ANALYSIS OF LASING PERFORMANCES OF Yb3+-DOPED YAG, FAP, KYW CRYSTALS

The Yb³⁺ laser emitting at a 1.03μm wavelength has been evoking strong interest recently due to its advantages of long fluorescence lifetime, broad absorption band and the fact that it never shows concentration quenching. On the other hand, as a laser of three-level system it has, in general, a relatively high threshold power, which makes it important to seek some suitable host crystals to reduce this. Here, we present a comparison of the lasing performances of Yb³⁺-doped YAG [Y₃Al₅O₁₂], FAP [Ca₅(PO₄)₃F] and KYW [KY(WO₄)₂] crystals, including threshold power and slope efficiency, with those of the Nd:YAG laser based on the threshold formula of three-and four-level systems deduced by the authors. The results show that the Yb³⁺ laser can output a power larger than the Nd:YAG laser does in the case of comparably higher pumping power, if the length of the lasing rod and the concentration of the active ions satisfy some conditions. The theoretical results are also close to the experimental results reported.     

Crystal Structure and Characterization of a Dye with Two-photon Pumoed Frequency-upconverted Lasing Properties

The title compound, trans-4-[ p-( N-ethyl-N-(hydroxyethyl ) amino) styryl ]-N-methylpyridiniumtetraphenylborate (abbreviated as ESMT, C46H49N4OB) crystallizes in a space group P1- with a= 0. 983 23 (15)nm, b=1.410 73(16) nm, c=1.54 21(12) nm, a=95.252(13)°, β=91.959(17)°, γ= 107.421(12)°, Z=2, F(000)=712, μ= 0.1 mm-1 Mo Ka radiation, R=0. 093 8. The result shows that the cation of themolecule almost lies in one plane, the hydroxyethyl group is perpendicular to the plane, the anion takes a slightdistorted tetrahedral geometry. Also the thermal stability, two-photon fluorescence, two-photon pumped lasingproperty for the title compound were studied.     

Synthesis and Properties of Oligo-/Polymers Based on a “Flexible” Swivel-Cruciform Structure

We have introduced the concept of the so-called swivel type cruciforms as a highly flexible tool to tune the molecular properties from amorphous to highly crystalline features. Simple alkoxy substituted binaphthyl building blocks have been introduced randomly into poly(9,9-dioctylfluorene) (PFO) thereby suppressing the formation of side-chain crystallization. On the other hand the all aryl penta-thiophene based cruciform exhibited strong π–π interaction between the arms and gave one of the highest values reported to date for wet processed organic field effect transistors (OFETs) utilising oligothiophenes.     

失谐对开放的四能级系统无粒子数反转激光的影响

提出开放的四能级双驱动场无反转激光系统的理论模型,由电偶极和旋转波近似得到其密度矩阵方程,讨论无反转激光产生的物理机制,利用数值计算结果分析探测场和驱动场失谐对系统无反转激光增益和粒子数差的影响.     

Actively mode-locked dual-wavelength fiber laser with close wavelength spacing using a fiber Bragg grating

A simple actively mode-locked fiber ring laser is proposed and successfully demonstrated to generate dual-wavelength picosecond pulses with close wavelength spacing using one Bragg grating in standard single-mode fiber. The proposed laser can be made to operate in stable dual-wavelength at room temperature, due to the birefringence characteristic of the FBG induced by transverse strain. Transverse strain loading on the FBG allows the wavelength spacing to be controlled. Generation of stable dual-wavelength pulses with a pulsewidth of 212–234 ps and a tunable wavelength separation from 0.2 to 0.44 nm at a pulse rate of 1.05 GHz was demonstrated.     

染料掺杂光子晶体荧光带隙边缘的激射研究

利用激光全息光刻技术, 在重铬酸盐明胶 感光材料中制备了掺杂有机染料的层状光子晶体. 在532 nm纳秒脉冲激光激励下, 样品的荧光光谱表现出良好的带隙特征; 随着抽运能量的增加, 在荧光带隙带边位置获得了激射光, 并进一步研究了光子晶体的带边位置与染料荧光峰的匹配对激射的影响.带边位置越靠近染料的荧光峰, 激射阈值越低, 反之则不易产生激射.该研究为超低阈值光子晶体激光器的发展提供了思路和方法. 关键词： 全息光刻 光子晶体 荧光带隙 低阈值激射     

应用于2.1μm激光的Tm~(3+)/Ho~(3+)共掺氟碲酸盐微结构光纤研究

采用棒管法制备了低羟基含量的Tm~(3+)/Ho~(3+)共掺氟碲酸盐微结构光纤。当使用波长为1 560 nm的激光器泵浦Tm~(3+)/Ho~(3+)共掺光纤时,处于Tm~(3+)基态3H6的电子被激发至3F4能级,进一步通过Tm~(3+)和Ho~(3+)间的能量传递过程3F4→3H6(Tm~(3+)):5I8→5I7(Ho~(3+))(能量失配为745 cm-1)布居Ho~(3+)的5I7能级,5I7能级上的电子向5I8能级跃迁发射出2.1μm的光。使用1 560 nm光纤激光器作为泵浦源,18 cm长的Tm~(3+)/Ho~(3+)氟碲酸盐微结构光纤作为增益介质,获得了波长为2 063 nm的激光输出。所得激光的斜率效率为12.9%,激光阈值为163 m W,未饱和的最大输出功率为40 m W。研究结果表明,Tm~(3+)/Ho~(3+)共掺氟碲酸盐微结构光纤可用于制作2.1μm光纤激光器。     

Luminescence and lasing properties of neodymium- and uranium-activated inorganic laser liquids

An attempt was made to describe and show the possibilities of new inorganic neodynium- and uranium-activated laser liquids: SO₂-GaCl₃-NdCl₄; SO₂Cl₂-GaCl₃-NdCl₃-UO₂Cl₂; POCl₂-MCl_n-NdCl₃-UO₂Cl₂ for development and synthesis of direct nuclear reaction-excited lasers. Luminescence data presented in the work were used to calculate the luminescence parameters of the laser liquids such as oscillator strengths f, probability of spontaneous radiation A, intermultiplet luminescence branching coefficient β, cross-section for induced radiation σ, luminescence decay time τ, quantum yield η, and others. It is shown that the oscillator strengths of the normal absorption bands of Na³⁺, which play the main part in the pumping processes, exceed the oscillator strengths of Na³⁺ for aqueous and many other nonaqueous systems. In the luminescence excitation spectra of the Na³⁺ ion, bands are isolated in the range 400–1000 nm atλ _rec =1.06 μm. With excitation, luminescence occurs through the⁴F_3/2→⁴I_{9/2,11/2.13/2} channels. Luminescence spectral data are related to the lasing parameters. The threshold lasing energy is∼18 J/cm³. For a resonator with mirros h₁=100% and h₂=20, 40, 56, and 80%, the lasing energy is∼20–120 MJ/cm³ in the pumping energy range 18–180 J/cm³. The differential efficiency is ∼0.2% The substantial angular radiation divergence (θ∼4·10⁻² rad) and strong thermostatic distortions that occur in the active element (dn/dT≈−1.9·10⁻⁴K⁻¹) are a disadvantage of laser liquids. It is shown that operation of neodymium- and uranium-activated inorganic liquid lasers is stable under the present conditions. A. I. Gertsen Russian State Pedagogical University, Moika Embankment, 48, St. Petersburg, 191186, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 607–619, September–October, 1997.     

阴极射线激发下ZnO薄膜室温紫外发光的超线性增长规律

研究了直接溅射ＺｎＯ薄膜在阴极射线激发下紫外光（约３９０ｎｍ）和绿光（约５２０ｎｍ）的发光与激发电子束电流密度的关系。随激发电流密度增加绿光相对下降，紫外光相对增强，使得ＺｎＯ薄膜的发光颜色从绿变蓝紫，ＺｎＯ薄膜绿光随电子束流密度的增长呈亚线性增长，并在不高的束流密度下达到饱和，而紫外发光随电子束流密度呈超线性增长，这是ＺｎＯ薄膜在室温阴极射线激发下紫外受激发光的迹象，是高密度激发下的一种超辐射受     

本征态的局域化与增益介质中局域态的放大

用时域有限差分方法(FDTD)模拟了二维增益、非增益随机介质中的光学现象。在非增益介质中，观察到了局域态空间分布及其频率特征。在增益介质中，观察到局域态的放大过程。模拟结果显示非增益介质中的局域态相当于传统激光腔的腔模，随机激光是由局域态谐振产生的。