| 1. |
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| 2. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 4. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 5. |
- Bhat, Goutam, et al.
(författare)
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NTIRE 2022 Burst Super-Resolution Challenge
- 2022
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Ingår i: 2022 IEEE/CVF CONFERENCE ON COMPUTER VISION AND PATTERN RECOGNITION WORKSHOPS (CVPRW 2022). - : IEEE. - 9781665487399 - 9781665487405 ; , s. 1040-1060
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Konferensbidrag (refereegranskat)abstract
- Burst super-resolution has received increased attention in recent years due to its applications in mobile photography. By merging information from multiple shifted images of a scene, burst super-resolution aims to recover details which otherwise cannot be obtained using a simple input image. This paper reviews the NTIRE 2022 challenge on burst super-resolution. In the challenge, the participants were tasked with generating a clean RGB image with 4x higher resolution, given a RAW noisy burst as input. That is, the methods need to perform joint denoising, demosaicking, and super-resolution. The challenge consisted of 2 tracks. Track 1 employed synthetic data, where pixel-accurate high-resolution ground truths are available. Track 2 on the other hand used real-world bursts captured from a handheld camera, along with approximately aligned reference images captured using a DSLR. 14 teams participated in the final testing phase. The top performing methods establish a new state-of-the-art on the burst super-resolution task.
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| 6. |
- Zhao, Li-Juan, et al.
(författare)
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Lysine demethylase LSD1 delivered via small extracellular vesicles promotes gastric cancer cell stemness
- 2021
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Ingår i: EMBO Reports. - : EMBO. - 1469-221X .- 1469-3178. ; 22:8
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Tidskriftsartikel (refereegranskat)abstract
- Several studies have examined the functions of nucleic acids in small extracellular vesicles (sEVs). However, much less is known about the protein cargos of sEVs and their functions in recipient cells. This study demonstrates the presence of lysine-specific demethylase 1 (LSD1), which is the first identified histone demethylase, in the culture medium of gastric cancer cells. We show that sEVs derived from gastric cancer cells and the plasma of patients with gastric cancer harbor LSD1. The shuttling of LSD1-containing sEVs from donor cells to recipient gastric cancer cells promotes cancer cell stemness by positively regulating the expression of Nanog, OCT4, SOX2, and CD44. Additionally, sEV-delivered LSD1 suppresses oxaliplatin response of recipient cells in vitro and in vivo, whereas LSD1-depleted sEVs do not. Taken together, we demonstrate that LSD1-loaded sEVs can promote stemness and chemoresistance to oxaliplatin. These findings suggest that the LSD1 content of sEV could serve as a biomarker to predict oxaliplatin response in gastric cancer patients.
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| 7. |
- Gharibi, Arash, et al.
(författare)
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Tunable transient evolutional behaviours of a four-level atomic vapour and the application to photonic logic gates
- 2009
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 42:5, s. 055502-
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Tidskriftsartikel (refereegranskat)abstract
- The evolutional optical behaviours (turn-on dynamics) of a four-level N-configuration atomic system are considered based on the transient solution to the equations of motion of atomic probability amplitudes. It is shown that the quantum interference between the signal and control fields can lead to the controllable absorption and transparency properties of the atomic vapour. One of the most remarkable properties of the present scheme is that the absorption (or transmittance) of the probe light in the atomic vapour depends on the intensity ratio of the signal field to the control field, and thus the tunable optical features (transparency or opaqueness to the probe light) can be realized by tuning the quantum interferences between the signal and control fields. The present mechanism can be applicable to designs of some new photonic and quantum optical devices such as logic and functional devices as well as optical switches. Two typical photonic logic gates (NOT and NOR gates) designed based on the tunable four-level optical responses are presented as illustrative examples.
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| 8. |
- Huang, Ke, et al.
(författare)
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Tailoring magnetic order via atomically stacking 3d/5d electrons to achieve high-performance spintronic devices
- 2020
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Ingår i: Applied Physics Reviews. - : AMER INST PHYSICS. - 1931-9401. ; 7:1
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Forskningsöversikt (refereegranskat)abstract
- The ability to tune magnetic orders, such as magnetic anisotropy and topological spin texture, is desired to achieve high-performance spintronic devices. A recent strategy has been to employ interfacial engineering techniques, such as the introduction of spin-correlated interfacial coupling, to tailor magnetic orders and achieve novel magnetic properties. We chose a unique polar-nonpolar LaMnO3/SrIrO3 superlattice because Mn (3d)/Ir (5d) oxides exhibit rich magnetic behaviors and strong spin-orbit coupling through the entanglement of their 3d and 5d electrons. Through magnetization and magnetotransport measurements, we found that the magnetic order is interface-dominated as the superlattice period is decreased. We were able to then effectively modify the magnetization, tilt of the ferromagnetic easy axis, and symmetry transition of the anisotropic magnetoresistance of the LaMnO3/SrIrO3 superlattice by introducing additional Mn (3d) and Ir (5d) interfaces. Further investigations using in-depth first-principles calculations and numerical simulations revealed that these magnetic behaviors could be understood by the 3d/5d electron correlation and Rashba spin-orbit coupling. The results reported here demonstrate a new route to synchronously engineer magnetic properties through the atomic stacking of different electrons, which would contribute to future applications in high-capacity storage devices and advanced computing.
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| 9. |
- Ji, Xuemei, et al.
(författare)
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Identification of susceptibility pathways for the role of chromosome 15q25.1 in modifying lung cancer risk
- 2018
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Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 9, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Genome-wide association studies (GWAS) identified the chromosome 15q25.1 locus as a leading susceptibility region for lung cancer. However, the pathogenic pathways, through which susceptibility SNPs within chromosome 15q25.1 affects lung cancer risk, have not been explored. We analyzed three cohorts with GWAS data consisting 42,901 individuals and lung expression quantitative trait loci (eQTL) data on 409 individuals to identify and validate the underlying pathways and to investigate the combined effect of genes from the identified susceptibility pathways. The KEGG neuroactive ligand receptor interaction pathway, two Reactome pathways, and 22 Gene Ontology terms were identified and replicated to be significantly associated with lung cancer risk, with P values less than 0.05 and FDR less than 0.1. Functional annotation of eQTL analysis results showed that the neuroactive ligand receptor interaction pathway and gated channel activity were involved in lung cancer risk. These pathways provide important insights for the etiology of lung cancer.
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| 10. |
- Lango Allen, Hana, et al.
(författare)
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Hundreds of variants clustered in genomic loci and biological pathways affect human height.
- 2010
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 467:7317, s. 832-8
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Tidskriftsartikel (refereegranskat)abstract
- Most common human traits and diseases have a polygenic pattern of inheritance: DNA sequence variants at many genetic loci influence the phenotype. Genome-wide association (GWA) studies have identified more than 600 variants associated with human traits, but these typically explain small fractions of phenotypic variation, raising questions about the use of further studies. Here, using 183,727 individuals, we show that hundreds of genetic variants, in at least 180 loci, influence adult height, a highly heritable and classic polygenic trait. The large number of loci reveals patterns with important implications for genetic studies of common human diseases and traits. First, the 180 loci are not random, but instead are enriched for genes that are connected in biological pathways (P = 0.016) and that underlie skeletal growth defects (P<0.001). Second, the likely causal gene is often located near the most strongly associated variant: in 13 of 21 loci containing a known skeletal growth gene, that gene was closest to the associated variant. Third, at least 19 loci have multiple independently associated variants, suggesting that allelic heterogeneity is a frequent feature of polygenic traits, that comprehensive explorations of already-discovered loci should discover additional variants and that an appreciable fraction of associated loci may have been identified. Fourth, associated variants are enriched for likely functional effects on genes, being over-represented among variants that alter amino-acid structure of proteins and expression levels of nearby genes. Our data explain approximately 10% of the phenotypic variation in height, and we estimate that unidentified common variants of similar effect sizes would increase this figure to approximately 16% of phenotypic variation (approximately 20% of heritable variation). Although additional approaches are needed to dissect the genetic architecture of polygenic human traits fully, our findings indicate that GWA studies can identify large numbers of loci that implicate biologically relevant genes and pathways.
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| 11. |
- Lin, Qi, et al.
(författare)
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Organic carbon burial in a large, deep alpine lake (southwest China) in response to changes in climate, land use and nutrient supply over the past ~100 years
- 2021
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Ingår i: Catena (Cremlingen. Print). - : Elsevier. - 0341-8162 .- 1872-6887. ; 202
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Tidskriftsartikel (refereegranskat)abstract
- Inland waterbodies play an important role in the global carbon cycle, acting both as carbon sources with organic carbon (OC) mineralization and as sinks with OC burial in sediments. Under recent impacts of global warming, anthropogenic land-use change and nutrient supply, however, there is a limited knowledge regarding OC dynamics in sediments of large, deep lakes especially in subtropical alpine regions. Here, we studied the patterns of OC burial and the potential regulating factors using multiple sedimentary proxies and observational records in Lugu Lake (southwest China) over the past ~100 years. Comparisons of 15 sediment cores in different areas of the lake reveal similar temporal trends in OC content and other sediment parameters, indicating coherent patterns of whole-lake sedimentary environmental change dominated by watershed human perturbation. Based on C/N ratios and δ13Corg analyses, the sediment OC has primarily been autochthonous in source. OC accumulation rates (OCAR) increased during 1880–1980, from ~14 to 43 g C m−2 yr−1 in a central core (LGS), mainly resulting from elevated primary production under increased phosphorus input and soil erosion. Subsequently, OCAR decreased considerably to ~15 g C m−2 yr−1, although the phosphorus supply and lake primary productivity remained high. We infer the OCAR decline likely resulted from increased organic matter decomposition and OC mineralization in the water column because of climate warming and lake-water thermal stratification. This phenomenon might mask the positive contribution of primary production to OC burial. Our findings suggest that the commonly observed synergistically positive effects of warming and eutrophication on sediment OC burial may be impaired in deep lakes, which needs further investigations across ecological, climatic and land-use gradients.
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| 12. |
- Shen, Jian Qi
(författare)
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A Three-Dimensionally Isotropic and Perfectly Vacuum-Impedance-Matched Negative-Index Material
- 2014
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Ingår i: Journal of the Physical Society of Japan. - 0031-9015 .- 1347-4073. ; 83:12, s. 124401-
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Tidskriftsartikel (refereegranskat)abstract
- A new scenario for realizing a gain left-handed atomic vapor medium based on both dressed-state mixed-parity transitions (for simultaneous electric-and magnetic-dipole resonance) and incoherently-pumped population transfer (for high gain amplification) in a four-level atomic system is suggested. Dressed-state assisted simultaneous electric-and magnetic-dipole allowed transitions in such a four-level atomic system (of, e.g., neutral alkali-metal atoms such as lithium and potassium atoms) are utilized for achieving negative refractive index with impedance perfectly matched to vacuum. The attractive features of the present scenario include: i) three-dimensionally isotropic negative indices; ii) incoherent-gain wave amplification; iii) perfect impedance matching to vacuum. All these important properties of the double-negative medium would have potential applications in designing some optical and photonic devices, including particularly subwavelength focusing system and negative-index superlens for perfect imaging.
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| 13. |
- Shen, Jian Qi
(författare)
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A three-level dark state and double-control single-photon logic gates via quantum coherent control
- 2012
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Ingår i: Annalen der Physik. - : Wiley-Blackwell. - 0003-3804 .- 1521-3889. ; 524:2, s. 85-96
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Tidskriftsartikel (refereegranskat)abstract
- Multilevel quantum coherence and its quantum-vacuum counterpart, where a three-level dark state is involved, are suggested in order to achieve new photonic and quantum optical applications. It is shown that such a three-level dark state in a four-level tripod-configuration atomic system consists of three lower levels, where constructive and destructive quantum interference between two control transitions (driven by two control fields) arises. We point out that the controllable optical response due to the double-control tunable quantum interference can be utilized to design some fascinating new photonic devices such as logic gates, photonic transistors and switches at quantum level. A single-photon two-input XOR logic gate (in which the incident gate photons are the individual light quanta of the two control fields) based on such an effect of optical switching control with an EIT (electromagnetically induced transparency) microcavity is suggested as an illustrative example of the application of the dark-state manipulation via the double-control quantum interference. The present work would open up possibility of new applications in both fundamental physics (e.g., field quantization and relevant quantum optical effects in artificial systems that can mimic atomic energy levels) and applied physics (e.g., photonic devices such as integrated optical circuits at quantum level).
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| 14. |
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| 15. |
- Shen, Jian Qi
(författare)
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Automatic generation of nonadiabatic conditional geometric phase shift with a noncoplanar fibre system
- 2006
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 73:1, s. 79-83
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Tidskriftsartikel (refereegranskat)abstract
- A new scheme for realizing a nonadiabatic conditional geometric phase shift via a noncoplanar (coiled) fibre system is presented. It is shown that the effective Hamiltonian that describes the interaction of polarized photons with a fibre medium is just the Wang-Matsumoto type of Hamiltonian. This, therefore, means that the coiled fibre system may be an ideal implementation for realizing the nonadiabatic geometric phase gates involved in the topological quantum computation. A remarkable feature of the present method is that it can automatically meet the conditions and requirements proposed in the Wang-Matsumoto nuclear magnetic resonance (NMR) scheme: specifically, (i) in the coiled fibre system, the dynamical phase of photon wavefunction caused by the interaction Hamiltonian automatically vanishes; (ii) the Wang-Matsumoto requirement for the parameters in the Wang-Matsumoto NMR Hamiltonian can be exactly satisfied automatically in such a fibre system; and (iii) the conditional initial state can be easily achieved by manipulating the initial wave vector of polarized photons.
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| 16. |
- Shen, Jian Qi
(författare)
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Canonical Acoustics and Its Application to Surface Acoustic Wave on Acoustic Metamaterials
- 2016
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Ingår i: Journal of the Physical Society of Japan. - : Physical society of Japan. - 0031-9015 .- 1347-4073. ; 85:8
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Tidskriftsartikel (refereegranskat)abstract
- In a conventional formalism of acoustics, acoustic pressure p and velocity field u are used for characterizing acoustic waves propagating inside elastic/acoustic materials. We shall treat some fundamental problems relevant to acoustic wave propagation alternatively by using canonical acoustics (a more concise and compact formalism of acoustic dynamics), in which an acoustic scalar potential and an acoustic vector potential (Phi, V), instead of the conventional acoustic field quantities such as acoustic pressure and velocity field (p, u) for characterizing acoustic waves, have been defined as the fundamental variables. The canonical formalism of the acoustic energy-momentum tensor is derived in terms of the acoustic potentials. Both the acoustic Hamiltonian density and the acoustic Lagrangian density have been defined, and based on this formulation, the acoustic wave quantization in a fluid is also developed. Such a formalism of acoustic potentials is employed to the problem of negative-mass-density assisted surface acoustic wave that is a highly localized surface bound state (an eigenstate of the acoustic wave equations). Since such a surface acoustic wave can be strongly confined to an interface between an acoustic metamaterial (e.g., fluid-solid composite structures with a negative dynamical mass density) and an ordinary material (with a positive mass density), it will give rise to an effect of acoustic field enhancement on the acoustic interface, and would have potential applications in acoustic device design for acoustic wave control.
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| 17. |
- Shen, Jian Qi
(författare)
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Coherent Manipulation of Optical Waves with Microwave Quantum Interference
- 2013
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Ingår i: Journal of the Physical Society of Japan. - 0031-9015 .- 1347-4073. ; 82:4, s. 044001-
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Tidskriftsartikel (refereegranskat)abstract
- An experimentally feasible scheme of a four-level atomic system driven by two microwaves and one optical field is suggested in order to realize destructive and constructive quantum interference between the two microwave-driven transition pathways and hence to coherently manipulate the applied optical field. The destructive quantum interference can be switched to the constructive interference and vice versa if one tunes the intensity ratio of the two microwaves. Such an effect of tunable optical response based on microwave quantum interference may have some potential applications to the technique for designing new photonic and quantum optical devices, e. g., photonic logic gates, optical switches, and photonic transistors.
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| 18. |
- Shen, Jian Qi
(författare)
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Dispersion-sensitive surface plasmon wave assisted by incoherent gain
- 2014
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Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 329, s. 15-22
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Tidskriftsartikel (refereegranskat)abstract
- A three-level system with pumped electric-dipole allowed transition for incoherent-gain negative permittivity is suggested in order to realize dispersion-sensitive surface plasmon wave. The present surface wave modes occurring at an interface between an incoherent-gain negative-permittivity "plasmonic" medium (e.g., a semiconductor-quantum-dot material) and an ordinary dielectric can be amplified due to population transfer in the three-level system of the negative-permittivity medium. The issues of complex phase constant and the attenuation coefficients in the adjacent media are considered for addressing the problem of loss compensation of surface plasmon wave. The effect of incoherent-gain amplification exhibited by the dispersion-sensitive surface plasmon wave can be utilized for designing new quantum optical and photonic devices, e.g., photonic transistors and logic gates.
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| 19. |
- Shen, Jian Qi
(författare)
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Double-negative atomic vapor assisted by two-photon quantum coherence
- 2012
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : The Optical Society. - 0740-3224 .- 1520-8540. ; 29:11, s. 3192-3200
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Tidskriftsartikel (refereegranskat)abstract
- A scenario for realizing simultaneously negative permittivity and permeability of a two-photon quantum-coherent atomic vapor is suggested in order to achieve a left-handed atomic medium with a negative refractive index. One of the remarkable features of the present scheme is that it can lead to a controllable manipulation of the negative refractive index of the atomic vapor. Since the electric- and magnetic-dipole allowed transitions of atoms can be excited by visible and infrared lightwaves, the refractive index of the atomic vapor can exhibit its negative refractive index at optical and near-optical frequency bands. This may be a new scheme to fabricate a negatively refracting material based on the quantum optical approach. Such a three-dimensionally isotropic negative refractive index at visible and infrared wavelengths induced by the two-photon-resonant quantum coherence would find a potential application in fabrication of superlenses for perfect imaging and subwavelength focusing.
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| 20. |
- Shen, Jian Qi
(författare)
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Electric and magnetic dipole allowed transitions of atoms for three-dimensionally isotropic left handedness in a mixed atomic vapor
- 2014
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Ingår i: Progress of Theoretical and Experimental Physics. - : Oxford University Press (OUP). - 2050-3911. ; :3, s. 033A01-
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Tidskriftsartikel (refereegranskat)abstract
- Since previous negative-index atomic media based on quantum optical approaches are highly lossy, a proposal for realizing a three-dimensionally isotropic left-handed atomic vapor medium is suggested based on a mechanism of incoherent gain assisted atomic transitions. Two three-level atomic systems are utilized for producing simultaneously negative permittivity and negative permeability, respectively, in the same frequency band. We suggest that fine and hyperfine level transitions of atoms (e.g., a hyperfine level transition in a hydrogen atomic system and a fine level transition in an alkali-metal atomic system) would be applicable to realization of such a negatively refracting atomic vapor. The attractive features of the present scenario include: i) three-dimensionally isotropic negative indices; ii) incoherent gain wave amplification in the negative-index atomic vapor; iii) tunable negative indices depending upon external fields. Such a left-handed quantum optical medium can serve as a supporting substrate for lossy negative-index materials for loss compensation. It can also be used in designing new quantum optical and photonic devices (e.g., a subwavelength focusing system and a negative-index superlens for perfect imaging) because of its attractive properties of three-dimensional isotropy and high-gain wave amplification.
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| 21. |
- Shen, Jian Qi
(författare)
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Electromagnetically-induced-transparency plasmonics : Quantum-interference-assisted tunable surface-plasmon-polariton resonance and excitation
- 2014
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society (APS). - 1050-2947 .- 1094-1622. ; 90:2, s. 023814-
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Tidskriftsartikel (refereegranskat)abstract
- An experimentally feasible configuration of a prism coupler with an electromagnetically-induced-transparency (EIT) medium layer, e.g., a semiconductor-quantum-dot (SQD) medium, deposited upon its prism base is suggested for generating tunable surface-plasmon-polariton resonance. Such surface-plasmon-polariton resonance and optical excitation of a surface plasmon wave can be manipulated by switchable quantum interference among SQD multilevel transitions driven by two external control fields. When an incident probe field is coupled into a surface plasmon wave excitation mode, the surface-plasmon-polariton (SPP) resonance at the interface between the SQD medium layer and the substrate will arise, and the quantum-coherently controllable reflection spectrum of the probe field on the prism base can be achieved. In this process, destructive and constructive quantum interference (determined by the intensity ratio of the two external control fields) in the SQD multilevel system plays a key role for achieving the tunable reflection spectrum. The EIT-based surface-plasmon-polariton resonance presented here will have three characteristics (some of them would be attractive): (i) switchable quantum interference exhibited by surface plasmon wave excitation, (ii) quantum-coherently controllable surface plasmon polaritons by external optical fields, (iii) surface wave sensitive to dispersion of the SQD quantum coherent medium. Such an effect of controllable optical response based on the quantum-interference switchable surface-plasmon-polariton resonance in the EIT-prism coupler may find some potential applications in design of new photonic and quantum optical devices.
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| 22. |
- Shen, Jian Qi
(författare)
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Fine-Structure Level Transition for Incoherent-Gain Isotropic Negative Permeability
- 2013
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Ingår i: Journal of the Physical Society of Japan. - 0031-9015 .- 1347-4073. ; 82:12, s. 124003-
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Tidskriftsartikel (refereegranskat)abstract
- A three-dimensionally isotropic negative permeability of a neutral alkali-metal atomic medium, in which a fine-structure magnetic dipole-allowed transition in terahertz band is pumped for population transfer (and hence incoherent gain for negative permeability can be realized), is suggested based on quantum optical approach. The effects relevant to photonic resonance and quantum coherence are involved in the present quantum optical scheme of pumped magnetic-dipole allowed transition. The incoherent-gain assisted atomic medium (with fine-structure transition involved) may have some attractive features, e. g., three-dimensionally isotropic and homogeneous negative permeability for high-gain wave amplification at terahertz frequencies. Such a gain-assisted negative-permeability medium can be a candidate of magnetically resonant materials for artificial composite metamaterials, e.g., it may serve as a substrate of lossy negative-index materials for loss compensation or as a supporting medium for high-gain amplification of a TE-mode surface plasmon-like wave.
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| 23. |
- Shen, Jian Qi
(författare)
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Isotropic negatively-refracting atomic-vapor medium
- 2007
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Ingår i: Modern physics letters B. - 0217-9849. ; 21:12, s. 717-728
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Tidskriftsartikel (refereegranskat)abstract
- A new scenario to realize negative refraction with a photonic-resonant vapor material that can exhibit both electric and magnetic responses via multilevel quantum coherence is suggested. Compared with the previous method of artificial composite metamaterial, where the mechanism was considered by means of classical electromagnetic theory and the materials produced have anisotropic millimetre-scale composite structures, the present scheme suggested within the framework of quantum optics can be used to design and fabricate isotropic negatively-refracting materials with atomic-scale microscopic structure units. Such an advantage may lead to a potentially important application in the techniques of superlens and perfect imaging.
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| 24. |
- Shen, Jian Qi, et al.
(författare)
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Momentum transfer at quantum-vacuum level inside an anisotropic magnetoelectric medium
- 2007
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Ingår i: Wuli xuebao. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 56:5, s. 2719-2724
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Tidskriftsartikel (refereegranskat)abstract
- The breaking of universal symmetry of electromagnetic field distribution in an anisotropic magnetoelectric material will give rise to nonzero vacuum momentum. This may lead to the transfer of momentum between the anisotropic quantum vacuum and the magnetoelectric material. Very recently, Feigel considered the quantum vacuum contribution to the momentum transfer effect [Phys. Rev. Lett. 92 (2004) 020404]. An alternative approach is proposed based on the eigenvector equation of electromagnetic field to calculate the total mechanical contribution of all anisotropic quantum-vacuum modes to the material momentum. It is suggested that the said macroscopic mechanical effect of quantum vacuum on the anisotropic material can be detected by current technology (e. g. fiber optical sensor), which can measure nanoscale velocity. Physical mechanism of such quantum vacuum effects and potential applications are discussed.
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| 25. |
- Shen, Jian Qi, et al.
(författare)
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Momentum transfer from vacuum field to anisotropic electromagnetic media
- 2006
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Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 257:1, s. 84-90
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Tidskriftsartikel (refereegranskat)abstract
- it is demonstrated that many novel vacuum effects will be caused if an anisotropic electromagnetic environment, which can break the universal symmetry of vacuum, is achieved. It is thus possible for the momentum to be transferred from the vacuum zero-point field to the anisotropic electromagnetic media. In addition to the effect considered by Feigel more recently [A. Feigel, Phys. Rev. Lett. 92 (2004) 020404], there may exist another vacuum-fluctuation contribution to the momentum of a medium. Such an effect has a relativistic origin (resulting from the relativistic transformation of the optical constants), which, however, was not taken into account by Feigel.
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| 26. |
- Shen, Jian Qi
(författare)
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Negatively refracting atomic vapour
- 2006
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 53:15, s. 2195-2205
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Tidskriftsartikel (refereegranskat)abstract
- A new mechanism for realizing negative refractive index with a four-level atomic system is suggested. The explicit expressions for the electric permittivity and magnetic permeability at probe frequency are presented. It is shown that there is a frequency band in which the four-level photonic-resonant atomic vapour may exhibit simultaneously negative permittivity and permeability, and that such an atomic vapour may become a left-handed material ( negatively refracting medium). Compared with the previous schemes to realize negative refraction within the framework of classical electromagnetic theory, the most remarkable features of the present scenario are as follows: ( i) isotropic material with microscopic structure units at atomic-scale level, ( ii) negative refraction in visible and infrared frequency bands, ( iii) controllable manipulation by external fields and ( iv) based on quantum coherence in a multilevel atomic system.
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| 27. |
- Shen, Jian Qi
(författare)
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Photonic-resonant left-handed medium
- 2006
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Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 357:1, s. 54-60
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Tidskriftsartikel (refereegranskat)abstract
- A new scheme to realize simultaneously negative permittivity and permeability in a coherent atomic vapor medium (photonic-resonant material) via a coherent driving mechanism is suggested. It is verified that the atomic system coherently driven by a strong optical field will give rise to a negative refractive index in certain probe frequency ranges. One of the most remarkable features of the present scheme is such that a slab fabricated by the left-handed vapor medium is an ideal candidate for designing perfect lenses since the photonic-resonant atomic vapor cannot only exhibit an isotropic negative refractive index, but also provide a good impedance match at the air-medium interfaces.
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| 28. |
- Shen, Jian Qi
(författare)
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Sensitive Optical Behavior in an Electromagnetically Induced Transparency Waveguide via Double-Control Quantum Interference
- 2012
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Ingår i: Journal of the Physical Society of Japan. - : Physical Society of Japan. - 0031-9015 .- 1347-4073. ; 81:2, s. 024403-
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Tidskriftsartikel (refereegranskat)abstract
- A tripod-configuration four-level atomic system can exhibit nontrivial quantum destructive and constructive interference that could manipulate the optical response of an atomic vapour. It is shown that the tunable double-control electromagnetically induced transparency (EIT) would be controlled via the quantum interference between two control fields interacting with the present atomic system. If a metallic waveguide is filled with such a double-control four-level atomic vapour, the quantum vacuum mode structure in the present EIT waveguide would have a novel influence on the atomic spontaneous emission decay (and hence on the EIT optical behavior). As the waveguide dimension change (i.e., the change in length scale of cross section of waveguide) can vary the vacuum mode structure, which can lead to spontaneous emission enhancement or inhibition, the optical response (including absorption and transparency induced by the tunable double-control quantum destructive and constructive interference) of the atomic vapour in the waveguide is quite sensitive to small change in the waveguide dimension caused by external environmental factors (such as electric signal voltage, environmental temperature change and acoustic pressure). The sensitive optical response based on the mechanisms of both double-control quantum interference and quantum-vacuum manipulation presented here may have some potential applications to the technique for designing new photonic and quantum optical devices.
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| 29. |
- Shen, Jian Qi
(författare)
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Simultaneous negative permittivity and permeability in a coherent atomic vapour
- 2007
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Ingår i: Chinese Physics. - : IOP Publishing. - 1009-1963 .- 1741-4199. ; 16:7, s. 1976-1985
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Tidskriftsartikel (refereegranskat)abstract
- A new quantum optical mechanism to realize simultaneously negative electric permittivity and magnetic permeability is suggested. In order to obtain a negative permeability, we choose a proper atomic configuration that can dramatically enhance the contribution of the magnetic- dipole allowed transition via the atomic phase coherence. It is shown that the atomic system chosen with proper optical parameters can give rise to striking electromagnetic responses (leading to a negative refractive index) and that the atomic vapour becomes a left-handed medium in an optical frequency band. Differing from the previous schemes of artificial composite metamaterials (based on classical electromagnetic theory) to achieve the left-handed materials, which consist of anisotropic millimetre- scale composite structure units, the left- handed atomic vapour presented here is isotropic and homogeneous at the atomic-scale level. Such an advantage may be valuable in realizing the superlens (and hence perfect image) with left- handed atomic vapour.
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| 30. |
- Shen, Jian Qi
(författare)
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Strong and weak confinement of parity-time-symmetric acoustic surface wave
- 2014
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 105:1, s. 17006-
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Tidskriftsartikel (refereegranskat)abstract
- A strongly confined acoustic surface wave is an acoustic eigenstate localized on an interface between an ordinary acoustic medium and an acoustic metamaterial with negative effective dynamical mass density. Here we show that there is a new unconventional acoustic surface wave sustained by a parity-time (PT)-symmetric acoustic interface system, in which the negative effective dynamical mass density is not required (but the effective mass densities of the two adjacent acoustic media should fulfill the parity-time symmetry). Such an acoustic parity-time symmetry in the effective mass density can be used to manipulate acoustic wave propagation, e. g., it can exhibit both weak and strong confinement of the unusual PT -symmetric acoustic surface wave, and can offer mechanisms for designing acoustic metamaterial devices that would have specific functions in controlling and guiding acoustic wave, including acoustic field enhancement and extraordinary acoustic transmission.
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| 31. |
- Shen, Jian Qi
(författare)
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Three-dimensionally isotropic negative refractive index assisted by two-photon resonance via quantum coherence
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:18, s. 181102-
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Tidskriftsartikel (refereegranskat)abstract
- An experimentally feasible and promising scheme for realizing simultaneously negative permittivity and permeability in a single-photon off-resonant atomic vapor is suggested by taking full advantage of the mechanism of two-photon resonance that is assisted by atomic phase coherence. The present quantum-coherent atomic vapor can exhibit three-dimensionally isotropic negative refractive index (NRI) at visible and near-infrared wavelengths, and would find potential applications in design of NRI-based quantum optical and photonic devices.
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| 32. |
- Shen, Jian Qi
(författare)
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Total Reflection Enhancement in an Incoherent-Gain Prism Coupler towards Optical Switches and Photonic Transistors
- 2014
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Ingår i: Journal of the Physical Society of Japan. - 0031-9015 .- 1347-4073. ; 83:4, s. 044401-
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Tidskriftsartikel (refereegranskat)abstract
- An incoherent-gain prism coupler that can lead to enhanced total reflection is suggested by taking full advantage of pumped electric-dipole allowed transition that leads to gain-assisted negative permittivity. The tunable reflection spectrum of the prism coupler is quite sensitive to frequency detuning (e.g., 10(7) times that in conventional metal-substrate prism couplers) since the incoherent-gain optical response presented here results from atomic dipole-allowed transition. The present gain-assisted prism coupler, which can exhibit an unusual effect of dispersion-sensitive tunable reflection enhancement, has potential applications in design of new quantum optical and photonic devices, e.g., frequency-sensitive optical switches and photonic transistors.
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