charge effects are not important. At smaller bias in the injection limited regime, thermionic emission is the dominant injection mechanism. For this case the thermionic emissioninjection current and a backward flowing interface recombination current, which is the time reversed process of thermionic emission, combine to establish a quasi-equilibrium carrier density. The quasi-equilibrium density is bias dependent because of image force lowering of the injection barrier. The net device current is determined by the drift of these carriers in the nearly constant electric field. The net device current is much smaller than either the thermionic emission or interface recombination current which nearly cancel. At higher bias, injection is dominated by tunneling. The bias at which tunneling exceeds thermionic emission depends on the size of the Schottky energy barrier. When tunneling is the dominant injection mechanism, a combination of tunnelinginjection current and the backflowing interface recombination current combine to establish the carrier density. We compare the model results with experimental measurements on devices fabricated using the electroluminescent conjugated polymer poly[2-methoxy, 5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] which by changing the contacts can show either injection limited behavior or space charge limited behavior.

We show simulation results of the integration of a nanoantenna in close proximity to the active material of a photodetector. The nanoantenna allows a much thinner active layer to be used for the same amount of incident light absorption. This is accomplished through the nanoantenna coupling incoming radiation to surface plasmon modes bound to the metal surface. These modes are tightly bound and only require a thin layer of active material to allow complete absorption. Moreover, the nanoantenna impedance matches the incoming radiation to the surface waves without the need for an antireflection coating. While the nanoantenna concept may be applied to any active photodetector material, we chose to integrate the nanoantenna with an InAsSb photodiode. The addition of the nanoantenna to the photodiode requires changes to the geometry of the stack beyond the simple addition of the nanoantenna and thinning the active layer. We will show simulations of the electric fields in the nanoantenna and the active region and optimized designs to maximize absorption in the active layer as opposed to absorption in the metal of the nanoantenna. We will review the fabrication processes.

We present a device model to describe polymer light‐emitting diodes (PLEDs) under bias conditions for which strong electrical injection does not occur (i.e., reverse, zero, and weak forward bias). The model is useful to interpret: capacitance–voltage measurements, which probe the charged trap density in the PLEDs; electroabsorption measurements on PLEDs, which probe the built‐in electric field in the device; and internal photoemission measurements, which probe the effective Schottky barriers at the contacts of the PLED. The device model is based on the low‐density nondegenerate continuum model for the electronic structure of polymers. Polarons and bipolarons are the principal charged excitations in this model. Polarons are singly charged excitations which play the primary role in charge injection and in experiments such as internal photoemission which probe single particle interface properties. Bipolarons are doubly charged excitations which can play an important role in establishing Schottky barriers at ...

A multifunction low-power, high-speed silicon photonic chip consisting of a resonant modulator and germanium detector is quilt packaged with CMOS receiver and driver electronics. Experimental data demonstrates this new route for intimate 2D-integration.

We review the physics of photon-phonon coupling in guided wave systems, and discuss new opportunities for information transduction aorded by nanoscale connement of light and phonons within a novel class of optome- chanical waveguide systems. We present a fundamental analysis of optical forces generated through nanoscale light-matter interactions, and use these insights to develop new approaches for broadband signal processing via optomechanics. Recent experimental results will also be discussed.

We demonstrate the effects of integrating a nanoantenna to a midwave infrared (MWIR) focal plane array (FPA). We model an antenna-coupled photodetector with a nanoantenna fabricated in close proximity to the active material of a photodetector. This proximity allows us to take advantage of the concentrated plasmonic fields of the nanoantenna. The role of the nanoantenna is to convert free-space plane waves into surface plasmons bound to a patterned metal surface. These plasmonic fields are concentrated in a small volume near the metal surface. Field concentration allows for a thinner layer of absorbing material to be used in the photodetector design and promises improvements in cutoff wavelength and dark current (higher operating temperature). While the nanoantenna concept may be applied to any active photodetector material, we chose to integrate the nanoantenna with an InAsSb photodiode. The geometry of the nanoantenna-coupled detector is optimized to give maximal carrier generation in the active region of the photodiode, and fabrication processes must be altered to accommodate the nanoantenna structure. The intensity profiles and the carrier generation rates in the photodetector active layers are determined by finite element method simulations, and iteration between optical nanoantenna simulation and detector modeling is used to optimize the device structure.

Recent advance in controlling optical forces using nanostructures suggests that nanoscale optical waveguides are capable of generating coherent acoustic phonons efficiently through a combination of radiation pressure and electrostriction. We discuss the critical roles of group velocity in such processes. This photon-phonon coupling would allow an acoustic intermediary to perform on-chip optical delay with a capacity 10 5 greater than photonic delay lines of the same size.

We show that the nature of stimulated Brillouin scattering (SBS) radically changes at nanoscales due to tremendous internal radiation pressures. Coherent interplay between radiation pressure and electrostriction yields giant enhancement of SBS and tailorable photon-phonon coupling.

We propose and experimentally demonstrate nano-antenna emitters coupled to a dielectric waveguide. Initial measured emitter efficiencies are 4.9–13% with simulations predicting > 50% efficiencies with bandwidths exceeding 300nm in more advanced and ideally fabricated geometries.

We examine a new class of infrared (IR) plasmonic devices that convert thermal radiation into bound surface plasmon polaritons (SPP's). The coupling of these SPP's into nanometer scale metal insulator metal (MIM) channels is investigated both theoretically and experimentally. A new mechanism for detection of the IR radiation is examined that is based on direct rectification of a traveling MIM surface plasmon mode.

Radiation pressure is known to scale to large values in engineered micro and nanoscale photonic waveguide systems. In addition to radiation pressure, dielectric materials also exhibit strain-dependent refractive index changes, through which optical fields can induce electrostrictive forces. To date, little attention has been paid to the electrostrictive component of optical forces in high-index contrast waveguides. In this paper, we examine the magnitude, scaling, and spatial distribution of electrostrictive forces through analytical and numerical models, revealing that electrostrictive forces increase to large values in high index-contrast waveguides. Similar to radiation pressure, electrostrictive forces increase quadratically with the optical field. However, since electrostrictive forces are determined by the material photoelastic tensor , the sign of the electrostrictive force is highly material-dependent, resulting in cancellation with radiation pressure in some instances. Furthermore, our analysis reveals that the optical forces resulting from both radiation pressure and electrostriction can scale to remarkably high levels (i.e., greater than 10(4)(N/m(2))) for realistic guided powers. Additionally, even in simple rectangular waveguides, the magnitude and distribution of both forces can be engineered at the various boundaries of the waveguide system by choice of material system and geometry of the waveguide. This tailorability points towards novel and simple waveguide designs which enable selective excitation of elastic waves with desired symmetries through engineered stimulated Brillouin scattering processes in nanoscale waveguide systems.

Radiation pressure is known to scale to large values in the context of micro and nano-scale photonic waveguide systems. However, little has been done to address electrostrictively induced forces, which also scale quadratically with electric field. In this paper, we perform detailed analysis of both radiation pressure and electrostricitve optical forces generated in high-index contrast optical waveguides. Through analysis of the material- and geometry-dependent design degrees of freedom associated with the electrostrictive and radiation pressure induced forces, we show that the magnitude and distribution of such forces can be tailored at the various boundaries of the waveguide system.

Plasmonic integrated optics is an attempt to bridge the length scale gap between optics and nanometer scale electronic devices. Here we present a hybrid optical interconnect scheme which utilizes low loss dielectric waveguides for global interconnection and plasmonic structures for tightly confining light for local routing and mode manipulation.

We present design, fabrication, and characterization results of a highly absorptive surface in the thermal infrared that draws on concepts from the frequency selective surface and metamaterials communities. At normal incidence this optically thin surface has an absorption of over 99%. Furthermore, it has a broad angular range (over 90% absorption at 60 degrees from normal). The simple structure is composed of a reflective metal layer, a roughly quarter-wave layer of lossy dielectric, and a top metal layer that is patterned with an array of subwavelength apertures. The design of the aperture allows spectral and angular control of the absorption/emission band. We will present simulation and measured results. Change in waveband and polarization could easily be changed from pixel to pixel in a focal plane array.

Plasmonic structures open up new opportunities in photonic devices, sometimes offering an alternate method to perform a function and sometimes offering capabilities not possible with standard optics. In this LDRD we successfully demonstrated metal coatings on optical surfaces that do not adversely affect the transmission of those surfaces at the design frequency. This technology could be applied as an RF noise blocking layer across an optical aperture or as a method to apply an electric field to an active electro-optic device without affecting optical performance. We also demonstrated thin optical absorbers using similar patterned surfaces. These infrared optical antennas show promise as a method to improve performance in mercury cadmium telluride detectors. Furthermore, these structures could be coupled with other components to lead to direct rectification of infrared radiation. This possibility leads to a new method for infrared detection and energy harvesting of infrared radiation.

Fabrication and optical characterization of surfaces covered with open-ended metallic waveguides are presented along with numerical modeling of these structures. Both modeling and measurement of the structures indicate that the 2-D array of 3D metallic waveguides modify both the direction and spectral content of the emissivity, resulting in directionality normal to the surface due to the optical axis of the waveguides and spectrally narrow emissivity due to the lateral dimensions of the waveguides. Furthermore, the optical behavior of these structures is placed in the broader context of other structured emission/absorption surfaces such as organ pipe modes, surface plasmon modes, and coherent thermal emission from gratings.

A complementary metal oxide semiconductor (CMOS) compatible version of membrane projection lithography (MPL) for fabrication of micrometer-scale three-dimensional structures is presented. The approach uses all inorganic materials and standard CMOS processing equipment. In a single layer, MPL is capable of creating all 5 2D-Bravais lattices. Furthermore, standard semiconductor processing steps can be used in a layer-by-layer approach to create fully three dimensional structures with any of the 14 3D-Bravais lattices. The unit cell basis is determined by the projection of the membrane pattern, with many degrees of freedom for defining functional inclusions. Here we demonstrate several unique structural motifs, and characterize 2D arrays of unit cells with split ring resonators in a silicon matrix. The structures exhibit strong polarization dependent resonances and, for properly oriented split ring resonators (SRRs), coupling to the magnetic field of a normally incident transverse electromagnetic wave, a response unique to 3D inclusions.

We present experimental and device model results for the current–voltage characteristics of a series of organic diodes. We consider three general types of structures: electron only, hole only, and bipolar devices. Electron and hole mobility parameters are extracted from the corresponding single carrier structures and then used to describe the bipolar devices. The device model successfully describes the experimental results for: electron only devices as thickness is varied, hole only devices as the contact metals are varied, and bipolar devices are both the thickness and the contact metals are varied.

We present device model calculations of the current–voltage (I–V) characteristics of organic diodes and compare them with measurements of structures fabricated using MEH-PPV. The structures are designed so that all of the current is injected from one contact. The I–V characteristics are considered as a function of the Schottky energy barrier to charge injection from the contact. Experimentally, the Schottky barrier is varied from essentially zero to more than 1 eV by using different metal contacts. A consistent description of the device I–V characteristics is obtained as the Schottky barrier is varied from small values, less than about 0.4 eV, where the current flow is space-charge limited to larger values where it is contact limited.

We present device model calculations for the current–voltage (I–V) characteristics of organic diodes and compare them with measurements of structures fabricated using MEH‐PPV. The measured I–V characteristics have a Fowler–Nordheim (FN) functional form, but are more than three orders of magnitude smaller than the calculated FN tunneling current. We find that the low mobility of the organic materials leads to a large backflow of injected carriers into the injecting contact. These results account for the experimental observations and also demonstrate how transport layers in multilayer organic light‐emitting diodes can be used to improve carrier injection.

Spoof surface modes on nanostructured metallic surfaces are known to have tailorable dispersion dependent on the geometric characteristics of the periodic pattern. Here we examine the spoof plasmon dispersion on an isolated grating and a grating-planar mirror cavity configuration. The spoof polariton dispersion in the cavity is obtained using the scattering matrix approach, and the related differential modal density of states is introduced to obtain the mode dispersion and classify the cavity polariton modes. The grating-mirror cavity geometry is an example of periodically nanostructured metals above a planar ground plane. The properties discussed here are relevant for applications ranging from thin electromagnetic perfect absorbers to near-field radiative heat transfer., Comment: 14 pages, 7 figures

An optical phased array of nanoantenna fabricated in a CMOS compatible silicon photonics process is presented. The optical phased array is fed by low loss silicon waveguides with integrated ohmic thermo-optic phase shifters capable of 2π phase shift with ∼ 15 mW of applied electrical power. By controlling the electrical power to the individual integrated phase shifters fixed wavelength steering of the beam emitted normal to the surface of the wafer of 8° is demonstrated for 1 × 8 phased arrays with periods of both 6 and 9 μm.

We present a compact 1.3 × 4 μm2 Germanium waveguide photodiode, integrated in a CMOS compatible silicon photonics process flow. This photodiode has a best-in-class 3 dB cutoff frequency of 45 GHz, responsivity of 0.8 A/W and dark current of 3 nA. The low intrinsic capacitance of this device may enable the elimination of transimpedance amplifiers in future optical data communication receivers, creating ultra low power consumption optical communications.

We examine the long-wave infrared (LWIR) optical characteristics of heavily-doped silicon and explore engineering of surface plasmons polaritons (SPP) in this spectral region. Both phosphorus (n-type Si) and boron (p-type Si) implants are evaluated and various cap layers and thermal annealing steps are examined. The optical properties are measured using ellipsometry and fit to a Drude model for the infrared (IR) permittivity. The predicted metallic behavior for Si in the thermal IR and its impact on the spatial confinement and dispersion for surface plasmons is studied. We find that the transverse spatial confinement for a surface plasmon on highly doped Si is strongly sub-wavelength near the plasma edge, and the confinement to the surface is enhanced to greater than 10× that of the metal confined SPP over the entire LWIR spectrum.

Compact, low capacitance optical modulators are vital for efficient, high-speed chip to chip optical interconnects. Electro-optic (EO) polymer cladding micro-ring resonator modulators have been fabricated and their performance is characterized. Optical modulators with ring diameters smaller than 50 microm have been demonstrated in a silicon nitride based waveguide system on silicon oxide with a top cladding of an electro-optic polymer. Optical modulation has been observed with clock signals up to 10 GHz.