Photoinduced Second Harmonic Generation of Bi_2S_3 Microcrystallite Doped Silica Glass

Silica glasses doped with Bi2S3 microcystallite was prepared by the sol-gel process. Photoinduced second harmonic generation (SHG) was observed in the glass when it was irradiated with intense 1.06 mum and frequency doubled laser beams from a mode-locked Nd: YAG laser. It was found that the signal intensity increased with the irradiating time and approached a saturation gradually. The effect may be explained reasonably by the DC field model.

Tunable Second Harmonic Generation with High Conversion Efficiency in Periodically Poled Lithium Niobate Channel Waveguide

The experiment on quasi-phase-matched second harmonic generation (SHG) in a channel waveguide was reported. The waveguide was made by annealed proton exchange in the periodically poled lithium niobate (PPLN) with the period of PPLN of 14.9 μm, which was designed for cascading wavelength conversion in dense wavelength division multiplexer optical communications. The measurement results of SHG conversion efficiency as a function of fundamental wavelength at room temperature fit well to sinc^2 shape. The peak of SHG conversion efficiency was 75%·W~ -1 ·cm~ -2 as well as reported. The relationship between the center fundamental wavelength and temperature shows that SHG can be effectively tuned by the temperature in PPLN waveguide.

Irradiation Effect on Second Harmonic Generation of Dyes Doped KDP Crystals

Most irradiation studies in the hydrogen bonded ferroelectrics have been concentrated on the transient defects induced by ionising radiation, such as ultraviolet （UV） light, where the defects are closely related to the optical properties. But heavy ion beam irradiation effects have rarely been studied. The structural, optical, and non-linear optical properties of the doped crystals were analyzed with the characterization studies, such as powder XRD, UV-Visible and second harmonic generation （SHG） measurements, respectively. The results for doped KDP crystal were compared with the results of the pure KDP crystals. The experiment results showed that Li^3＋ irradiation leads to the development of a well-defined surface H peak in dye doped KDP crystals. The stability of KDP single crystal was improved by doping organic dyes. The nano-islands of dye in KDP were likely to be dissolved and enhance the non-linear optical properties of these materials.

Modulation of the second-harmonic generation in MoS_(2) by graphene covering

Nonlinear optical frequency mixing,which describes new frequencies generation by exciting nonlinear materials with intense light field,has drawn vast interests in the field of photonic devices,material characterization,and optical imaging.Investigating and manipulating the nonlinear optical response of target materials lead us to reveal hidden physics and develop applications in optical devices.Here,we report the realization of facile manipulation of nonlinear optical responses in the example system of MoS_(2) monolayer by van der Waals interfacial engineering.We found that,the interfacing of monolayer graphene will weaken the exciton oscillator strength in MoS_(2) monolayer and correspondingly suppress the second harmonic generation(SHG)intensity to 30%under band-gap resonance excitation.While with off-resonance excitation,the SHG intensity would enhance up to 130%,which is conjectured to be induced by the interlayer excitation between MoS_(2) and graphene.Our investigation provides an effective method for controlling nonlinear optical properties of two-dimensional materials and therefore facilitates their future applications in optoelectronic and photonic devices.

Cylindrical vector beam-excited frequency-tunable second harmonic generation in a plasmonic octamer

We report a method to tune the second harmonic generation(SHG) frequency of a metallic octamer by employing cylindrical vector beams as the excitation. Our method exploits the ability to spatially match the polarization state of excitations with the fundamental target plasmonic modes, enabling flexible control of the SHG resonant frequency.It is found that SHG of the octamer is enhanced over a broad band(400 nm) by changing the excitation from the linearly polarized Gaussian beam to radially and azimuthally polarized beams. More strikingly, when subjected to an azimuthally polarized beam, the SHG intensity of the octamer becomes 30 times stronger than that for the linearly polarized beam even in the presence of Fano resonance.

Properties of second harmonic generation in nonlinear optical crystals CsLiB_6O_(10) and K_2Al_2B_2O_7

The phase-matching for nonlinear optical crystal, the nonlinear phase matching angle, effective nonlinear coefficient, walk-off angles, permitted angle, and permitted wavelength are obtained in type-I and type-II phase matching in ultraviolet （UV） nonlinear optical crystals CsLiB6O10 （CLBO） and K2Al2B2O7 （KABO） by detailed theoretical simulation. Through analysis and comparison, the phase matching characteristics of the second harmonic generation in the crystals are discussed when the wavelengths of the basic frequency lights turn continually.

Imaging the structure and organization of mouse cerebellum and brain stem with second harmonic generation microscopy

To visualize the structure and organization of the brain is a fundamental requirement in the research of neuroscience. Here, combining with two-photon excitation fluorescence microscopy and transgenetic mouse GAD67,we demonstrate a custom-built second harmonic generation（SHG） microscope to discriminate brain layers and sub regions in the cerebellum and brain stem slices with cellular resolution. In particular, the cell densities of neurons in different brain layers are extracted due to the cell soma appearing as dark shadow on an SHG image.Further, the axon initial segments of the Purkinje cell are easily recognized without labeling, which would be useful for guiding micropipettes for electrophysiology.

生物组织背向SHG和TPEF的影响因素

由于生物组织的复杂性和多样性,以及样品制备等因素的影响,实验观察到的生物组织的背向二次谐波(second harmonic generation,SHG)和双光子激发荧光(two-photon excitation fluorescence,TPEF)效应的差异较大。以鼠尾组织作为实验对象,共40个切片,分为横向和纵向、HE染色和未染色四组,采用飞秒激光器作为激发光,用双光子激光扫描共焦显微镜(two-photon laser scanning confocal microscope,TPLSCM)观察和分析了样品在不同的制备方式、激发波长、激发功率、扫描深度等条件下的背向SHG和TPEF的变化曲线,讨论和比较了生物组织的背向SHG和TPEF的影响因素以及二者之间的异同,并尝试对实验现象做出了一定的解释。

Experimental Research on Single-Pass SHG from Periodically Poled LiNbO_3 Crystal

Quasi phase matching (QPM) periodical poled LiNbO 3(PPLN) is designed and successfully fabricated to enable second harmonic generation(SHG).The samples were Z cut 0.5 mm thick and grating period is Λ=6.8 μm for the first order QPM of continual wave λ=1.064 μm which is emitted by Nd∶YAG laser at room temperature 27 ℃. The output single pass SHG power was tested by an authorized optical system. The normalized max conversion efficiency is calculated to be 0.25 0 0(W·cm) -1 .The fabrication and parameters calculated method are introduced, and testing scheme is described in this paper. Even some ideas to improve conversion efficiency are offered.

Experimental investigation of nonlinear process based on cSHG/DFG in PPLN waveguide

Effects of second harmonic generation （SHG） and cascaded second harmonic generation/difference frequency generation（cSHG/DFG） based on the quasi-phase-matching （QPM） condition in periodically poled lithium niobate （PPLN） waveguide were investigated experimentally. SHG conversion efficiency of -13.6dB and QPM bandwidth of 0.45nm were achieved using a 16.1dBm power of fundamental wave at 1550.4nm. Using pulsed all-fiber passive mode locked laser and tunable continuous wave laser, cSHG/DFG effect utilized for optical sampling was observed. Conversion efficiencies were calculated, and 11.88nm-wide QPM bandwidth was achieved through changing the wavelength of input signal. Conversion efficiency of cSHG/DFG effect increased linearly with the total injected power.

Performance of Optical Sampling Based on SHG in CPPLN Waveguide

Sampling efficiency and bandwidth of the optical sampling system based on second harmonic generation （SHG） in chirped periodically poled LiNbO3 （CPPLN） are numerically researched. A broad sampling bandwidth can be obtained by adjusting chirp coefficient and waveguide length of CPPLN, and sampling efficiency can be improved by using higher pump power, increasing waveguide length and choosing appropriate chirp coefficient. Results show that both sampling bandwidth and efficiency in CPPLN waveguides are controllable and that CPPLN waveguides are more suitable for multiwavelength optical sampling systems.

KBa2(PO3)5： Properties and Comparison with Isostructural Polyphosphate Compounds

A noncentrosymmetric polyphosphate compound, KBa2（PO3）5, 1 was prepared and characterized. It features 1D [PO3]∞ chains of condensed [PO4]^（3-） tetrahedral units. The polycrystalline sample of 1 exhibits second harmonic generation（SHG） response, demonstrating that the activity of the title compound is about 0.6 times that of KDP that is comparable to the isostructural RbBa2（PO3）5（2） and KPb2（PO3）5（3）. Additionally, powder X-ray diffraction（PXRD）, thermal analysis, IR spectroscopy, UV-Vis-near-IR diffuse reflectance spectroscopy, and theoretical calculations have been also studied, and the structure and property comparison among this type of polyphosphates are summarized.

Growth and Characterization of Bisthiourea Nickel Bromide—New Semiorganic Nonlinear Optical Crystal

A new semiorganic nonlinear optical crystal of bisthiourea nickel bromide (BTNB) was grown successfully by slow evaporation technique using water as solvent. The lattice parameters of the grown crystal have been determined by X-ray diffraction studies. Vibrational spectrum is recorded to determine symmetries of molecular vibrations. Optical absorbance spectrum recorded revealed that this crystal has good transparency in the visible region. The second harmonic generation test of BTNB confirmed the nonlinear nature of the crystal. The BTNB crystal was analyzed by a differential thermal analysis and thermogravimetric analysis (DTA-TGA) to obtain its thermal stability. Vickers microhardness test done on the crystal shows that the crystal has greater physical strength.

Single Crystal Growth of Lanthanum(III) Molybdate(VI) (La₄Mo₇O₂₇) Using H₃BO₃Flux

Single crystals of La4Mo7O27 have been successfully grown by the flux growth method H3BO3 as the flux in a plantium crucible using the starting materials of La2O3, H3BO3 and MoO3 in a molar ratio of 0.16:0.16:0.68, in which H3BO3 acted as a flux. Transparent colorless crystals were obtained with size of 0.8 × 0.3 × 0.2 mm3 under the optimized crystal growth conditions: growth temperature of 727°C, growth time of 95 h and cooling rate of 0.5°C/hr. A well-developed morphology of the crystals was observed and analyzed. The preparation process of starting materials on crystal growth was investigated. The grown crystals were characterized by powder X-ray diffraction (PXRD), EDAX, SEM, UV-Vis, photoluminescence studies, thermal analysis, dielectric studies and second harmonic generation (SHG). The results are presented and discussed.

Structural analysis of processed corneas

Background:Disruption of the microstructure in corneal stroma can lead to the loss of transparency.The lack of a characterization method for the microstructure prevents such scaffolds to be implemented in tissue transplantation.The non-invasive,three-dimensional(3D)rendering multiphoton microscopy(MPM)poses the potential to solve this problem.Methods:MPM images and data analyses were performed with three kinds of samples with known and different quality.Isosurfaces(ISOs)were constructed for the evaluation of void volume and collagen distribution.Results:The differences in the microstructures of these samples were revealed with clear indications and links to their behaviours in rehydration and possible transparency.According to this analysis,the scaffold with the highest void space ratio amongst the three presented the highest successful rates to be thoroughly rehydrated.Conclusions:Such a method can be developed for assessing the quality of tissue engineered corneas,or donated corneas,and be useful as a powerful research tool in cornea related research.

二次谐波成像技术在生物组织的应用进展

成像技术已正式被大量运用到医学研究中。近十几年具有重要意义的研发已研制出新的检测手段,本文章就以二次谐波成像技术这一高端的现代光谱成像作为讨论对象,并作展望。在成像仪器的技术和电脑处理系统的发展进步的帮助下,二次谐波成像技术得到人们越来越多的关注,并且有望成为临床应用。

The Fabrication and SHG Test of QPM Periodically Poled KTiOPO_4

The Quasi-phase-matching periodically poled flux-grown KTP by high electrical field method is researched. A 8×5×1mm3,∧=9.0μm PPKTP wafer is successfully fabricated for the first order QPM SHG. The interactive length of the sample is about 3mm. The SHG scheme of Nd: YAG at 1064nm tested that the output power of cw 532nm green light is 0.2mw at room temperature with fundamental power of 1.2w. The normalized conversion efficiency is about 0.09% (W·cm)-1.

Interaction between nitric oxide and lipid-like DDPA LB film investigated with SHG and AFM

Interactions between Nitric oxide (NO) and DDPA Langmuir-Blodgett (LB) film are investigated with second harmonic generation (SHG) and atomic force microscopy (AIM). It has been found mat the adsorption of NO molecules on DDPA LB film only changes the value of the second-order susceptibility of the DDPA molecule on film but not its orientation.

Two Low-temperature Phase Transition Compounds Based on Quinuclidine Derivatives with Fluorescence

Two phase transition materials[iPrQ]2MnBr4(1,iPrQ=N-isopropyl-quinuclidinium)and[iPrQ]_(2)MnCl_(4)(2)were synthesized and characterized.Dielectric measurements and differential scanning calorimetry showed that the two compounds underwent reversible phase transitions at ca.–47 and–37℃,respectively.Variable-temperature single-crystal X-ray diffraction suggested that the two compounds underwent the same phase transitions from space group C2/c to Cc but at different temperature.The variable crystal structures indicated that the structural phase transitions of the compound were ascribed to the torsional movement of quinuclidine ring and the disappearance of the c-slide plane.The second harmonic generation(SHG)response further proved this structural phase transition.Fluorescence tests showed that the two compounds have strong fluorescence.The strong variations in dielectric anomalies make compounds 1 and 2 suitable for promising switchable dielectric materials.