Showing papers in "Nature Photonics in 2015"
TL;DR: In this paper, the authors provide an overview of the fundamental origins and important applications of the main spin-orbit interaction phenomena in modern optics that play a crucial role at subwavelength scales, including spin-Hall effects in inhomogeneous media and at optical interfaces, spindependent effects in non-paraxial (focused or scattered) fields, spin-controlled shaping of light using anisotropic structured interfaces (metasurfaces).
Abstract: This Review article provides an overview of the fundamental origins and important applications of the main spin–orbit interaction phenomena in modern optics that play a crucial role at subwavelength scales. Light carries both spin and orbital angular momentum. These dynamical properties are determined by the polarization and spatial degrees of freedom of light. Nano-optics, photonics and plasmonics tend to explore subwavelength scales and additional degrees of freedom of structured — that is, spatially inhomogeneous — optical fields. In such fields, spin and orbital properties become strongly coupled with each other. In this Review we cover the fundamental origins and important applications of the main spin–orbit interaction phenomena in optics. These include: spin-Hall effects in inhomogeneous media and at optical interfaces, spin-dependent effects in nonparaxial (focused or scattered) fields, spin-controlled shaping of light using anisotropic structured interfaces (metasurfaces) and robust spin-directional coupling via evanescent near fields. We show that spin–orbit interactions are inherent in all basic optical processes, and that they play a crucial role in modern optics.
1,642 citations
TL;DR: In this paper, a photoactive layer made from a newly developed semiconducting polymer with a deepened valence energy level is used to reduce the tail state density below the conduction band of the electron acceptor.
Abstract: Organic solar cells with efficiency greater than 10% are fabricated by incorporating a semiconductor polymer with a deepened valence energy level. Polymer solar cells are an exciting class of next-generation photovoltaics, because they hold promise for the realization of mechanically flexible, lightweight, large-area devices that can be fabricated by room-temperature solution processing1,2. High power conversion efficiencies of ∼10% have already been reported in tandem polymer solar cells3. Here, we report that similar efficiencies are achievable in single-junction devices by reducing the tail state density below the conduction band of the electron acceptor in a high-performance photoactive layer made from a newly developed semiconducting polymer with a deepened valence energy level. Control over band tailing is realized through changes in the composition of the active layer and the structure order of the blend, both of which are known to be important factors in cell operation4,5,6. The approach yields cells with high power conversion efficiencies (∼9.94% certified) and enhanced photovoltage.
1,585 citations
TL;DR: In this article, the exciton binding energy, dielectric constant and refractive index of planar perovskite solar cells were measured and compared with planar polysilicon solar cells.
Abstract: Measurements reveal the exciton binding energy, dielectric constant and refractive index of planar perovskite solar cells.
1,479 citations
TL;DR: In this paper, a hybrid perovskite single-crystal photodetector with a very narrow spectral response with a full width at half-maximum of <20 nm was presented.
Abstract: Organolead trihalide perovskite is an emerging low-cost, solution-processable material with a tunable bandgap from the violet to near-infrared, which has attracted a great deal of interest for applications in high-performance optoelectronic devices. Here, we present hybrid perovskite single-crystal photodetectors that have a very narrow spectral response with a full-width at half-maximum of <20 nm. The response spectra are continuously tuned from blue to red by changing the halide composition and thus the bandgap of the single crystals synthesized by solution processes. The narrowband photodetection can be explained by the strong surface-charge recombination of the excess carriers close to the crystal surfaces generated by short-wavelength light. The excess carriers generated by below-bandgap excitation locate away from the surfaces and can be much more efficiently collected by the electrodes, assisted by the applied electric field. This provides a new design paradigm for a narrowband photodetector with broad applications where background noise emission needs to be suppressed. Perovskite-based devices typically exhibit broadband spectral responses. Here narrowband (< 20 nm FWHM) response is achieved for a photodetector application.
1,133 citations
TL;DR: In this paper, a direct bandgap GeSn alloy, grown directly onto Si(001), was used for experimentally demonstrating lasing threshold and linewidth narrowing at low temperatures.
Abstract: Lasing is experimentally demonstrated in a direct bandgap GeSn alloy, grown directly onto Si(001). The authors observe a clear lasing threshold as well as linewidth narrowing at low temperatures.
1,027 citations
TL;DR: In this article, microcavity polaritons were observed in a dielectric cavity containing a monolayer of molybdenum disulphide at room temperature.
Abstract: Microcavity polaritons—the bosonic quasiparticles that result from strong light–matter coupling—are observed for the first time in a dielectric cavity containing a monolayer of molybdenum disulphide at room temperature.
967 citations
TL;DR: In this paper, a red, green and blue quantum-dot LEDs are realized by customizing the nanostructure of the quantum dots. But their performance was not as good as those of traditional LEDs.
Abstract: Bright, efficient red, green and blue quantum-dot LEDs are realized by customizing the nanostructure of the quantum dots.
832 citations
TL;DR: Here it is demonstrated a possibility to use such inexpensive semiconductors for sensitive detection of X-ray photons by direct photon-to-current conversion and a compelling combination of fast photoresponse and a high absorption cross-section for X-rays, owing to the heavy Pb and I atoms.
Abstract: The evolution of real-time medical diagnostic tools such as angiography and computer tomography from radiography based on photographic plates was enabled by the development of integrated solid-state X-ray photon detectors, based on conventional solid-state semiconductors. Recently, for optoelectronic devices operating in the visible and near infrared spectral regions, solution-processed organic and inorganic semiconductors have also attracted immense attention. Here we demonstrate a possibility to use such inexpensive semiconductors for sensitive detection of X-ray photons by direct photon-to-current conversion. In particular, methylammonium lead iodide perovskite (CH3NH3PbI3) offers a compelling combination of fast photoresponse and a high absorption cross-section for X-rays, owing to the heavy Pb and I atoms. Solution processed photodiodes as well as photoconductors are presented, exhibiting high values of X-ray sensitivity (up to 25 µC mGyair-1 cm-3) and responsivity (1.9×104 carriers/photon), which are commensurate with those obtained by the current solid-state technology.
830 citations
TL;DR: An on-chip integrated wavelength demultiplexer designed using an inverse computational algorithm is experimentally demonstrated in this paper, where 1,300 and 1,550 nm wavelength light is sorted in a device area of just 2.8 µm2.
Abstract: An on-chip integrated wavelength demultiplexer designed using an inverse computational algorithm is experimentally demonstrated. 1,300 and 1,550 nm wavelength light is sorted in a device area of just 2.8 × 2.8 μm2.
817 citations
TL;DR: Researchers use phase-change materials to demonstrate an integrated optical memory with 13.4 pJ switching energy with real-time switching energy.
Abstract: Researchers use phase-change materials to demonstrate an integrated optical memory with 13.4 pJ switching energy.
806 citations
TL;DR: In this paper, a gated multilayer black phosphorus photodetector integrated on a silicon photonic waveguide operating in the telecom band is demonstrated with intrinsic responsivity up to 135
Abstract: A gated multilayer black phosphorus photodetector integrated on a silicon photonic waveguide operating in the telecom band is demonstrated with intrinsic responsivity up to 135 mA W−1 and 657 mA W−1 in 11.5-nm- and 100-nm-thick devices, respectively.
TL;DR: In this article, a solution-processed small-molecule solar cells with almost 100% internal quantum efficiency and a power conversion efficiency of 9% were reported, making use of a donor molecule called DRCN7T and use PC71BM as an acceptor.
Abstract: Solution-processed small-molecule solar cells with almost 100% internal quantum efficiency and a power conversion efficiency of 9% are reported. The cells make use of a donor molecule called DRCN7T and use PC71BM as an acceptor.
TL;DR: Molecular orientation in polymer solar cells has been shown to play an important role in device performance as discussed by the authors, and it is shown that the orientation plays a crucial role in the performance of solar cells.
Abstract: Molecular orientation in polymer solar cells is shown to play an important role in device performance.
TL;DR: In this article, the authors realized a graphene electro-optic modulator operating with a 30 GHz bandwidth and with a state-of-the-art modulation efficiency of 1.5 dB V−1, paving the way for fast digital communications.
Abstract: Scientists have realized a graphene electro-optic modulator operating with a 30 GHz bandwidth and with a state-of-the-art modulation efficiency of 1.5 dB V−1, paving the way for fast digital communications.
TL;DR: In this article, a simple, non-toxic and low-cost antimony selenide (Sb2Se3) material with an optimal solar bandgap of ∼1.1
Abstract: Solar cells based on inorganic absorbers, such as Si, GaAs, CdTe and Cu(In,Ga)Se2, permit a high device efficiency and stability. The crystals’ three-dimensional structure means that dangling bonds inevitably exist at the grain boundaries (GBs), which significantly degrades the device performance via recombination losses. Thus, the growth of single-crystalline materials or the passivation of defects at the GBs is required to address this problem, which introduces an added processing complexity and cost. Here we report that antimony selenide (Sb2Se3)—a simple, non-toxic and low-cost material with an optimal solar bandgap of ∼1.1 eV—exhibits intrinsically benign GBs because of its one-dimensional crystal structure. Using a simple and fast (∼1 μm min–1) rapid thermal evaporation process, we oriented crystal growth perpendicular to the substrate, and produced Sb2Se3 thin-film solar cells with a certified device efficiency of 5.6%. Our results suggest that the family of one-dimensional crystals, including Sb2Se3, SbSeI and Bi2S3, show promise in photovoltaic applications. Materials with a one-dimensional crystal structure, such as antimony selenide, show considerable potential for making efficient thin-film solar cells.
TL;DR: In this paper, a review of state-of-the-art quantum teleportation technologies, from photonic qubits and optical modes to atomic ensembles, trapped atoms and solid-state systems, is presented.
Abstract: This review covers state-of-the-art quantum teleportation technologies, from photonic qubits and optical modes to atomic ensembles, trapped atoms and solid-state systems. Open issues and potential future implementations are also discussed. Quantum teleportation is one of the most important protocols in quantum information. By exploiting the physical resource of entanglement, quantum teleportation serves as a key primitive across a variety of quantum information tasks and represents an important building block for quantum technologies, with a pivotal role in the continuing progress of quantum communication, quantum computing and quantum networks. Here we summarize the basic theoretical ideas behind quantum teleportation and its variant protocols. We focus on the main experiments, together with the technical advantages and disadvantages associated with the use of the various technologies, from photonic qubits and optical modes to atomic ensembles, trapped atoms and solid-state systems. After analysing the current state-of-the-art, we finish by discussing open issues, challenges and potential future implementations.
TL;DR: Tuning the bandgap of multiferroic solar cells made from Bi2FeCrO6 is achieved by cationic ordering and is shown to dramatically improve their performance as discussed by the authors.
Abstract: Tuning the bandgap of multiferroic solar cells made from Bi2FeCrO6 is achieved by cationic ordering and is shown to dramatically improve their performance.
TL;DR: In this paper, the authors used an inverse design algorithm and experimentally demonstrated an integrated polarization beamsplitter with a footprint of 2.4×××2.4 μm2.
Abstract: Researchers used an inverse design algorithm and experimentally demonstrated an integrated polarization beamsplitter with a footprint of 2.4 × 2.4 μm2.
TL;DR: In this article, plasmonics enable the opposite transfer direction, transferring the plasmanic energy towards the short-wavelength direction to induce charge separation in a semiconductor.
Abstract: In Forster resonance energy transfer (FRET), energy non-radiatively transfers from a blue-shifted emitter to a red-shifted absorber by dipole–dipole coupling. This study shows that plasmonics enables the opposite transfer direction, transferring the plasmonic energy towards the short-wavelength direction to induce charge separation in a semiconductor. Plasmon-induced resonance energy transfer (PIRET) differs from FRET because of the lack of a Stoke's shift, non-local absorption effects and a strong dependence on the plasmon's dephasing rate and dipole moment. PIRET non-radiatively transfers energy through an insulating spacer layer, which prevents interfacial charge recombination losses and dephasing of the plasmon from hot-electron transfer. The distance dependence of dipole–dipole coupling is mapped out for a range of detuning across the plasmon resonance. PIRET can efficiently harvest visible and near-infrared sunlight with energy below the semiconductor band edge to help overcome the constraints of band-edge energetics for single semiconductors in photoelectrochemical cells, photocatalysts and photovoltaics. Plasmon-induced resonance energy transfer is revealed and explored for solar energy harvesting from visible and near-infrared light.
TL;DR: In this paper, a pair of 87Sr optical lattice clocks with a statistical agreement of 2'×'10−18 within 6'000's has been developed.
Abstract: A pair of 87Sr optical lattice clocks with a statistical agreement of 2 × 10−18 within 6,000 s has been developed. To this end, the behaviour of the blackbody radiation—a major perturbation for optical lattice clocks—was directly investigated. The accuracy of atomic clocks relies on the superb reproducibility of atomic spectroscopy, which is accomplished by careful control and the elimination of environmental perturbations on atoms. To date, individual atomic clocks have achieved a 10−18 level of total uncertainties1,2, but a two-clock comparison at the 10−18 level has yet to be demonstrated. Here, we demonstrate optical lattice clocks with 87Sr atoms interrogated in a cryogenic environment to address the blackbody radiation-induced frequency shift3, which remains the primary source of systematic uncertainty2,4,5,6 and has initiated vigorous theoretical7,8 and experimental9,10 investigations. The systematic uncertainty for the cryogenic clock is evaluated to be 7.2 × 10−18, which is expedited by operating two such cryo-clocks synchronously11,12. After 11 measurements performed over a month, statistical agreement between the two cryo-clocks reached 2.0 × 10−18. Such clocks' reproducibility is a major step towards developing accurate clocks at the low 10−18 level, and is directly applicable as a means for relativistic geodesy13.
TL;DR: In this article, a laser is made from the two-dimensional material WS2 by embedding it into a microdisk resonator, and the laser is used to generate a laser beam.
Abstract: A laser is made from the two-dimensional material WS2 by embedding it into a microdisk resonator.
TL;DR: In this article, dark pulse combs are formed in normal-dispersion microresonators with mode-interaction-assisted excitation, increasing freedom in micro-resonator design and potentially extending Kerr comb generation into the visible wavelength regime.
Abstract: Dark pulse combs are formed in normal-dispersion microresonators with mode-interaction-assisted excitation, increasing freedom in microresonator design and potentially extending Kerr comb generation into the visible wavelength regime.
TL;DR: A discrete-variable quantum key distribution system that is capable of distributing a provably-secure cryptographic key over 307 kilometres is demonstrated at a telecom wavelength.
Abstract: A discrete-variable quantum key distribution system that is capable of distributing a provably-secure cryptographic key over 307 kilometres is demonstrated at a telecom wavelength.
TL;DR: Nanophotonic systems, including photonic crystal microcavities and plasmonic metal nanoparticles, that are capable of changing the rate of spontaneous emission are reviewed and compared as discussed by the authors.
Abstract: Nanophotonic systems, including photonic crystal microcavities and plasmonic metal nanoparticles, that are capable of changing the rate of spontaneous emission are reviewed and compared.
TL;DR: A new 3D microscopy technique that allows volumetric imaging of living samples at ultra-high speeds: Swept, confocally-aligned planar excitation (SCAPE) microscopy, demonstrated by imaging spontaneous neuronal firing in the intact brain of awake behaving mice, as well as freely moving transgenic Drosophila larvae.
Abstract: We report a new 3D microscopy technique that allows volumetric imaging of living samples at ultra-high speeds: Swept, confocally-aligned planar excitation (SCAPE) microscopy. While confocal and two-photon microscopy have revolutionized biomedical research, current implementations are costly, complex and limited in their ability to image 3D volumes at high speeds. Light-sheet microscopy techniques using two-objective, orthogonal illumination and detection require a highly constrained sample geometry, and either physical sample translation or complex synchronization of illumination and detection planes. In contrast, SCAPE microscopy acquires images using an angled, swept light-sheet in a single-objective, en-face geometry. Unique confocal descanning and image rotation optics map this moving plane onto a stationary high-speed camera, permitting completely translationless 3D imaging of intact samples at rates exceeding 20 volumes per second. We demonstrate SCAPE microscopy by imaging spontaneous neuronal firing in the intact brain of awake behaving mice, as well as freely moving transgenic Drosophila larvae.
TL;DR: In this paper, the authors demonstrate a 70 GHz modulator in a 10-μm-long two-dimensionally localized gap-plasmon waveguide system, where the modulator can be used to achieve a 2.
Abstract: The authors demonstrate a 70 GHz modulator in a 10-μm-long two-dimensionally localized gap-plasmon waveguide system.
TL;DR: Recently developed 'guidestar' mechanisms that provide feedback for intra-tissue focusing are summarized and potential applications of guidestar-assisted focusing include optogenetic control over neurons, targeted photodynamic therapy and deep tissue imaging.
Abstract: In the field of biomedical optics, optical scattering has traditionally limited the range of imaging within tissue to a depth of one millimetre. A recently developed class of wavefront-shaping techniques now aims to overcome this limit and achieve diffraction-limited control of light beyond one centimetre. By manipulating the spatial profile of an optical field before it enters a scattering medium, it is possible to create a micrometre-scale focal spot deep within tissue. To successfully operate in vivo, these wavefront-shaping techniques typically require feedback from within the biological sample. This Review summarizes recently developed 'guidestar' mechanisms that provide feedback for intra-tissue focusing. Potential applications of guidestar-assisted focusing include optogenetic control over neurons, targeted photodynamic therapy and deep tissue imaging.
TL;DR: The benefits of designing and constructing organic solar cells featuring more than a single donor and single acceptor material are discussed in this paper, where the authors summarize progress in developing ternary OSCs and discuss many of the designs, chemistries and mechanisms that have been investigated.
Abstract: The benefits of designing and constructing organic solar cells featuring more than a single donor and single acceptor material are discussed. In the past few years, ternary organic solar cells (OSCs) featuring multiple donor or acceptor materials in the active layer have emerged as a promising structure to simultaneously improve all solar cell parameters compared with traditional binary OSCs. Power conversion efficiencies around 10% have been achieved for conjugated polymers in a ternary structure, showing the great potential of ternary systems. In this review, we summarize progress in developing ternary OSCs and discuss many of the designs, chemistries and mechanisms that have been investigated. We conclude by highlighting the challenges and future directions for further development in the field of ternary blend OSCs.
TL;DR: The fundamental physics underpinning laser diode chaos and the opportunities for harnessing it for potential applications are discussed in this paper, where the availability and ease of operation of laser diodes, in a wide range of configurations, make them a convenient testbed for exploring basic aspects of nonlinear and chaotic dynamics.
Abstract: This Review Article provides an overview of chaos in laser diodes by surveying experimental achievements in the area and explaining the theory behind the phenomenon. The fundamental physics underpinning laser diode chaos and also the opportunities for harnessing it for potential applications are discussed. The availability and ease of operation of laser diodes, in a wide range of configurations, make them a convenient testbed for exploring basic aspects of nonlinear and chaotic dynamics. It also makes them attractive for practical tasks, such as chaos-based secure communications and random number generation. Avenues for future research and development of chaotic laser diodes are also identified.
TL;DR: In this article, the authors report on recent developments of optics with light carrying transverse spin, and also highlight new capabilities and future applications emerging from this young yet already advanced field of research.
Abstract: This Progress Article details the latest achievements and underlying principles of light carrying transverse spin.The capabilities and future applications of this young yet already advanced field are highlighted. Scientists have known for more than a century that light possesses both linear and angular momenta along the direction of propagation. However, only recent advances in optics have led to the notion of spinning electromagnetic fields capable of carrying angular momenta transverse to the direction of motion. Such fields enable numerous applications in nano-optics, biosensing and near-field microscopy, including three-dimensional control over atoms, molecules and nanostructures, and allowing for the realization of chiral nanophotonic interfaces and plasmonic devices. Here, we report on recent developments of optics with light carrying transverse spin. We present both the underlying principles and the latest achievements, and also highlight new capabilities and future applications emerging from this young yet already advanced field of research.