连续波锁模P_r~（3＋）：YLF激光器

本文报导了采用氩离子激光器来泵浦Ｒｒ￣（３＋）：ＹＬＦ晶体，应用声光调制器实现了主动锁模；同时应用振动─高反射平面镜也实现了被动锁模，两种锁模均得到了ｐｓ光脉冲。据作者了解这是这种晶体材料的第一次锁模运转。     

C轴YLF激光发射光谱和锁模性质

本文研究了C轴YLF晶体的光谱性质,并利用这种新型激光晶体,进行了主动锁模,被动锁模和主被动锁模实验.C轴YLF激光器直接发射1.053μm激光,锁模脉冲序列能量起伏小于±4%,脉宽起伏不大于±10%.     

掺铬硅酸镁晶体实现全固化自启动1.3 μm波长自锁模激光运转

掺铬硅酸镁晶体 ( Cr:Forsterite)锁模激光器发射的 1 .3μm激光在生物图像及非线性激光显微学上的应用前景已得到充分证明 ,因此促进了实用化掺铬硅酸镁锁模激光器的研究。最近国际上有报道 :将半导体可饱和布拉格反射镜 ( SBR)或可饱和吸收体镜 ( SESAM)应用于克尔棱镜锁模激光器 ,成功实现其自启动过程。这一技术大大推动了掺铬硅酸镁锁模激光器向全固化、小型化发展。本文报道了中国科学院上海光学精密机械研究所生长的优质 Cr:Forsterite晶体 ,运用半导体可饱和反射镜技术 ,在国内首次实现全固化自启动 1 .3μm波长自锁模激光运转…     

自由耦合输出的大模场面积光子晶体光纤锁模激光器

对一种基于高增益掺Yb³⁺大模场面积光子晶体光纤（PCF）的锁模激光器进行了简化线型腔结构的实验和理论研究.实验中直接使用塌陷打磨为0°角的光纤端面作为一端腔镜,利用其端面反馈获得了激光振荡,并进一步利用半导体可饱和吸收镜（SESAM）和光栅对的滤波作用实现了稳定的锁模运转.通过调节滤波程度,使激光器实现了从宽带滤波锁模到窄带滤波锁模的连续可调谐.在宽带滤波锁模的条件下,得到了最大平均输出功率2.2 W,单脉冲能量29.3 nJ,脉冲宽度367 fs的锁模脉冲输出;在窄带滤波锁模的条 关键词： 飞秒激光 光纤激光器 光子晶体光纤 大模场面积光纤     

基于非线性偏振旋转锁模的高功率光子晶体光纤飞秒激光振荡器

为了探索大模场面积光子晶体光纤锁模激光器在全正色散锁模域内的耗散孤子锁模机理, 以获得更大的单脉冲能量和更高的峰值功率, 本文搭建了以掺镱大模场面积光子晶体光纤作为增益介质的耗散孤子锁模激光器. 激光器使用环形腔结构, 利用非线性偏振旋转以及滤光片提供的耗散作用实现了稳定的锁模运转. 实验中, 从激光器振荡级直接获得了平均功率10 W, 重复频率49.09 MHz(对应202 nJ的单脉冲能量), 脉冲宽度为1.03 ps的稳定锁模脉冲输出, 经过腔外色散补偿得到的脉冲宽度为95.5 fs.     

用倍频晶体KTP实现Nd：YAG激光锁模的研究

报道用倍频晶体KTP实现Nd:YAG激光锁模的系统研究,给出了该锁模激光器输出脉宽的表达式,并和实验测量值相比较,计算值跟实验结果符合较好.文中还分析了各种参数对该锁模激光输出性能的影响.     

高能量掺Yb偏振型大模场面积光子晶体光纤孤子锁模飞秒激光器

实验研究了基于掺Yb偏振型大模场面积光子晶体光纤的孤子锁模激光器,获得了高脉冲能量的飞秒激光输出. 激光器基于线形腔结构,利用光栅对补偿腔内色散,并通过半导体可饱和吸收镜实现锁模的自启动. 实验中从振荡级直接获得了平均功率为700mW, 重复频率为47.3MHz(对应于14.8 nJ的单脉冲能量),脉冲宽度为518 fs的稳定锁模脉冲输出. 与普通孤子锁模飞秒光纤激光器相比,输出的单脉冲能量提高了两个数量级. 关键词： 光子晶体光纤 飞秒 光纤激光器 孤子锁模     

10kHz腔倒空锁模皮秒激光器研究

将半导体可饱和吸收体(SESAM)锁模技术与腔倒空技术结合,采用半导体端面抽运方式实现了具有高重复频率、大单脉冲能量的皮秒激光器的运转.从理论上分析了腔倒空锁模输出的机理,建立起腔倒空锁模激光器运行的物理图像,并对影响激光器倒空率的一些因素进行了研究.实验上,实现端面抽运Nd:YVO4晶体的SESAM连续锁模后,在锁模...     

利用被动锁模技术实现超短脉冲激光输出实验

基于被动锁模技术,设计了结构紧凑的Z型谐振腔,采用半导体可饱和吸收镜作为被动锁模元件,利用激光二极管泵浦增益线宽较宽的Nd∶YVO4晶体,最终实现了连续锁模的脉冲输出.在输入功率为8.20W时,获得了输出功率为1.72W的1 064nm连续锁模脉冲激光输出,光-光转换效率达21%,锁模脉冲重复频率为110MHz.     

GHz重复频率亚百飞秒克尔透镜锁模Yb:CaYAlO4激光器

GHz重复频率飞秒激光具有高单纵模功率和高采样速率等优点,在科学前沿和工业加工等领域具有重要的应用价值.受限于锁模原理和泵浦源的可用功率, GHz重复频率克尔透镜锁模激光器的平均输出功率通常仅为数十到百毫瓦量级,限制了其直接应用.基于此,本文报道了利用高功率单模光纤激光器泵浦的GHz重复频率高功率克尔透镜锁模飞秒激光器.通过合理的腔模设计,构建了四镜环形腔结构,使晶体中激光模式可以和整形后的泵浦光形成良好匹配,以利于软孔克尔透镜锁模的实现.在8 W的泵浦功率下,首次在Yb:CaYAlO₄激光器中实现了GHz重复频率的亚百飞秒高功率锁模运转,平均输出功率为2.1 W,重复频率为1.8 GHz,脉冲宽度为88 fs,对应峰值功率大于10 kW.该实验结果表明Yb:CaYAlO₄晶体具有产生GHz重复频率高功率飞秒激光的潜力,高功率短脉宽GHz飞秒激光器可为光学频率梳和微加工等领域提供优质光源.     

Study of Multi-Quasiparticle Excited States in 139Ce

High-spin states in ¹³⁹Ce have been populated using the ¹³⁰Te(¹²C,3n) reaction at beam energy of 50MeV. The level scheme of ¹³⁹Ce has been revised and extended greatly up to E=5765.0keV. The level structure of ¹³⁹Ce shows typical characteristics of spherical nucleus, and the high-spin states were formed by the excitations of valence nucleons. Energies of the yrast and near yrast high-spin states in ¹³⁹Ce have been calculated by the empirical shell model, and the multi-quasiparticle nature of high-spin excited states has been discussed.     

First Study of Weak (EC+β+) Decay Branch for the Neutron-Deficient Isotoep 209Fr

²⁰⁹Fr has been produced by irradiation of ¹⁹⁷Au with ¹⁶O from SFC accelarator uia the fusion-evaporation 4n channel.The(EC+β⁺)decay of ²⁰⁹Fr has been studied by a He-jet tape transport system.The decay scheme is proposed for the first time based on γ-t,X-γ-t,γ-γ-t coincidece and γ-γ delay coincidence measurements,which takes account of 20 observed γ ray.Five members of low-lying states in ²⁰⁹Rn can be explained by the multi-plet [(²¹⁰Rn2⁺)(νf_5/2)^－1].The branching ratio for(EC+β⁺) decay of ²⁰⁹Fr has been estimated experimentaly to be(3.0±1.5)%.     

The Decay Scheme of 175Er

The ¹⁷⁵Er activity was produced via the reaction ¹⁷⁶Yb(n,2p) ¹⁷⁵Er by 14MeV neutron irradiation of a natural ytterbium metal target with a thickness of～80mg/cm2.X-γ and γ-γ coincidence measurements were employed to identify ¹⁷⁵Er activity.The half-life of ¹⁷⁵Er has been determined to be (1.2±0.3)min. Eight new gamma rays were assigned to the decay of ¹⁷⁵Er. A partial decay scheme of ¹⁷⁵Er has been proposed for the first time, from which a ground rotational band has been assigned to ¹⁷⁵Tm.     

The Decay of 120Ba

¹²⁰Ba was produced by 68MeV ¹⁶O beam bombarding a 2mg/cm² thick ¹⁰⁶Cd target and fluorated in a halium-jet ion source.The decay of on-line mass separated activity ¹²⁰Ba has been studied by γ-X,γ-γ γ-β coincidence measurements.Its halflife was measured to be 24±2s.The total decay energy was extracted to be Q_EC=5.0±0.3MeV.A simple decay scheme has been proposed.     

Study on the Excited States of 124Cs by Heavy Ion Reaction

Excited states of ¹²⁴Cs have been studied by means of in beam γ-ray technique via the reaction ¹⁰⁹Ag(¹⁹F,p3n).Based on the observation of the high spin bands and their decay to the ground state,a level scheme of ¹²⁴Cs has been established.     

CHARGE DENSITY DISTRIBUTIONS OF DEFORMED NUCLEI

A simple calculation method for charge for charge density distributions of deformed nuclei by using macroscopic model has been proposed.The calculations of charge density distributions for ¹⁹²Os,¹⁵⁴Gd,¹⁵²Sm,¹⁷⁴Yb, and ^{144,148,150,152}Sm nuclei have been performed.The results show that the calculated charge densities are in good agreement with experiments.Consequently,on the base of experimental data of the transition probabilities for ground state to 2⁺,4⁺,6⁺ rotational states or its electric multipole moments,The charge density distributions of deformed nuclei can be predicted theoretically by this method.     

High-Spin States and Negative Parity Levels in Neutron-Rich 116,118,120Cd Nuclei

High spin states in neutron-rich ^116,118,120Cd nuclei have been investigated by observing high-fold prompt γ-ray coincidence events from the spontaneous fission of ²⁵²Cf with the Gammasphere detector array. The yrast bands have been extended with spin up to 18h in¹¹⁸Cd and 16h in ^116,120Cd respectively. The band structures are calculated using the cranked shell model and possible origination for the backbends in the yrast bands is discussed. Proposed 5^－ and 7^－ levels are observed in each of these cadmium isotopes, and possible explanation for the negative states is discussed based on systematic comparison. A quasi-rotational band based on 7^－ level in ¹¹⁸Cd has been established.     

Study of Collective Rotational Bands in 179Pt

High-spin states in ¹⁷⁹Pt have been studied experimentally using the ¹⁴⁹Sm(³⁵Cl, p4n) fusion-evaporation reaction at beam energies of 164—180MeV. Measurements of γ-ray excitation function, X-γ coincidences and γ-γ-t coincidences were carried out with 13 BGO(AC) HPGe and 3 LOAX detectors. Based on the measured results, three rotational bands built on intrinsic states assigned to the 1/2^－[521], 5/2^－[512] and 7/2⁺[633] Nilsson configurations have been established for ¹⁷⁹Pt. It has been observed that the aligned angular moment in the 1/2^－[521] band increases suddenly around hω=0.27MeV. The big signature splitting has been observed in the 7/2⁺[633] band. These phenomena are discussed by referring to the systematics of the level structure in the Pt isotopes and isotones of ¹⁷⁹Pt.     

Octupole Deformed Band and Quasi-γ Band in 146Ce Nucleus

High-spin structures in ¹⁴⁶Ce nucleus have been re-investigated by measuring the prompt γ rays from spontaneous fission of ²⁵²Cf. The previously reported level scheme of ¹⁴⁶Ce has been updated. The octupole deformed collective bands have been extended up to higher spin states. A possible quasi-γ band structure was examined and reconstructed according to our data analysis. In addition, the reflection asymmetric shell model was applied to describe the octupole deformed bands in ¹⁴⁶Ce, and the calculated results are in good agreement with the experimental data at lower spins.     

Study on KC1 Colorated Center Doped with Na+ Crystal by Positron Annihilation

The relation of the live times and S parameters with doped quantities of Na⁺ have been studied by positron annihilation method in pure,colourable and irradiant KC1 single crystals,The results show that the concentration of vacancies of KC1 doped with 800ppm Na⁺ is 4.24×10¹⁷/cm³.It is close to that of the pure KC1 crystal.The obvious F centers exist in the colorated crystal.The S parameters are mainly influenced by the external electrons of halide ions.Mechanism of annihilation of KC1 crystal doped with Na⁺ has been discussed.