This paper describes a high pulse repetition frequency Nd:YAG twisted-mode laser that uses an RTP crystal as the electro-optic Q-switch. Stable single-longitudinal-mode laser beams at 1, 5, and 10 kHz were obtained with a linewidth less than 0.1 GHz. Under an incident pump power of 7.5 W and a PRF of 10 kHz, the maximum output power of the single-longitudinal-mode laser was 1.19 W. The corresponding conversion efficiency, single pulse energy and pulse peak power were 15.8%, 119 μJ, and 2.5 kW, respectively.
The compact LD end-pumped passively Q-switched c-cut Nd:YVO4/Cr4+:YAG self-Raman laser is realized, and its output performance is investigated in detail. The maximum average output power at 1178nm is 800mW with the pulse repetition frequency of 44kHz and pulse width of 2.6ns, and the first Stokes conversion efficiency is 10.1%. The outputs of fundamental and first Stokes laser are found to be linearly polarized along the diagonals of the rectangular cross section of the c-cut Nd:YVO4 crystal, and the polarization mode competition is observed in the outputs of fundamental and first Stokes laser.
In recent years, flash droughts with a rapid onset and strong intensity have attracted extensive attention due to their impact on agriculture and ecosystems. However, there is still no feasible method for flash drought forecasting and early warning. This paper employs the thresholds of several meteorological variables to identify flash droughts in Zhejiang Province, China, and build a probabilistic flash drought forecasting model through numeric weather forecast (NWF) and the generalized Bayesian model (GBM). The results show that the northern part of Zhejiang Province has the highest risk of flash drought. The NWF is a viable method to provide future information for flash drought forecasting and early warning, but its forecasting accuracy tends to decline with the increase in the lead time and is very limited when the lead time is over 5 days, especially for the precipitation forecast. Due to the low performance of the NWF, the flash drought forecast based on the raw NWF may be unreliable when the lead time is over 5 days. To solve this problem, probabilistic forecasting based on GBM is employed to quantify the uncertainty in the NWF and is tested through an example analysis. In the example analysis, it was found that the probability of a flash drought exceeds 30% from the probabilistic forecasting when the lead time is 12 days, while the deterministic forecasting via the raw NWF cannot identify a flash drought when the lead time is over 5 days. In conclusion, probabilistic forecasting can identify a potential flash drought earlier and can be used to evaluate the risk of a flash drought, which is conducive for the early warning of flash droughts and the development of response measures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.