High Coupling Efficiency of the Fiber-Coupled Module Based on Photonic-Band-Crystal Laser Diodes

The coupling efficiency of the beam combination and the fiber-coupled module is limited due to the large vertical divergent angle of conventional semiconductor laser diodes. We present a high coupling efficiency module using photonic-band-crystal （PBC） laser diodes with narrow vertical divergent angles. Three PBC single-emitter laser diodes are combined into a fiber with core diameter of 105μm and numerical aperture of 0.22. A high coupling efficiency of 94.4% is achieved and the brightness is calculated to be 1.T MW/（cm2.sr） with the injection current of 8A.

2-μm single longitudinal mode GaSb-based laterally coupled distributed feedback laser with regrowth-free shallow-etched gratings by interference lithography

We report a type-I Ga Sb-based laterally coupled distributed-feedback（LC-DFB） laser with shallow-etched gratings operating a continuous wave at room temperature without re-growth process. Second-order Bragg gratings are fabricated alongside the ridge waveguide by interference lithography. Index-coupled LC-DFB laser with a cavity of 1500 μm achieves single longitudinal mode continuous-wave operation at 20℃ with side mode suppression ratio（SMSR） as high as 24 dB.The maximum single mode continuous-wave output power is about 10 mW at room temperature（uncoated facet）. A low threshold current density of 230 A/cm^2 is achieved with differential quantum efficiency estimated to be 93 mW/A. The laser shows a good wavelength stability against drive current and working temperature.

Phase Control of Transient Optical Properties of Double Coupled Quantum-Dot Nanostructure via Gaussian Laser Beams

We theoretically analyze the transient properties of a probe field absorption and dispersion in a coupled semiconductor double-quantum-dot nanostructure.We show that in the presence of the Gaussian laser beams,absorption and dispersion of the probe field can be dramatically influenced by the relative phase between applied fields and intensity of the Gaussian laser beams.Transient and steady-state behaviors of the probe field absorption and dispersion are discussed to estimate the required switching time.The estimated range is between 5-8 ps for subluminal to superluminal light propagation.

Multi-target ranging using an optical reservoir computing approach in the laterally coupled semiconductor lasers with self-feedback

We utilize three parallel reservoir computers using semiconductor lasers with optical feedback and light injection to model radar probe signals with delays.Three radar probe signals are generated by driving lasers constructed by a threeelement laser array with self-feedback.The response lasers are implemented also by a three-element lase array with both delay-time feedback and optical injection,which are utilized as nonlinear nodes to realize the reservoirs.We show that each delayed radar probe signal can be predicted well and to synchronize with its corresponding trained reservoir,even when parameter mismatches exist between the response laser array and the driving laser array.Based on this,the three synchronous probe signals are utilized for ranging to three targets,respectively,using Hilbert transform.It is demonstrated that the relative errors for ranging can be very small and less than 0.6%.Our findings show that optical reservoir computing provides an effective way for applications of target ranging.

Static and Dynamic Analysis of Lasing Action from Single and Coupled Photonic Crystal Nanocavity Lasers

The single and coupled photonic crystal nanocavity lasers are fabricated in the InGaAsP material system and their static and dynamic features are compared. The coupled-cavity lasers show a larger lasing e^ciency and generate an output power higher than the single-cavity lasers, results that are consistent with the theoretical results obtained by rate equations. In dynamic regime, the single-cavity lasers produce pulses as short as 113 ps, while the coupled-cavity lasers show a significantly longer lasing duration. These results indicate that the photonic crystal laser is a promising candidate for the light source in high-speed photonic integrated circuit.

Mg/Ca,Ba/Ca,and S/Ca ratios as environmental and growth proxies for bivalve shells from the Haima cold seep,South China Sea

Bivalve shell fossils,cemented by authigenic carbonates,are widely spread in the Haima cold seep,Qiongdongnan Basin of the South China Sea(SCS).In this study,we examined an element profile of Gigantidas platifrons in the Haima cold seeps at a water depth of 1381 m.Based on the scanning electron microscope(SEM)analyses,the prismatic layer and nacreous layer were identified,which are characterized by prismatic structure and stratified structure,respectively.In addition,the profile can be subdivided into two parts:altered and unaltered zones.Laser inductively coupled plasma mass spectrometry(LA-ICP-MS)mapping shows that the element concentrations of the altered zones were influenced by the authigenic carbonate rocks,whereas the element concentrations of unaltered zones remain stable.In-situ X-ray diffraction(XRD)analyses show that the mineral constituent of the prismatic layer is mainly composed of aragonite.Along with the growth profile,Mg/Ca ratios of unaltered zones have minor variations,ranging 0.72-0.97 mmol/mol(mean=0.87 mmol/mol),with estimated temperatures of 3.8-4.1℃,indicating that the temperature of the surrounding seawater remains constant and agree with the measured data of 3.9℃which was conducted by a conductivity-temperature-depth system(CTD).The minor variations of Ba/Ca ratios(0.01-0.06 mmol/mol;mean=0.04 mmol/mol)indicate a relatively stabilized salinity of the surrounding seawater.S/Ca ratios show large variations of 0.04-4.15 mmol/mol(mean=1.37 mmol/mol).S/Ca ratios have regular variations which generally correspond to the variations of the Mg/Ca ratios,highlighting that the S/Ca ratios of bivalve shells show the potential to reflect the growth rate of the Gigantides.However,further studies should be carried out on the understanding of the links between the S/Ca ratios and seepage intensity of cold-seep fluids.

Researching the 915 nm high-power and high-brightness semiconductor laser single chip coupling module

Based on the high-speed development of the fiber laser in recent years, the development of researching 915 nm semiconductor laser as main pumping sources of the fiber laser is at a high speed. Because the beam quality of the laser diode is very poor, the 915 nm laser diode is generally based on optical fiber coupling module to output the laser. Using the beam-shaping and fiber-coupling technology to improve the quality of output beam light, we present a kind of high-power and high-brightness semiconductor laser module, which can output 13.22 W through the optical fiber. Based on 915 nm GaAs semiconductor laser diode which has output power of 13.91 W, we describe a thoroughly detailed procedure for reshaping the beam output from the semiconductor laser diode and coupling the beam into the optical fiber of which the core diameter is 105 μm and the numerical aperture is 0.18. We get 13.22 W from the output fiber of the module at 14.5 A, the coupling efficiency of the whole module is 95.03% and the brightness is 1.5 MW/cm2-str. The output power of the single chip semiconductor laser module achieves the advanced level in the domestic use.

Fabrication of EAM-Integrated DFB Lasers With A Coupling Waveguide

EAM-DFB monolithic light sources with the coupling waveguide between laser and modulator have been developed. 10mw output light power at 90mA and 18dB extinction ratio at -2V has been achieved.

Effect of ballistic electrons on ultrafast thermomechanical responses of a thin metal film

The ultrafast thermomechanical coupling problem in a thin gold film irradiated by ultrashort laser pulses with different electron ballistic depths is investigated via the ultrafast thermoelasticity model. The solution of the problem is obtained by solving finite element governing equations. The comparison between the results of ultrafast thermomechanical coupling responses with different electron ballistic depths is made to show the ballistic electron effect. It is found that the ballistic electrons have a significant influence on the ultrafast thermomechanical coupling behaviors of the gold thin film and the best laser micromachining results can be achieved by choosing the specific laser technology（large or small ballistic range）.In addition, the influence of simplification of the ultrashort laser pulse source on the results is studied, and it is found that the simplification has a great influence on the thermomechanical responses, which implies that care should be taken when the simplified form of the laser source term is applied as the Gaussian heat source.

Experimental research on impulse coupling effect of a multi-pulse laser on an aluminum target

Impact and torsion pendulums are applied in impulse coupling experiments of high-energy laser irradiation of space debris. It is difficult to achieve a multi-pulse experiment and thus hard to analyze the multi-pulse impulse coupling effect. Here, we designed a new recoil impulse experimental measurement system of non-contact, multidegrees of freedom, and multi-pulse irradiation. The system used a low-pressure and low-temperature vacuum chamber to simulate the space environment, the pinning effect of magnetic levitation to achieve aluminum target suspension, and high-speed cameras to record the displacement over time to calculate the impulse of the target.Then the impulse coupling experiment of multi-pulse laser irradiation on the aluminum target was performed.The result shows that the multi-pulse impulse coupling effect is not the linear accumulation of coupling results by every single-pulse and multi-pulse coefficient that decreases with the increase of the number of pulses, and eventually stabilizes as the decrease gets smaller.

InAs/GaAs quantum dot laterally coupled distributed feedback lasers at 1.3μm

We report the InAs/GaAs quantum dot laterally coupled distributed feedback(LC-DFB)lasers operating at room temperature in the wavelength range of 1.31μm.First-order chromium Bragg gratings were fabricated alongside the ridge waveguide to obtain the maximum coupling coefficient with the optical field.Stable continuous-wave single-frequency operation has been achieved with output power above 5 mW/facet and side mode suppression ratio exceeding 52 dB.Moreover,a single chip integrating three LC-DFB lasers was tentatively explored.The three LC-DFB lasers on the chip can operate in single mode at room temperature,covering the wavelength span of 35.6 nm.

Elemental Quantitative Distribution and Statistical Analysis on Cross Section of Stainless Steel Sheet by Laser Ablation Inductively Coupled Plasma Mass Spectrometry

An innovative application of laser ablation inductively coupled plasma mass spectrometry （LA-ICP-MS） technique in illustrating elemental distributions on stainless steel sheets was presented. The technique proved to be a systematic and accurate ap- proach in producing visual images or maps of elemental distributions at cross-sectional surface of a stainless steel sheet. Two stain- less steel sheets served as research objects： 3 mm×l 300 mm hot-rolled stainless steel plate and 1 mm×l 260 mm cold-rolled plate. The cross-sectional surfaces of the two samples at 1/4 position along the width direction were scanned （raster area -44 mm2 and 11 mm2） with a focused laser beam （wavelength 213 nm, diameter of laser crater 100 μm, and laser power 1.6 mJ） in a laser abla- tion chamber. The laser ablation system was coupled to a quadrupole ICP-MS, which made the detection of ion intensities of 27A1＋, 44Ca＋, 47Ti-, 55Mn＋ and 56Fe＋ within an area of interest possible. One-dimensional （ID） content line distribution maps and two- dimensional （2D） contour maps for specific positions or areas were plotted to indicate the element distribution of a target area with high accuracy. Statistic method was used to analyze the acquired data by calculating median contents, maximum segregation, sta- tistic segregation and content-frequency distribution.

Demonstration of an ultra-low-threshold phonon laser with coupled microtoroid resonators in vacuum

We demonstrate an ultra-low-threshold phonon laser using a coupled-microtoroid-cavity system by introducing a novel coupling approach.The scheme exhibits both high optical quality factors and high mechanical quality factors.We have experimentally obtained the mechanical quality factor up to 18,000 in vacuum for a radialbreathing mode of 59.2 MHz.The measured phonon lasing threshold is as low as 1.2μW,which is～5 times lower than the previous result.

1.65μm square-FP coupled cavity semiconductor laser for methane gas detection

We report a 1.65μm square-Fabry–Pérot[FP]coupled cavity semiconductor laser for methane gas detection.The laser output optical power can reach 7.4 m W with the side mode suppression ratio about 40 d B.The wavelength tuning range is 2 nm by adjusting the FP cavity injection current,covering the methane absorption line at 1653.72 nm.The lasing wavelength can also be tuned by adjusting the square microcavity injection current or temperature,respectively.Methane gas detection is successfully demonstrated utilizing this laser.

Conversion of out-of-phase to in-phase order in coupled laser arrays with second harmonics

A novel method for converting an array of out-of-phase lasers into one of in-phase lasers that can be tightly focused is presented.The method exploits second-harmonic generation and can be adapted for different laser arrays geometries.Experimental and calculated results,presented for negatively coupled lasers formed in a square,honeycomb,and triangular geometries are in good agreement.

Subnanosecond KTiOPO4 optical parametric oscillator intracavity pumped by a Kerr-lens, mode-locked YVO4/Nd:YVO4 laser coupled with an acousto-optic modulator

A Kerr-lens, mode-locked YVO4∕Nd:YVO4laser coupled with an acousto-optic modulator（AOM） Q-switching near1064 nm was employed to pump an intracavity KTi OPO4（KTP） optical parametric oscillator. A subnanosecond signal wave near 1572 nm with low repetition rate was realized. At an AOM repetition rate of 8 kHz, the maximum output power was 165 mW. The highest average pulse energy, the shortest duration, and the highest peak power of a mode-locking signal pulse were estimated to be ～10.3 μJ, ～120 ps, and ～82 kW, respectively.

Design and Analysis of Compact Directionally Coupled Bistable Laser Diodes

A compact optical flip-flop with a directional coupler has been designed and analyzed. Using a narrow gap directional coupler, we have predicted the device length could be reduced down to 500μm from 1300μm.

Stable anticipation synchronization in mutually coupled vertical-cavity surface-emitting lasers system

Two vertical-cavity surface-emitting lasers（VCSELs） are mutually coupled through a partially transparent mirror （PTM） placed in the pathway. The PTM plays the role of external mirror, which controls the feedback strength and coupling strength. We numerically simulate this system by establishing a visible SIMULINK model. The results demonstrate that the anticipation synchronization is achieved and it can tolerate some extent frequency detuning. Moreover, the system shows similar chaos-pass filtering effect on unidireetionally coupled system even both VCSELs are modulated. This system allows simultaneously bidirectional secure message transmission on public channels.

Accumulation, transportation, and distribution of tetracycline and cadmium in rice

Co-exposure to heavy metal and antibiotic pollution might result in complexation and synergistic interactions,affecting rice growth and further exacerbating pollutant enrichment.Therefore,our study sought to clarify the influence of different Tetracycline (TC) and Cadmium(Cd) concentration ratios (both alone and combined) on rice growth,pollutant accumulation,and transportation during the tillering stage in hydroponic system.Surprisingly,our findings indicated that the interaction between TC and Cd could alleviate the toxic effects of TC/Cd on aerial rice structures and decrease pollutant burdens during root elongation.In contrast,TC and Cd synergistically promoted the accumulation of TC/Cd in rice roots.However,their interaction increased the accumulation of TC in roots while decreasing the accumulation of Cd when the toxicant doses increased.The strong affinity of rice to Cd promoted its upward transport from the roots,whereas the toxic effects of TC reduced TC transport.Therefore,the combined toxicity of the two pollutants inhibited their upward transport.Additionally,a low concentration of TC promoted the accumulation of Cd in rice mainly in the root tip.Furthermore,a certain dose of TC promoted the upward migration of Cd from the root tip.Laser ablation-inductively coupled plasma mass spectrometry demonstrated that Cd mainly accumulated in the epidermis and stele of the root,whereas Fe mainly accumulated in the epidermis,which inhibited the absorption and accumulation of Cd by the rice roots through the generation of a Fe plaque.Our findings thus provide insights into the effects of TC and Cd co-exposure on rice growth.

Direct Quantitative Determination of Rare Earth Elements in REE-rich Mineral Powders by LA-ICP-MS

For direct quantitative determination of rare earth elements（REE） in REE-rich minerals, a most acceptable reference material NIST 610 might be an alternative external calibration standard due to the lack of matrix-matched reference materials. Here, we aimed to develop an analytical method for direct quantitative determination of REE concentrations in REE-rich minerals via laser ablation-inductively coupled plasma-mass spectrometry（LA-ICP-MS）. The results show that the REE concentrations measured via LA-ICP-MS using NIST 610 as an extemal standard are in good agreement with reference values with relative percentage difference（Dr） mainly less than 15%. Overall, these results demonstrate that our proposed analytical method is robust and accurate for direct quantitative determination of REE concentrations in REE-rich minerals.