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Optical nonlinear functions are crucial for various applications in integrated photonics, such as all-optical information processing, photonic neural networks and on-chip ultrafast light sources. Due to the weak nonlinearities in most integrated photonic platforms, realizing optical nonlinear functions typically requires large driving energies in the picojoules level or beyond, thus imposing a barrier for most applications. Here, we tackle this challenge and demonstrate an integrated nonlinear splitter device in lithium niobate nano-waveguides by simultaneous engineering of the dispersion and quasi-phase matching. We achieve non-resonant all-optical switching with ultra-low energies down to tens of femtojoules, a near instantaneous switching time of 18 fs, and a large extinction ratio of more than 5 dB. Our nonlinear splitter simultaneously realizes switch-on and -off operations and features a state-of-the-art switching energy-time product as low as $1.4 \times10^{-27}$ J$\cdot$s. We also show a path toward attojoule level all-optical switching by further optimizing the device geometry. Our results can enable on-chip ultrafast and energy-efficient all-optical information processing, computing systems, and light sources.

The DNA damage response (DDR) pathway generally protects against genome instability, and defects in DDR have been exploited therapeutically in cancer treatment. We have reported that histone demethylase PHF8 demethylates TOPBP1 K118 mono-methylation (K118me1) to drive the activation of ATR kinase, one of the master regulators of replication stress. However, whether dysregulation of this physiological signalling is involved in tumorigenesis remains unknown. Here, we showed PHF8-promoted TOPBP1 demethylation is clinically associated with breast tumorigenesis and patient survival. Mammary gland tumors from Phf8 knockout mice grow slowly and exhibit higher level of K118me1, lower ATR activity, and increased chromosomal instability. Importantly, we found that disruption of PHF8-TOPBP1 axis suppresses breast tumorigenesis and creates a breast tumor-specific vulnerability to PARP inhibitor (PARPi) and platinum drug. CRISPR/Cas9 mutation modelling of the deleted or truncated mutation of PHF8 in clinical tumor samples demonstrated breast tumor cells expressing the mimetic variants are more vulnerable to PARPi. Together, our study supports the pursuit of PHF8-TOPBP1 signalling pathway as promising avenues for targeted therapies of PHF8-TOPBP1 proficient tumors, and provides proof-of-concept evidence for loss-of-function of PHF8 as a therapeutic indicator of PARPis.

The microbolometer is the cornerstone device for imaging in the long-wavelength infrared range (LWIR) at room temperature. The state-of-the-art commercial microbolometers usually have a large thermal time constant (TTC) of over 10 ms, limited by their substantial device heat capacity. Moreover, the minimal pixel size of state-of-the-art bolometer is around 10 μm by 10 μm to ensure sufficient power absorption per pixel. Here, we demonstrate an ultrafast silicon nanomembrane microbolometer with a small heat capacity of around 1.9 × 10⁻¹¹J/K, which allows for its operation at a speed of over 10 kHz, corresponding to a TTC of less than 16 μs. Moreover, a compact diabolo antenna is leveraged for efficient LWIR light absorption, enabling the downscaling of the active area size to 6.2 μm by 6.2 μm. Because of the complementary metal oxide semiconductor (CMOS)-compatible fabrication processes, our demonstration here may lead to a future high-resolution and high-speed LWIR imaging solution.

The last decade has witnessed the realization of numerous different types of graphene photodetectors with a strong focus on the visible and near-infrared spectral range, in which various high-perfo...

Having a sizable band gap and high carrier mobility, black phosphorus (BP) is a promising two-dimensional material for high-frequency electronic and optoelectronic devices. Further, for metal-oxide-semiconductor field-effect transistors (MOSFETs) operating at high frequencies, they must have a top gate of submicron length instead of the commonly used global back gate. However, without the global back gate to electrostatically induce doping in BP, top-gated submicron BP MOSFETs have not reached their full potential mainly due to large contact resistances. Here, we report top-gated submicron BP MOSFETs with local contact bias electrodes to induce doping in the contact region. This resulted in reduced contact resistance and, in turn, orders of magnitude improvement in current capacity (500 μA/μm) and peak transconductance (40 μS/μm), if compared with top-gated BP transistors without any back-gating scheme. In turn, these improvements resulted in a forward current gain cutoff frequency of 37 GHz and a maximum frequency of oscillation of 22 GHz at room temperature, the highest reported for BP MOSFETs up to date.

One of the most fundamental quantum states of light is squeezed vacuum, in which noise in one of the quadratures is less than the standard quantum noise limit. Significant progress has been made in the generation of optical squeezed vacuum and its utilization for numerous applications. However, it remains challenging to generate, manipulate, and measure such quantum states in nanophotonics with performances required for a wide range of scalable quantum information systems. Here, we overcome this challenge in lithium niobate nanophotonics by utilizing ultrashort-pulse phase-sensitive amplifiers for both generation and all-optical measurement of squeezed states on the same chip. We generate a squeezed state spanning over more than 25 THz of bandwidth supporting only a few optical cycles, and measure a maximum of 4.9 dB of squeezing ($\sim$11 dB inferred). This level of squeezing surpasses the requirements for a wide range of quantum information systems. Our results on generation and measurement of few-optical-cycle squeezed states in nanophotonics enable a practical path towards scalable quantum information systems with THz clock rates and open opportunities for studying non-classical nature of light in the sub-cycle regime., 8 pages, 4 figures

In recent years, the computational demands of deep learning applications have necessitated the introduction of energy-efficient hardware accelerators. Optical neural networks are a promising option; however, thus far they have been largely limited by the lack of energy-efficient nonlinear optical functions. Here, we experimentally demonstrate an all-optical Rectified Linear Unit (ReLU), which is the most widely used nonlinear activation function for deep learning, using a periodically-poled thin-film lithium niobate nanophotonic waveguide and achieve ultra-low energies in the regime of femtojoules per activation with near-instantaneous operation. Our results provide a clear and practical path towards truly all-optical, energy-efficient nanophotonic deep learning.

We demonstrate 4.2 dB (∼11 dB inferred) of few-cycle vacuum squeezing over more than 25 THz of bandwidth in lithium niobate nanophotonics enabling practical paths towards scalable photonic quantum information systems with THz clock rates.

We demonstrate broadly-tunable synchronously-pumped optical parametric oscillators in nanophotonic lithium niobate. A picosecond 1-µm pump generates subpicosecond signal/idler frequency combs tunable between 1.5 and 3.3 µm with up-conversion to the visible on the same chip.

We demonstrate an ultra-high-gain sync-pumped OPO using a dispersion-engineered lithium niobate nanowaveguide in a free-space cavity with minimal spectral dependence. It generates a three-octave-wide spectrum from visible to mid-IR with only 4.5 pJ of pump.

We demonstrate mid-infrared frequency combs from synchronously-pumped optical parametric oscillators in nanophotonic lithium niobate at 19 GHz. With a picosecond pump at ~1 µm, the output can be tuned between 1.5 and 3.3 µm supporting sub-picosecond pulses.

We present on-chip optical parametric oscillators in nanophotonic periodically-poled lithium niobate, which are pumped near 1 µm and generate outputs tunable over an octave from 1.53 µm to 3.25 µm in the mid-IR.

We introduce and experimentally demonstrate an all-optical ReLU nonlinear activation function based on the strong quadratic nonlinearity of lithium niobate nanophotonic waveguides and achieve a record-breaking energy-time product per activation of 1.2 × 10 − 27 J · s to overcome the nonlinearity bottleneck in photonic neural networks.

Diabetic nephropathy (DN) is a common clinically relevant complication of diabetes that is associated with damage to the capillaries, yet the etiology of this condition remains unclear. Nuclear factor-kappa B (NF-κB) activation is known to be associated with DN-related inflammation and disease progression. Recent work indicated that microRNAs are diagnostic biomarkers of DN progression associated with inflammation in the progression of DN. miR-218 is known to play key regulatory roles in certain cancers in humans, while its influence on DN pathology remains uncertain. The present study, therefore, sought to assess how miR-218 influences the progression of disease in both a rat streptozotocin-induced model of DN and as well as an in vitro model system in which mouse podocytes were stimulated with high glucose levels. We found miR-218 to be markedly downregulated in both model systems relative to appropriate controls, and this downregulation was associated with IKK-β upregulation. In DN rat model, overexpressing miR-218 was sufficient to reduce renal injury. We further determined that podocyte proliferation was markedly impaired by glucose treatment, leading to the apoptotic death of these cells, and miR-218 mimics were able to reduce these phenotypes. Overexpressing miR-218 also significantly dampened inflammatory responses in this model system, as evidenced by reduced tumor necrosis factor-α, interleukin-6 (IL-6), IL-1β, and MCP-1 levels. We then confirmed that miR-218 targeting the messenger RNA encoding IKK-β using a dual-luciferase reporter assay. Together, our results provide clear evidence that miR-218 regulate NF-κB-mediated inflammation, which is central to DN progression.

Recently rediscovered layered black phosphorus (BP) provides rich opportunities for investigations of device physics and applications. The band gap of BP is widely tunable by its layer number and a vertical electric field, covering a wide electromagnetic spectral range from visible to mid-infrared. Despite much progress in BP optoelectronics, the fundamental photoluminescence (PL) properties of thin-film BP in mid-infrared have rarely been investigated. Here, we report bright PL emission from thin-film BP (with thickness of 4.5 to 46 nm) from 80 to 300 K. The PL measurements indicate a band gap of 0.308 ± 0.003 eV in 46 nm thick BP at 80 K, and it increases monotonically to 0.334 ± 0.003 eV at 300 K. Such an anomalous blueshift agrees with the previous theoretical and photoconductivity spectroscopy results. However, the observed blueshift of 26 meV from 80 to 300 K is about 60% of the previously reported value. Most importantly, we show that the PL emission intensity from thin-film BP is only a few times weaker than that of an indium arsenide (InAs) multiple quantum well (MQW) structure grown by molecular beam epitaxy. Finally, we report the thickness-dependent PL spectra in thin-film BP in mid-infrared regime. Our work reveals the mid-infrared light emission properties of thin-film BP, suggesting its promising future in tunable mid-infrared light emitting and lasing applications.

The efficiency of homologous recombination (HR) in the repair of DNA double-strand breaks (DSBs) is closely associated with genome stability and tumor response to chemotherapy. While many factors have been functionally characterized in HR, such as TOPBP1, their precise regulation remains unclear. Here, we report that TOPBP1 interacts with the RNA-binding protein HTATSF1 in a cell-cycle- and phosphorylation-dependent manner. Mechanistically, CK2 phosphorylates HTATSF1 to facilitate binding to TOPBP1, which promotes S-phase-specific TOPBP1 recruitment to damaged chromatin and subsequent RPA/RAD51-dependent HR, genome integrity, and cancer-cell viability. The localization of HTATSF1-TOPBP1 to DSBs is potentially independent of the transcription-coupled RNA-binding and processing capacity of HTATSF1 but rather relies on the recognition of poly(ADP-ribosyl)ated RPA by HTATSF1, which can be blunted with PARP inhibitors. Together, our study provides a mechanistic insight into TOPBP1 loading at HR-prone DSB sites via HTATSF1 and reveals how RPA-RAD51 exchange is tuned by a PARylation-phosphorylation cascade.

The checkpoint kinase ATR [ATM (ataxia-telangiectasia mutated) and rad3-related] is a master regulator of DNA damage response. Yet, how ATR activity is regulated remains to be investigated. We report here that histone demethylase PHF8 (plant homeodomain finger protein 8) plays a key role in ATR activation and replication stress response. Mechanistically, PHF8 interacts with and demethylates TOPBP1 (DNA topoisomerase 2-binding protein 1), an essential allosteric activator of ATR, under unperturbed conditions, but replication stress results in PHF8 phosphorylation and dissociation from TOPBP1. Consequently, hypomethylated TOPBP1 facilitates RAD9 (RADiation sensitive 9) binding and chromatin loading of the TOPBP1-RAD9 complex to fully activate ATR and thus safeguard the genome and protect cells against replication stress. Our study uncovers a demethylation and phosphorylation code that controls the assembly of TOPBP1-scaffolded protein complex, and provides molecular insight into non-histone methylation switch in ATR activation.

Strong amplification in integrated photonics is one of the most desired optical functionalities for computing, communications, sensing, and quantum information processing. Semiconductor gain and cubic nonlinearities, such as four-wave mixing and stimulated Raman and Brillouin scattering, have been among the most studied amplification mechanisms on chip. Alternatively, material platforms with strong quadratic nonlinearities promise numerous advantages with respect to gain and bandwidth, among which nanophotonic lithium niobate is one of the most promising candidates. Here, we combine quasi-phase matching with dispersion engineering in nanophotonic lithium niobate waveguides and achieve intense optical parametric amplification. We measure a broadband phase-sensitive on-chip amplification larger than 45 dB/cm in a 2.5-mm-long waveguide. We further confirm high gain operation in the degenerate and non-degenerate regimes by amplifying vacuum fluctuations to macroscopic levels in a 6-mm-long waveguide, with on-chip gains exceeding 100 dB/cm over 600 nm of bandwidth around 2 $\mu$m. Our results unlock new possibilities for on-chip few-cycle nonlinear optics, mid-infrared photonics, and quantum photonics., Comment: 6 pages, 4 figures

We demonstrate phase-sensitive amplification and confirm aga in exceeding 100 dB/cm on a dispersion-engineered thin-film lithium niobate waveguide, using less than 20 pJ of pump energy, and exhibiting a gain bandwidth larger than 600 nm around 2.09 μm.

We introduce and demonstrate an integrated nonlinear splitter in quasi-phase matched lithium niobate nanophotonic waveguide featuring femtojoule all-optical switching with instantaneous response and 8.5 dB extinction, opening opportunities for on-chip ultrafast energy-efficient all-optical information processing.

We report widely tunable mid-IR photoluminescence from 3.7 to 7.7 μm by an external electric field in thin-film black phosphorus., Thin-film black phosphorus (BP) is an attractive material for mid-infrared optoelectronic applications because of its layered nature and a moderate bandgap of around 300 meV. Previous photoconduction demonstrations show that a vertical electric field can effectively reduce the bandgap of thin-film BP, expanding the device operational wavelength range in mid-infrared. Here, we report the widely tunable mid-infrared light emission from a hexagonal boron nitride (hBN)/BP/hBN heterostructure device. With a moderate displacement field up to 0.48 V/nm, the photoluminescence (PL) peak from a ~20-layer BP flake is continuously tuned from 3.7 to 7.7 μm, spanning 4 μm in mid-infrared. The PL emission remains perfectly linear-polarized along the armchair direction regardless of the bias field. Moreover, together with theoretical analysis, we show that the radiative decay probably dominates over other nonradiative decay channels in the PL experiments. Our results reveal the great potential of thin-film BP in future widely tunable, mid-infrared light-emitting and lasing applications.

The checkpoint kinase ATR is a master regulator of DNA damage response. Yet, how ATR activity is regulated remains to be investigated. We report here that histone demethylase PHF8 is critically required for ATR activation and cellular response to ATR-activating DNA lesions. With a combined approach of structural and biochemical analysis, we unveiled an extraordinary feature of the association/dissociation of PHF8 with TOPBP1, an essential allosteric activator of ATR. PHF8 removes TOPBP1 K118 mono-methylation to facilitate the association of TOPBP1 with RAD9, thus loading the TOPBP1-RAD9 complex to damaged chromatin and eventually activating ATR signaling and protecting cells against replication stress. We demonstrated that PHF8-promoted TOPBP1 demethylation contributes to breast tumorigenesis, and targeting PHF8 or PHF8-TOPBP1 binding sensitized breast cancer cells to chemotherapeutic drugs. Our study provides molecular insight into non-histone methylation switch in ATR activation and genome integrity and supports pursuing PHF8 as a potential therapeutic target for cancers.

Valley-related physics, optics, and electronics have been extensively investigated in transition metal dichalcogenides with a honeycomb lattice such as molybdenum disulfide. Their photoemission properties exhibit a circular dichroism due to energy degenerate but inequivalent valleys located at K and K′ in momentum space. Recently linear dichroism was observed in few-layer black phosphorus with highly anisotropic in-plane optical properties. Here, we report a novel valley-selective linear dichroism of the photoluminescence in layered thin-film tin sulfide (SnS). We identified two PL emission peaks, exhibiting an orthogonal linear dichroism, arising from two inequivalent valleys in the energy band. The photon emission from the Γ-X valley is completely x-polarized, while in contrast, the photon emission from the Γ-Y valley is purely y-polarized. This unique valley-selective linear dichroism in SnS is further confirmed by the band-edge absorption measurements along the Γ-X and Γ-Y directions, respectively. Ou...

The detection of terahertz electromagnetic waves is crucial for emerging applications within this frequency band, such as spectroscopy, imaging, and communication. Extending the well-developed uncooled infrared focal plane array technology to terahertz frequency regime would be very attractive, but high absorption in the terahertz region with a subwavelength pixel is necessary. In this paper, we proposed a meander line nanoantenna (MLNA) absorber with a metal-insulator-metal structure for subwavelength terahertz absorption. 89% absorption is achieved at the wavelength of 155 μm with a 10 μm pitch size. The MLNA absorber is polarization insensitive and can maintain a high absorption when the incident angle is within 40°. We expect that the proposed MLNA absorber can be integrated with the small pixels of uncooled infrared focal plane array for terahertz detection.

Layered black phosphorus (BP) has attracted wide attention for mid-infrared photonics and high-speed electronics, due to its moderate band gap and high carrier mobility. However, its intrinsic band gap of around 0.33 electronvolt limits the operational wavelength range of BP photonic devices based on direct interband transitions to around 3.7 μm. In this work, we demonstrate that black arsenic phosphorus alloy (b-AsxP1–x) formed by introducing arsenic into BP can significantly extend the operational wavelength range of photonic devices. The as-fabricated b-As0.83P0.17 photodetector sandwiched within hexagonal boron nitride (hBN) shows peak extrinsic responsivity of 190, 16, and 1.2 mA/W at 3.4, 5.0, and 7.7 μm at room temperature, respectively. Moreover, the intrinsic photoconductive effect dominates the photocurrent generation mechanism due to the preservation of pristine properties of b-As0.83P0.17 by complete hBN encapsulation, and these b-As0.83P0.17 photodetectors exhibit negligible transport hystere...

Graphene plasmonics has recently attracted remarkable attention, with reports of numerous intriguing properties and novel device demonstrations. As a two-dimensional (2-D) semimetal with ultrahigh carrier mobility, graphene can host plasmon waves that exhibit extremely tight spatial confinement, exceptionally long plasmon lifetime, and an electrostatically tunable response in the mid-infrared (mid-IR) and terahertz (THz). These properties render graphene a viable plasmonic material for achieving novel functionalities in various mid-IR to THz photonic systems. From the device perspective, we review the key distinguishing features of graphene plasmons and highlight the latest developments, such as mid-IR and THz tunable infrared sources, modulators, and photodetectors. Finally, we discuss future challenges and new opportunities for graphene plasmonics in infrared photonic systems.

Recently rediscovered black phosphorus is a layered semiconductor with promising electronic and photonic properties. Dynamic control of its bandgap can allow for the exploration of new physical phenomena. However, theoretical investigations and photoemission spectroscopy experiments indicate that in its few-layer form, an exceedingly large electric field in the order of several volts per nanometre is required to effectively tune its bandgap, making the direct electrical control unfeasible. Here we reveal the unique thickness-dependent bandgap tuning properties in intrinsic black phosphorus, arising from the strong interlayer electronic-state coupling. Furthermore, leveraging a 10 nm-thick black phosphorus, we continuously tune its bandgap from ∼300 to below 50 meV, using a moderate displacement field up to 1.1 V nm−1. Such dynamic tuning of bandgap may not only extend the operational wavelength range of tunable black phosphorus photonic devices, but also pave the way for the investigation of electrically tunable topological insulators and semimetals., Layered black phosphorous has gained significant attention in the 2D materials community, and dynamical control of its bandgap is key to enable novel applications. Here, the authors demonstrate continuous electrical bandgap tuning using moderate displacement fields.

Black phosphorus is a fascinating layered material, with extraordinary anisotropic mechanical, optical and electronic properties. However, the sensitivity of black phosphorus to oxygen and moisture poses significant challenges for technological applications of this unique material. Here, we report a viable solution that overcomes degradation of few-layer black phosphorus by passivating the surface with self-assembled monolayers of octadecyltrichlorosilane that provide long-term stability in ambient conditions. Importantly, we show that this treatment does not cause any undesired carrier doping of the bulk channel material, thanks to the emergent hierarchical interface structure. Our approach is compatible with conventional electronic materials processing technologies thus providing an immediate route toward practical applications in black phosphorus devices. Black phosphorus is a leading contender among new semiconductors for nanoscale optoelectronics, but its use is impeded by rapid degradation in air. A team of Israeli and US scientists, led by Doron Naveh from Bar Ilan University, has devised an inexpensive and scalable approach for long-term stabilization of black phosphorus, bringing it one step closer to real-world applications. By treating black phosphorus with octadecyltrichlorosilane (OTS), a chemical commonly used in semiconductor processing, Naveh and coworkers were able to produce self-assembled polymer coatings that protect black phosphorus from oxygen and moisture. Importantly, this chemical treatment does not alter the overall electronic properties of black phosphorus nor does it complicate subsequent device fabrication. With this advance, researchers can now stabilize and study black phosphorus devices with relative ease under normal operating conditions.