Raman lasing and other nonlinear effects based on ultrahigh-Q CaF_(2)optical resonator

The calcium fluoride(CaF_(2))whispering gallery mode crystalline resonator is an excellent platform for nonlinear optical applications because of the decreasing in threshold caused by ultrahigh quality(Q)factor.In this paper,we achieved the observation of Raman lasing,first-order Raman comb,and second-order Raman lasing in a CaF_(2)disk resonator with a diameter of 4.96 mm and an ultrahigh-Q of 8.43×10^(8)at 1550-nm wavelength.We also observed thermal effects in CaF_(2)disk resonator,and the threshold of thermo-optical oscillation is approximately coincident with Raman lasing,since the intracavity power increases rapidly when the power reaches the threshold,and higher input pump power results in longer thermal drift and higher Raman emission power.With a further increase in pump power,the optical frequency combs range is from 1520 nm to 1650 nm,with a wavelength interval of 4×FSR.It is a promising candidate for optical communication,biological environment monitoring,spectral analysis,and microwave signal sources.

Investigating the ENSO prediction skills of the Beijing Climate Center climate prediction system version 2

The El Niño-Southern Oscillation(ENSO)ensemble prediction skills of the Beijing Climate Center(BCC)climate prediction system version 2(BCC-CPS2)are examined for the period from 1991 to 2018.The upper-limit ENSO predictability of this system is quantified by measuring its“potential”predictability using information-based metrics,whereas the actual prediction skill is evaluated using deterministic and probabilistic skill measures.Results show that:(1)In general,the current operational BCC model achieves an effective 10-month lead predictability for ENSO.Moreover,prediction skills are up to 10–11 months for the warm and cold ENSO phases,while the normal phase has a prediction skill of just 6 months.(2)Similar to previous results of the intermediate coupled models,the relative entropy(RE)with a dominating ENSO signal component can more effectively quantify correlation-based prediction skills compared to the predictive information(PI)and the predictive power(PP).(3)An evaluation of the signal-dependent feature of the prediction skill scores suggests the relationship between the“Spring predictability barrier(SPB)”of ENSO prediction and the weak ENSO signal phase during boreal spring and early summer.

BCC-ESM1 Model Datasets for the CMIP6 Aerosol Chemistry Model Intercomparison Project (AerChemMIP)

BCC-ESM1 is the first version of the Beijing Climate Center’s Earth System Model,and is participating in phase 6 of the Coupled Model Intercomparison Project(CMIP6).The Aerosol Chemistry Model Intercomparison Project(AerChemMIP)is the only CMIP6-endorsed MIP in which BCC-ESM1 is involved.All AerChemMIP experiments in priority 1 and seven experiments in priorities 2 and 3 have been conducted.The DECK(Diagnostic,Evaluation and Characterization of Klima)and CMIP historical simulations have also been run as the entry card of CMIP6.The AerChemMIP outputs from BCC-ESM1 have been widely used in recent atmospheric chemistry studies.To facilitate the use of the BCC-ESM1 datasets,this study describes the experiment settings and summarizes the model outputs in detail.Preliminary evaluations of BCC-ESM1 are also presented,revealing that:the climate sensitivities of BCC-ESM1 are well within the likely ranges suggested by IPCC AR5;the spatial structures of annual mean surface air temperature and precipitation can be reasonably captured,despite some common precipitation biases as in CMIP5 and CMIP6 models;a spurious cooling bias from the 1960s to 1990s is evident in BCC-ESM1,as in most other ESMs;and the mean states of surface sulfate concentrations can also be reasonably reproduced,as well as their temporal evolution at regional scales.These datasets have been archived on the Earth System Grid Federation(ESGF)node for atmospheric chemistry studies.

Research on the Satisfaction Impact Factors of China-Eurasia Expo:From the Perspectives of Local Residents and Exhibitors

Understanding the satisfaction impact factors of China-Eurasia Expo is important to hold and improve the Expo.This paper divides the impact factors of satisfaction into local residents and exhibitors’aspects.Firstly,this paper constructs a five-dimension conceptual model to measure the local residents’satisfaction which consists of the degree of promoting economic development,environmental protection,cultural quality,urban convenience and urban brand image of the China-Eurasia Expo.898 valid questionnaires were collected and structural equation model(SEM)was used to validate the constructed model and the proposed hypotheses were proved;the path coefficients of cultural quality,urban convenience and urban brand image to locals’satisfaction are all greater than 0.90,indicating that they have high impacts on local residents’satisfaction,while the path coefficient of the degree of promoting economic development to residents’satisfaction is 0.695,indicating a relatively low impact.Secondly,this paper constructs a five-dimension conceptual model of exhibitors’satisfaction which includes infrastructure,management level,service quality,organizing effect,and advancement.708 valid questionnaires were collected and SEM was used to valid the constructed model and the proposed hypotheses.The results show that the five path coefficients to exhibitors’satisfaction are higher than0.7,all hypotheses were proved.

An ultrahigh sensitivity acoustic sensor system for weak signal detection based on an ultrahigh-Q CaF_(2) resonator

Acoustic sensors with ultrahigh sensitivity,broadband response,and high resolution are essential for high-precision nondestructive weak signal detection technology.In this paper,based on the size effect of an ultrahigh-quality(Q)calcium fluoride(CaF_(2))resonator,a weak acoustic signal is detected by the dispersive response regime in which an acoustic,elastic wave modulates the geometry and is converted to a resonance frequency shift.Through the structural design of the resonator,the sensitivity reaches 11.54 V/Pa at 10 kHz in the experiment.To our knowledge,the result is higher than that of other optical resonator acoustic sensors.We further detected a weak signal as low as 9.4µPa/Hz1/2,which greatly improved the detection resolution.With a good directionality of 36.4 dB and a broadband frequency response range of 20 Hz-20 kHz,the CaF_(2) resonator acoustic sensing system can not only acquire and reconstruct speech signals over a long distance but also accurately identify and separate multiple voices in noisy environments.This system shows high performance in weak sound detection,sound source localization,sleep monitoring,and many other voice interaction applications.