Search

Broadband terahertz spectroscopy is a valuable analytical tool in science and a promising technology for industrial non-destructive, non-contact testing, e.g. thickness measurements of thin dielectric layers. Optoelectronic conversion using photomixers is a widespread approach for coherent terahertz spectroscopy. State-of-the-art spectrometers consist of discrete, fiber-based components, leading to complex and costly setups. In cost-sensitive applications, this prevents the use of these spectrometers. We developed a terahertz spectrometer based on a dedicated photonic integrated circuit and commercial electronic integrated circuits to overcome these limitations. The photonic subsystem can be connected to commercial tunable lasers and provides the optical signal processing to drive the photoconductive antennas. The electronic subsystem includes the required drivers, analog signal processing, and data acquisition. Combined, the system measures $10 \times 16 \times 7.5$ cm3 only. We compare both subsystems individually and as a whole to state-of-the-art lab equipment in terms of spectral performance and measurement speed. Due to the flexibility in measurement modes, the integrated system can be adapted to specific measurement tasks, e.g. 2.8 THz-wide spectra within 0.5 s for high-speed, or 3.6 THz bandwidth with >80 dB dynamic range in less than 3 minutes for high-precision. This is the first realization of a terahertz spectrometer based on photonic and electronic integration rivaling state-of-the-art and non-integrated commercial spectrometers. This approach paves the way for compact and economic terahertz systems, providing access to terahertz technology for cost-sensitive sectors in research and industry.

The performance of an optoelectronic reservoir computing (RC) system for recognizing apple leaf diseases is numerically investigated. The disease spot feature extraction and selection methods suitable for time-delay RC are investigated. Two masking methods of sequence extension masking and matrix transformation masking are examined, with appropriate parameters, the optoelectronic RC achieves minimum errors of 0.01 and 0.03 under sequence extension masking and matrix masking methods, respectively. The nonlinear dynamics of the optoelectronic reservoir in the absence of data injection are compared with its recognition performance to establish the relationship between recognition capabilities and the system’s nonlinear dynamics. Additionally, we compared the recognition errors of optoelectronic RC, linear RC, and k-nearest neighbor algorithms. It illustrates that optoelectronic RC, under the nonlinear transformation of the Mach-Zehnder Modulator (MZM) and delayed feedback, can map input information nonlinearly to a high-dimensional state space, enabling effective classification along linear hyperplanes in this high-dimensional space.

We report growth and characterization of n-Si/p-SnOx heterojunction using RF sputtering for deposition of p-type SnOx under controlled growth oxygen pressure over n-type silicon (Si) wafer. The heterojunction properties of Si/SnOx were varied by controlling the growth oxygen pressure of SnOx. Several characterization techniques, including PL (photoluminescence), AFM (atomic force microscopy), FESEM (field emission scanning electron microscopy), XRD, I-V characteristics and Hall measurement, were conducted to analyze the structural, optical, and electrical properties of the n-Si/p-SnOx heterojunction. The knee voltage (Vknee), or cut-in voltage, was calculated by analyzing the gradient of the dark current-voltage (J-V) curves when the bias was applied in the forward direction. The Vknee values for type-I, type-II, and type-III n-Si/p-SnOx heterojunctions were determined to be 0.62 V, 0.84 V, and 1.0 V, respectively. The ideality factors (n1 and n2) were determined to be 1.52, 2.22, 3.52, and 8.41, 9.31, 10.34, respectively, for various heterojunction types. The reverse saturation current densities, J01 and J02 ranging from approximately 10−7 to 10−6 A/cm2, and 10−5 to 10−4 A/cm2, respectively. The objective of this experimental work is to investigate especially, the prospect of silicon /metal-oxide (Si/SnOx) based heterojunction to be used as optical sensors with tunable optoelectronic properties of SnOx.

The thermoelectric effect forms the basis of Peltier cooling that has attracted interest for solid-state refrigeration for more than a century. The dearth of materials level efficiency in converting between heat and electricity has limited widespread applications. With renewed focus on energy technologies in the past three decades, the thermoelectric effect has been intensely explored in new materials using state-of-the-art advances in materials fabrication, characterization techniques, and theory. This article aims to navigate the complex landscape of these studies to identify credible advances, pinpoint continuing problems, and lay out future prospects for both research and applications, with emphasis on electronics cooling. [ABSTRACT FROM AUTHOR]

Exploring mmWave frequencies and adopting small-cell architectures are two key enablers for increased wireless data rates. To make these evolutions economically viable, centralized architectures based on radio-over-fiber (RoF) are devised. To reduce the complexity of the cellular network even further, RF-over-Fiber transmission schemes are adopted in combination with reflective uplink operation. This paper relies on a very low complexity narrowband GaAs electronics / Si photonics transceiver for scalable RFoF architectures with which we demonstrate a fiber-wireless link capable of transmitting over 7 Gb/s in down- and uplink for a 2 km fiber and 5 m wireless link in the 28 GHz band. Furthermore, it is shown that Rayleigh degradation caused by reflective uplink operation can be avoided by using a coherent detection scheme. [ABSTRACT FROM AUTHOR]

Imaging sensors as a critical technology are greatly significant in numerous light detection applications including security monitor, smart mobile devices, machine vision, navigation, self-driving, drones and remote sensing etc. In particular, spectral imaging technology such as multispectral and hyperspectral imaging are attracting more and more attention due to the available spectral and spatial information, which provide an opportunity for deeper cognition of the detected object. However, conventional strategy for wavelength sensing by complicated optical system has obstacle in achieving lightweight, low cost, high quality image and high pixel densities. Therefore, new emerging strategies based on the nanomaterials and nanostructures involving filter-assisted and filter-free light detection are explored to achieve precise spectral discrimination. Here, we review the latest advances of these emerging approaches for spectral discrimination. Furthermore, every filter-assisted and filter-free strategy was discussed and compared in detail by analyzing their fundamental physical principles. [ABSTRACT FROM AUTHOR]

With accelerating the miniaturization process of electronic devices, multifunctional optoelectronic devices that increases the compactness between the integrated devices have attracted much attention. In this work, we prepared a 1.0 cm2 two-dimensional Bi2Te2.7Se0.3 material by pulsed laser deposition technology, and fabricated Pd/Bi2Te2.7Se0.3/SiO2/Si multifunctional optoelectronic devices. Under the light illumination, the electron separation and aggregation at the Bi2Te2.7Se0.3/SiO2 interface lead to reducing a lower interface barrier. Meanwhile, electrons in the narrow-bandgap Bi2Te2.7Se0.3 photosensitive material easily escape from shackles and are trapped at the Pd/Bi2Te2.7Se0.3 surface, resulting in the resistance switching for monolithic devices. In addition, the capture of electrons at the interface enables the device to achieve long-term storage of information. The device can perform single functions of logical sum calculation (“OR” gate), multilevel information storage, photodetection and optical information demodulation. Meanwhile, the device might simultaneously implement photodetection and demodulation, logical calculation and memory, and demodulation and storage functions, which will increase the compactness of integrated circuits and reduce power consumption. [ABSTRACT FROM AUTHOR]

Migrating toward higher frequencies and densification of the communication cells are two key enablers for increased wireless data rates. To make these trends economically viable, centralized architectures based on radio-over-fiber (RoF) are explored. This article describes the design of a photoreceiver that can be applied at the remote radio head in a 28 GHz analog RoF link. The devised photoreceiver comprises a Ge-on-Si photodetector and co-designed GaAs low noise amplifier offering 24 dB gain, corresponding to 224 V/W external conversion gain, over a 3-dB bandwidth between 23.5 and 31.5 GHz. The associated noise figure is 2.1 dB and an output referred third order intercept point up to 26.5 dBm can be obtained with a power consumption of 303 mW. Two possible applications are demonstrated in this article. First, the photoreceiver is tested in a 5G New Radio environment resulting in rms-EVM values below 2.46/3.47% for 100/400-MBaud 16-QAM transmission over the 24.25–29.5 GHz band. Secondly, very high data rates can also be supported, demonstrated by a 36 Gb/s link with an rms-EVM of 5.2%. [ABSTRACT FROM AUTHOR]

In contrast to pressure distributions that can, nowadays, easily be measured using commercial sensor sheets, this is not yet the case for frictional or shear stresses. Those stresses act parallel to a surface, which makes it more challenging to develop suitable sensors. A number of shear sensor prototypes have been reported until now, but realizing a matrix of shear sensors remains a big challenge because of cost and complexity issues. Therefore, this article presents a fabrication approach for realizing a matrix of shear sensors using standard PCB and molding technologies. The presented sensor is based on changing the coupling of optical power between a light-emitting diode and a set of photodiodes in combination with an overmolding step, as realizing a mechanical transducer. To demonstrate the fabrication flow, a first demonstrator incorporating a five-taxel sensor matrix has been realized, which is able to record the in-plane shear stress magnitude and direction. [ABSTRACT FROM AUTHOR]

The field of perovskite heterostructures (PHSs) has seen considerable progress in recent years. Particularly, these structures have attracted interest because of their remarkably efficient photovoltaic and optoelectronic properties. This paper reviews a wide range of potential applications of PHSs. The review begins by introducing and summarizing the fundamental theory of PHSs and pays special attention to their basic properties. The optical and electronic properties of PHSs are subsequently described in detail, with an emphasis on the approaches that were followed to discover these properties. The crystal structures of heterostructures are examined by observing representative studies of the perovskite crystal. Recent progress in research involving PHSs demonstrates the important role of the optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this paper, the Ga2Se3 crystals are used to design a Yb/Ga2Se3/C Schottky barrier. The device structure is investigated by the X-ray diffraction technique, which reveals a monoclinic-face-centered cubic interfacing type of structure. The barrier is studied by means of current ( $I$ )–voltage ( V$ ) characteristics in the dark and under light through photoexcitation from tungsten lamp and from the He–Ne laser. In addition, the impedance spectroscopy of these devices is studied in the frequency range of 10–1400 MHz. The photoexcited I-V$ curve analysis allowed investigating the biasing voltage, illumination power, and energy effects on the diode physical parameters, which are presented by the rectification ratio, the Schottky barrier height, the ideality factor, the series resistance, the photosensitivity, the responsivity, and the external quantum efficiency (EQE). While a maximum photosensitivity of 42 was observed for laser excitation with a wavelength of 632 nm at a reverse bias of 4.4 V, the EQE reached value of 1652% at 19.0 V. On the other hand, the ac current conduction analysis of the electrical conductivity, which was determined from the impedance spectral analysis, indicated that the ac signal processing through the Yb/Ga2Se3/C samples is due to the correlated hopping conduction through localized states of Fermi density of . The high-and biasing-dependent EQE% nominates the Yb/Ga2Se3/C as a tunable optoelectronic device. [ABSTRACT FROM PUBLISHER]

A buried quad junction (BQJ) photodetector has been designed and fabricated with a high-voltage CMOS process. It implements four vertically stacked p-n junctions with four different spectral responses. This feature allows high spectral discriminating ability, greater than both conventional buried double junction and buried triple junction detectors. In this paper, we propose a SPICE-like model, based on the physical properties of the device structure. The proposed model has been integrated in EDA software. It could be used for rapid and reliable design of system on chip, integrating the BQJ sensor, and its signal processing. The analytical expressions of the four BQJ photocurrents, as well as dark currents, have been developed. The spectral characteristics of the photodetector, computed with the proposed model, have been compared with those from TCAD simulations and experimental measurements. The analytical is close to the measurement with an average error on spectral responses in the range of 3%–17%, depending on the considered junction. [ABSTRACT FROM PUBLISHER]

A sub-bandgap optoelectronic differential ideality factor technique is proposed for extraction of the intrinsic density-of-states (DOS) over the bandgap in amorphous semiconductor thin-film transistors (TFTs). In the proposed technique, the gate bias-dependent differential change in the difference of ideality factors ( \(d\Delta \eta (V_{\mathrm {GS}})/dV_{\mathrm {GS}}\) ) between dark and sub-bandgap photonic excitation condition is employed. With the sub-bandgap photons ( \(h\nu < E_{g}\) ), the photonic excitation of electrons is confined only from the localized DOS over the bandgap. We applied the proposed technique to a-InGaZnO TFTs with \(W/L = 50/25 \mu \) m/ \(\mu \) m and extracted the energy distribution of the intrinsic DOS for the localized states over the bandgap. [ABSTRACT FROM PUBLISHER]

We present an overview of the photo-injected Fresnel zone plate antenna (piFZPA) method for non-mechanical optoelectronic beam steering. The piFZPA method enables rapid beam steering, over moderate field-of-views, at both mm-wave and submm-wave frequencies, that is suitable for a wide range of imaging and non-imaging applications. This paper develops a theoretical framework that details the design of piFZPAs and provides an understanding to, and optimization of, the piFZPA performance. As an example device, we present preliminary experimental scanning data on a transmission-type piFZPA, operating at 94 GHz, that relies on commercially available visible display technologies for plasma generation and reconfiguration. The experimental data is shown to agree well with numerical simulations and validates the theoretical framework. [ABSTRACT FROM AUTHOR]

With germanium showing significant promise in the design of electroabsorption modulators for full complementary metal oxide semiconductor integration, we present a simple electroabsorption calculator for Ge/SiGe quantum wells. To simulate the quantum-confined Stark effect electroabsorption profile, this simple quantum well electroabsorption calculator (SQWEAC) uses the tunneling resonance method, 2-D Sommerfeld enhancement, the variational method and an indirect absorption model. SQWEAC simulations are compared with experimental data to validate the model before presenting optoelectronic modulator designs for the important communication bands of 1310 nm and 1550 nm. These designs predict operation with very low energy per bit (<30∼fJ/bit). [ABSTRACT FROM AUTHOR]

In oxygenic plants, photons are captured with high quantum efficiency by two specialized reaction centers (RC) called Photosystem I (PS I) and Photosystem II (PS II). The captured photon triggers rapid charge separation and the photon energy is converted into an electrostatic potential across the nanometer-scale (\sim6~\nm) reaction centers. The exogenous photovoltages from a single PS I RC have been previously measured using the technique of Kelvin force probe microscopy (KFM). However, biomolecular photovoltaic applications require two-terminal devices. This paper presents for the first time, a micro-device for detection and characterization of isolated PS I RCs. The device is based on an AlGaN/GaN high electron mobility transistor (HEMT) structure. AlGaN/GaN HEMTs show high current throughputs and greater sensitivity to surface charges compared to other field-effect devices. PS I complexes immobilized on the floating gate of AlGaN/GaN HEMTs resulted in significant changes in the device characteristics under illumination. An analytical model has been developed to estimate the RCs of a major orientation on the functionalized gate surface of the HEMTs. [ABSTRACT FROM PUBLISHER]

Packaging is a core technology to leverage the functions and the performances of micro- and nano-structures in a system. In order to bring them to application, the gap between component and environment has to be bridged by providing reliable interfaces. This paper reviews the packaging of optoelectronic, photonic, and microelectromechanical systems (MEMS) components. State-of-the-art requirements, standard technologies, and approaches are considered. Recent trends and research results in the packaging of advanced photonic, MEMS, Si-photonic components, and in 3-D, heterogeneous integration, and SiP are discussed. [ABSTRACT FROM PUBLISHER]

This paper presents a study of millimeter-wave optoelectronic downconversion using the self-oscillating mixer concept. Baseband data are transmitted using a 40-GHz electrical carrier; however, detection only requires a much lower speed photodiode. Both homodyne and heterodyne configurations are presented with the former requiring injection locking which can limit the maximum baseband data rate. [ABSTRACT FROM PUBLISHER]

We describe the design and development of an optoelectronic lock-in amplifier (LIA) for optical sensing and spectroscopy applications. The prototype amplifier is fabricated using Taiwan Semiconductor Manufacturing Co. complementary metal–oxide semiconductor 0.35-\mum technology and uses a phototransistor array (total active area is 400 \mu\ m\times \ 640 \mum) to convert the incident optical signals into electrical currents. The photocurrents are then converted into voltage signals using a transimpedance amplifier for subsequent convenient signal processing by the LIA circuitry. The LIA is optimized to be operational at 20-kHz modulation frequency but is operational in the frequency range from 13 kHz to 25 kHz. The system is tested with a light-emitting diode (LED) as the light source. The noise and signal distortions are suppressed with filters and a phase-locked loop (PLL) implemented in the LIA. The output dc voltage of the LIA is proportional to the incident optical power. The minimum measured dynamic reserve and sensitivity are 1.31 dB and 34 \ mV/\mu\ W, respectively. The output versus input relationship has shown good linearity. The LIA consumes an average power of 12.79 mW with a 3.3-V dc power supply. [ABSTRACT FROM PUBLISHER]

High-performance and low-power network-on-chips (NoCs) will be required to support the increasing number of cores in future chip multiprocessors. In this paper, we propose a scalable low-power 64-core NoC design called PROPEL that uses emerging nanophotonic technology. PROPEL strikes a balance between cheaper electronics and more expensive optics by facilitating nanophotonic interconnects for long distance interrouter communication and electrical switching for routing and flow control. In addition, PROPEL reduces the number of required components by facilitating communication in both the x- and y-directions. We also propose a 256-core scaled version of PROPEL called E-PROPEL that uses four separate PROPEL networks connected together by an optical crossbar. We also propose two different optical crossbar implementations using single and double microring resonators, where the single microring design has minimal optical losses (-4.32 dB) and the double microring design has minimal area overhead (0.0576 mm^2). We have simulated both PROPEL and E-PROPEL using synthetic and SPLASH-2 traffic, where our results indicate that PROPEL and E-PROPEL significantly reduce power (tenfold) and increase performance (twofold) over other well-known electrical networks. [ABSTRACT FROM PUBLISHER]

The ring imaging Cherenkov (RICH) detector at LHCb is now read out by hybrid photon detectors. In view of its upgrade, a possible option is the adoption of the flat-panel photon multiplier tube (PMT). An important issue for good reconstruction of the Cherenkov rings is a negligible level of crosstalk. We have experimentally studied the crosstalk from the 16 x 16-pixels Hamamatsu H9500 PMT. Results have shown that, for the single-photon response, the statistics tied to the small number of electrons generated at the first dynode of the PMT chain (a few units) leads to a number of crosstalk signals that are a small fraction of the fired pixel.With the H9500, in a Cherenkov ring, only one or two pixels are expphoton mulected to generate crosstalk. As a consequence, crosstalk cannot be considered a limit in the use of the H9500 for the upgrade of the RICH at LHCb. [ABSTRACT FROM AUTHOR]

An indium phosphide heterojunction bipolar transistor (InP HBT) oscillator chip was monolithically integrated with an on chip p-i-n photodiode. A controllable locking range was obtained in unidirectional injection locking. High-purity optoelectronic oscillator with parasitic modes lower than -4 dBc resulted from bidirectional injection locking. The optoelectronic oscillator power consumption was 50 mW while providing output power of - 2 dBm . The overall chip size is 1.3 times 0.8 mm. [ABSTRACT FROM PUBLISHER]

We give an overview over several all-optoelectronic measurement systems which we have developed for transmittive and reflective imaging in the terahertz (THz) frequency range. The systems employ either pulsed or continuous-wave THz radiation. In both cases, they work on the basis of single-pixel scanning. Addressing the potential for imaging in the medical and dental field, and the application of THz radiation for industrial surface and interface characterization, we explore dark-field imaging where the imaging contrast originates from diffraction and scattering effects coming from topography or refractive-index variations. [ABSTRACT FROM AUTHOR]

For many micromachined sensors such as microphones and accelerometers, optical displacement sensing may have advantages over capacitive sensing—offering potentially high-displacement sensitivity independent of sensor area and gap height. A particular diffraction-based optical displacement sensor design consisting of a sensing diaphragm suspended over a rigid grated electrode has demonstrated advantages in terms of sensitivity, integration and stability. When illuminated from the backside, this structure generates a zeroth and complementary higher order diffracted beams whose intensities are modulated by the diaphragm displacement with the sensitivity of a regular Michelson interferometer, in previous work, acoustic devices surface micromachined on quartz substrates using aluminum for the diaphragm and grating were presented and characterized. in this work, we present the fabrication and characterization of a surface- and bulk-silicon micromachined diffraction-based optical microphone structure fabricated with Sandia National Laboratories' SwIFT-Lite™ process, which uses silicon nitride and polysilicon structural materials that have been employed extensively in MEMS and form a more thermally matched material set robust against corrosion and fatigue. The process introduces a new design space to microscale optical displacement sensing. enabling large, soft structures with perforated back-plates ideal for microphone and inertial-sensor designs. [ABSTRACT FROM AUTHOR]

Photonic crystals, artificial, wavelength-scale multidimensional periodic structures, have given birth to a number of realizations in semiconductors. Photonic integrated circuits, especially around new integrated lasers, are challenging directions of research for miniaturization and new functions in optical telecommunications. We review the basic physics behind such applications and underline the current status of this very active research field worldwide. [ABSTRACT FROM AUTHOR]

A Si-based light modulator working in the near infrared at frequencies up to 300 kHz is proposed. The device proposed is a bipolar mode field effect transistor (BMFET) integrated in an Si rib waveguide. The operation principle is the light dispersion/absorption by a plasma of free carriers that can be moved in or out of the optical path. It works as a pure amplitude light modulator; hence, it can be shrunk. Its small dimensions, only 100 mum in length and less than 50 mum in width in the proposed version, make it suitable for monolithic integration for applications where the major constraints are the device dimensions. As an example, the device application to an integrated gas sensing or chemical absorption spectroscopy system is also described [ABSTRACT FROM PUBLISHER]

We propose a novel method to monitor the carrier plasma distribution in a bipolar mode field effect transistor light modulator, using standard emission microscopy. Our bi-dimensional maps validate the theoretical predictions of plasma distribution as a function of the device bias. Dynamical measurements provide an experimental evidence of a frequency threshold in the electric field induced plasma distribution. Below 500 kHz generation/recombination processes while above drift phenomena allow the plasma localization in the device. An effective carrier lifetime ≥ 2 ps was extrapolated. [ABSTRACT FROM AUTHOR]

In this paper, the response of a surface-normal p-i-n photodetector that was incorporated in an optically controlled optical gate was analyzed using short-pulsed, high-energy optical inputs with small spot sizes. Simulation results based in part on diffusive conduction were compared against the experimental data, providing an understanding of the device response. Results also demonstrated that p-i-n photodetectors may be designed so that reducing the spot size, counterintuitively, results in negligible additional field screening. [ABSTRACT FROM AUTHOR]

We present optoelectronic mixing phenomenon in graphene FET (GFET) and give a brief analysis for the first time. Demonstrated by a measurement system, two operating modes of optoelectronic mixer (OE-mixer) circuits are proposed, either of them mixing optical and electrical signals directly using a single GFET. Optoelectronic conversion losses of 24 and 35 dB are obtained in a 50- $\Omega $ impedance system, respectively. GFET OE-mixer might be of strong importance for radio over fiber systems, millimeter wave, and terahertz frequencies applications. [ABSTRACT FROM AUTHOR]

We present a novel realization of a multiloop optoelectronic oscillator based on a wavelength multiplexed optical source and fiber Bragg grating reflectors. The oscillator exhibits a phase noise of -108 dBc/Hz at 10-kHz offset from the 10.2-GHz carrier while suppressing parasitic modes to below -80 dBc. [ABSTRACT FROM PUBLISHER]