铜蒸气激光泵浦的飞秒光脉冲染料放大器

建立了频率为８ｋＨｚ的铜蒸气激光泵浦的二级共焦飞秒光脉冲染料放大器，把从对撞脉冲锁模环形染料激光器中输出的光脉冲能量放大到０．６μＪ，放大倍数为３×１０３，放大光脉冲宽度为６０飞秒，因此得到放大光脉冲峰值功率为１０ＭＷ。     

皮秒染料激光放大器

近几年来,由于采用了对撞脉冲锁模(CPM)的方法,使激光脉冲的宽度达到飞秒量级,但由于产生的激光单脉冲能量只有100pJ左右,使它的应用受到很大的限制,因此我们必须用高功率的激光脉冲泵浦染料放大器使飞秒光脉冲的能量达100μJ左右,期望用放大的飞秒光脉冲作为有效的手段,在物理学、化学、生物学及光电子学等领域,以求获得突破性的进展。     

一种准分子激光泵浦的微微秒染料激光脉冲放大器

本文叙述一种在一个泵浦周期内讯号脉冲三次通过染料池的微微秒激光脉冲放大器,它有效地利用泵浦能量,可以得到4×10~4的高增益,低的放大自发荧光以及没有脉冲变宽,并且结构简单,工作稳定。用四能级分子模型,以及作速率方程的数值解,对放大器的特性做了计算机模拟。计算与实验结果相符。     

激光等离子体诊断用微微秒紫外高功率激光脉冲的产生

氙灯泵浦的可调谐染料激光器锁模脉冲用XeCl准分子激光器泵浦的三级染料激光放大器放大后,经倍频再用XeCl准分子激光器放大,在308毫微米处获得了微微秒高功率激光脉冲输出,其峰值功率可达500兆瓦,功率净增益为200。     

1975年美国激光工程和应用会议技术报告摘要选辑

1.3 Nd:YAC激光泵浦的一种同步锁模染料激光器的非线性混频,放大和微微秒脉冲的产生利用锁模激光器泵浦的染料激光器,可产生与泵浦脉冲时间同步的极短脉冲。本文介绍利用条纹照相机进行的微微秒脉冲形成的研究。这是一种同步锁模染料激光器,用被动锁模Nd:YAG倍频激光器泵浦。利用光源的同步性质,并通过非线性方法,就可以制成高增益的短脉冲染料放大器,获得可调波长(紫外和红外)的超短(微微秒级)     

飞秒染料激光放大器

本文用重复率为10Hz、调Q、Nd∶YAG激光器的二倍频输出泵浦四级染料放大器,把从对撞脉冲锁模(CPM)环形染料激光器中产生的43fs的光脉冲能量放大到100μJ,脉冲宽度为125fs,峰值功率为800MW,在用一组四棱镜系统对放大的光脉冲进行群速度色散补偿以后,得到了宽度为70fs的放大光脉冲输出,峰值功率达GW。     

微微秒相干反斯托克斯喇曼散射

我们用锁模Nd~(3 )玻璃微微秒脉冲激光序列同步泵浦染料激光器产生的锁模运转染料激光作为ω_2,斯托克斯光束,Nd~(3 )玻璃激光倍频绿光作为固定频率ω_1光束和探测光束,对材料相干激发和探测。实验装置如图1所示。泵浦源采用一级振荡、二级放大主被动锁模钕玻璃激光系统。     

基于光子晶体光纤放大系统的皮秒方波产生

在光子晶体光纤飞秒激光放大系统中,利用液晶空间光调制器的调制特性,实现了对超短激光脉冲实时、可控的脉冲振幅整形,分析了大线性啁啾方波脉冲在放大过程中的频域和时域形状随泵浦功率的变化规律,在此基础上,通过液晶空间光调制器对主放大器前的脉冲频谱形状进行了预先调整,放大后获得了中心波长为1 031 nm,光谱宽度为13 nm,脉宽为15 ps的方波脉冲,证实了采用光谱优化后的飞秒脉冲作种子,可以较好地克服光子晶体光纤放大器增益不均引起的频谱形状的变化。     

超短行波放大自发辐射的研究

用泵浦能量具有梯度分布的横向同步泵浦方案,产生超短行波自发辐射光脉冲。以N_2激光为泵浦源,获得约50ps的染料光脉冲输出,以锁模Nd:YAG倍频光作泵浦源,获得8～15ps光脉冲。用条纹照相机和光学多道分析器测量了脉冲波形和光谱。 计算机模拟了行波放大自发辐射的瞬态行为,计算结果与实验结果相符合。     

增益分布对皮秒脉冲自相似放大的影响

采用数值模拟的方法,研究了增益分布对皮秒脉冲自相似放大的影响。构建了掺镱光纤内超短激光脉冲自相似放大的理论模型,以不同的泵浦方式、光纤长度和总增益系数实现不同的增益分布,探究了不同增益分布对增益光纤中皮秒脉冲的自相似放大过程和结果的影响。结果表明,皮秒脉冲在不同的增益分布下存在最佳的自相似放大结果,可以得到近变换极限的百飞秒高质量脉冲输出。发现同一信号光脉冲在增益光纤中演化至自相似放大过程时,正向泵浦方式下的演化速度比反向泵浦快。对于不同的增益光纤长度和总增益系数,正向泵浦方式下的信号光自相似区域主要集中在低入射脉冲能量和长波长区域,反向泵浦方式下的信号光自相似区域主要集中在高入射脉冲能量和短波长区域。     

Enhanced green electrophosphorescence by using polyfluorene host via interfacial energy transfer from polyvinylcarbazole

For green-emitting Ir complex-doped polymer devices, high efficiencies have been achieved only when non-conjugated poly(N-vinylcarbazole) (PVK) was used as the host polymer. It is commonly believed that conjugated polyfluorenes (PFO) are not suitable for the use as host of green phosphorescent complexes due to the presence of the low-lying triplet state. In this paper we reported that despite very inefficient PL phosphorescent emission of Ir(Bu-PPy)₃ in the PFO films, strong green electroluminescence (EL) and high device efficiencies have been observed for devices from such blend films when multilayer device with PVK was used as anode buffer. We analyze the PL spectra in steady state and transient response and found that the energy transfer via PVK interlayer plays important role in the efficient EL performance. This fact clearly indicates the efficient electrophosphorescence might be achieved even if the triplet energy of phosphorescence dye is higher than that of the host. These findings could significantly broaden our selection in polymer hosts for phosphorescent devices.     

有机材料ZnTBP/CA/PhR体系的反饱和吸收特性研究

报道了有机材料ＺｎＴＢＰ／ＣＡ／ＰｈＲ对激光的反饱和吸收特性。理论分析从该材料特有的五能级结构出发，指出三重态的第一激发态在反饱和吸收过程中的重要作用，并用两束光同时照射样品的实验方法进行了验证。该材料的反饱和吸收效应可在功率不太高的连续光下操作     

Low‐Threshold Organic Semiconductor Lasers with the Aid of Phosphorescent Ir(III) Complexes as Triplet Sensitizers

Organic semiconductor lasers (OSLs) have emerged as particularly challenging. One of the major issues preventing the successful realization of lasing from organic emitters under electrically pumped conditions is the inevitable population of triplet excitons. Herein, a novel concept is presented to construct triplet–singlet guest–host gain systems with incorporating iridium complexes as the triplet sensitizers and a fluorescent conjugated polymer as the gain media to achieve light amplification. The direct triplet–singlet energy transfer process is confirmed by photoluminescence excitation spectra, photoinduced absorption spectroscopy, and fluorescence transients of the blend samples. Successful light amplification with a threefold lower amplified spontaneous emission threshold and much better lasing performance is demonstrated for the resulting triplet–singlet guest–host system as compared with the corresponding gain system without triplet sensitizers. Moreover, under electrically driven conditions, the fluorescent organic light‐emitting diodes (OLEDs) based on the triplet–singlet guest–host systems with “triplet sensitizers” exhibit enhanced electrical performance relative to those without. The work suggests an effective general methodology to utilize both the singlet and triplet excitons to contribute to the light amplification with excellent electrical performance in OLEDs, opening prospects toward attempting electrically pumped OSLs.     

Flashlamp-excited organic dye lasers

The flashlamp-excited dye laser is presently the only type of laser capable of tunable emission throughout most of the visible spectrum. Gain and power output of the device are comparable to solid-state systems although the laser performance is hindered by thermal effects, produced by spatially nonuniform excitation of the dye, and optical losses associated with the molecular triplet state. In most of the known laser dyes, steady-state lasing is prevented by triplet state effects. The analysis of the gain of the dye laser is discussed in terms of the singlet-state absorption and fluorescence and triplet-state absorption spectra. The gain analysis is used to study the influence of the triplet state upon the critical inversion, and application of the analysis to a specific system is illustrated by the detailed discussion of the rhodamine 6G laser. A criterion for the maximum permissible triplet-state lifetime consistent with CW operation is given. The quenching of the triplet state of rhodamine 6G is shown to be rapid enough to allow CW operation, although thermal effects seem to be serious. The investigation of thermal effects is reviewed and the advantages of uniform excitation of the dye are pointed out. The minimum optical excitation power required for CW operation of a 7-cm-long rhodamine 6G laser of 2 mm diameter is estimated to be 850 watts neglecting thermal effects. A catalog of dyes, with their structures, that have been used in flashlamp-excited dye lasers is given. Various methods of tuning and mode locking the dye laser are reviewed. With a single dye a tuning range of 40 nm may be obtained by substituting a diffraction grating for one of the laser mirrors. Mode locking can be produced by placing a saturable dye absorber in the cavity.     

连续波与脉冲激光器在三重态-三重态湮灭上转换中的应用（特邀）

三重态?三重态湮灭上转换是一种新型光子上转换技术,具有使用连续波光源激发、上转换波长灵活可调和上转换量子效率高等优点。在该上转换过程中,三重态光敏剂吸收激发光、发生系间窜越并作为三重态能量给体,通过三重态能量转移过程,敏化能量受体,处于三重态的受体分子发生三重态–三重态湮灭,产生能发生高效荧光过程的单重激发态（即上转换发光）,从而将低能量的光子转换为高能量的光子,这为提高太阳能电池的光电转换效率或光催化的效率等,提供了一种新的途径。实验中需要选用合适的激光器激发上转换体系产生上转换发光,并研究其具体光物理过程。如选用连续波二极管泵浦固体激光器（DPSSL）作为光源,激发光敏剂/受体体系进行上转换实验,可方便地研究激光功率密度对上转换发光效率的影响。此外,为了研究上转换发光的动力学过程,使用光学参量振荡器（OPO）可调谐纳秒脉冲激光器激发上转换体系,可以研究光敏剂的三重态寿命、分子间能量转移以及三重态–三重态湮灭等过程的动力学特征。文中介绍了在三重态–三重态湮灭上转换实验中连续波和脉冲激光器的使用方法。     

Triplet Exciton and Polaron Dynamics in Phosphorescent Dye Blended Polymer Photovoltaic Devices

The triplet exciton and polaron dynamics in phosphorescent dye (PtOEP) blended polymer (MEH‐PPV) photovoltaic devices are investigated by quasi‐steady‐state photo‐induced absorption (PIA) spectroscopy. According to the low‐temperature PIA and photoluminescence (PL) results, the increase in strength of the triplet‐triplet (T₁‐T_n) absorption of MEH‐PPV in the blend system originates from the triplet‐triplet energy transfer from PtOEP to MEH‐PPV. The PtOEP blended MEH‐PPV/C₆₀ bilayer photovoltaic device shows a roughly 30%–40% enhancement in photocurrent and power‐conversion efficiency compared to the device without PtOEP. However, in contrast to the bilayer device results, the bulk heterojunction photovoltaic devices do not show a noticeable change in photocurrent and power‐conversion efficiency in the presence of PtOEP. The PIA intensity, originating from the polaron state, is only slightly higher (within the experimental error), indicating that carrier generation in the bulk heterojunction is not enhanced in the presence of PtOEP. The rate and probability of the exciton dissociation between PtOEP and PCBM is much faster and higher than that of the triplet‐triplet energy transfer between PtOEP and MEH‐PPV.     

Experimental measurement of the critical population inversion for the dye solution laser

The quenching of stimulated emission from organic dye solutions has previously been attributed to optical absorption by dye molecules in the metastable triplet state. By comparing the critical inversion expected for a dye laser with no triplet losses to that obtained from an analysis of the laser that includes the triplet-state loss, the magnitude of the optical loss due to the triplet state can be determined in terms of the absorption and emission spectra, fluorescence decay time, quantum yield, and laser wavelength for a given dye. Measurements of the critical inversion and triplet-state concentration for a flashlamp-excited laser are presented for the xanthene dyes acridine red, fluorescein disodium salt, rhodamine B, and rhodamine 6G. Experiments with 7-hydroxycoumarin were also performed but, due to lack of triplet-state absorption data, the triplet-state concentration could not be determined. It is possible from the measurements to conclude that triplet-state absorption is important in 7-hydroxycoumarin. The critical inversion is found to be approximately 10¹⁵cm^-3for the xanthenes. This value is, in all cases, many times larger than the critical inversion calculated in the absence of triplet losses.     

Self‐Protective Room‐Temperature Phosphorescence of Fluorine and Nitrogen Codoped Carbon Dots

The unstable triplet excited state is a core problem when developing self‐protective room temperature phosphorescence (RTP) in carbon dots (CDs). Here, fluorine and nitrogen codoped carbon dots (FNCDs) with long‐lived triplet excited states, emitting pH‐stabilized blue fluorescence and pH‐responsive green self‐protective RTP, are reported for the first time. The self‐protective RTP of FNCDs arises from n–π * electron transitions for C? N/C?N bonds with a small energy gap between singlet and triplet states at room temperature. Moreover, the interdot/intradot hydrogen bonds and steric protection of C? F bonds reduce quenching of RTP by oxygen at room temperature. The RTP emission of FNCDs shows outstanding reversibility, while the blue fluorescence emission has good pH stability. Based on these FNCDs, a data encoding/reading strategy for advanced anticounterfeiting is proposed via time‐resolved luminescence imaging techniques, as well as steganography of complex patterns.     

Low‐Power‐Photon Up‐Conversion in Dual‐Dye‐Loaded Polymer Nanoparticles

Sensitized triplet–triplet annihilation in multicomponent organic systems is already demonstrated to be suitable for obtaining efficient up‐conversion in solution with excitation power densities comparable to solar irradiance, but loses efficiency in the solid state. Here, it is demonstrated that it is possible to reduce this limitation by incorporating a standard bicomponent system in polymer nanoparticles. The confinement of all of the involved photophysical processes in a nanometer‐scale volume makes each nanoparticle a single and isolated high‐efficiency up‐converting unit. As a consequence, these dual‐dye‐loaded nanoparticles can be used to produce drop‐cast films, as well as dopants for polymeric matrices, preserving the performances of the starting moieties in solution.     

Dye lasers with ultrafast transverse flow

Extension of the molecular rate equations for a dye laser to include the effect of very rapid transverse flow shows that spatial transit times comparable to the dye intersystem crossing time prevent the buildup of a large triplet state population. This new technique enables limiting the triplet-triplet absorption loss without using triplet quenching agents. An air-turbine driven rotating disk of rhodamine 6G dye in polymethyl methacrylate is used to exchange the dye5 times 10^{6}times per second by 250-m/s transverse flow through the pump beam waist in an end-pumped near-spherical cavity (W_{0} sim 25 mu). In pulse experiments, transverse flow enabled increase of power output by a factor of 2.5 with a corresponding decrease in threshold power of about 30 percent. Thermal defocusing effects are eliminated at much slower flow rates. The ultrafast transverse-flow technique should also be applicable to liquid dye lasers and would be most important for cases where no effective triplet quenching agent can be found.