As Lewis proposed his octet rule, itself inspired by Abegg’s rule, that a molecule is stable when all its composing atoms have eight electrons in their valence shell, it perfectly applied to the vast majority of know...As Lewis proposed his octet rule, itself inspired by Abegg’s rule, that a molecule is stable when all its composing atoms have eight electrons in their valence shell, it perfectly applied to the vast majority of known stable molecules. Only a few stable molecules were known that didn’t fall under this rule, such as PCl5 and SF6, and Lewis chose to leave them aside at the time of his research. With further advances in chemistry, more exceptions to this rule of eight have been found, usually with the central atom of the structure having more or less than eight electrons in its valence shell. Theories have been developed in order to modify the octet rule to suit these molecules, defining these as hyper- or hypo-valent molecules and using other configurations for the electrons. The present paper aims to propose a representation rule for gaseous single-bonded molecules that makes it possible to reconcile both;molecules following the octet theory and those which do not. In this representation rule, each element of the molecule is subscripted with two numbers that follow a set of simple criteria. The first represents the number of valence electrons of the element;while the second is calculated by adding the first number to the number of the element’s covalent bonds within the molecule. The latter is equal to eight for organic molecules following the octet rule. Molecules being exceptions to the octet rule are now encompassed by this new even-odd rule: they have a valid chemical structural formula in which the second number is even but not always equal to eight. Both rules—octet and even-odd—are discussed and compared, using several well-known gaseous molecules having one or several single-bonded elements. A future paper will discuss the application of the even-odd rule to charged molecules.展开更多
Lewis developed a 2D-representation of molecules, charged or uncharged, known as structural formula, and stated the criteria to draw it. At the time, the vast majority of known molecules followed the octet-rule, one o...Lewis developed a 2D-representation of molecules, charged or uncharged, known as structural formula, and stated the criteria to draw it. At the time, the vast majority of known molecules followed the octet-rule, one of Lewis’s criteria. The same method was however rapidly applied to represent compounds that do not follow the octet-rule, i.e. compounds for which some of the composing atoms have greater or less than eight electrons in their valence shell. In a previous paper, an even-odd rule was proposed and shown to apply to both types of uncharged molecules. In the present paper, the even-odd rule is extended with the objective to encompass all single-bonded ions in one group: Lewis’s ions, hypo- and hypervalent ions. The base of the even-odd representation is compatible with Lewis’s diagram. Additionally, each atom is subscripted with an even number calculated by adding the valence number, the number of covalent bonds of the element, and its electrical charge. This paper describes how to calculate the latter number and in doing so, how charge and electron-pairs can actually be precisely localized. Using ions known to be compatible with Lewis’s rule of eight, the even-odd rule is compared with the former. The even-odd rule is then applied to ions known as hypo- or hypervalent. An interesting side effect of the presented rule is that charge and electron-pairs are unambiguously assigned to one of the atoms composing the single-charged ion. Ions that follow the octet rule and ions that do not, are thus reconciled in one group called “electron-paired ions” due to the absence of unpaired electrons. A future paper will focus on the connection between the even-odd rule and molecules or ions having multiple bonds.展开更多
In organic chemistry, as defined by Abegg, Kossel, Lewis and Langmuir, compounds are normally represented using structural formulas called Lewis structures. In these structures, the octet rule is used to define the nu...In organic chemistry, as defined by Abegg, Kossel, Lewis and Langmuir, compounds are normally represented using structural formulas called Lewis structures. In these structures, the octet rule is used to define the number of covalent bonds that each atom forms with its neighbors and multiple bonds are frequent. Lewis’ octet rule has unfortunately shown limitations very early when applied to non-organic compounds: most of them remain incompatible with the “rule of eight” and location of charges is uncertain. In an attempt to unify structural formulas of octet and non-octet molecules or single-charge ions, an even-odd rule was recently proposed, together with a procedure to locate charge precisely. This even-odd rule has introduced a charge-dependent effective-valence number calculated for each atom. With this number and the number of covalent bonds of each element, two even numbers are calculated. These numbers are both used to understand and draw structuralformulas of single-covalent-bonded compounds. In the present paper, a procedure is proposed to adjust structural formulas of compounds that are commonly represented with multiple bonds. In order to keep them compatible with the even-odd rule, they will be represented using only single covalent bonds. The procedure will then describe the consequences of bond simplification on charges locations. The newly obtained representations are compared to their conventional structural formulas, i.e. single-bond representation vs. multiple-bond structures. Throughout the comparison process, charges are precisely located and assigned to specific atoms. After discussion of particular cases of compounds, the paper finally concludes that a rule limiting representations of multiplecovalent bonds to single covalent bonds, seems to be suitable for numerous known compounds.展开更多
Optical parametric amplification(OPA)represents a powerful solution to achieve broadband amplification in wavelength ranges beyond the scope of conventional gain media,for generating high-power optical pulses,optical ...Optical parametric amplification(OPA)represents a powerful solution to achieve broadband amplification in wavelength ranges beyond the scope of conventional gain media,for generating high-power optical pulses,optical microcombs,entangled photon pairs and a wide range of other applications.Here,we demonstrate optical parametric amplifiers based on silicon nitride(Si3N4)waveguides integrated with two-dimensional(2D)layered graphene oxide(GO)films.We achieve precise control over the thickness,length,and position of the GO films using a transfer-free,layer-by-layer coating method combined with accurate window opening in the chip cladding using photolithography.Detailed OPA measurements with a pulsed pump for the fabricated devices with different GO film thicknesses and lengths show a maximum parametric gain of~24.0 dB,representing a~12.2 dB improvement relative to the device without GO.We perform a theoretical analysis of the device performance,achieving good agreement with experiment and showing that there is substantial room for further improvement.This work represents the first demonstration of integrating 2D materials on chips to enhance the OPA performance,providing a new way of achieving high performance photonic integrated OPA by incorporating 2D materials.展开更多
Robust laser sources are a fundamental building block for contemporary information technologies.Originating from condensed-matter physics,the concept of topology has recently entered the realm of optics,offering funda...Robust laser sources are a fundamental building block for contemporary information technologies.Originating from condensed-matter physics,the concept of topology has recently entered the realm of optics,offering fundamentally new design principles for lasers with enhanced robustness.In analogy to the well-known Majorana fermions in topological superconductors,Dirac-vortex states have recently been investigated in passive photonic systems and are now considered as a promising candidate for robust lasers.Here,we experimentally realize the topological Diracvortex microcavity lasers in InAs/InGaAs quantum-dot materials monolithically grown on a silicon substrate.We observe room-temperature continuous-wave linearly polarized vertical laser emission at a telecom wavelength.We confirm that the wavelength of the Dirac-vortex laser is topologically robust against variations in the cavity size,and its free spectral range defies the universal inverse scaling law with the cavity size.These lasers will play an important role in CMOS-compatible photonic and optoelectronic systems on a chip.展开更多
Ions or molecules are said to be isoelectronic if they are composed of different elements but have the same number of electrons, the same number of covalent bonds and the same structure. This criterion is unfortunatel...Ions or molecules are said to be isoelectronic if they are composed of different elements but have the same number of electrons, the same number of covalent bonds and the same structure. This criterion is unfortunately not sufficient to ensure that a chemical structure is a valid chemical compound. In a previous article, a procedure has been described to draw 2D valid structural formulas: the even-odd rule. This rule has been applied first to single-bonded molecules then to single-charged single-bonded ions. It covers hypovalent, hypervalent or classic Lewis’ octet compounds. The funding principle of the even-odd rule is that each atom of the compound possesses an outer-shell filled only with pairs of electrons. The application of this rule guarantees validity of any single-covalent-bond chemical structure. In the present paper, this even-odd rule and its electron-pair criterion are checked for coherence with an effective-valence isoelectronic rule using numerous known compounds having single-covalent-bond connections. The test addresses Lewis’ octet ions or molecules as well as hypovalent and hypervalent compounds. The article concludes that the even-odd rule and the effective-valence isoelectronicity rule are coherent for known single-covalent-bond chemical compounds.展开更多
Sleep is a critical part of our daily routine.It impacts every organ and system of our body,from the brain to the heart and from cellular metabolism to immune function.A consistent daily schedule of quality of sleep m...Sleep is a critical part of our daily routine.It impacts every organ and system of our body,from the brain to the heart and from cellular metabolism to immune function.A consistent daily schedule of quality of sleep makes a world of difference to our health and well-being.Despite its importance,so many individuals have trouble sleeping well.Poor quality sleep has such a detrimental impact on many aspects of our lives;it affects our thinking,learning,memory,and movements.Further,and most poignantly,poor quality sleep over time increases the risk of developing a serious medical condition,including neurodegenerative disease.In this review,we focus on a potentially new non-pharmacological treatment that improves the quality of sleep.This treatment,called photobiomodulation,involves the application of very specific wavelengths of light to body tissues.In animal models,these wavelengths,when applied at night,have been reported to stimulate the removal of fluid and toxic waste-products from the brain;that is,they improve the brain’s inbuilt house-keeping function.We suggest that transcranial nocturnal photobiomodulation,by improving brain function at night,will help improve the health and well-being of many individuals,by enhancing the quality of their sleep.展开更多
In the course of time, numerous rules were proposed to predict how atoms connect through covalent bonds. Based on the classification of elements in the periodic table, the rule of eight was first proposed to draw form...In the course of time, numerous rules were proposed to predict how atoms connect through covalent bonds. Based on the classification of elements in the periodic table, the rule of eight was first proposed to draw formulas of organic compounds. The later named octet rule exhibited shortcomings when applied to inorganic compounds. Another rule, the rule of two, using covalent bonds between atoms, was proposed as an attempt to unify description of organic and inorganic molecules. This rule unfortunately never managed to expand the field of application of the octet rule to inorganic compounds. In order to conciliate organic and inorganic compounds, the recently put forward even-odd and the isoelectronicity rules suggest the creation of one group of compounds with pairs of electrons. These rules compass the rule of two for covalent bonds as well as the octet rule for organic compounds and suggest transforming bonds of multi-bonded compounds in order to unify representations of both groups of compounds. The aim of the present paper is fourfold: to extend the rule of two to every atom shells;to replace the well-known octet rule by the even-odd rule;to apply the isoelectronicity rule to each atom and to reduce the influence range of the charge of an atom in a compound. According to both rules, the drawing of one atom with its single-covalent bonds is described with electron pairs and charge positions. To illustrate the rules, they are applied to 3D configurations of clusters.展开更多
Light emission of europium(Eu^(3+))ions placed in the vicinity of optically resonant nanoantennas is usually controlled by tailoring the local density of photon states(LDOS).We show that the polarization and shape of ...Light emission of europium(Eu^(3+))ions placed in the vicinity of optically resonant nanoantennas is usually controlled by tailoring the local density of photon states(LDOS).We show that the polarization and shape of the excitation beam can also be used to manipulate light emission,as azimuthally or radially polarized cylindrical vector beam offers to spatially shape the electric and magnetic fields,in addition to the effect of silicon nanorings(Si-NRs)used as nanoantennas.The photoluminescence(PL)mappings of the Eu^(3+)transitions and the Si phonon mappings are strongly dependent of both the excitation beam and the Si-NR dimensions.The experimental results of Raman scattering and photoluminescence are confirmed by numerical simulations of the near-field intensity in the Si nanoantenna and in the Eu^(3+)-doped film,respectively.The branching ratios obtained from the experimental PL maps also reveal a redistribution of the electric and magnetic emission channels.Our results show that it could be possible to spatially control both electric and magnetic dipolar emission of Eu^(3+)ions by switching the laser beam polarization,hence the near field at the excitation wavelength,and the electric and magnetic LDOS at the emission wavelength.This paves the way for optimized geometries taking advantage of both excitation and emission processes.展开更多
Epilepsy is synonymous with individuals suffering repeated“fits”or seizures.The seizures are triggered by bursts of abnormal neuronal activity,across either the cerebral cortex and/or the hippocampus.In addition,the...Epilepsy is synonymous with individuals suffering repeated“fits”or seizures.The seizures are triggered by bursts of abnormal neuronal activity,across either the cerebral cortex and/or the hippocampus.In addition,the seizure sites are characterized by considerable neuronal death.Although the factors that generate this abnormal activity and death are not entirely clear,recent evidence indicates that mitochondrial dysfunction plays a central role.Current treatment options include drug therapy,which aims to suppress the abnormal neuronal activity,or surgical intervention,which involves the removal of the brain region generating the seizure activity.However,~30%of patients are unresponsive to the drugs,while the surgery option is invasive and has a morbidity risk.Hence,there is a need for the development of an effective non-pharmacological and non-invasive treatment for this disorder,one that has few side effects.In this review,we consider the effectiveness of a potential new treatment for epilepsy,known as photobiomodulation,the use of red to near-infrared light on body tissues.Recent studies in animal models have shown that photobiomodulation reduces seizure-like activity and improves neuronal survival.Further,it has an excellent safety record,with little or no evidence of side effects,and it is non-invasive.Taken all together,this treatment appears to be an ideal treatment option for patients suffering from epilepsy,which is certainly worthy of further consideration.展开更多
Monolithic integration of Ⅲ-Ⅴ lasers with small footprint, good coherence, and low power consumption based on a CMOS-compatible Si substrate have been known as an efficient route towards high-density optical interco...Monolithic integration of Ⅲ-Ⅴ lasers with small footprint, good coherence, and low power consumption based on a CMOS-compatible Si substrate have been known as an efficient route towards high-density optical interconnects in the photonic integrated circuits. However, the material dissimilarities between Si and Ⅲ-Ⅴ materials limit the performance of monolithic microlasers. Here, under the pumping condition of a continuous-wave 632.8 nm He–Ne gas laser at room temperature, we achieved an InAs/GaAs quantum dot photonic crystal bandedge laser, which is directly grown on an on-axis Si(001) substrate, which provides a feasible route towards a low-cost and large-scale integration method for light sources on the Si platform.展开更多
Ultraviolet Nanosecond Laser Annealing(LA)is a powerful tool for both fundamental investigations of ultrafast,nonequilibrium phase-change phenomena and technological applications(e.g.,the processing of 3D sequentially...Ultraviolet Nanosecond Laser Annealing(LA)is a powerful tool for both fundamental investigations of ultrafast,nonequilibrium phase-change phenomena and technological applications(e.g.,the processing of 3D sequentially integrated nano-electronic devices)where strongly confined heating and melting is desirable.Optimizing the LA process along with the experimental design is challenging,especially when involving complex 3D-nanostructured systems with various shapes and phases.To this purpose,it is essential to model critical nanoscale physical LA-induced phenomena,such as shape changes or formation and evolution of point and extended defects.To date,LA simulators are based on continuum models,which cannot fully capture the microscopic kinetics of a solid–liquid interface.In this work a fully atomistic LA simulation methodology is presented,based on the parallel coupling of a continuum,finite elements,μm-scale electromagnetic-thermal solver with a super-lattice Kinetic Monte Carlo atomistic model for melting.Benchmarks against phase-field models and experimental data validate the approach.LA of a Si(001)surface is studied varying laser fluence and pulse shape,assuming both homogeneous and inhomogeneous nucleation,revealing how liquid Si nuclei generate,deform and coalesce during irradiation.The proposed methodology is applicable to any system where the atom kinetics is determined by a strongly space-and time-dependent field,such as temperature or strain.展开更多
We present several laser sources dedicated to advanced microwave photonic applications.A quantum-dash mode-locked laser delivering a high-power,ultra-stable pulse train is first described.We measure a linewidth below ...We present several laser sources dedicated to advanced microwave photonic applications.A quantum-dash mode-locked laser delivering a high-power,ultra-stable pulse train is first described.We measure a linewidth below 300 kHz at a 4.3 GHz repetition rate for an output power above 300 mW and a pulse duration of 1.1 ps after compression,making this source ideal for microwave signal sampling applications.A widely tunable(5–110 GHz),monolithic millimeter-wave transceiver based on the integration of two semiconductor distributed feedback lasers,four amplifiers,and two high-speed uni-traveling carrier photodiodes is then presented,together with its application to the wireless transmission of data at 200 Mb∕s.A frequency-agile laser source dedicated to microwave signal processing is then described.It delivers arbitrary frequency sweeps over 20 GHz with high precision and high speed(above 400 GHz∕ms).Finally,we report on a low-noise(below 1 kHz linewidth),solid-state,dual-frequency laser source.It allows independent tuning of the two frequencies in the perspective of the implementation of a tunable optoelectronic oscillator based on a high-Q optical resonator.展开更多
MOS bulk transistor is reaching its limits： sub-threshold slope （SS）, drain induced barrier lowering （DIBL）, threshold voltage （VT） and VDD scaling slowing down, more power dissipation, less speed gain, less ac...MOS bulk transistor is reaching its limits： sub-threshold slope （SS）, drain induced barrier lowering （DIBL）, threshold voltage （VT） and VDD scaling slowing down, more power dissipation, less speed gain, less accuracy, variability and reliability issues. Fully depleted devices are mandatory to continue the technology roadmap. FDSOI technology relies on a thin layer of silicon that is over a buried oxide （BOx）. Called ultra thin body and buried oxide （UTBB） transistor, FDSOI transistors correspond to a simple evolution from conventional MOS bulk transistor. The capability to bias the back-gate allows us to implement calibration techniques without adding transistors in critical blocks. We have illustrated this technique on a very low power voltage-controlled oscillator （VCO） based on a ring oscillator （RO） designed in 28 nm FDSOI technology. Despite the fact that such VCO topology exhibits a larger phase noise, this design will address aggressively the size and power consumption reduction. Indeed we are using the efficient back-gate biasing offered by the FDSOI MOS transistor to compensate the mismatches between the different inverters of the ring oscillator to decrease jitter and phase noise. We will present the reasons which led us to use the FDSOI technology to reach the specifications of this PLL. The VCRO exhibits a 0.8 mW power consumption, with a phase noise about -94 dBc/Hz@l MHz.展开更多
Nanoimprint Lithography has been demon-strated to be one of the most promising next genera-tion techniques for large-area structure replicationin the nanometer scale. This fast and low costmethod becomes an increasing...Nanoimprint Lithography has been demon-strated to be one of the most promising next genera-tion techniques for large-area structure replicationin the nanometer scale. This fast and low costmethod becomes an increasingly important instru-ment for fabrication of biochemistry,m-fluidic, m-TAS and telecommunication devices, as well as for awide variety of fields in the nm range, like biomedical,nano-fluidics,nano-optical applications, datastorage, etc.Due to the restrictions on wavelength and theenormous development works, linked to high pro-cess and equipment costs on standard lithographysystems, nanoimprint lithography might become areal competitive method in mainstream IC industry.There are no physical limitations encountered withimprinting techniques for much smaller replicatedstructures, down to the sub-10nm range [1]. Amongseveral Nanoimprint lithography techniques resultsof two promising methods, hot embossing lithogra-phy (HEL) and UV-nanoimprinting (UV-NIL) will bepresented. Both techniques allow rapid prototypingas well as high volume production of fully patternedsubstrates for a wide range of materials.This paper will present results on HE and UV-NIL, among them full wafer imprints up to 200mmwith high-resolution patterns down to nm range.展开更多
文摘As Lewis proposed his octet rule, itself inspired by Abegg’s rule, that a molecule is stable when all its composing atoms have eight electrons in their valence shell, it perfectly applied to the vast majority of known stable molecules. Only a few stable molecules were known that didn’t fall under this rule, such as PCl5 and SF6, and Lewis chose to leave them aside at the time of his research. With further advances in chemistry, more exceptions to this rule of eight have been found, usually with the central atom of the structure having more or less than eight electrons in its valence shell. Theories have been developed in order to modify the octet rule to suit these molecules, defining these as hyper- or hypo-valent molecules and using other configurations for the electrons. The present paper aims to propose a representation rule for gaseous single-bonded molecules that makes it possible to reconcile both;molecules following the octet theory and those which do not. In this representation rule, each element of the molecule is subscripted with two numbers that follow a set of simple criteria. The first represents the number of valence electrons of the element;while the second is calculated by adding the first number to the number of the element’s covalent bonds within the molecule. The latter is equal to eight for organic molecules following the octet rule. Molecules being exceptions to the octet rule are now encompassed by this new even-odd rule: they have a valid chemical structural formula in which the second number is even but not always equal to eight. Both rules—octet and even-odd—are discussed and compared, using several well-known gaseous molecules having one or several single-bonded elements. A future paper will discuss the application of the even-odd rule to charged molecules.
文摘Lewis developed a 2D-representation of molecules, charged or uncharged, known as structural formula, and stated the criteria to draw it. At the time, the vast majority of known molecules followed the octet-rule, one of Lewis’s criteria. The same method was however rapidly applied to represent compounds that do not follow the octet-rule, i.e. compounds for which some of the composing atoms have greater or less than eight electrons in their valence shell. In a previous paper, an even-odd rule was proposed and shown to apply to both types of uncharged molecules. In the present paper, the even-odd rule is extended with the objective to encompass all single-bonded ions in one group: Lewis’s ions, hypo- and hypervalent ions. The base of the even-odd representation is compatible with Lewis’s diagram. Additionally, each atom is subscripted with an even number calculated by adding the valence number, the number of covalent bonds of the element, and its electrical charge. This paper describes how to calculate the latter number and in doing so, how charge and electron-pairs can actually be precisely localized. Using ions known to be compatible with Lewis’s rule of eight, the even-odd rule is compared with the former. The even-odd rule is then applied to ions known as hypo- or hypervalent. An interesting side effect of the presented rule is that charge and electron-pairs are unambiguously assigned to one of the atoms composing the single-charged ion. Ions that follow the octet rule and ions that do not, are thus reconciled in one group called “electron-paired ions” due to the absence of unpaired electrons. A future paper will focus on the connection between the even-odd rule and molecules or ions having multiple bonds.
文摘In organic chemistry, as defined by Abegg, Kossel, Lewis and Langmuir, compounds are normally represented using structural formulas called Lewis structures. In these structures, the octet rule is used to define the number of covalent bonds that each atom forms with its neighbors and multiple bonds are frequent. Lewis’ octet rule has unfortunately shown limitations very early when applied to non-organic compounds: most of them remain incompatible with the “rule of eight” and location of charges is uncertain. In an attempt to unify structural formulas of octet and non-octet molecules or single-charge ions, an even-odd rule was recently proposed, together with a procedure to locate charge precisely. This even-odd rule has introduced a charge-dependent effective-valence number calculated for each atom. With this number and the number of covalent bonds of each element, two even numbers are calculated. These numbers are both used to understand and draw structuralformulas of single-covalent-bonded compounds. In the present paper, a procedure is proposed to adjust structural formulas of compounds that are commonly represented with multiple bonds. In order to keep them compatible with the even-odd rule, they will be represented using only single covalent bonds. The procedure will then describe the consequences of bond simplification on charges locations. The newly obtained representations are compared to their conventional structural formulas, i.e. single-bond representation vs. multiple-bond structures. Throughout the comparison process, charges are precisely located and assigned to specific atoms. After discussion of particular cases of compounds, the paper finally concludes that a rule limiting representations of multiplecovalent bonds to single covalent bonds, seems to be suitable for numerous known compounds.
基金supported by the Australian Research Council Centre of Excellence Project in Optical Microcombs for Breakthrough Science(No.CE230100006)the Australian Research Council Discovery Projects Programs(DP190103186,FT210100806)+5 种基金Linkage Program(LP210200345)the Swinburne ECR-SUPRA program,the Industrial Transformation Training Centers scheme(Grant No.IC180100005)the Beijing Natural Science Foundation(No.Z180007)the Agence Nationale de la Recherche(ANR)(Grant No.MIRSiCOMB,ANR-17-CE24-0028)the H2020 European Research Council(ERC)(Grant No.GRAPHICS,648546)supported by the International Associated Laboratory in Photonics between France and Australia(LIA ALPhFA).
文摘Optical parametric amplification(OPA)represents a powerful solution to achieve broadband amplification in wavelength ranges beyond the scope of conventional gain media,for generating high-power optical pulses,optical microcombs,entangled photon pairs and a wide range of other applications.Here,we demonstrate optical parametric amplifiers based on silicon nitride(Si3N4)waveguides integrated with two-dimensional(2D)layered graphene oxide(GO)films.We achieve precise control over the thickness,length,and position of the GO films using a transfer-free,layer-by-layer coating method combined with accurate window opening in the chip cladding using photolithography.Detailed OPA measurements with a pulsed pump for the fabricated devices with different GO film thicknesses and lengths show a maximum parametric gain of~24.0 dB,representing a~12.2 dB improvement relative to the device without GO.We perform a theoretical analysis of the device performance,achieving good agreement with experiment and showing that there is substantial room for further improvement.This work represents the first demonstration of integrating 2D materials on chips to enhance the OPA performance,providing a new way of achieving high performance photonic integrated OPA by incorporating 2D materials.
基金This work was supported by the Research Grants Council of Hong Kong(14209519,C4050-21E)The Chinese University of Hong Kong(Group Research Scheme),National Natural Science Foundation of China(62174144)+4 种基金Shenzhen Fundamental Research Fund(JCYJ20210324115605016,JCYJ20210324120204011)Shenzhen Key Laboratory Project(ZDSYS201603311644527),Optical Communication Core Chip Research Platform,UK Engineering and Physical Sciences Research Council(EP/P006973/1,EP/T01394X/1,EP/T028475/1)National Epitaxy Facility,European project H2020-ICT-PICTURE(780930)Royal Academy of Engineering(RF201617/16/28)French National Research Agency under the Investissements d’avenir ANR-10-IRT-05 and ANR-15-IDEX-02 and French RENATECH network.The devices were partially fabricated in the Core Research Facilities at Southern University of Science and Technology,whose engineers provided technical support.
文摘Robust laser sources are a fundamental building block for contemporary information technologies.Originating from condensed-matter physics,the concept of topology has recently entered the realm of optics,offering fundamentally new design principles for lasers with enhanced robustness.In analogy to the well-known Majorana fermions in topological superconductors,Dirac-vortex states have recently been investigated in passive photonic systems and are now considered as a promising candidate for robust lasers.Here,we experimentally realize the topological Diracvortex microcavity lasers in InAs/InGaAs quantum-dot materials monolithically grown on a silicon substrate.We observe room-temperature continuous-wave linearly polarized vertical laser emission at a telecom wavelength.We confirm that the wavelength of the Dirac-vortex laser is topologically robust against variations in the cavity size,and its free spectral range defies the universal inverse scaling law with the cavity size.These lasers will play an important role in CMOS-compatible photonic and optoelectronic systems on a chip.
文摘Ions or molecules are said to be isoelectronic if they are composed of different elements but have the same number of electrons, the same number of covalent bonds and the same structure. This criterion is unfortunately not sufficient to ensure that a chemical structure is a valid chemical compound. In a previous article, a procedure has been described to draw 2D valid structural formulas: the even-odd rule. This rule has been applied first to single-bonded molecules then to single-charged single-bonded ions. It covers hypovalent, hypervalent or classic Lewis’ octet compounds. The funding principle of the even-odd rule is that each atom of the compound possesses an outer-shell filled only with pairs of electrons. The application of this rule guarantees validity of any single-covalent-bond chemical structure. In the present paper, this even-odd rule and its electron-pair criterion are checked for coherence with an effective-valence isoelectronic rule using numerous known compounds having single-covalent-bond connections. The test addresses Lewis’ octet ions or molecules as well as hypovalent and hypervalent compounds. The article concludes that the even-odd rule and the effective-valence isoelectronicity rule are coherent for known single-covalent-bond chemical compounds.
文摘Sleep is a critical part of our daily routine.It impacts every organ and system of our body,from the brain to the heart and from cellular metabolism to immune function.A consistent daily schedule of quality of sleep makes a world of difference to our health and well-being.Despite its importance,so many individuals have trouble sleeping well.Poor quality sleep has such a detrimental impact on many aspects of our lives;it affects our thinking,learning,memory,and movements.Further,and most poignantly,poor quality sleep over time increases the risk of developing a serious medical condition,including neurodegenerative disease.In this review,we focus on a potentially new non-pharmacological treatment that improves the quality of sleep.This treatment,called photobiomodulation,involves the application of very specific wavelengths of light to body tissues.In animal models,these wavelengths,when applied at night,have been reported to stimulate the removal of fluid and toxic waste-products from the brain;that is,they improve the brain’s inbuilt house-keeping function.We suggest that transcranial nocturnal photobiomodulation,by improving brain function at night,will help improve the health and well-being of many individuals,by enhancing the quality of their sleep.
文摘In the course of time, numerous rules were proposed to predict how atoms connect through covalent bonds. Based on the classification of elements in the periodic table, the rule of eight was first proposed to draw formulas of organic compounds. The later named octet rule exhibited shortcomings when applied to inorganic compounds. Another rule, the rule of two, using covalent bonds between atoms, was proposed as an attempt to unify description of organic and inorganic molecules. This rule unfortunately never managed to expand the field of application of the octet rule to inorganic compounds. In order to conciliate organic and inorganic compounds, the recently put forward even-odd and the isoelectronicity rules suggest the creation of one group of compounds with pairs of electrons. These rules compass the rule of two for covalent bonds as well as the octet rule for organic compounds and suggest transforming bonds of multi-bonded compounds in order to unify representations of both groups of compounds. The aim of the present paper is fourfold: to extend the rule of two to every atom shells;to replace the well-known octet rule by the even-odd rule;to apply the isoelectronicity rule to each atom and to reduce the influence range of the charge of an atom in a compound. According to both rules, the drawing of one atom with its single-covalent bonds is described with electron pairs and charge positions. To illustrate the rules, they are applied to 3D configurations of clusters.
基金We acknowledge funding from Agence Nationale de la Recherche under project HiLight(ANR-19-CE24-0020-01)support by the Toulouse computing facility HPC CALMIP(grants p12167 and p19042)the LAAS-CNRS micro and nanotechnologies platform,a member of the French RENATECH network.ICB is partner of the French Investissements d’Avenir program EUR-EIPHI(17-EURE-0002).
文摘Light emission of europium(Eu^(3+))ions placed in the vicinity of optically resonant nanoantennas is usually controlled by tailoring the local density of photon states(LDOS).We show that the polarization and shape of the excitation beam can also be used to manipulate light emission,as azimuthally or radially polarized cylindrical vector beam offers to spatially shape the electric and magnetic fields,in addition to the effect of silicon nanorings(Si-NRs)used as nanoantennas.The photoluminescence(PL)mappings of the Eu^(3+)transitions and the Si phonon mappings are strongly dependent of both the excitation beam and the Si-NR dimensions.The experimental results of Raman scattering and photoluminescence are confirmed by numerical simulations of the near-field intensity in the Si nanoantenna and in the Eu^(3+)-doped film,respectively.The branching ratios obtained from the experimental PL maps also reveal a redistribution of the electric and magnetic emission channels.Our results show that it could be possible to spatially control both electric and magnetic dipolar emission of Eu^(3+)ions by switching the laser beam polarization,hence the near field at the excitation wavelength,and the electric and magnetic LDOS at the emission wavelength.This paves the way for optimized geometries taking advantage of both excitation and emission processes.
文摘Epilepsy is synonymous with individuals suffering repeated“fits”or seizures.The seizures are triggered by bursts of abnormal neuronal activity,across either the cerebral cortex and/or the hippocampus.In addition,the seizure sites are characterized by considerable neuronal death.Although the factors that generate this abnormal activity and death are not entirely clear,recent evidence indicates that mitochondrial dysfunction plays a central role.Current treatment options include drug therapy,which aims to suppress the abnormal neuronal activity,or surgical intervention,which involves the removal of the brain region generating the seizure activity.However,~30%of patients are unresponsive to the drugs,while the surgery option is invasive and has a morbidity risk.Hence,there is a need for the development of an effective non-pharmacological and non-invasive treatment for this disorder,one that has few side effects.In this review,we consider the effectiveness of a potential new treatment for epilepsy,known as photobiomodulation,the use of red to near-infrared light on body tissues.Recent studies in animal models have shown that photobiomodulation reduces seizure-like activity and improves neuronal survival.Further,it has an excellent safety record,with little or no evidence of side effects,and it is non-invasive.Taken all together,this treatment appears to be an ideal treatment option for patients suffering from epilepsy,which is certainly worthy of further consideration.
基金This research was supported by the National Natural Science Foundation of China(No.62174144)Shenzhen Fundamental Research Fund(Nos.JCYJ20210324115605016 and JCYJ20210324120204011)+7 种基金Optical Communication Core Chip Research Platform,Shenzhen Key Laboratory Project(No.ZDSYS201603311644527)Longgang Key Laboratory Project(Nos.ZSYS2017003 and LGKCZSYS2018000015)Longgang Matching Support Fund(Nos.CXPTPT-2017-YJ-002 and 201617486)President's Fund(PF01000154)UK Engineering and Physical Sciences Research Council(EP/P006973/1 and National Epitaxy Facility)European project H2020-ICT-PICTURE(780930)Royal Academy of Engineering(RF201617/16/28)French government managed by ANR under the Investissements davenir ANR-10-IRT-05 and ANR-15-IDEX-02 and French RENATECH network.
文摘Monolithic integration of Ⅲ-Ⅴ lasers with small footprint, good coherence, and low power consumption based on a CMOS-compatible Si substrate have been known as an efficient route towards high-density optical interconnects in the photonic integrated circuits. However, the material dissimilarities between Si and Ⅲ-Ⅴ materials limit the performance of monolithic microlasers. Here, under the pumping condition of a continuous-wave 632.8 nm He–Ne gas laser at room temperature, we achieved an InAs/GaAs quantum dot photonic crystal bandedge laser, which is directly grown on an on-axis Si(001) substrate, which provides a feasible route towards a low-cost and large-scale integration method for light sources on the Si platform.
基金We gratefully acknowledge funding from the European Union’s Horizon 2020 Research and Innovation program under grant agreement No.871813 MUNDFAB.
文摘Ultraviolet Nanosecond Laser Annealing(LA)is a powerful tool for both fundamental investigations of ultrafast,nonequilibrium phase-change phenomena and technological applications(e.g.,the processing of 3D sequentially integrated nano-electronic devices)where strongly confined heating and melting is desirable.Optimizing the LA process along with the experimental design is challenging,especially when involving complex 3D-nanostructured systems with various shapes and phases.To this purpose,it is essential to model critical nanoscale physical LA-induced phenomena,such as shape changes or formation and evolution of point and extended defects.To date,LA simulators are based on continuum models,which cannot fully capture the microscopic kinetics of a solid–liquid interface.In this work a fully atomistic LA simulation methodology is presented,based on the parallel coupling of a continuum,finite elements,μm-scale electromagnetic-thermal solver with a super-lattice Kinetic Monte Carlo atomistic model for melting.Benchmarks against phase-field models and experimental data validate the approach.LA of a Si(001)surface is studied varying laser fluence and pulse shape,assuming both homogeneous and inhomogeneous nucleation,revealing how liquid Si nuclei generate,deform and coalesce during irradiation.The proposed methodology is applicable to any system where the atom kinetics is determined by a strongly space-and time-dependent field,such as temperature or strain.
基金Natioanle de la Recherche(project TELDOT)European Community(project IPHOS)Direction Généraleàl’Armement(projects ORGE and MINOTOR).
文摘We present several laser sources dedicated to advanced microwave photonic applications.A quantum-dash mode-locked laser delivering a high-power,ultra-stable pulse train is first described.We measure a linewidth below 300 kHz at a 4.3 GHz repetition rate for an output power above 300 mW and a pulse duration of 1.1 ps after compression,making this source ideal for microwave signal sampling applications.A widely tunable(5–110 GHz),monolithic millimeter-wave transceiver based on the integration of two semiconductor distributed feedback lasers,four amplifiers,and two high-speed uni-traveling carrier photodiodes is then presented,together with its application to the wireless transmission of data at 200 Mb∕s.A frequency-agile laser source dedicated to microwave signal processing is then described.It delivers arbitrary frequency sweeps over 20 GHz with high precision and high speed(above 400 GHz∕ms).Finally,we report on a low-noise(below 1 kHz linewidth),solid-state,dual-frequency laser source.It allows independent tuning of the two frequencies in the perspective of the implementation of a tunable optoelectronic oscillator based on a high-Q optical resonator.
文摘MOS bulk transistor is reaching its limits： sub-threshold slope （SS）, drain induced barrier lowering （DIBL）, threshold voltage （VT） and VDD scaling slowing down, more power dissipation, less speed gain, less accuracy, variability and reliability issues. Fully depleted devices are mandatory to continue the technology roadmap. FDSOI technology relies on a thin layer of silicon that is over a buried oxide （BOx）. Called ultra thin body and buried oxide （UTBB） transistor, FDSOI transistors correspond to a simple evolution from conventional MOS bulk transistor. The capability to bias the back-gate allows us to implement calibration techniques without adding transistors in critical blocks. We have illustrated this technique on a very low power voltage-controlled oscillator （VCO） based on a ring oscillator （RO） designed in 28 nm FDSOI technology. Despite the fact that such VCO topology exhibits a larger phase noise, this design will address aggressively the size and power consumption reduction. Indeed we are using the efficient back-gate biasing offered by the FDSOI MOS transistor to compensate the mismatches between the different inverters of the ring oscillator to decrease jitter and phase noise. We will present the reasons which led us to use the FDSOI technology to reach the specifications of this PLL. The VCRO exhibits a 0.8 mW power consumption, with a phase noise about -94 dBc/Hz@l MHz.
文摘Nanoimprint Lithography has been demon-strated to be one of the most promising next genera-tion techniques for large-area structure replicationin the nanometer scale. This fast and low costmethod becomes an increasingly important instru-ment for fabrication of biochemistry,m-fluidic, m-TAS and telecommunication devices, as well as for awide variety of fields in the nm range, like biomedical,nano-fluidics,nano-optical applications, datastorage, etc.Due to the restrictions on wavelength and theenormous development works, linked to high pro-cess and equipment costs on standard lithographysystems, nanoimprint lithography might become areal competitive method in mainstream IC industry.There are no physical limitations encountered withimprinting techniques for much smaller replicatedstructures, down to the sub-10nm range [1]. Amongseveral Nanoimprint lithography techniques resultsof two promising methods, hot embossing lithogra-phy (HEL) and UV-nanoimprinting (UV-NIL) will bepresented. Both techniques allow rapid prototypingas well as high volume production of fully patternedsubstrates for a wide range of materials.This paper will present results on HE and UV-NIL, among them full wafer imprints up to 200mmwith high-resolution patterns down to nm range.
