Localization and delocalization of light in photonic moiré lattices.

Moiré lattices consist of two superimposed identical periodic structures with a relative rotation angle. Moiré lattices have several applications in everyday life, including artistic design, the textile industry, architecture, image processing, metrology and interferometry. For scientific studies, they have been produced using coupled graphene-hexagonal boron nitride monolayers1,2, graphene-graphene layers3,4 and graphene quasicrystals on a silicon carbide surface5. The recent surge of interest in moiré lattices arises from the possibility of exploring many salient physical phenomena in such systems; examples include commensurable-incommensurable transitions and topological defects2, the emergence of insulating states owing to band flattening3,6, unconventional superconductivity4 controlled by the rotation angle7,8, the quantum Hall effect9, the realization of non-Abelian gauge potentials10 and the appearance of quasicrystals at special rotation angles11. A fundamental question that remains unexplored concerns the evolution of waves in the potentials defined by moiré lattices. Here we experimentally create two-dimensional photonic moiré lattices, which-unlike their material counterparts-have readily controllable parameters and symmetry, allowing us to explore transitions between structures with fundamentally different geometries (periodic, general aperiodic and quasicrystal). We observe localization of light in deterministic linear lattices that is based on flat-band physics6, in contrast to previous schemes based on light diffusion in optical quasicrystals12, where disorder is required13 for the onset of Anderson localization14 (that is, wave localization in random media). Using commensurable and incommensurable moiré patterns, we experimentally demonstrate the two-dimensional localization-delocalization transition of light. Moiré lattices may feature an almost arbitrary geometry that is consistent with the crystallographic symmetry groups of the sublattices, and therefore afford a powerful tool for controlling the properties of light patterns and exploring the physics of periodic-aperiodic phase transitions and two-dimensional wavepacket phenomena relevant to several areas of science, including optics, acoustics, condensed matter and atomic physics.

Plasmonic hotspot arrays boost second harmonic generation in thin-film lithium niobate.

Focusing light down to subwavelength scales to enhance the light-matter interaction has been highly sought after, which has promoted significant researches and applications in nanophotonics. Plasmonic nanoantennae are a significant tool to achieve this goal since they can confine light into ultra-small volumes far below the diffraction limit. However, metallic materials have the property of central symmetry, resulting in weak second-order nonlinear effects. Here, we design plasmonic bowtie nanoantennae on thin-film lithium niobate (TFLN) for deep-subwavelength light confinement to boost the second-harmonic generation (SHG) in TFLN via the plasmonic hotspot enhancement. The SHG enhancement factor of about 20 times as compared to unpatterned TFLN is achieved in the experiment when resonantly excited by femtosecond laser. This work proposes a route for subwavelength nonlinear optics on the TFLN platform.

Noncritical birefringence phase-matched second harmonic generation in a lithium-niobate-on-insulator micro-waveguide for green light emission.

Lithium niobate on insulator (LNOI) holds great potential for frequency conversion, where a variety of high-performance nonlinear devices based on different structures has been demonstrated. Here, we report on second harmonic generation (SHG) in MgO-doped LNOI ridge micro-waveguides for efficient green light emission, via an exact type-I noncritical birefringence phase matching (BPM). The LNOI micro-waveguide has a cross section of ∼3×4 µm2, featuring low coupling loss with lens fiber. The normalized conversion efficiency from a continuous-wave (cw) pump to its second harmonic is measured to be 37%/Wcm2 in a single-pass configuration. The device shows both relatively high efficiency and a void of periodic poling, offering a potential solution for efficient and scalable green light sources and frequency converters.

Monolithic tunable dual-wavelength laser utilizing erbium-doped lithium niobate on an insulator.

We demonstrate a monolithic tunable dual-wavelength laser fabricated on erbium-doped lithium niobate on an insulator (Er:LNOI). The dual-wavelength laser enables independent tuning with a continuously linear electro-optic (EO)-modulated tuning range of 11.875 GHz at a tuning efficiency of 0.63 pm/V. Tunable microwave generation within 50 GHz with a maximum extinction ratio of 35 dB is experimentally demonstrated by further exploring the charge accumulation effect in LNOI. The monolithic design of this work paves the way for microscale integration of laser devices, presenting significant prospects in photonics research and applications.

High-speed optical pulse shaping based on programmable lithium niobate spatial light modulators.

Pulse shaping plays a key role in various applications of ultrafast lasers, such as optical communications, laser micromachining, microscopy, and quantum coherent control. Conventional pulse shaping devices based on liquid crystal spatial light modulators (LCSLMs) or digital micromirror devices (DMDs) only have the shaping speed of several hertz to kilohertz, which is not suitable for applications requiring a high-speed response. Here, we demonstrate a high-speed programmable lithium niobate spatial light modulator (LNSLM) with 128 individual modulation channels and a modulation speed that can reach 1 MHz. Then we establish a high-speed LNSLM-based Fourier-transform (FT) pulse shaper to realize high-speed pulse shaping, and the update rate can reach 350 kHz, only limited by the electric circuit. The proposed high-speed pulse shaper scheme opens new avenues for future applications of ultrafast science, such as microscopic imaging, interaction between light and matter, and spectroscopy.

Broadband second-harmonic generation in an angle-cut lithium niobate-on-insulator waveguide by a temperature gradient.

Frequency conversion via nonlinear wave mixing is an important technology to broaden the spectral range of lasers, propelling their applications in optical communication, spectroscopy, signal processing, and quantum information. Many applications require not only a high conversion efficiency but also a broad phase matching bandwidth. Here, we demonstrate broadband birefringence phase matching (BPM) second-harmonic generation (SHG) in angle-cut lithium niobate-on-insulator (LNOI) ridge waveguides based on a temperature gradient scheme. The bandwidth and shift of the phase matching spectrum can be effectively tuned by controlling the temperature gradient of the waveguide. Broadband SHG of a telecom C-band femtosecond laser is also demonstrated. The approach may open a new avenue for tunable broadband nonlinear frequency conversion in various integrated photonics platforms.

Controllable EIT-like mode splitting in a chiral microcavity.

Two coupled resonance modes can lead to exotic transmission spectra due to internal interference processes. Examples include electromagnetically induced transparency (EIT) in atoms and mode splitting in optics. The ability to control individual modes plays a crucial role in controlling such transmission spectra for practical applications. Here we experimentally demonstrate a controllable EIT-like mode splitting in a single microcavity using a double-port excitation. The mode splitting caused by internal coupling between two counter-propagating resonances can be effectively controlled by varying the power of the two inputs, as well as their relative phase. Moreover, the presence of asymmetric scattering in the microcavity leads to chiral behaviors in the mode splitting in the two propagating directions, manifesting itself in terms of a Fano-like resonance mode. These results may offer a compact platform for a tunable device in all-optical information processing.

Second and cascaded harmonic generation of pulsed laser in a lithium niobate on insulator ridge waveguide.

Nonlinear crystalline ridge waveguides, e.g., lithium niobate-on-insulator ridge waveguides, feature high index contrast and strong optical confinement, thus dramatically enhancing nonlinear interaction and facilitating various nonlinear effects. Here, we experimentally demonstrate efficient second-harmonic generation (SHG) and cascaded fourth-harmonic generation (FHG) in a periodically poled lithium niobate (PPLN) ridge waveguide pumped with pulsed laser at the quasi-phase matching (QPM) wavelength, as well as simultaneous SHG and cascaded third-harmonic generation (THG) waves when pumped at the non-QPM wavelength. Furthermore, the ridge waveguide achieves an efficient single-pass SHG conversion efficiency of picosecond pulsed laser at ∼62%. These results may be beneficial for on-chip nonlinear frequency conversion.

Technologically feasible quasi-edge states and topological Bloch oscillation in the synthetic space.

The dimensionality of a physical system is one of the major parameters defining its physical properties. The recently introduced concept of synthetic dimension has made it possible to arbitrarily manipulate the system of interest and harness light propagation in different ways. It also facilitates the transformative architecture of system-on-a-chip devices enabling far reaching applications such as optical isolation. In this report, a novel architecture based on dynamically-modulated waveguide arrays with the Su-Schrieffer-Heeger configuration in the spatial dimension is proposed and investigated with an eye on a practical implementation. The propagation of light through the one-dimensional waveguide arrays mimics time evolution of the field in a synthetic two-dimensional lattice. The addition of the effective gauge potential leads to an exotic topologically protected one-way transmission along adjacent boundary. A cosine-shape isolated band, which supports the topological Bloch oscillation in the frequency dimension under the effective constant force, appears and is localized at the spatial boundary being robust against small perturbations. This work paves the way to improved light transmission capabilities under topological protections in both spatial and spectral regimes and provides a novel platform based on a technologically feasible lithium niobate platform for optical computing and communication.

Thin-film lithium niobate polarization modulator without polarization diversity.

With the development of photonic integrated circuits and optical information processing on thin-film lithium niobate (TFLN), the realization of the TFLN-based polarization device is becoming more and more crucial. Here, we demonstrate a polarization modulator on the TFLN platform without polarization diversity. Without polarization manipulation elements, the device only composes a phase modulator and a two-dimensional grating coupler. The structure features small footprint and high fabrication tolerance. The device holds promise for polarization encoding telecommunication.

Highly tunable birefringent phase-matched second-harmonic generation in an angle-cut lithium niobate-on-insulator ridge waveguide.

Phase-matched nonlinear wave mixing, e.g., second-harmonic generation (SHG), is crucial for frequency conversion for integrated photonics and applications, where phase matching wavelength tunability in a wide manner is important. Here, we propose and demonstrate a novel design of angle-cut ridge waveguides for SHG on the lithium niobate-on-insulator (LNOI) platform via type-I birefringent phase matching (BPM). The unique strong birefringence of LN is used to achieve flexible temperature tuning. We experimentally demonstrate a normalized BPM conversion efficiency of 2.7%W-1cm-2 in an angle-cut LN ridge waveguide with a thermo tuning slope of 1.06 nm/K at the telecommunication C band. The approach effectively overcomes the spatial walk-off effect and avoids the need for periodic domain engineering. Furthermore, the angle-cut ridge waveguide scheme can be universally extended to other on-chip birefringent platforms where domain engineering is difficult or immature. The approach may open up an avenue for tunable nonlinear frequency conversion on integrated photonics for broad applications.

Optically Controlled Femtosecond Polariton Switch at Room Temperature.

Exciton polaritons have shown great potential for applications such as low-threshold lasing, quantum simulation, and dissipation-free circuits. In this paper, we realize a room temperature ultrafast polaritonic switch where the Bose-Einstein condensate population can be depleted at the hundred femtosecond timescale with high extinction ratios. This is achieved by applying an ultrashort optical control pulse, inducing parametric scattering within the photon part of the polariton condensate via a four-wave mixing process. Using a femtosecond angle-resolved spectroscopic imaging technique, the erasure and revival of the polariton condensates can be visualized. The condensate depletion and revival are well modeled by an open-dissipative Gross-Pitaevskii equation including parametric scattering process. This pushes the speed frontier of all-optical controlled polaritonic switches at room temperature towards the THz regime.

Docetaxel-loaded M1 macrophage-derived exosomes for a safe and efficient chemoimmunotherapy of breast cancer.

The conversion of tumor-promoting M2 macrophage phenotype to tumor-suppressing M1 macrophages is a promising therapeutic approach for cancer treatment. However, the tumor normally provides an abundance of M2 macrophage stimuli, which creates an M2 macrophage-dominant immunosuppressive microenvironment. In our study, docetaxel (DTX) as chemotherapeutic modularity was loaded into M1 macrophage-derived exosomes (M1-Exo) with M1 proinflammatory nature to establish DTX-M1-Exo drug delivery system. We found that DTX-M1-Exo induced naïve M0 macrophages to polarize to M1 phenotype, while failed to repolarize to M2 macrophages upon Interleukin 4 restimulation due to impaired mitochondrial function. This suggests that DTX-M1-Exo can achieve long-term robust M1 activation in immunosuppressive tumor microenvironment. The in vivo results further confirmed that DTX-M1-Exo has a beneficial effect on macrophage infiltration and activation in the tumor tissues. Thus, DTX-M1-Exo is a novel macrophage polarization strategy via combined chemotherapy and immunotherapy to achieve great antitumor therapeutic efficacy.

Active mode selection by defects in lithium niobate on insulator microdisks.

Whispering gallery mode (WGM) optical microcavities are important building blocks in photonic integrated circuits. Operation of such cavities on specific lower- or higher- order transverse modes has much interest in application perspectives. Here, we demonstrate active mode selection by introducing defects in lithium niobate on insulator microdisks. A focused ion beam is applied to precisely inscribe nano slits into the perimeter of the microdisk. The transmission spectra can be significantly thinned out without severe quality factor degradation. Either fundamental or high-order transverse WGMs can be retained by properly designing the size and location of the defects. The approach may have promising applications in single-mode lasing and nonlinear optics.

High-speed programmable lithium niobate thin film spatial light modulator.

High-speed spatial modulation of light is the key technology in various applications, such as optical communications, imaging through scattering media, video projection, pulse shaping, and beam steering, in which spatial light modulators (SLMs) are the underpinning devices. Conventional SLMs, such as liquid crystal (LC), digital micromirror device (DMD), and micro-electro-mechanical system (MEMS) ones, operate at a typical speed on the order of several kilohertz as limited by the slow response of the pixels. Achieving high-speed spatial modulation is still challenging and highly desired. Here, we demonstrate a one-dimensional (1D) high-speed programmable spatial light modulator based on the electro-optic effect in lithium niobate thin film, which achieves a low driving voltage of 10 V and an overall high-speed modulation speed of 5 MHz. Furthermore, we transfer an image by using parallel data transmission based on the proposed lithium niobate SLM as a proof-of-principle demonstration. Our device exhibits improved performance over traditional SLMs and opens new avenues for future high-speed and real-time applications, such as light detection and ranging (LiDAR), pulse shaping, and beam steering.

Second-harmonic and sum-frequency generation based on birefringence phase matching of BaMgF4 crystal.

BaMgF4 is a ferroelectric nonlinear crystal with a very wide transparency window ranging from 125 nm to 13µm of the wavelength. Therefore, it is a candidate material to generate ultraviolet or deep ultraviolet laser, which is very important in lithography, semiconductor manufacturing, and advanced instrument development. Here, the second-order birefringence phase-matching processes of the BaMgF4 crystal were studied, including second-harmonic generation (SHG) and sum-frequency generation (SFG). In the experiments, we measured the phase-matching angle, nonlinear frequency conversion efficiency, and angle bandwidth of SHG and SFG processes of BaMgF4 crystal, which are in well agreement with the theoretical calculations. This study may promote the research of nonlinear optical process of BaMgF4 crystal and also the further development of all-solid-state vacuum ultraviolet lasers.

C-Jun/C7ORF41/NF-κB axis mediates hepatic inflammation and lipid accumulation in NAFLD.

Nonalcoholic fatty liver disease (NAFLD) is an expanding health problem worldwide. Although many studies have made great efforts to elucidate the pathogenesis of NAFLD, the molecular basis remains poorly understood. Here, we showed that hepatic C7ORF41, a critical regulator of innate immune response, was markedly decreased in diet or genetic-induced NAFLD model. We also demonstrated that C7ORF41 overexpression significantly ameliorated hepatic inflammation and lipid accumulation in palmitic acid (PA)-treated hepatocytes, whereas C7ORF41 knockdown showed the opposite effects. Mechanistically, we found the anti-inflammatory role of C7ORF41 was attributed to the suppression of NF-κB p65-mediated induction of inflammatory cytokines. Moreover, we demonstrated that the suppression of C7ORF41 expression in hepatocytes is due to JNK activation, which promotes c-Jun-mediated transcriptional repression of C7ORF41. In conclusion, our findings suggested that a c-Jun/C7ORF41/NF-κB regulatory network controls the inflammatory response and lipid accumulation in NAFLD and may benefit the development of novel and promising therapeutic targets for NAFLD.

Conditional Inactivation of Pen-2 in the Developing Neocortex Leads to Rapid Switch of Apical Progenitors to Basal Progenitors.

The transition of apical progenitors (APs) to basal progenitors (BPs) is an important neurogenic process during cortical expansion. Presenilin enhancer 2 (Pen-2, also named as Psenen) is a key subunit of γ-secretase and has been implicated in neurodevelopmental disease. However, it remains unknown how Pen-2 may regulate the maintenance of APs. To address this question, we generated a conditional KO (cKO) mouse in which Pen-2 is specifically inactivated in neural progenitor cells in the telencephalon. Both male and female embryos were used. We show that Pen-2 cKO cortices display remarkable depletion of Aps, but transient increase on BPs, compared with controls. We demonstrate that the proliferation rate of APs or BPs is not changed, but the switch of APs to BPs is dramatically accelerated in Pen-2 cKO cortices. Molecular analyses reveal decreased levels of Hes1 and Hes5 but increased levels of Ngn2 and NeuroD1 in Pen-2 KO cells. We report that expression of Notch1 intracellular domain in Pen-2 cKO cortices restores the population of APs and BPs. In summary, these findings highlight a central role of the Notch signaling in Pen-2-dependent maintenance of neural stem cells in the developing neocortex.SIGNIFICANCE STATEMENT Presenilin enhancer 2 (Pen-2) has been implicated in neurodevelopmental disease. However, mechanisms by which Pen-2 regulates cortical development are not understood. In this study, we generated neural progenitor cell-specific Pen-2 conditional KO mice. We observe depletion of apical progenitors and transiently increased the number of basal progenitors in the developing neocortex of Pen-2 mutant mice. Mechanistic analyses reveal decreased levels of Hes1 and Hes5, but increased levels of neurogenic transcription factors in Pen-2 mutant cortices, compared with controls. We demonstrate that reintroduction of Notch intracellular domain into mutant mice restores the population of apical progenitors to basal progenitors. The above findings strongly suggest that the Pen-2-Notch pathway plays an essential role in the maintenance of neural stem cells during cortical development.

Diastereo- and Enantioselective Construction of Biologically Important Chiral 1,3-Dioxolochroman Frameworks via Catalytic Asymmetric [4+2] Cycloaddition.

A diastereo- and enantioselective construction of biologically important chiral 1,3-dioxolochroman frameworks has been established via chiral phosphoric acid (CPA)-catalyzed asymmetric [4+2] cycloaddition of ortho-quinone methides with 3-methyl-2-vinylindoles. By using this approach, a series of indole-based chiral 1,3-dioxolochromans were synthesized with structural diversity in generally good yields, excellent diastereoselectivities and high enantioselectivities (up to 98% yields, >95:5 dr, 97% ee). The evaluation on the cytotoxic activity of some selected products indicated that this class of chiral 1,3-dioxolochroman derivatives had some extent of anti-cancer activity. This reaction not only provides an efficient synthetic method for accessing chiral 1,3-dioxolochroman derivatives with structural diversity and optical purity but also will enrich the research contents of catalytic asymmetric [4+2] cycloadditions involving ortho-quinone methides. In addition, the bioassay of these compounds will cast a light on discovering useful bioactivities of chiral 1,3-dioxolochroman derivatives, which will be helpful for finding lead compounds.

ZNF300 stimulates fatty acid oxidation and alleviates hepatosteatosis through regulating PPARα.

ZNF300 plays an important role in the regulation of HBV-related hepatocellular carcinoma. However, little is known about the role of ZNF300 in lipid metabolism and NAFLD. In the present study, we observed that ZNF300 expression was markedly decreased in free fatty acid (FFA)-induced fatty liver. Overexpressed ZNF300 alleviated hepatic lipid accumulation, whereas knockdown of ZNF300 enhanced the FFA-induced lipid accumulation. Investigations of the underlying mechanisms revealed that ZNF300 directly binds to and regulates the PPARα expression, thus promoting fatty acid oxidation. Furthermore, bisulfite pyrosequencing PCR (BSP) analysis identified the hypermethylation status of ZNF300 gene in FFA-treated hepatocytes. Importantly, the suppression of ZNF300 could be blocked by DNA methyltransferase inhibitor (5-azadC) or DNMT3a-siRNA. These results suggested that ZNF300 plays an important role in hepatic lipid metabolism via PPARα promoting fatty acid oxidation and this effect might be blocked by DNMT3a-mediated methylation of ZNF300. Therefore, in addition to ZNF300 expression levels, the methylation status of this gene also has a potential as a prognostic biomarker.