Octave-spanning Kerr soliton frequency combs in dispersion-and dissipation-engineered lithium niobate microresonators

Dissipative Kerr solitons from optical microresonators,commonly referred to as soliton microcombs,have been developed for a broad range of applications,including precision measurement,optical frequency synthesis,and ultrastable microwave and millimeter wave generation,all on a chip.An important goal for microcombs is self-referencing,which requires octave-spanning bandwidths to detect and stabilize the comb carrier envelope offset frequency.Further,detection and locking of the comb spacings are often achieved using frequency division by electro-optic modulation.The thin-film lithium niobate photonic platform,with its low loss,strong second-and third-order nonlinearities,as well as large Pockels effect,is ideally suited for these tasks.However,octave-spanning soliton microcombs are challenging to demonstrate on this platform,largely complicated by strong Raman effects hindering reliable fabrication of soliton devices.Here,we demonstrate entirely connected and octave-spanning soliton microcombs on thin-film lithium niobate.With appropriate control over microresonator free spectral range and dissipation spectrum,we show that soliton-inhibiting Raman effects are suppressed,and soliton devices are fabricated with near-unity yield.Our work offers an unambiguous method for soliton generation on strongly Raman-active materials.Further,it anticipates monolithically integrated,self-referenced frequency standards in conjunction with established technologies,such as periodically poled waveguides and electro-optic modulators,on thin-film lithium niobate.

既有建成区零碳更新改造的经验模式探索——博鳌东屿岛零碳更新改造回顾

针对既有建成区零碳更新改造的问题,利用国家住房城乡建设部与海南省共同建设博鳌零碳示范区的契机,将东屿岛按照一个典型城市建成区来开展更新改造探索,紧扣城区碳排放的核心要素,通过建立现场指挥部、引入社会企业参与、开展全过程技术管理、引入第三方评估等方式,探索形成了零碳城区更新改造的规划、建设、管理模式,零碳更新改造的技术实施路径,零碳城区社会治理的相关经验等内容。

Safety and feasibility of ultra-early lumbar puncture in patients with aneurysmal subarachnoid hemorrhage

Objective:to evaluate the clinical efficacy and safety of ultra-early lumbar puncture drainage of cerebrospinal fluid(CSF)in patients with aneurysmal subarachnoid hemorrhage(SAH).Methods:patients(n=140)with aneurysmal SAH were randomly divided into observation group(n=70)and control group(n=70).After admission,CSF was drained by ultra-early lumbar puncture in the observation group and intermittent lumbar puncture after aneurysm operation in the control group.The incidences of early aneurysm rupture,acute hydrocephalus and delayed hydrocephalus were compared between the two groups.Results:there was no significant diflerence in the incidence of early-ruptured aneurysm and acute hydrocephalus between the two groups,but the incidence of delayed hydrocephalus in the observation group was significantly lower than that in the control group.Conclusion:ultra-early lumbar puncture drainage of CSF in anexirysmal SAH can effectively reduce the incidence of long-term delayed hydrocephalus and it is a safe and effective treatment.

Effect of improving prehospital hypotension and hypoxemia on the prognosis of patients with traumatic brain injury

Objective:to investigate the effect of improving prehospital hypotension and hypoxemia on the prognosis of different subgroups of patients with traumatic brain injury(TBI).Methods:medical staff were trained about the prehospital first aid for 2 months to fully master the methods of improving prehospital hypotension and hypoxemia,then the prognosis of TBI patients pre-and post-training for 12 months was collected and recorded.The prognostic differences of different TBI subgroups were discussed through data analysis.Results:after the training,the proportion of prehospital hypotension and hypoxemia in TBI patients decreased by 77%(8.5%vs.1.9%)and 63%(9.9%vs.3.6%,P<0.05),respectively.However,only the prognosis of moderate and severe TBI patients was improved,the proportion of patients with"good prognosis^increased by 14%(61.4%vs.70.5%,respectively)and 62%(35.6%vs.58%),and no significant effect showed in mild and critical TBI patients.Conclusion:reducing the incidence of prehospital hypoxemia and hypotension can improve the prognosis of moderate and severe TBI patients,while no significant effect on mild and critical TBI patients.

Twenty-nine million intrinsic Q-factor monolithic microresonators on thin-film lithium niobate

The recent emergence of thin-film lithium niobate(TFLN)has extended the landscape of integrated photonics.This has been enabled by the commercialization of TFLN wafers and advanced nanofabrication of TFLN such as high-quality dry etching.However,fabrication imperfections still limit the propagation loss to a few dB/m,restricting the impact of this platform.Here,we demonstrate TFLN microresonators with a record-high intrinsic quality(Q)factor of twenty-nine million,corresponding to an ultra-low propagation loss of 1.3 dB/m.We present spectral analysis and the statistical distribution of Q factors across different resonator geometries.Our work pushes the fabrication limits of TFLN photonics to achieve a Q factor within 1 order of magnitude of the material limit.

Spectral control of nonclassical light pulses using an integrated thin-film lithium niobate modulator

Manipulating the frequency and bandwidth of nonclassical light is essential for implementing frequency-encoded/multiplexed quantum computation,communication,and networking protocols,and for bridging spectral mismatch among various quantum systems.However,quantum spectral control requires a strong nonlinearity mediated by light,microwave,or acoustics,which is challenging to realize with high efficiency,low noise,and on an integrated chip.Here,we demonstrate both frequency shifting and bandwidth compression of heralded single-photon pulses using an integrated thin-film lithium niobate(TFLN)phase modulator.We achieve record-high electro-optic frequency shearing of telecom single photons over terahertz range(±641 GHz or±5.2 nm),enabling high visibility quantum interference between frequency-nondegenerate photon pairs.We further operate the modulator as a time lens and demonstrate over eighteen-fold(6.55 nm to 0.35 nm)bandwidth compression of single photons.Our results showcase the viability and promise of on-chip quantum spectral control for scalable photonic quantum information processing.