Simultaneously Suppressing Low-Frequency and Relaxation Oscillation Intensity Noise in a DBR Single-Frequency Phosphate Fiber Laser

Effective multiple optoelectronic feedback circuits for simultaneously suppressing low-frequency and relaxation oscillation intensity noise in a single-frequency phosphate fiber laser are demonstrated. The forward transfer function, which relates the laser output intensity to the pump modulations, is measured and analyzed. A custom two-path feedback system operating at different frequency bands is designed to adjust the pump current directly. The relative intensity noise is decreased by 20dB from 0.2 to 5kHz and over lOdB from 5 to lOkHz. The relaxation oscillation peak is suppressed by 22dB. In addition, a long term （24h） laser instability of less than 0.05% is achieved.

Intraseasonal oscillation intensity over the western North Pacific:Projected changes under global warming

The 30-60-day intraseasonal oscillation(ISO) and 10-20-day ISO are two dominant oscillation modes over the western North Pacific during boreal summer.With daily data derived from eight CMIP5 models,changes of the ISO intensities are projected under the 1.5 and 2.0℃ global warming levels under the Representative Concentration Pathway(RCP) 4.5 and RCP8.5 scenarios.Most of the models agree that the ISO intensities increase along a belt region from the south Indochina Peninsula(ICP) to the east to the Philippines.The variation pattern shows little difference between different warming levels or scenarios.Results indicate that the spatial distribution of ISO anomalies is related with the variation of background fields.Enriched lower-level humidity and moist static energy favor the intensity increases of ISOs,which are projected to be larger over the whole western North Pacific,with the most conspicuous changes located over the east to the Philippines for humidity but over the south of the ICP for moist static energy.In contrast,the ISOs over the west to Indonesia and northeast to the Philippines decrease,which is consistent with the local descending motions.

Improving continuous-variable quantum key distribution under local oscillator intensity attack using entanglement in the middle

A modified continuous-variable quantum key distribution （CVQKD） protocol is proposed by originating the entangled source from a malicious third party Eve in the middle instead of generating it from the trustworthy Alice or Bob. This method is able to enhance the efficiency of the CVQKD scheme attacked by local oscillator （LO） intensity attack in terms of the generated secret key rate in quantum communication. The other indication of the improvement is that the maximum transmission distance and the maximum loss tolerance can be increased significantly, especially for CVQKD schemes based on homodyne detection.

Growth Model for Pulsed-Laser Deposited Perovskite Oxide Films

We present a multi-level growth model that yields some of the key features of perovskite oxide film growth as observed in the reflection high energy electron diffraction （RHEED） and ellipsometry studies. The model describes the effect of deposition, temperature, intra-layer transport, interlayer transport and Ostwald ripening on the morphology of a growth surface in terms of the distribution of terraces and step edges during and after deposition. The numerical results of the model coincide well with the experimental observation.

Experimental studies on the heat transfer characteristics of helium-based cryogenic oscillating heat pipes

Purpose Copper is a cooling transfer material used in cryogenic superconducting systems.The effective thermal conductivity(ETC)of copper in the 4K region is only about 400 W/(m K).Its heat transfer performance is poor,there are some shortcomings such as large temperature difference,temperature fluctuation lag,cryogenic system layout limited.The ETC value of helium-based cryogenic oscillating heat pipes(COHP)in the 4K region is much higher than that of copper.However,the choice of heating power interval is very important,and the heating power will affect the oscillation characteristics of COHP.Methods In this study,a helium-based COHP heat transfer performance test platform was built in the 4K region,and the effects of heating power and liquid filling rate on oscillation conditions and ETC were studied.The heating power ranges from 0.1 to 0.5 W,and the liquid filling rate ranges from 20%to 87%.Results and conclusion The heating power interval suitable for oscillation behavior is given quantitatively.The intrinsic correlation between ETC and amplitude is further discussed.The results are of great significance for improving the performance of cryogenic superconducting systems.

Direct prejudgement of hot images with detected diffraction rings in high power laser system

A direct prejudgement strategy that takes the diffraction ring as the analysis target is put forward to predict hot images induced by defects of tens of microns in the main amplifier section of high power laser systems. Analysis of hot-image formation process shows that the hot image can be precisely calculated with the extracted intensity oscillation of the diffraction ring on the front surface of the nonlinear plate. The gradient direction matching （GDM） method is adopted to detect diffraction tings. Recognition of simulated diffraction rings shows that it is feasible to directly prejudge hot images induced by those closely spaced defects and the defects that are far apart from each other. Image compression and cluster analysis are utilized to optimize the performance of the GDM method in recognizing actually collected diffraction images. Results show that hot images induced by defects of tens of microns can be directly prejudged without redundant information.