Proceedings of the SPIE PHOTONICS EUROPE Conference on Biophotonics in Point-of-Care, 6-10 April 2020, Online Only, France. Proc. SPIE volume 11361
The goal of this International Roadmap for Devices and Systems (IRDS) chapter is to survey, catalog, and assess the status of technologies in the areas of cryogenic electronics and quantum information processing. Application drivers are identified for sufficiently developed technologies and application needs are mapped as a function of time against projected capabilities to identify challenges requiring research and development effort. Cryogenic electronics (also referred to as low-temperature electronics or cold electronics) is defined by operation at cryogenic temperatures (below −150 °C or 123.15 K) and includes devices and circuits made from a variety of materials including insulators, conductors, semiconductors, superconductors, or topological materials. Existing and emerging applications are driving development of novel cryogenic electronic technologies. Information processing refers to the input, transmission, storage, manipulation or processing, and output of data. Information processing systems to accomplish a specific function, in general, require several different interactive layers of technology. A top-down list of these layers begins with the required application or system function, leading to system architecture, micro- or nano-architecture, circuits, devices, and materials. A fundamental unit of information (e.g., a bit) is represented by a computational state variable, for example, the position of a bead in the ancient abacus calculator or the voltage (or charge) state of a node capacitance in CMOS logic. A binary computational state variable serves as the foundation for von Neumann computational system architectures that dominated conventional computing. Quantum information processing is different in that it uses qubits, two-state quantum-mechanical systems that can be in coherent superpositions of both states at the same time, which can have computational advantages. Measurement of a qubit in a given basis causes it to collapse to one of the basis states. Technology categories covered in this report include: • Superconductor electronics (SCE) • Cryogenic semiconductor electronics (Cryo-Semi) • Quantum information processing (QIP)
Continuing miniaturization of electronic devices, together with the quickly growing number of nanotechnological applications, demands a profound understanding of the underlying physics. Most of the fundamental problems of modern condensed matter physics involve various aspects of quantum transport and fluctuation phenomena at the nanoscale. In nanostructures, electrons are usually confined to a limited volume and interact with each other and lattice ions, simultaneously suffering multiple scattering events on impurities, barriers, surface imperfections, and other defects. Electron interaction with other degrees of freedom generally yields two major consequences, quantum dissipation and quantum decoherence. In other words, electrons can lose their energy and ability for quantum interference even at very low temperatures. These two different, but related, processes are at the heart of all quantum phenomena discussed in this book.This book presents copious details to facilitate the understanding of the basic physics behind a result and the learning to technically reproduce the result without delving into extra literature. The book subtly balances the description of theoretical methods and techniques and the display of the rich landscape of the physical phenomena that can be accessed by these methods. It is useful for a broad readership ranging from master's and PhD students to postdocs and senior researchers.
The materials of The International Scientific – Practical Conference is presented below.
The Conference reflects the modern state of innovation in education, science, industry and social-economic sphere, from the standpoint of introducing new information technologies.
It is interesting for a wide range of researchers, teachers, graduate students and professionals in the field of innovation and information technologies.
We investigate superconductor–insulator quantum phase transitions in ultrathin capacitively coupled superconducting nanowires with proliferating quantum phase slips. We derive a set of coupled Berezinskii–Kosterlitz–Thouless-like renormalization group equations demonstrating that interaction between quantum phase slips in one of the wires gets modified due to the effect of plasma modes propagating in another wire. As a result, the superconductor–insulator phase transition in each of the wires is controlled not only by its own parameters but also by those of the neighboring wire as well as by mutual capacitance. We argue that superconducting nanowires with properly chosen parameters may turn insulating once they are brought sufficiently close to each other.
The distribution of charge carriers in metal halide perovskites draws strong interest of the solar cell community, with experiments demonstrating that edges of various microstructures can improve material performance. This is rather surprising since edges and grain boundaries are often viewed as the main source of charge traps. We demonstrate by ab initio quantum dynamics simulations that edges of the CH3NH3PbBr3 perovskite create shallow trap states that mix well with the valence and conduction bands of the bulk, and therefore, support mobile charge carriers. Charges are steered to the edges energetically, facilitating dissociation of photo−generated excitons into free carriers. The edge−driven charge separation extends carrier lifetimes due to decreased overlap of the electron and hole wave functions, which leads to reduction of the nonadiabatic coupling responsible for nonradiative electron−hole recombination. Reduction of spatial symmetry near the edges activates additional vibrational modes that accelerate coherence loss within the electronic subsystem, further extending carrier lifetimes. Enhanced atomic motions at edges increase fluctuations of edge energy levels, enhancing mixing with band states and improving charge mobility. The simulations contribute to the atomistic understanding of the unusual properties of metal halide perovskites, generating the fundamental knowledge needed to design high−performance optoelectronic devices.
An InAs/InGaAs quantum dot laser with a heterostructure epitaxially grown on a silicon substrate was used to fabricate injection microdisk lasers of different diameters (15-31 μm). A post-growth process includes photolithography and deep dry etching. No surface protection/passivation is applied. The microlasers are capable of operating heatsink-free in a continuous-wave regime at room and elevated temperatures. A record-low threshold current density of 0.36 kA/cm2 was achieved in 31 μm diameter microdisks operating uncooled. In microlasers with a diameter of 15 μm, the minimum threshold current density was found to be 0.68 kA/cm2. Thermal resistance of microdisk lasers monolithically grown on silicon agrees well with that of microdisks on GaAs substrates. The ageing test performed for microdisk lasers on silicon during 1000 h at a constant current revealed that the output power dropped by only ~9%. A preliminary estimate of the lifetime for quantum-dot (QD) microlasers on silicon (defined by a double drop of the power) is 83,000 h. Quantum dot microdisk lasers made of a heterostructure grown on GaAs were transferred onto a silicon wafer using indium bonding. Microlasers have a joint electrical contact over a residual n+ GaAs substrate, whereas their individual addressing is achieved by placing them down on a p-contact to separate contact pads. These microdisks hybridly integrated to silicon laser at room temperature in a continuous-wave mode. No effect of non-native substrate on device characteristics was found.
We review epitaxial formation, basic properties, and device applications of a novel type of nanostructures of mixed (0D/2D) dimensionality that we refer to as quantum well-dots (QWDs). QWDs are formed by metalorganic vapor phase epitaxial deposition of 4–16 monolayers of InxGa1−xAs of moderate indium composition (0.3 < x < 0.5) on GaAs substrates and represent dense arrays of carrier localizing indium-rich regions inside In-depleted residual quantum wells. QWDs are intermediate in properties between 2D quantum wells and 0D quantum dots and show some advantages of both of those. In particular, they offer high optical gain/absorption coefficients as well as reduced carrier diffusion in the plane of the active region. Edge-emitting QWD lasers demonstrate low internal loss of 0.7 cm−1 and high internal quantum efficiency of 87%. as well as a reasonably high level of continuous wave (CW) power at room temperature. Due to the high optical gain and suppressed non-radiative recombination at processed sidewalls, QWDs are especially advantageous for microlasers. Thirty-one μm in diameter microdisk lasers show a high record for this type of devices output power of 18 mW. The CW lasing is observed up to 110 °C. A maximum 3-dB modulation bandwidth of 6.7 GHz is measured in the 23 μm in diameter microdisks operating uncooled without a heatsink. The open eye diagram is observed up to 12.5 Gbit/s, and error-free 10 Gbit/s data transmission at 30 °C without using an external optical amplifier, and temperature stabilization is demonstrated.
The operation speed of microdisk lasers with quantum dots working at room temperature without thermal stabilization has been experimentally examined, and the widest modulation bandwidth of microdisks with various diameters has been calculated. It was shown that taking into account the effect of self-heating of a microlaser at high bias currents, which is manifested in a decrease of the ultimate operation speed and in an increase in the current at which the widest modulation bandwidth is reached, enables a good description of the experimental data. The self-heating most strongly affects microlasers with a small diameter (less than 20 μm).
Considerable attention has been given in recent years to microlasers based on microdisk and microring cavities with an active region based on quantum dots (QDs), which is due to the possibility of achieving small device sizes (down to 1 μm under optical pumping and to less than 10 μm under injection pumping ) and low threshold currents (250 A/cm2 at room temperature ) combined with the ease of fabrication of microlasers of this kind. There is no need to use distributed Bragg reflectors, current apertures, and multiple-stage lithography for fabricating these lasers, nor for epitaxial heterostructures similar to those in fabrication of stripe-contact lasers. One of the main proposed applications of microdisk lasers is optical data transmission to ultrashort distances and, in the limiting case, within an optoelectronic integrated circuit, including those based on silicon. Therefore, one of the most important device characteristics of a microdisk laser is modulation bandwidth f3 dB, defined as the frequency at which the efficiency of direct modulation decreases by 3 dB relative to its low-frequency value.
The modulation frequency can be limited due to a multitude of factors , one of which is the increase in the temperature of a device through which a high-density electric current is passed. The self-heating phenomenon is characteristic to the greatest extent of lasers with small current flow area and, therefore, has been actively studied for vertical cavity surface emitting lasers, VCSELs [4, 5]. At the same time, the influence exerted by the self-heating on the high-frequency characteristics of microdisk lasers has not, to our knowledge, been studied [6, 7]. In the present study, we examine by comparing experimental data with results of a numerical simulation the relative contribution of the self-heating to the limitation of the maximum modulation frequency of injection-type microdisk lasers with QDs, which operate at room temperature without forced cooling.
The experimental values of modulation bandwidth f3 dB reported in this Letter were determined from small-signal amplitude–frequency characteristic A(f) measured in the frequency range of 0.1–20 GHz at various bias currents. We analyzed the results obtained in studying microlasers with high-density (In,Ga)As QDs . The microlasers were formed by deep etching of an epitaxial heterostructure, followed by fabrication of electrical contacts to the substrate and to the top of the cylindrical mesa. Microlasers of this kind currently demonstrate the widest modulation bandwidth exceeding 6 GHz , which made it possible to perform an optical data transmission at a rate of 10 Gb/s .
The microlaser parameters used in our calculations are listed in Table 1. The threshold current of the microdisk lasers under study is characterized by a two-component dependence on the microlaser diameter: the summand proportional to the device area can be associated with the recombination in the bulk of the active region, while the summand proportional to its perimeter may be connected with the surface recombination on the lateral walls. The K-factor shows no regular dependence on the microlaser diameter, in agreement with theoretical predictions . According to these predictions, the diameter-dependent radiation loss caused by the cavity curvature becomes noticeable only when the cavity size is comparable with the emission wavelength. The nonlinear gain saturation coefficient is negligible, which is due to the low optical power of microdisk lasers.
We show that the density of states and gain spectra of InGaAs/GaAs quantum well-dot (QWD) hybrid nanostructures qualitatively differ from that of quantum wells (QWs) and quantum dots. In QWDs, the density of states does not increase to higher energies and ground-state lasing is maintained up to shorter cavities (higher output loss) as compared to QW lasers emitting in the same optical range. The QWD lasers show lower threshold current densities and better temperature stability than the QW ones.
Fully atomistic molecular dynamics simulations are employed to study impregnation of the poly(methyl methacrylate) (PMMA) matrix with carbamazepine (CBZ) in supercritical carbon dioxide. The simulation box consists of 108 macromolecules of the polymer sample with the polymerization degree of 100, 57 molecules of CBZ, and 242,522 CO2 molecules. The simulation is performed at 333 K and 20 MPa. It is found that by the end of the simulation, the CBZ uptake reaches 1.09 wt % and 50 molecules are sorbed by PMMA. The main type of interaction between PMMA and CBZ is hydrogen bonding between the carbonyl oxygen of PMMA and the hydrogen atoms of the CBZ NH2-group. At the polymer surface, CBZ exists not only in the molecular form, as inside the polymer and in the bulk solution, but also in the form of dimers and trimers. The energy of formation of the hydrogen-bonded complexes is estimated within ab initio calculations.
The transport properties of ion-exchange membranes depend on many factors, primarily, on ion-exchange capacity and chemical composition. Therefore, the correlation of transport properties with a single particular parameter is generally not quite strict. In this study, the dependence of transport properties of several perfluorinated sulfonated cation-exchange membranes that differ in side chain length and fraction of fragments containing ether groups on ion-exchange capacity is analyzed. It is shown that, with a decrease in the ion-exchange capacity from 1.35 to 0.66 mg-equiv/g, the proton conductivity of membranes contacting water and their diffusion permeability with respect to a 0.1 M HCl solution decrease by two orders of magnitude. A decrease in relative humidity leads to the most significant decrease in the conductivity of membranes with a low ion-exchange capacity. Thus, at a relative humidity of 32%, the conductivity of the studied membranes decreases more than 600-fold with a decrease in ion-exchange capacity. In general, the oxygen permeability of membranes is characterized by a similar dependence. However, in this set of membranes, it varies as little as threefold.
Adsorption of fluids in nanoporous media causes mechanical stresses which results in deformation. This phenomenon is ubiquitous and its magnitude depends on the pore size and geometry. Adsorption and adsorption-induced deformation are typically modeled in slit-shape or convex (cylindrical or spherical) pores. However, many porous materials are composed of spherical grains, so that the pores are formed by the intergranular spaces between the convex solid surfaces. Here we present a first theoretical study of adsorption-induced deformation in non-convex pores, in particular we studied the templated mesoporous carbons. The model is based on classical density functional theory within the local density approximation applied to the description of hard sphere interactions. We predict the adsorption isotherms and solvation pressure isotherms for nitrogen adsorption in CMK-3 carbons. The shape of adsorption isotherm matches the shape of experimental isotherm. The predicted solvation pressure isotherms are qualitatively different from the solvation pressure isotherms in cylindrical pores. We attribute this difference to formation of liquid bridges between the adjacent rods. Our results suggest that adsorption-induced deformation in materials with non-convex pores cannot be predicted within the existing models. These results may shed some light on understanding adsorption-induced deformation of consolidated granular media.