Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Al2O3-YAG:Ce composite phosphor ceramic: a thermally robust and efficient color converter for solid state laser lighting
No full textJSPS KAKENHI [15K06448]; National Natural Science Foundation of China [51272259, 5157223, 51472087, 51561135015]; China Scholarship CouncilSolid state laser lighting is a newly emerging technology that combines a blue laser diode (LD) with a yellow-emitting phosphor converter to generate high-brightness white tight. Due to high flux irradiation as well as thermal attack from the incident laser, this technology draws a demanding requirement on the thermal performance of the color converter. In this work, we design a Al2O3-YAG:Ce phosphor ceramic with a unique composite structure, where yellow-emitting YAG:Ce particles are embedded in a non-luminescent Al2O3 matrix having high thermal conductivity. The large YAG:Ce particles (5-20 mu m) show good crystallinity and a high external quantum efficiency of 76% (upon 460 nm excitation) white the fine Al2O3 grains (0.5-2 mu m) contribute to the superior in-line transmittance of 55% at 800 nm by minimizing the birefringence related scattering. The phosphor ceramic exhibits a high thermal conductivity of 18.5 W m(-1) K-1 and a remarkable improvement in thermal stability (only an 8% reduction at 200 degrees C). When irradiated under 445 nm blue laser diodes, the phosphor ceramic shows no luminescence saturation even under a high power density of 50 W mm(-2), validating its suitability for high-power solid state laser lighting
Continuous-Wave Passively Mode-Locked Nd:CGA Lasers
No full text采用X型谐振腔,实验研究了二极管抽运Nd:CGA激光器的连续和被动锁模激光特性。当Nd:CGA激光器实现连续运转时,采用不同透过率的输出镜优化激光器的连续输出功率。采用透射率为20%的输出镜时,获得了1.8 W的最高连续输出功率,斜率效率达到30.8%,中心波长为1079 nm;采用半导体可饱和吸收反射镜作为锁模元件、透射率为1.6%的平面镜作为输出镜,获得了脉冲宽度为2.7 ps、重复频率为177 MHz的被动锁模脉冲输出。当抽运功率为6.9 W时,获得锁模脉冲的最大平均输出功率为524 mW,相应的光国家973计划; 国家自然科学基金国际联合研究项目The continuous wave (CW) and passive mode-locking features of a diode-pumped Nd : CGA laser are experimentally demonstrated with a typical X-type cavity. Under the CW operation, different output couplers (OCs) were used to optimize the CW output power of the Nd: CGA laser. With the OC of 20% transmission, the maximum CW output power of 1. 8 W is achieved and the slope efficiency is 30. 8% at the central wavelength of 1079 nm. By employing a semiconductor saturable absorber mirror for passive mode-locking, pulses as short as 2. 7 ps with 177 MHz repetition rate are achieved for OC with transmission of 1.6%. The maximum average output power of 524 mW is obtained under a pump power of 6. 9 W. The optical-to-optical conversion efficiency and the slope efficiency are 7.6% and 8.0%, respectively
Dispersion of nonlinear refractive index in layered WS2 and WSe2 semiconductor films induced by two-photon absorption
No full textNational Natural Science Foundation of China (NSFC) [61308034, 61405225, 61308087, 61522510]; External Cooperation Program of BIC, CAS [181231KYSB20130007]; Science Foundation Ireland (SFI) [14/TIDA/2329, PI_10/IN.1/I3030]; Strategic Priority Research ProBoth the nonlinear absorption and nonlinear refraction properties of WS2 and WSe2 semiconductor films have been characterized by using Z-scan technique with femtosecond pulses at the wavelength of 1040 nm. It is found that these films have two-photon absorption response with the nonlinear absorption coefficient of similar to 103 cmGW-1, and a dispersion of nonlinear refractive index in the WS2 films that translated from positive in the monolayer to negative in bulk materials. (C) 2016 Optical Society of Americ
Design of intense 1.5-cycle pulses generation at 3.6 mu m through a pressure gradient hollow-core fiber
No full textNational Natural Science Foundation of China (NSFC) [11204328, 61221064, 61078037, 11127901, 11134010, 61205208]; National Basic Research Program of China [2011CB808101]; Natural Science Foundation of Shanghai, China [13ZR1414800]uWe theoretically study the nonlinear compression of the 10-mJ, 62-fs, 3.6-mu m laser pulses in an argon gas-filled hollow-core fiber with large diameter of 1000 mu m. Using a pressure gradient to restrict undesirable nonlinear effect such as ionization, especially at the entrance, we obtain the intense 18.3-fs (similar to 1.5 cycle) pulses at 3.6 mu m only through compression with CaF2 crystal, which can be used as an ultrafast source for strong field driven experiments. In addition, we calculate and discuss the relation between optimal fiber length and coupling efficiency for a given bandwidth. These results are useful for the design of using hollow-core fiber to compress the high-energy pulses with long wavelength. (C) 2016 Optical Society of Americ
Enhanced hole boring with two-color relativistic laser pulses in the fast ignition scheme
No full textNational Natural Science Foundation of China [11425418, 61521093, 11304271, 11205228, 11505263]; Natural Science Foundation of Shanghai [14ZR1444800]A scheme of using two-color laser pulses for hole boring into overdense plasma as well as energy transfer into electron and ion beams has been studied using particle-in-cell simulations. Following an ultra-short ultra-intense hole-boring laser pulse with a short central wavelength in extreme ultraviolet range, the main infrared driving laser pulse can be guided in the hollow channel preformed by the former laser and propagate much deeper into an overdense plasma, as compared to the case using the infrared laser only. In addition to efficiently transferring the main driving laser energy into energetic electrons and ions generation deep inside the overdense plasma, the ion beam divergence can be greatly reduced. The results might be beneficial for the fast ignition concept of inertial confinement fusion. Published by AIP Publishing
Light reversing and folding based on a superluminal flying mirror in a plasma with increasing density
No full textMinistry of Science and Technology [2011CB808104]; National Natural Science Foundation of China [11125526, 11335013, 11404355, 11127901, 61221064]A superluminal flying mirror (SFM) is proposed using the electron density spike in the tail of a wake-field excited in a plasma with an increasing density profile. The wavelength of the wake-field is shrunk in the direction of the increasing plasma density, which increases the phase velocity of the wake wave-namely the flying mirror velocity-in excess of the speed of light. The SFM exhibits some novel characteristics. When it up-shifts the light frequency, just as with a normal flying mirror, because the velocity of the SFM is quicker than light, the reflected light penetrates the electron density spike and propagates behind it. The transmitted light can gain extra energy from the wake wave so that the transmission coefficient is higher than one. Most interestingly, the reflected light may be reversed or folded in time during the reflection, if the SFM velocity gradually decreases and goes through the speed of light. The proposed SFM mechanism can provide potential applications in the production of highfrequency ultrashort pulses
Localization of laser-driven HD+ and H-3(+) fragments
No full textNational Natural Science Foundation of China [11127901, 61521093, 11134010, 11227902, 11222439, 11274325]; National 973 Project [2011CB808103]Electron localization during the dissociation of HD+ and H3+ is investigated by solving the corresponding time-dependent Schrodinger equation. Two different dissociation channels HD+ + n gamma H + d or HD+ + n gamma p + D and H-3(+) + n gamma H-2 + p or H-3(+) + n gamma H-2(+) + H for HD+ and H3+ are investigated, respectively. The numerical simulation demonstrates that for HD+ is in a single ultraviolet laser pulse, the electron localization distribution is symmetric for the symmetric distribution of the Coulomb potential wells though HD+ is a heteronuclear diatomic molecular ion. While for H-3(+), 92.6% electrons of all the dissociation events are localized at the potential well with higher energies (H+) for the asymmetric distribution of the Coulomb potential of H-3(+). When a terahertz pulse is used to steer the electron motion after the excitation of the ultraviolet laser pulse, more than 96.4% electrons of the dissociation state move opposite to the electric field force and stabilize at the one of the nuclei
Manipulation of tribological properties of stainless steel by picosecond laser texturing and quenching
No full textNational Natural Science Foundation of China [61178024, 11374316]We reported on the manipulation of tribological properties of stainless steel by picosecond laser texturing and quenching. The micro-grooved textures were formed on the steel surface, accompanied with the appearance of nanostructures with grain sized of 80-400 nm, oxides thin film (Fe2O3 and Cr2O3) and martensite during picosecond laser surface texturing process. The tribological tests indicated that the average friction coefficients and wear rates of textured surfaces initially increased then decreased with the increase of spacing of micro-grooves. The well-controlled friction and wear properties are attributed to the combined effects of induced micro-/nanostructures, martensitic transformation and oxides thin film in the local quenched zone of stainless steel samples. (C) 2016 Elsevier Ltd. All rights reserved
Preliminary Discussion on Composite Coating of TiO_2 and SiO_2 on Sericite and Corresponding Photocatalytic Performance
No full text以四氯化钛为钛源,在绢云母表面水解、沉积二氧化钛,制备了绢云母@二氧化钛结构,在此基础上以水玻璃为硅源制备了绢云母@二氧化钛/二氧化硅复合体系,探讨了合成影响因素以及复合材料的光催化性能。X射线衍射、红外光谱等测试表明:绢云母与四氯化钛固液比为2:10时,二氧化钛包覆效果最优;二氧化硅对绢云母@二氧化钛包覆作用较好。以罗丹明B为污染物测试材料光催化性能,结果表明,绢云母@二氧化钛体系的光催化性能优于未经处理的市售纳米二氧化钛,而绢云母@二氧化钛/ 二氧化硅复合体系则可进一步提高降解效果。After hydrolyzation of TiCl_4,TiO_2 was coated on the surface of sericite (Ser) to form a Ser@ TiO_2 structure, with which as the substrate, a Ser@ TiO_2/SiO_2 composite was prepared with water glass as Si source. The influences of synthesizing parameters on structure and photocatalysis performance of the composite were discussed. XRD and IR results show that the best coating effect of TiO_2 can be observed at a Ser/TiCl_4 ratio of 2:10,and Ser@ TiO_2 can be well-coated by SiO_2. The photocatalysis properties of these composite films were evaluated by checking their influences on degradation of a typical dye pollutant rhodamine B under UV radiation. The results indicate that the performance of Ser@ TiO_2 is better than that of the commercial nano-sized TiO_2 powder, while the composite system Ser@ TiO_2/SiO_2 can further improve the degradation effect
