Compact and robust dual-color linearly polarized illumination source for three-photon fluorescence imaging

The miniaturized femtosecond laser in near infrared-Ⅱregion is the core equipment of threephoton microscopy.In this paper,we design a compact and robust illumination source that emits dual-color linearly polarized light for three-photon microscopy.Based on an all-polarizationmaintaining passive mode-locked fiber laser,we shift the center wavelength of the pulses to the 1.7m band utilizing cascade Raman effect,thereby generate dual-wavelength pulses.To enhance clarity,the two wavelengths are separated through the graded-index multimode fiber.Then we obtain the dual-pulse sequences with 1639.4 nm and 1683.7 nm wavelengths,920 fs pulse duration,and 23.75 MHz pulse repetition rate.The average power of the signal is 53.64mW,corresponding to a single pulse energy of 2.25 nJ.This illumination source can be further amplified and compressed for three-photon fluorescence imaging,especially dual-color three-photon fluorescence imaging,making it an ideal option for biomedical applications.

Lipid droplets imaging with three-photon microscopy

Lipid droplets(LDs)participate in many physiological processes,the abnormality of which will cause chronic diseases and pathologies such as diabetes and obesity.It is crucial to monitor the distribution of LDs at high spatial resolution and large depth.Herein,we carried three-photon imaging of LDs in fat liver.Owing to the large three-photon absorption cross-section of the luminogen named NAP-CF_(3)(1:67×10^(-79) cm^(6) s^(2)),three-photon fluorescence fat liver imaging reached the largest depth of 80μm.Fat liver diagnosis was successfully carried out with excellent performance,providing great potential for LDs-associated pathologies research.

Synthesis and Three-photon Induced Nonlinear Properties of a Novel Organic Chromophore

A novel organic chromophore 4, 4＇-bis（9-carbazyl-trans-styryl）-biphenyl （BCSBP） has been synthesized and characterized by IHNMR and elemental analysis. Three-photon absorption（3PA） induced upconvention fluorescence was observed and large 3PA cross section as high as 10^-74 cm^6 s^2 was obtained for nanosecond laser pulses at 1064 nm from optical limiting measurements.

The entanglement of two moving atoms interacting with a single-mode field via a three-photon process

In this paper, the entanglement of two moving atoms induced by a single-mode field via a three-photon process is investigated. It is shown that the entanglement is dependent on the category of the field, the average photon number N, the number p of half-wave lengths of the field mode and the atomic initial state. Also, the sudden death and the sudden birth of the entanglement are detected in this model and the results show that the existence of the sudden death and the sudden birth depends on the parameter and the category of the mode field. In addition, the three-photon process is a higher order nonlinear process.

Three-photon-excited fluorescence of Tb^(3+)-doped CaO-Al_2O_3-SiO_2 glass by femtosecond laser irradiation

A near infrared to visible blue, green, and red upconversion luminescence in a Tb^3＋-doped CaO-Al2O3-SiO2 glass was studied, which was excited using 800 nm femtosecond laser irradiation. The upconversion luminescence was attributed to ^5D3→^7F5, ^5D3→^7F4, ^5D3→^7F3, ^5D4→^7F6, ^5D4→^7F5, ^5D4→^7F4, and ^5D4→^7F3 transitions of Tb^3＋. The relationship between upconversion luminescence intensity and the pump power indicated that a three-photon simultaneous absorption process was dominant in this upconversion luminescence. The intense red, green, and blue upconversion luminescence of Tb^3＋-doped CaO-Al2O3-SiO2 glass may be potentially useful in developing three-dimensional display applications.

Nonlinear spectroscopy of three-photon excitation of cesium Rydberg atoms in vapor cell

We present nonlinear spectra of four-level ladder cesium atoms employing 6 S1/2→6 P3/2→7 S1/2→30 P3/2 scheme of a room temperature vapor cell.A coupling laser drives Rydberg transition,a dressing laser couples two intermediate levels,and a probe laser optically probes the nonlinear spectra via electromagnetically induced transparency(EIT).Nonlinear spectra are detected as a function of coupling laser frequency.The observed spectra exhibit an enhanced absorption(EA) signal at coupling laser resonance to Rydberg transition and enhanced transmission(ET) signals at detunings to the transition.We define the enhanced absorption(transmission) strength,HEA(HET),and distance between two ET peaks,γET,to describe the spectral feature of the four-level atoms.The enhanced absorption signal HEA is found to have a maximum value when we vary the dressing laser Rabi frequency Ωd,corresponding Rabi frequency is defined as a separatrix point,ΩdSe.The values of ΩdSe and further η=ΩdSe/Ωc are found to depend on the probe and coupling Rabi frequency but not the atomic density.Based on ΩdSe,the spectra can be separated into two regimes,weak and strong dressing ranges,Ωd≤ΩdSe and Ωd≥QdSe,respectively.The spectroscopies display different features at these two regimes.A four-level theoretical model is developed that agrees well with the experimental results in terms of the probe-beam absorption behavior of Rabi frequency-dependent dressed states.

Aggregation-induced emission luminogen for in vivo three-photon fuorescence lifetime microscopic imaging

Compared with visible light,near infrared(NIR)light has deeper penetration in biological tisues.Three-photon fuorescence microscopy(3PFM)can effectively utilize the NIR excitation to obtain high-contrast images in the deep tisue.However,the weak three photon fluorescence signals may be not well presented in the traditional fuorescence intensity imaging mode.Fluorescence lifetime of certain probes is insensitive to the intensity of the excitation laser.Moreover,fluorescence lifetimne imaging microscopy(FLIM)can detect weak signals by utilizing time correlated single photon counting(TCSPC)technique.Thus,it would be an improved strategy to combine the 3PFM imaging with the FLIM together.Herein,DCDPP-2TPA,a novel agegation-induced emission luminogen(AIEgen),was adopted as the fluorescent probes.The three-photon absorption cros-section of the AlEgen,which has a deep-red fluorescence emission,was proved to be large.DCDPP-2TPA nanoparticles were synthesized,and the three photon fluorescence lifetime of which was measured in water.Moreover,in vrivo thre-photon fuorescence lifetime microscopic imaging of a craniotomy mouse was conducted via a home made optical system.High contrast cerebrovascular images of different vertical depths were obtained and the maximun depth was about 600 pumn.Even reaching the depth of 600 pum,tiny capillary vessels as small as 1.9 pum could still be distinguished.The three photon fuorescence lifetimes of the capillaries in some representative images were in accord with that of DCDPP-2TPA nanoparticles in water.A vivid 3D reconstruction was further organized to present a wealth of lifetime information.In the future,the combination strategy of 3PFM and FLIM could be further applied in the brain functional imaging.

Thiophene-fluorene derivatives with high three-photon absorption activities and their application to optical power limiting

The three-photon absorption （3PA） properties of two thiophene-fluorene derivatives （abbreviated as MOTFTBr and ATFTBr） have been determined by using a Q-switched Nd：YAG laser pumped with 38ps pulses at 1064nm in DMF. The measured 3PA cross-sections are 152×10^-78cm^6s^2 and 139× 10^-78cm^6s^2, respectively. The optimized structures were obtained by AM1 calculations and the results indicate that these two molecules show nonplanar structures, and attaching different donors has different effects on the molecular structure. The charge density distributions during the excitation were also systematically studied by using AM1 method. In addition, an obvious optical power limiting effect induced by 3PA has been demonstrated for both derivatives.

Steady-state analysis of three-photon absorption spectra via density-matrix method in a three-coupled-quantum-well nanostructure

We numerically simulate three-photon absorption spectra in a three-coupled-quantum-well nanostructure interacting with a pump field, a coherent coupling field, and a probe field. We find that the three-photon absorption spectra can be dramatically influenced due to the intensities of the coupling field and pump field changing under the three-photon resonance condition. The effect of the frequency detuning of the pump field on the three-photon absorption spectra is also discussed. The study in our case is much more practical than the study in the case of its atomic counterpart in the sense of flexible design and the wide adjustable parameters. Thus it may open up some new possibilities for technological applications in optoelectronics and solid-state quantum information science.

Simulating the resonance-mediated(1+2)-three-photon absorption enhancement in Pr3+ions by a rectangle phase modulation

Enhancing the upconversion luminescence of rare earth ions is crucial for their applications in the laser sources,fiber optic communications,color displays,biolabeling,and biomedical sensors.In this paper,we theoretically study the resonance-mediated(1+2)-three-photon absorption in Pr^(3+) ions by a rectangle phase modulation.The results show that the resonance-mediated(1+2)-three-photon absorption can be effectively enhanced by properly designing the depth and width of the rectangle phase modulation,which can be attributed to the constructive interference between on-resonant and near-resonant three-photon excitation pathways.Further,the enhancement efficiency of resonance-mediated(1+2)-threephoton absorption can be affected by the pulse width(or spectral bandwidth)of femtosecond laser field,final state transition frequency,and absorption bandwidths.This research can provide a clear physical picture for understanding and controlling the multi-photon absorption in rare-earth ions,and also can provide theoretical guidance for improving the up-conversion luminescence.

Spectroscopic Properties and Three-photon Absorption Induced Optical Limiting of Series of Novel Nonlinear Chromophores

有对称的 D 的三新奇非线性的色基 -- D 分子的结构和扩大结合的长度被综合。Solvatochromism 分析显示出在在地面和激动的状态之间的偶极子时刻由改进发生在色基的大对称的 intramolecular 充电转移。限制由三光子的吸收(3PA ) 导致了的光力量的性质被表明。大 3PA coeficients 和象 1074 cm6 s2 一样高的相应的分子的生气的节从非线性的传播大小在 1.06 m 为毫微秒激光脉搏被获得。

NIR-IIb excitable bright polymer dots with deep-red emission for in vivo through-skull three-photon fluorescence bioimaging

It is of great significance to study the brain structure and function in deep-tissue for neuroscience research and bio-medical applications because of the urgent demand for precise theranostics.Three-photon fluorescence microscopic(3PFM)bioimaging excited by the light in near-infrared IIb(NIR-IIb,1,500–1,700 nm)spectral region is one of the most promising imaging techniques with the advantages of high spatial resolution,large imaging depth,and reduced scattering.Herein,a type of NIR-IIb light excitable deep-red emissive semiconducting polymer dots(P-dots)with bright 3PF and large three-photon absorption cross-section(σ3)at 1,550 nm was prepared.Then the P-dots were functionalized with polystyrene polymer polystyrene graft ethylene oxide functionalized with carboxyl groups(PS-PEG-COOH)and modified with NH2-poly(ethylene glycol)(PEG)to synthesis photochemically stable and biocompatible P-dots nanoparticles(NPs).Further the P-dots NPs were utilized for in vivo 3PFM bioimaging of cerebral vasculature with and without the brain skull under 1,550 nm femtosecond(fs)laser excitation.In vivo 3PFM bioimaging of the mice cerebral vasculature at various vertical depths was obtained.Moreover,a vivid three-dimensional structure of the mice vascular architecture beneath the skull was reconstructed.At the depth of 350μm beneath the brain skull,3.8μm blood vessels could still be clearly recognized.NIR-IIb excitable P-dots assisted 3PFM bioimaging has great potential in accurate deep tissue bioimaging.

Toxicity assessment and long-term three-photon fluorescence imaging of bright aggregation-induced emission nanodots in zebrafish

Aggregation-induced emission （AIE） luminogen displays bright fluorescence and has photobleaching resistance in its aggregation state. It is an ideal fluorescent contrast agent for bioimaging. Multiphoton microscopy is an important tool for bioimaging since it possesses the ability to penetrate deep into biological tissues. Herein, we used AIE luminogen together with multiphoton microscopy for long-term imaging of zebrafish. A typical AIE luminogen, 2,3-bis（4-（phenyl（4- （1,Z2-triphenylvinyl） phenyl）amino）phenyl） fumaronitrile （TPE-TPA-FN or TTF）, was encapsulated with 1,2-distearoyl-sn-glycero-3-phosphoethanola-mine-N- [methoxy（polyethylene glycol）-2000] （DSPE-mPEG2000） to form nanodots that exhibited bright three-photon fluorescence under 1,560 nm-femtosecond （fs） laser excitation. The TTF-nanodots were chemically stable in a wide range of pH values and showed no in vivo toxicity in zebrafish according to a series of biological tests. The TTF-nanodots were microinjected into zebrafish embryos, and the different growth stages of the labeled embryos were monitored with a three-photon fluorescence microscope. TTF-nanodots could be traced inside the zebrafish body for as long as 120 hours. In addition, the TTF-nanodots were utilized to target the blood vessel of zebrafish, and three-photon fluorescence angiogram was performed. More importantly, these nanodots were highly resistant to photobleaching under 1,560 nm-fs excitation, allowing long-term imaging of zebrafish.

Three-photon absorption in a push-pull type chromophore containing tricyanofuran acceptor

Three-photon absorption（3PA） of a push-pull chromophore,2-（3-cyano-（3-（4-（dimethylamino）styryl）-5,5-dimethylcyclohex- 2-enylidene）methyl）-5,5-dimethylfuran-2-ylidene） malononitrile（CFM） including TCF group was measured by the nonlinear transmission method using a femto-second Ti：Sapphire oscillator-amplifier laser system.Its three-photon absorption cross-sections at 1300 ran were 36.8×10^-79 cm^6 s^2 in the solution of DMF and 12.3×10^-79 cm^6 s^2 in the solution of CH_2Cl_2,respectively.The large values were got by experiments in this paper,which is a new exploration for these kinds of materials.The molecule has the potential application foreground of 3PA areas and optical power limiting.

Wide-field three-photon excitation in biological samples

Three-photon wide-field depth-resolved excitation is used to overcome some of the limitations in conventional point-scanning two-and three-photon microscopy.Excitation of chromophores as diverse as channelrhodopsins and quantum dots is shown,and a penetration depth of more than 700μm into fixed scattering brain tissue is achieved,approximately twice as deep as that achieved using two-photon wide-field excitation.Compatibility with live animal experiments is confirmed by imaging the cerebral vasculature of an anesthetized mouse;a complete focal stack was obtained without any evidence of photodamage.As an additional validation of the utility of wide-field three-photon excitation,functional excitation is demonstrated by performing threephoton optogenetic stimulation of cultured mouse hippocampal neurons expressing a channelrhodopsin;action potentials could reliably be excited without causing photodamage.

Long-term in vivo single-cell lineage tracing of deep structures using three-photon activation

Genetic labeling techniques allow for noninvasive lineage tracing of cells in vivo.Two-photon inducible activators provide spatial resolution for superficial cells,but labeling cells located deep within tissues is precluded by scattering of the far-red illumination required for two-photon photolysis.Three-photon illumination has been shown to overcome the limitations of two-photon microscopy for in vivo imaging of deep structures,but whether it can be used for photoactivation remains to be tested.Here we show,both theoretically and experimentally,that three-photon illumination overcomes scattering problems by combining longer wavelength excitation with high uncaging three-photon cross-section molecules.We prospectively labeled heart muscle cells in zebrafish embryos and found permanent labeling in their progeny in adult animals with negligible tissue damage.This technique allows for a noninvasive genetic manipulation in vivo with spatial,temporal and cell-type specificity,and may have wide applicability in experimental biology.

三维光子晶体结构色材料的制备与应用研究进展

三维光子晶体是指折射率不同的材料在三维空间呈周期性排列的结构。由于三维光子晶体结构形成的结构色材料具有颜色明艳,制备过程简易方便、生态环保等优点,近年来受到了广泛关注,在装饰、防伪、光催化、汽车涂料、纺织等领域展示出巨大潜力。文中主要综述了三维光子晶体结构生色材料制备与应用方面的研究进展,包括单分散胶体粒子和单分散复合胶体粒子的合成与组装,讨论了该类材料的应用现状,提出了目前存在的一些问题与发展方向。

具有三光子性质的碘代咔唑基三吡啶锰(Ⅱ)配合物的合成及光动力学活性

论文以三联吡啶为主体,设计合成碘代咔唑基三吡啶锰(Ⅱ)配合物MB3。MB3具有优良的光电性能,且价格低廉、毒性小。光物理测试表明MB3具有较强的三光子吸收性质。生物测试表明MB3具有良好的单线态氧生成效率,具有作为光敏剂的潜力。

(La_(0.97)Yb_(0.02)Tm_(0.01))F_(3)纳米晶的合成及其发光性能研究

以硫酸盐型稀土层状化合物[(La_(0.97)Yb_(0.02)Tm_(0.01))_(2)(OH)_(4)SO_(4)·2H_(2)O]为模板,通过牺牲模板法水热合成(La_(0.97)Yb_(0.02)Tm_(0.01))F_(3)纳米晶,合成过程不需添加任何有机物同时不需后续煅烧过程。反应模板和所制备的(La_(0.97)Yb_(0.02)Tm_(0.01))F_(3)纳米晶的晶体形貌、晶体结构以及上转换荧光性能分别由场发射扫描电子显微镜、透射电子显微镜、X射线衍射仪和荧光光谱仪测试分析得出。结果表明,在F^(-)与(La_(0.97)Yb_(0.02)Tm_(0.01))^(3+)摩尔比为5、水热温度为180℃、水热反应24h条件下,合成了六方结构的(La_(0.97)Yb_(0.02)Tm_(0.01))F_(3)上转换纳米晶。场发射扫描电子显微镜、透射电子显微镜分析表明模板结晶为超薄纳米板片,长度约490nm,厚度为40nm,(La_(0.97)Yb_(0.02)Tm_(0.01))F_(3)的平均粒径分布在30~65nm,厚度大约为10nm。当发射激光波长为978nm时,(La_(0.97)Yb_(0.02)Tm_(0.01))F_(3)纳米晶体在804nm(^(3)H_(4)→^(3)H_(6)跃迁)处显示近乎纯净的上转换发光,位于487nm附近的蓝光发射近乎完全淬灭。通过计算发光强度与泵浦功率的关系得出制备的纳米晶体的上转换发射过程为三光子过程。

1030nm单光子探测激光雷达技术

1μm波段单光子探测激光雷达因大气透过率高、背景噪声低、红外隐蔽性好、激光脉冲能量高,在远距离激光测距和成像方向极具发展前景。然而,传统的1064 nm激光器缺少对应的高性能的单光子探测器,成为1μm波段单光子探测激光雷达的发展瓶颈。盖革Si APD单光子探测器(Si SPAD)具有优异的探测性能,但是其在1064 nm波长的探测效率极低。针对这个激光器与探测器的矛盾,本文研究1030 nm波长单光子探测激光雷达技术,Si SPAD在1030 nm的探测效率是1064 nm的2.9倍,相同条件的单光子探测激光雷达探测距离提升67.8%。另外,本文搭建双棱镜光束扫描装置,演示了1030 nm波长的单光子三维成像。