Since its invention, optical frequency comb has revolutionized a broad range of subjects from metrology to spectroscopy. The recent development of microresonator-based frequency combs (microcombs) ...provides a unique pathway to create frequency comb systems on a chip. Indeed, microcomb-based spectroscopy, ranging, optical synthesizer, telecommunications and astronomical calibrations have been reported recently. Critical to many of the integrated comb systems is the broad coverage of comb spectra. Here, microcombs of more than two-octave span (450 nm to 2,008 nm) is demonstrated through χ
and χ
nonlinearities in a deformed silica microcavity. The deformation lifts the circular symmetry and creates chaotic tunneling channels that enable broadband collection of intracavity emission with a single waveguide. Our demonstration introduces a new degree of freedom, cavity deformation, to the microcomb studies, and our microcomb spectral range is useful for applications in optical clock, astronomical calibration and biological imaging.
Chirality is an asymmetric property widely found in nature. Here, we propose and demonstrate experimentally the spontaneous emergence of chirality in an on-chip ultrahigh-Q whispering-gallery ...microresonator, without broken parity or time-reversal symmetry. This counterintuitive effect arises due to the inherent Kerr-nonlinearity-modulated coupling between clockwise and counterclockwise propagating waves. Above an input threshold of a few hundred microwatts, the initial chiral symmetry is broken spontaneously, and the counterpropagating output ratio exceeds 20∶1 with bidirectional inputs. The spontaneous chirality in an on-chip microresonator holds great potential in studies of fundamental physics and applied photonic devices.
The coherent light source is one of the most important foundations in both optical physics studies and applied photonic devices. However, the whispering gallery microcavity, as a prime platform for ...novel light sources, has the intrinsically chiral symmetry and severely rules out access to directional light output, all-optical flip-flops, efficient light extraction, etc. Here, we demonstrate a reconfigurable symmetry-broken microlaser in an ultrahigh-Q whispering gallery microcavity with the symmetric structure, in which a chirality of lasing field is empowered spontaneously by the optical nonlinear effect. Experimentally, the ratio of counter-propagating lasing intensities is found to exceed 160:1, and the chirality can be controlled dynamically and all-optically by the bias in the pump direction. This work not only presents a distinct recipe for coherent light sources with robust and reconfigurable performance, but also opens up an unexplored avenue to symmetry-broken physics in optical micro-structures.
Quantum manipulation is challenging in localized-surface plasmon resonances (LSPRs) due to strong dissipations. To enhance quantum coherence, here we propose to engineer the electromagnetic ...environment of LSPRs by placing metallic nanoparticles (MNPs) in optical microcavities. An analytical quantum model is first built to describe the LSPR-microcavity interaction, revealing the significantly enhanced coherent radiation and the reduced incoherent dissipation. Furthermore, when a quantum emitter interacts with the LSPRs in the cavity-engineered environment, its quantum yield is enhanced over 40 times and the radiative power over one order of magnitude, compared to those in the vacuum environment. Importantly, the cavity-engineered MNP-emitter system can enter the strong coupling regime of cavity quantum electrodynamics, providing a promising platform for the study of quantum plasmonics, quantum information processing, precise sensing, and spectroscopy.
Second-order nonlinear optical processes lie at the heart of many applications in both classical and quantum regimes1–3. Inversion symmetry, however, rules out the second-order nonlinear ...electric-dipole response1,4,5 in materials widely adopted in integrated photonics (for example, SiO2, Si and Si3N4). Here, we report nonlinear optics induced by symmetry breaking6–10 at the surface of an ultrahigh-Q silica microcavity under a sub-milliwatt continuous-wave pump. By dynamically coordinating the double-resonance phase matching, a second harmonic is achieved with an unprecedented conversion efficiency of 0.049% W−1, 14 orders of magnitude higher than that of the non-enhancement case11. In addition, the nonlinear effect from the intrinsic symmetry breaking at the surface8,12 can be identified unambiguously, with guided control of the pump polarization and the recognition of the second-harmonic mode distribution. This work not only extends the emission frequency range of silica photonic devices, but also lays the groundwork for applications in ultra-sensitive surface analysis.
We report enhanced optical nonlinear effects at the surface of an ultrahigh-Q silica microcavity functionalized by a thin layer of organic molecules. The maximal conversion efficiency of third ...harmonic generation reaches ∼1680%/W2 and an absolute efficiency of 0.0144% at pump power of ∼2.90 mW, which is approximately 4 orders of magnitude higher than that in a reported silica microcavity. Further analysis clarifies the elusive dependence of the third harmonic signal on the pump power in previous literature. Molecule-functionalized microcavities may find promising applications in high-efficiency broadband optical frequency conversion and offer potential in sensitive surface analysis.
Hepatitis B virus (HBV) can integrate into the human genome, contributing to genomic instability and hepatocarcinogenesis. Here by conducting high-throughput viral integration detection and RNA ...sequencing, we identify 4,225 HBV integration events in tumour and adjacent non-tumour samples from 426 patients with HCC. We show that HBV is prone to integrate into rare fragile sites and functional genomic regions including CpG islands. We observe a distinct pattern in the preferential sites of HBV integration between tumour and non-tumour tissues. HBV insertional sites are significantly enriched in the proximity of telomeres in tumours. Recurrent HBV target genes are identified with few that overlap. The overall HBV integration frequency is much higher in tumour genomes of males than in females, with a significant enrichment of integration into chromosome 17. Furthermore, a cirrhosis-dependent HBV integration pattern is observed, affecting distinct targeted genes. Our data suggest that HBV integration has a high potential to drive oncogenic transformation.
Abstract
Optical microcavities have become an attractive platform for precision measurement with merits of ultrahigh sensitivity, miniature footprint and fast response. Despite the achievements of ...ultrasensitive detection, optical microcavities still face significant challenges in the measurement of biochemical and physical processes with complex dynamics, especially when multiple effects are present. Here we demonstrate operando monitoring of the transition dynamics of a phase-change material via a self-referencing optofluidic microcavity. We use a pair of cavity modes to precisely decouple the refractive index and temperature information of the analyte during the phase-transition process. Through real-time measurements, we reveal the detailed hysteresis behaviors of refractive index during the irreversible phase transitions between hydrophilic and hydrophobic states. We further extract the phase-transition threshold by analyzing the steady-state refractive index change at various power levels. Our technology could be further extended to other materials and provide great opportunities for exploring on-demand dynamic biochemical processes.
Obesity is one of the most serious public health problems. Peroxisome proliferator-activated receptor γ (PPARγ) plays the master role in adipocyte differentiation for obesity development. However, ...optimum anti-obesity drug has yet been developed, mandating more investigation to identify novel regulator in obesity pathogenesis. Heat shock protein 12A (HSPA12A) encodes a novel member of the HSP70 family. Here, we report that obese patients showed increased adipose HSPA12A expression, which was positively correlated with increase of body mass index. Intriguingly, knockout of HSPA12A (Hspa12a
) in mice attenuated high-fat diet (HFD)-induced weight gain, adiposity, hyperlipidemia, and hyperglycemia compared to their wild type (WT) littermates. Increased insulin sensitivity was observed in Hspa12a
mice compared to WT mice. The HFD-induced upregulation of PPARγ and its target adipogenic genes in white adipose tissues (WAT) of Hspa12a
mice were also attenuated. Loss- and gain-of-function studies revealed that the differentiation of primary adipocyte precursors, as well as the expression of PPARγ and target adipogenic genes during the differentiation, was suppressed by HSPA12A deficiency whereas promoted by HSPA12A overexpression. Importantly, PPARγ inhibition by GW9662 reversed the HSPA12A-mediated adipocyte differentiation. On the other hand, HSPA12A expression was downregulated by PPARγ inhibition but upregulated by PPARγ activation in primary adipocytes. A direct binding of PPARγ to the PPAR response element in the Hspa12a promoter region was confirmed by chromatin immunoprecipitation assay, and this binding was increased after differentiation of primary adipocytes. These findings indicate that HSPA12A is a novel regulator of adipocyte differentiation and diet-induced obesity through a positive feedback regulation with PPARγ. HSPA12A inhibition might represent a viable strategy for the management of obesity in humans.
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