Fano resonances giving rise to a rich variety of asymmetric spectral shapes have been investigated in optical nanostructures with multidimensional configurations. However, 1D nanostructure realizing ...Fano resonances with well‐controlled spectral shapes are yet to be demonstrated. Here, the authors present both numerically and experimentally a 1D nanostructure exhibiting rich Fano resonances induced by interference between a lossy background (continuum) provided by a metal thin film and a discrete optical Tamm state (OTS). A drastic change in the Fano line shape occurs from a narrowband perfect absorber into a narrowband perfect reflector by controlling the metal thin film. Independent from the metal‐related Fano profile, the OTS component determines the resonance frequency and guarantees a sharp resonance (with quality factors over 1000) on the flat mirror background. Taking advantage of its high‐Q property, the structure can be developed into a dispersion device with subnanometer spectral resolution, which even enables a direct imaging of spectral information of molecular fingerprint. The authors believe that this work not only demonstrates a planar nanostructure with versatile Fano resonances for various applications but also provides physical insights into how a metal thin film can induce and significantly affect the Fano resonances in 1D optical resonators.
The investigated 1D structure consists of a thin metal film on top of an OTS resonator (DBR1 + DBR2). A wide range of Fano line shapes (in absorptance spectra) with a narrow bandwidth (Q above 1000) can be obtained (from narrowband perfect absorber to narrowband perfect reflector) by utilizing different metals as the top layer.
Silicon solar cells among different types of solar energy harvesters have entered the commercial market owing to their high power conversion efficiency and stability. By replacing the electrode and ...the p‐type layer by a single layer of carbon nanotubes, the device can be further simplified. This greatly augments the attractiveness of silicon solar cells in the light of raw material shortages and the solar payback period, as well as lowering the fabrication costs. However, carbon nanotube‐based silicon solar cells still lack device efficiency and stability. These can be improved by chemical doping, antireflection coating, and encapsulation. In this work, the multifunctional effects of p‐doping, antireflection, and encapsulation are observed simultaneously, by applying a polymeric acid. This method increases the power conversion efficiency of single‐walled carbon nanotube‐based silicon solar cells from 9.5% to 14.4% and leads to unprecedented device stability of more than 120 d under severe conditions. In addition, the polymeric acid‐applied carbon nanotube‐based silicon solar cells show excellent chemical and mechanical robustness. The obtained stable efficiency stands the highest among the reported carbon nanotube‐based silicon solar cells.
Polymeric acid dopants in single‐walled carbon nanotube‐laminated silicon solar cells show multifunctional effects; strong and permanent p‐doping, antireflection, and encapsulation. A record‐high power conversion efficiency of 14.4% with a device stability of more than 120 d is obtained herein owing to the multifunctional effects that improve all three photovoltaic parameters upon application of the dopant.
Lead halide perovskites exhibit extraordinary optoelectronic performances and are being considered as a promising medium for high‐quality photonic devices such as single‐mode lasers. However, for ...perovskite‐based single‐mode lasers to become practical, fabrication and integration on a chip via the standard top‐down lithography process are strongly desired. The chief bottleneck to achieving lithography of perovskites lies in their reactivity to chemicals used for lithography as illustrated by issues of instability, surface roughness, and internal defects with the fabricated structures. The realization of lithographic perovskite single‐mode lasers in large areas remains a challenge. In this work, a self‐healing lithographic patterning technique using perovskite CsPbBr3 nanocrystals is demonstrated to realize high‐quality and high‐crystallinity single‐mode laser arrays. The self‐healing process is compatible with the standard lithography process and greatly improves the quality of lithographic laser cavities. A single‐mode microdisk laser array is demonstrated with a low threshold of 3.8 µJ cm−2. Moreover, the control of the lasing wavelength is made possible over a range of up to 6.4 nm by precise fabrication of the laser cavities. This work presents a general and promising strategy for standard top‐down lithography fabrication of high‐quality perovskite devices and enables research on large‐area perovskite‐based integrated optoelectronic circuits.
Large‐area single‐mode laser arrays are achieved through a self‐healing lithographic patterning technique by using CsPbBr3 nanocrystals. The self‐healing process is compatible with the standard lithography and enables the fabrication of high‐quality perovskite cavities with a significantly improved lasing performance. The fabricated single‐mode laser is realized with a low threshold of 3.8 µJ cm−2 and wavelength controllability up to 6.4 nm.
Tamm plasmonic (TP) structures, consisting of a metallic film and a distributed Bragg reflector (DBR), can exhibit pronounced light confinement allowing for enhanced absorption in the metallic film ...at the wavelength of the TP resonance. This wavelength dependent absorption can be converted into an electrical signal through the internal photoemission of energetic hot-electrons from the metallic film. Here, by replacing the metallic film at the top of a TP structure with a hot-electron device in a metal–semiconductor–ITO (M–S–ITO) configuration, for the first time, we experimentally demonstrate a wavelength-selective photoresponse around the telecommunication wavelength of 1550 nm. The M–S–ITO junction is deliberately designed to have a low energy barrier and asymmetrical hot-electron generation, in order to guarantee a measurable net photocurrent even for sub-bandgap incident light with a photon energy of 0.8 eV (1550 nm). Due to the excitation of TPs between the metallic film in the M–S–ITO structure and the underlying DBR, the fabricated TP coupled hot-electron photodetector exhibits a sharp reflectance dip with a bandwidth of 43 nm at a wavelength of 1581 nm. The photoresponse matches the absorptance spectrum, with a maximum value of 8.26 nA mW −1 at the absorptance peak wavelength that decreases by more than 80% when the illumination wavelength is varied by only 52 nm (from 1581 to 1529 nm), thus realizing a high modulation wavelength-selective photodetector. This study demonstrates a high-performance, lithography-free, and wavelength-selective hot-electron near-infrared photodetector using an M–S–ITO–DBR planar structure.
Plasmonic nanolasers provide a valuable opportunity for expanding sub‐wavelength applications. Due to the potential of on‐chip integration, semiconductor nanowire (NW)‐based plasmonic nanolasers that ...support the waveguide mode attract a high level of interest. To date, perovskite quantum dots (QDs) based plasmonic lasers, especially nanolasers that support plasmonic‐waveguide mode, are still a challenge and remain unexplored. Here, metallic NW coupled CsPbBr3 QDs plasmonic‐waveguide lasers are reported. By embedding Ag NWs in QDs film, an evolution from amplified spontaneous emission with a full width at half maximum (FWHM) of 6.6 nm to localized surface plasmon resonance (LSPR) supported random lasing is observed. When the pump light is focused on a single Ag NW, a QD‐NW coupled plasmonic‐waveguide laser with a much narrower emission peak (FWHM = 0.4 nm) is realized on a single Ag NW with the uniform polyvinylpyrrolidone layer. The QDs serve as the gain medium while the Ag NW serves as a resonant cavity and propagating plasmonic lasing modes. Furthermore, by pumping two Ag NWs with different directions, a dual‐wavelength lasing switch is realized. The demonstration of metallic NW coupled QDs plasmonic nanolaser would provide an alternative approach for ultrasmall light sources as well as fundamental studies of light matter interactions.
Quantum dot (QD)‐nanowire (NW) based plasmonic lasers are demonstrated by embedding Ag NWs in a CsPbBr3 QDs film. The evolution from amplified spontaneous emission to a localized surface plasmon resonance‐supported random lasing is observed. Further, a plasmonic‐waveguide laser is also achieved with a narrow bandwidth of 0.4 nm. By using the QD‐NW plasmonic‐waveguide lasers, a dual‐wavelength nanolaser switch is realized.
Laser devices produced via solution‐processed perovskite quantum dots (QDs) offer broad spectral tunability as well as ease of fabrication. Utilizing quasi‐bound states in the continuum (quasi‐BIC) ...modes, solution‐processed QD laser devices have been demonstrated with a nanostructure coated in a thin‐film gain media configuration. However, light leakage through thin‐film guiding from the cavity side edges becomes more pronounced when shrinking the cavity size, posing challenges for the miniaturization of quasi‐BIC‐based lasers. Here, the fabrication of well‐defined patterns of QDs via a solution process allows them to take advantage of the pattern edges to reduce losses through the cavity edges. A single‐mode BIC laser is reported by using CsPbBr3 QDs with a narrow linewidth of ≈0.1 nm. Importantly, a miniaturized quasi‐BIC laser is realized with a device size as small as 10 × 10 µm2, making it the smallest among existing solution‐processed BIC lasers. This work provides a strategy for developing ultra‐compact BIC lasers via solution‐processed gain media.
CsPbBr3 Quantum dot (QD) cavity‐supported BIC lasers are demonstrated by integrating an isolated CsPbBr3 QD cavity on a TiO2 nanocylinder array. The fabrication of well‐defined patterns of QDs via a solution process allows us to take advantage of the pattern edges to reduce losses. Finally, lasing with a miniaturized BIC laser having a cavity size down to 10 × 10 µm2 is achieved making it the smallest among existing solution‐processed BIC lasers.
Although chiral semiconductors have shown promising progress in direct circularly polarized light (CPL) detection and emission, they still face potential challenges. A chirality‐switching mechanism ...or approach integrating two enantiomers is needed to discriminate the handedness of a given CPL; additionally, a large material volume is required for sufficient chiroptical interaction. These two requirements pose significant obstacles to the simplification and miniaturization of the devices. Here, room‐temperature chiral polaritons fulfilling dual‐handedness functions and exhibiting a more‐than‐two‐order enhancement of the chiroptical signal are demonstrated, by embedding a 40 nm‐thick perovskite film with a 2D chiroptical effect into a Fabry–Pérot cavity. By mixing chiral perovskites with different crystal structures, a pronounced 2D chiroptical effect is accomplished in the perovskite film, featured by an inverted chiroptical response for counter‐propagating CPL. This inversion behavior matches the photonic handedness switch during CPL circulation in the Fabry–Pérot cavity, thus harvesting giant enhancement of the chiroptical response. Furthermore, affected by the unique quarter‐wave‐plate effects, the polariton emission achieves a chiral dissymmetry of ±4% (for the emission from the front and the back sides). The room‐temperature polaritons with the strong dissymmetric chiroptical interaction shall have implications on a fundamental level and future on‐chip applications for biomolecule analysis and quantum computing.
The light–matter interaction between a 2D chiroptical film and a Fabry–Pérot cavity is investigated. The chiroptical response inversion of the 2D chiroptical film shall be ideally suited to the circularly polarized light switching feature in the Fabry–Pérot cavity, resulting in the enhancement effect in the chiroptical signal.
Near-zero-index materials and structures, with their extraordinary optical behaviors of phase-free propagation resulting in directional radiation, provide a possible approach for directional coupling ...and optical logic gates in photonic integrated circuits. However, the radiation from the near-zero-index structures is limited to a short range of a few hundreds of nanometers. A Bloch surface wave (BSW), an electromagnetic surface wave that can be excited at the interface between an all-dielectric multilayer and a dielectric medium with a low-loss optical mode, provides a solution to increase the propagation length. In this work, we present a nanostructured near-zero-index slab integrated on the all-dielectric metal-free BSW platform for long-range surface wave radiation. By employing the long-range directional surface-wave radiation, a directional coupler and optical logic gates based on the BSW near-zero-index slabs are realized. The proposed directional couplers achieve long coupling distances (the electric-field magnitude ratio between the input slab and output slab is 0.22 with a 50 μm coupling distance), which is 2 orders of magnitude longer than that of conventional directional couplers based on evanescent wave coupling. By controlling the interference pattern of the BSW between the slabs, the XOR logic gate is experimentally demonstrated with a significant extinction ratio of 27.9 dB at telecommunications wavelengths. The BSW near-zero-index logic gates and the directional coupler with long-range light propagation provide an approach to the development of photonic integrated circuits and metal-free surface wave-based applications.
MIL-101(Cr) is considered a candidate for use as adsorbent materials in sorption-based heat exchangers because of its superior water uptake and high hydrothermal stability. Understanding the ...sorption–desorption behavior of water in MIL-101(Cr) is required for its real industrial applications. However, the sorption–desorption mechanism of water in MIL-101(Cr) cannot be revealed from the employed standard characterizations involving sorption–desorption isotherms. Here, we report a combined investigation of infrared molecular adsorption and molecular dynamics simulation to analyze the phase transitions of water confined in MIL-101(Cr). The water molecules at a low pressure preferentially coordinate with the metal sites and form one-dimensional water chains from the unsaturated Cr3+. As the pressure increases, the water chains grow in length and connect, gradually forming a water monolayer on the inner surface of the MIL cages. This monolayer changes the cage surface property from hydrophobic to hydrophilic, which induces the beginning of water condensation in the 29 and 34 Å cages. The entire pores are filled with condensed water as the experimental pressure gradually reaches 1 atm. A reverse behavior of water is observed as the pressure decreases, and this systematic analysis of water in MIL-101(Cr) suggests the further development of superior materials of sorption-based heat exchangers.
PDF
