一种新型有机染料HEASPS在不同波长时的双光子吸收和频率上转换性质研究

报道了一种新型双光子吸收染料 ,即反式 - 4- [4′- (N-羟乙基 - N-乙基胺基 )苯乙烯基 ]- N-甲基吡啶对甲苯磺酸盐的非线性光学性质 ;测试了染料在 72 0～ 110 0 nm波段的非线性透过率曲线。结果发现 :双光子吸收最强波长相对线性吸收峰波长的两倍处有明显蓝移 ;计算出的相应波长的双光子吸收截面在 930 nm处染料有最大双光子吸收截面(2 .0 6× 10 - 4 7cm4·s/ photon) ;测量了染料在 90 0～ 110 0 nm波段的上转换效率 ,在 10 2 0 nm处有最高效率 (5 .1% ) ,最高激射效率的波长相对最强双光子吸收的波长有明显红移     

有机染料CSPI的双光子吸收和上转换荧光性质

报道了一种有机染料Trans 4 [p carbazol 9 ylstyryl] ] N methylpyridiniumiodide的线性和非线性光学性质。当用 830nm皮秒激光激发时 ,可以得到强烈的黄绿色上转换荧光 ,中心波长在 538nm附近。该染料的双光子荧光寿命为 95 .6ps。测试了该染料在 72 0～ 1 0 50nm的非线性透过率 ,并求出了该染料在上述波长时的双光子吸收截面。双光子吸收最强在 80 0nm ,吸收截面为 9.2× 1 0 - 48cm4 ·s/ photon。     

CdSe/ZnS核-壳结构量子点的非线性光学吸收

利用开孔Z扫描技术研究了吸收峰分别为553nm和503nm的两种尺寸CdSe/ZnS核-壳结构量子点溶液的非线性吸收性质.对于532nm,6ns激光脉冲,两种材料均表现出饱和吸收向反饱和吸收转化的现象.数值模拟结果表明:当吸收峰波长大于激光波长时,饱和吸收过程由快、慢两种机制组成,分别对应基态载流子被激发至不同的激发态,而强光下的反饱和吸收与快过程相关;当吸收峰波长小于激光波长时,饱和吸收主要由快过程机制引起,强光下的反饱和吸收源自激发态吸收和双光子吸收.我们的研究结果表明半导体量子点是研制光开关和光限制器件的理想候选材料.     

CdSe/ZnS核-壳结构量子点的非线性光学吸收

利用开孔Z扫描技术研究了吸收峰分别为553 nm和503 nm的两种尺寸CdSe/ZnS核-壳结构量子点溶液的非线性吸收性质.对于532 nm,6 ns激光脉冲,两种材料均表现出饱和吸收向反饱和吸收转化的现象.数值模拟结果表明：当吸收峰波长大于激光波长时,饱和吸收过程由快、慢两种机制组成,分别对应基态载流子被激发至不同的激发态,而强光下的反饱和吸收与快过程相关;当吸收峰波长小于激光波长时,饱和吸收主要由快过程机制引起,强光下的反饱和吸收源自激发态吸收和双光子吸收.我们的研究结果表明半导体量子点是研制光开关和光限制器件的理想候选材料.     

反-4,4''-双(N,N-二丁胺基)二苯乙烯分子双光子吸收性质研究

对于实验室合成的反-4,4'-双(N,N-二丁胺基)二苯乙烯分子,实验测量了该分子的单光子和双光子荧光谱,然后从理论上研究了其单光子和双光子吸收特性.研究结果表明,在低能量范围内,分子的单光子吸收主要发生在分子的第一激发态,而分子的双光子吸收主要发生在分子的第二和第四激发态上.该分子在相应系列衍生物中具有最大的双光子吸收截面.分子的相关能对分子的激发态能量影响较大.我们给出了分子基态与电荷转移态的电荷转移过程,并从理论上定性解释了双光子聚合反应的聚合机理.     

一种新型偶氮化合物的纳秒光限幅特性研究

研究了反式—4—{[p—(N,N—二羟乙基胺基)偶氮苯]乙烯基}吡啶在N,N—二甲基甲酰胺(DMF)中的光限幅性能。实验结果表明,该偶氮化合物的DMF溶液对波长为532nm,脉冲宽度为8ns的激光脉冲具有很强的光限幅特性。理论分析表明,光限幅效应主要起源于材料的双光子吸收。利用双光子吸收模型拟合光限幅实验数据得到材料的双光子吸收系数β=1.6×10-9cm/W。     

1，4-二甲氧基-2，5-二乙烯基苯系列衍生物的双光子吸收截面

在HF水平上，利用解析响应函数方法，研究了1，4_二甲氧基_2，5_二乙烯基苯系列衍生物 分子的单光子和双光子吸收特性. 实验测量了反，反_2，5_双(4′_N,N_二丁胺基苯乙烯)_1 ，4_二甲氧基苯分子的单光子和双光子荧光谱. 研究结果表明该系列分子具有较强的双光子 吸收特性. 在低能量范围内，对于D_π-A型分子，分子的单光子吸收强度和双光子吸收截面 最大值都发生在分子的第一激发态. 对于D_π_D型分子，单光子吸收强度最大值出现在分子 的第一激发态，而最大双光子吸收值则对应于分子的第二激发态. 分子的单和双光子吸收强 度和分子官能团的电性有关. 对于由该类π中心部分构成的分子，其对称型不一定比不对称型更有利于提高双光子吸收截面. 分子基态与电荷转移态的电荷转移过程定性地解释了双光 子聚合反应的聚合机理. 关键词： 双光子吸收 响应函数方法 非线性光学     

4，4′-二甲氨基二苯乙烯双光子吸收理论研究——溶剂效应

对最近实验室合成的分子材料4，4′-二甲氨基二苯乙烯的双光子吸收特性在从头计算的基础上进行了理论研究。理论模型是建立在密度泛函理论的基础上的。利用含时的密度泛函理论来计算分子的非线性光学性质，而溶剂效应则通过自洽响应场方法的极化连续模型来模拟。计算结果表明，三态模型可以很好地给出该分子在低激发态范围内的双光子吸收截面。随着溶剂极性的增加，单光子波长红移，双光子吸收截面增加。双光子吸收截面的大小和实验给出的结果符合得较好。     

二苯乙烯衍生物分子双光子吸收截面：官能团对称性的影响

选取了具有不同对称性的二苯乙烯系列衍生物分子，在HF水平上，利用响应函数方法，研究了该系列分子的单光子和双光子特性. 研究结果表明，该系列分子具有较强的双光子特性. 在可见光范围内，反对称分子的最大双光子吸收态是第一激发态，而对称分子的最大双光子吸收出现在第四激发态. 相对于对称分子而言，反对称分子具有更大的双光子吸收截面. 因此，分子的对称性是否比不对称性更有利于增大分子的双光子吸收截面，还与分子的π中心部分的特性有关. 还给出了电荷转移态的电荷迁移过程. 关键词： 双光子吸收 响应函数方法 非线性光学     

铝镓氮薄膜双光子吸收效应

基于飞秒激发Z扫描实验技术,研究了氮化镓薄膜和不同铝掺杂含量的掺铝氮化镓(以下简称铝镓氮)薄膜的超快非线性光学响应特性。在开孔Z-scan测试中,纯Ga N晶体薄膜表现出典型的双光子吸收特性,双光子吸收系数为3.5 cm/GW,且随着激发光强的增大而逐渐减小。随后测试了不同铝掺杂含量的Al_xGa_(1-x)N薄膜的非线性吸收系数。结果表明,随着铝掺杂摩尔分数的提高(0,19%,32%,42%),非线性吸收系数逐渐减小(18,10,6,5.6 cm/GW)。结合半导体非线性吸收理论分析,Al_xGa_(1-x)N薄膜材料的非线性过程主要是双光子吸收主导非线性响应物理过程。实验结果与半导体双光子吸收过程Sheik-Bahae理论符合得很好。     

Nonlinear absorption and upconversion properties of two-photon absorption dye: ASPI

Two-photon absorption (TPA) cross sections of an organic dye, trans-4-[p-(N-hydroxyethyl-N-methylamino)tyryl]-N-methylpyridinium iodide (abbreviated as ASPI), from 720 to 1100 nm have been measured by using nonlinear transmittance method, which reflect the TPA degrees of the dye at different wavelengths. The maximum TPA wavelength is located at 930 nm. The upconversion efficiencies of ASPI in dimethyl formamide and benzyl alcohol at different pump wavelengths have also been measured. There is 90 nm red shift for the highest upconversion wavelength as comparing with the strongest TPA wavelength. The influences of the solvents on the TPA-induced emission spectrum and the conversion efficiencies have also been given.     

Two-photon absorption and nonlinear optical properties of a new organic dye PSPI

Trans-4-[p-(pyrrolidinyl)styryl]-N-methylpyridinium iodide (abbreviated as PSPI thereafter) is a two-photon absorption (TPA) dye newly synthesized by our research group. It possesses much larger TPA cross-section and much stronger upconversion fluorescence emission than those of common organic dye (such as rhodamine) when excited with near infrared (IR) radiation. TPA spectrum and upconversion efficiency spectrum of HEASPI solution at various wavelengths were measured. There is 34 nm blue shift for the central wavelength of the TPA induced absorption peak compared with two times of the linear absorption peak. The biggest molecular TPA cross-section σ₂^′ is 2.85×10⁻⁴⁷ cm⁴ s/photon at 930 nm. At 1064 nm, σ₂^′ is 3.12×10⁻⁴⁸ cm⁴ s/photon. The highest efficiency is 3.9% at 1010 nm, whereas 2.9% at 1064 nm. Its optical power limiting properties at 930 nm have also been illustrated.     

Theoretical studies on the one- and two-photon absorption properties of azulenylporphyrins and azulene-fused porphyrins

The electronic structures, one-photon absorption (OPA) and two-photon absorption (TPA) properties of the azulenylporphyrins and azulene-fused porphyrins have been comparatively studied by using DFT/B3LYP/6-31G(d) and the ZINDO/SDCI method. With the number of azulenyl groups increasing, the OPA wavelengths of all molecules are red-shifted in 400--600~nm and the two-photon absorption cross section is gradually enlarged. The azulene-fused structures facilitate an expanding conjugated area and increasing TPA cross section. The origin of TPA properties of studied compounds is studied with a two-level model. In summary, the azulene-fused porphyrins exhibit strong two-photon absorption.     

Properties of two-photon fluorescence and superradiance of a new organic dye C46H51N2B

Linear and nonlinear optical properties of a new organic dye, trans-4-[p-(N-n-butyl-N-n-butylamino)-styryl]-N-methyl-pyridinium tetraphenylborate solution in dimethyl formamide (DMF) have been studied systematically. When excited with mode-locked picosecond 1 064 nm laser beam, intense upconversion fluorescence and superradiance can be obtained. The temporal behaviors of one-photon absorption and two-photon absorption (TPA) fluorescence and superradiance have been studied. The highest upconversion efficiency was found to be 4.1% at a pump energy of 4 mJ. By using an optical parameter amplifier (OPA) as the pump laser, the nonlinear transmittance and upconversion efficiencies of the dye solution at different wavelengths were measured. The strongest linear absorption was found at a wavelength of 930 nm whereas the highest upconversion efficiency was at 1 030 nm. The 100 nm red-shift for the highest upconversion efficiency wavelength compared with the strongest nonlinear absorption are caused by excited state absorption. Received 17 October 2001 and Received in final form 21 December 2001     

Nonlinear absorption of CS2 at the wavelength of 400 nm with femtosecond pulses

Nonlinear absorption of carbon disulfide (CS₂) was investigated by Z-scan technique and time-resolved pump-probe technique with femtosecond pulses at 400 nm wavelength. By the two techniques, we confirmed that the nonlinear absorption of CS₂ arise from a combination of two-photon absorption (TPA) and the excited state absorption induced by TPA under the incident laser pulses with 400 nm wavelength. The coefficient of TPA, the absorption cross-section of low excited state and lifetime of low excited state were obtained by theoretical fitting the experimental results. The results indicated that the CS₂ has good optical limiting capability at 400 nm wavelength.     

Er<Superscript>3+</Superscript> excited-state absorption in an erbium-doped silica fiber at the wavelengths 1490–1580 and 978 nm

The spectral features of Er³⁺ excited-state absorption (ESA) in an erbium-doped silica fiber (EF) at the telecom wavelengths 1490–1580 nm and at the wavelength 978 nm are reported. The measurement of the EF nonlinear transmission coefficient upon pumping the fiber in these spectral ranges, supplied with a theoretical background, allows one to obtain the spectrally dependent ESA parameter for the EF, which is defined as the ratio of the ESA to the ground-state absorption cross section.     

溶胶CdS毫微晶的双光子吸收及其量子尺寸效应

本文利用单光束透过率法研究了溶胶CdS毫微晶的双光子吸收。对于毫微晶尺寸为5.5～11.0nm的样品,测得其在波长510.6nm时的双光子吸收系数为1.31～5.24/GW,并由此得到相应的x~(3)为2.8×10~(-12)～1.1×10~(-11)esu。文中还从理论上分析了CdS溶胶的双光子吸收与毫微晶尺寸的关系,理论计算与实验结果基本符合。     

Z-scan analytical theory for material with saturable absorption and two-photon absorption

By using the Adomian decomposition method, we present the transmitted optical intensity of a nonlinear medium with the concurrence of saturable absorption (SA) and two-photon absorption (TPA) processes. We obtain the analytical expression of the open-aperture Z-scan and investigate the interplay between SA and TPA in the Z-scan trace. Through Z-scan measurements at different levels of laser intensities, both the saturable intensity and TPA coefficient could be obtained quickly yet unambiguously.