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We utilize singular spectrum analysis (SSA) for post-processing distance measurement data obtained by a dual-comb femtosecond laser rangefinder. Signal denoising technique based on SSA allows detection of low amplitude vibrations from time series of distance data with limited signal-to-noise ratio (SNR). Various one-dimensional vibrations, including harmonic, amplitude modulated harmonic, and sinc-function vibrations, with micrometer amplitude comparable with measurement uncertainty of laser rangefinder, have been imposed on the target mirror by a piezo positioner. These vibrations have been extracted by SSA and the obtained vibration amplitudes agree with that imposed on the target very well. A commercial interferometer is used to evaluate the accuracy of SSA. Standard deviations of residuals between the SSA extractions and interferometer measurements are smaller than 0.6 $\mu$ m. This technique is promising for complex moving pattern detection in object tracking and remote sensing.

We report a single method for measuring the effective electro-optics (EO) coefficient only by spectral intensity modulation with a terahertz time-domain spectroscopy (THz-TDS) device. Compared with conventional methods, the measuring device based on THz-TDS by probing the spectral intensity modulation is simple, rapid, and highly sensitive. It does not require special preparation process, electrode contact or applying high voltage on the sensor samples. The EO coefficients of four kinds of materials, namely, ZnTe and GaP crystals, DAST wafer and GaSe film, are measured at 1040 nm. The results showed good agreement with literature data by the conventional methods.

In this letter, we propose and demonstrate a practically compact 1-GHz repetition-rate femtosecond optical parametric oscillator (OPO) based on MgO:PPLN crystal, which is harmonically pumped by a 53 MHz Yb-doped fiber laser. The multiplication of the repetition rate is derived by placing the nonlinear crystal in a miniaturized V-type cavity with 13.9 cm length. The near-infrared signal output pulses are tunable from 1350 nm to 1650 nm. The signal pulse duration across the complete tuning range is measured to be around 125 fs. Thanks to the high repetition rate, broadband tenability, and simplicity of the optical setup, this type of OPO holds promise for many applications.

Although the Raman fiber amplifiers are attractive for their unique advantages and various Raman fiber amplifiers in continuous wave (CW) regime were built, there are a few fundamental limitations for short-pulsed Raman fiber amplifiers. In this paper, we present a theoretical and experimental study on a novel method termed picosecond (ps) coherent Raman fiber amplification, where the stimulated Raman scattering is employed to generate high-quality femtosecond pulses from narrowband ps pump pulses, with high conversion efficiency and compact construction. Detailed numerical simulation reveals the nonlinear dynamics of the ps-coherent Raman fiber amplification in an Yb-doped gain fiber. The spectral filtering effect induced by finite Raman gain bandwidth significantly improves the temporal quality of the generated Raman pulses, similar to the well-known Mamyshev regenerator. By employing this method in a 4.5 m Yb-doped polarization maintaining double-clad fiber, 67 nJ, 76 fs nearly transmission limited Raman pulses are generated from narrowband (

We study on the timing jitter characteristics of a passively mode-locked dual-wavelength dual-comb Er-fiber laser that generates two femtosecond optical frequency combs with an offset repetition rate in a shared cavity. The relative timing jitter is characterized directly in the time domain with tens of attoseconds precision by utilizing the intrinsic asynchronous optical sampling process between the two laser beams. This sensitive measurement reveals an amplified spontaneous emission (ASE) noise dominated random walk of the relative pulse timing, which has not been observed before in a dual-comb laser. The quantum-limited relative timing jitter behavior shows that the common-mode noise suppression based on a shared cavity does not apply to quantum noise. We further conduct a time-of-flight ranging experiment and a Fourier-transform spectroscopy simulation based on this dual-comb laser, showing that the quantum-limited relative timing jitter sets an ultimate limit on the reachable performance in time- and frequency-domain dual-comb applications particularly when the high acquisition rate is desired.

The coupling dynamics between a dispersion-managed soliton oscillator and a nonlinear amplifier in an all-photonic crystal fiber-based laser system is emphasized. The intracavity and output pulse evolution dynamics with the dispersion management by a pair of gratings in the oscillator are investigated numerically and experimentally in detail. Then the relationship between the net intracavity dispersion in the oscillator and properties of amplification pulses from the nonlinear amplifier is studied. We find that the best performance in the laser amplification system is significantly dependent on the time-bandwidth product of the seed pulses and the amplifier pump power. As a consequence, the optimized seed output from the DM soliton oscillator for the nonlinear amplifier should be as close to the transform-limited pulse as possible and the intracavity anomalous dispersion should be as large as possible. The narrowest pulse duration of 43 fs without a pedestal and an average power of 28 W, is obtained at a pump power of 60 W. At a pump power of 70 W, 50-fs pulses with a highest output power of 34 W, corresponding to a peak power of 16.2 MW, can also be obtained.

Optical rectification is one of the most widely used methods to generate broadband terahertz (THz) radiation using femtosecond laser pulses. In this work, we report the generation of THz radiation from GaP crystals based on optical rectification using a pulsed Bessel beam, i.e., a beam with a spatial profile described by a zeroth-order Bessel function of the first kind. It is shown that the nondiffracting feature of the central spot of the Bessel beam allowed an enhancement of the THz radiation generation efficiency. Compared with a Gaussian beam having the same beam size and pump power as its central spot, the Bessel beam enabled an average increase of the THz radiation power by factors of 1.37, 2.12, and 2.06 from GaP crystals of 1, 3, and 5 mm, respectively. Measurements showed that the spatial profile of the THz radiation followed a Gaussian distribution for both pump beams and increased linearly after the emitters.

We design and investigate the optical properties of a novel hollow-core antiresonant fiber with nested elliptical cladding elements. This new structure shows low confinement loss even with a relatively small core. The lowest confinement loss of this structure is more than two orders of magnitude smaller than its circular-element counterparts. When the size of the cladding elements is properly designed, higher order core modes resonantly couple with the cladding modes effectively, resulting in an extremely high higher order-mode extinction ratio ( $>$ $10^4$ ). This good single mode performance can be achieved for a wide range of cladding element parameters, which would increase the fabrication tolerance. The new fiber also shows low bending loss for a wide range of bend radii. Moreover, dispersion properties of the new structure are also investigated under both unfilled and filled conditions. Numerical results show that antiresonant structures with the same core diameter and strut thickness have similar dispersion curves. The zero dispersion wavelength within the fundamental antiresonant transmission band can be tuned over tens of nanometers by increasing the pressure up to 50 bar when the fiber is filled with argon.

We demonstrate that third-order dispersion (TOD) precompensation accompanied with nonlinear compensation can improve the pulse quality of high energy pulses in fiber chirped-pulse amplification (FCPA) system. The negative TOD fiber is implemented as the precompensation of TOD mismatch, resulting small required B-integral, which benefits the pulse quality. The conclusion is given by analytical study and numerical simulations. Based on this method, we obtain high-energy pulses up to 10.4 μJ. The quality of the dechirped pulse is high and >90% of pulse energy is contained in the main pulse. The dechirped pulse duration is ~280 fs, which is nearly the same as the transform-limited pulse of the oscillator. The system also shows a wide tunable range of pulse energy from 5 to 10 μJ with the good pulse quality.

We experimentally investigate the polarization dynamics of three kinds of gain fiber, the single-polarizing photonic crystal fiber, double clad polarization-maintaining large mode area fiber and double clad large mode area nonpolarizing fiber, in a continuous wave fiber laser oscillator under different initial polarization directions and pumping powers. The comparison results demonstrate that there are some distinguishable differences for the polarization evolutions inside the three kinds of active fibers. The polarization operation status of the fiber oscillator strongly depends on not only the gain fiber’s kinds, but also the length of the fiber, initial polarization directions and pumping power. The results suggest that polarization instability in a fiber laser should be an inherent reason for the higher operation noise.

We numerically and experimentally demonstrate the influences of gain fiber length, initial pulse center wavelength, duration, chirp, and temporal profile for efficient parabolic self-similar evolution, accounting for the strong gain shaping effect in fiber amplifiers under high gains. A spectrally resolved numerical model allowing for realistic descriptions of the variable wavelength-dependent gain is developed. The results predict the specific regions of the initial center wavelength and the duration for the self-similar evolution, which move toward a longer center wavelength and a broader duration range with the increasing gain fiber length. For short-length high-gain amplifiers, a proper negative initial chirp can not only resist the gain-shaping deformation and facilitate the self-similar evolution but also provide a broadband output. In addition, a triangular initial profile is found to be of minimum sensitivity to the detrimental gain shaping and optimum for efficient self-similar evolution. The experimental results confirm the numerical predictions. The studies of the fast parabolic pulse formation in short-length high-gain amplifiers presented here demonstrate the potential for performance scaling of femtosecond fiber amplifiers, few-cycle pulse sources, high-power frequency combs, and related applications.

We report a multicore photonic crystal fiber (PCF) amplification system delivering about 110-W laser pulses with a duration of sub-100 fs. This amplifier is seeded by a large mode area (LMA) PCF mode-locked oscillator with a repetition rate of 100 MHz. By a one-stage nonlinear amplification, the pulse energy is scaled up to 1.1 $\mu\text{J}$ . In addition, the amplified pulses can be compressed to as short as 83 fs, corresponding to a peak power of 13 MW. For the multicore fiber used in this letter, the 110-W output average power has already made the mode distribution unstable. The results show that the potential output power of a multicore LMA fiber is mainly limited by the mode instability compared with the accumulated nonlinearity.

Fibers that operate by the photonic bandgap effect guide light only within a limited frequency range and broadband transmission is highly desirable for the terahertz (THz) frequency range. A semi-analytical approach is used for the design of broadband porous-core bandgap THz fibers based on a honeycomb and Kagome lattice of air holes. We show how the design approach allows a fast and accurate determination of the mode indices for different sizes of the core air holes. In particular, a reduction of the central air hole size from that of the cladding air holes allows both fibers to operate within the first bandgap, enabling broadband transmission within the frequency range of 0.7–2 THz. These fibers will be promising for THz wave transmission.

A comparative study of femtosecond pulse dynamics in a photonic crystal fiber amplifier with backward and forward pump schemes is demonstrated experimentally and numerically. The output power, pulse duration and spectrum width of the amplified soliton pulse at different pump powers under the two pump schemes are discussed. The results show that the evolution of the soliton pulse shape in the temporal and spectral domains is also dependent on the direction of pump besides the output power. A narrower pulse duration and spectral width (i.e. smaller time-bandwidth-product), the much less nonlinearity accumulation (i.e. smaller B-Integral value) and a higher output power can be obtained in the backward pump scheme compared to that in the forward pump scheme. The physical origin can be explained by the interaction among group-velocity dispersion, self-phase modulation and nonuniform gain distribution along the fiber due to different end-pump directions. The results provide convincing support to choose the backward pump scheme rather than the forward pump scheme in soliton amplification region in a femtosecond fiber amplifier.

Compressing picosecond laser pulses to the femtosecond level is an attractive shortcut for obtaining femtosecond laser pulses. However, dechirped pulses generated by nonlinear compression with self-phase modulation (SPM) show obvious pedestals, which are induced by nonlinear chirp accumulation in spectral broadening process and cannot be easily suppressed. Here, we report systematic numerical simulations and experimental studies on self-similar amplification of picosecond pulses in a short gain fiber for obtaining ~100-fs laser pulses with nearly transform-limited (TL) temporal quality. It is demonstrated that self-similar amplification with picosecond seed pulses is only sensitive to pulse duration and pulse energy. Based on this optimization guideline, we built a compact self-similar amplification fiber system with a picosecond fiber laser as the seed source. This system outputs 66-fs pulses with 6.1-W average power at a repetition rate of 30 MHz. Due to the linear chirp produced in self-similar evolution process, compressed pulses show nearly TL temporal quality. It promises an efficient way of obtaining high-quality femtosecond laser pulses from a picosecond laser source.

Femtosecond laser ranging has drawn great interest in recent years, particularly based on an asynchronous optical sampling implementation where a pair of femtosecond lasers are used. High precision absolute ranging either relies on tightly-phase-locked optical frequency combs (a dual-comb setup) or multiple averaging of the measurements from two free-running femtosecond lasers. The former technique is too complicated for practical applications, while the latter technique does not apply to moving targets. In this report, we propose a new route to utilizing a powerful singular spectrum analysis (SSA) filtering method to improve femtosecond laser ranging precision for moving targets with acceleration. The SSA method is capable of separating complex patterns in signals without a priori knowledge of the dynamical model. Here, we utilize the basic SSA filter to extract the target trajectory in the presence of measurement noise both in numerical simulation and in the absolute ranging experiment based on a pair of free-running femtosecond lasers. The experimentally-achieved absolute ranging uncertainty of a moving target is well below 110 nm at a 200-Hz update rate by applying the basic SSA filter. This method paves the way to the practical applications of femtosecond absolute ranging for dynamic objects.

The generation of high-power ultrashort pulses from a passively mode-locked fiber laser is reported based on the combination of a single-polarization large-mode-area (LMA) photonic crystal fiber with a nonlinear amplifying loop mirror design. The introduction of a non-reciprocal phase shift in the loop mirror enables self-starting of the mode-locked laser, while the polarizing LMA fiber supports environmentally stable high-power operation. Mode locking in the soliton-like, stretched-pulse, and all-normal-dispersion regime is characterized. The laser generates stable pulses with up to 2 W average power at a 72 MHz repetition rate, corresponding to a single-pulse energy of 28 nJ. The output pulses are dechirped to a near transform-limited duration of 152 fs. The proposed fiber oscillator presents an alternative approach to high-power ultrafast laser sources, along with environmental stability.

We demonstrate a high average power, widely tunable, dielectric-mirror-less optical parametric oscillator (OPO) based on MgO:PPLN (MgO-doped periodically poled lithium niobate), which is synchronously pumped by a 1040 nm femtosecond fiber laser. The OPO does not require any dielectric coating mirrors. By exploiting the four-prism sequence system, combined with the gold mirrors, the oscillating laser pulses could span the spectral regions in both the signal and idler, and the output pulses of OPO can be tuned across 1367–1914 nm in the signal, and 2152–4480 nm in the idler as well. This device can deliver as much as 1.2 W of average power at 1482 nm in the signal and up to 411 mW at 3487 nm in the idler, respectively. The ultrabroad-band spectra tunability, along with the high average output property, makes the dielectric-mirror-less OPO an attractive alternative to conventional OPOs.

We demonstrate a nonlinearity optimization method by altering distribution of passive fibers in a dissipative-soliton mode-locked fiber laser to level up output parameters. In the numerical simulation, we found that the passive fiber segment after gain fiber characterizes the highest average B-integral among fiber segments. By reducing the length of this fiber section and keeping the total passive fiber length as constant, the output pulse energy can be effectively scaled up while maintaining a short dechirped pulse duration, resulting in boosting peak power. With this method, 37-nJ pulses are generated from a dissipative-soliton mode-locked cladding pumped ytterbium-doped single-mode fiber laser in the experiment. The pulse can be dechirped to 66 fs with 350 kW peak power. Moreover, the pulse pedestal is suppressed by a vector-dispersion compressor.

We report a four-prism-pumped all-gold-mirror idler resonant optical parametric oscillator (OPO) driven by an Yb-fiber femtosecond laser. The idler is tuned from 2560–4180 nm, with the corresponding signal covering 1380–1825 nm.

We demonstrate an all polarization-maintaining (PM) fiber mode-locked laser seeded, hybrid fiber/solid-slab picosecond pulse laser system which outputs $40~\unicode[STIX]{x03BC}\text{J}$, 10 ps pulses at the central wavelength of 1064 nm. The beam quality factors $M^{2}$ in the unstable and stable directions are 1.35 and 1.31, respectively. $15~\unicode[STIX]{x03BC}\text{J}$ picosecond pulses at the central wavelength of 355 nm are generated through third harmonic generation (THG) by using two $\text{LiB}_{3}\text{O}_{5}$ (LBO) crystals, in order to get better processing efficiency on polycrystalline diamonds. The high pulse energy and beam quality of these ultraviolet (UV) picosecond pulses are confirmed by latter experiments of material processing on polycrystalline diamonds. This scheme which combines the advantages of the all PM fiber mode-locked laser and the solid-slab amplifier enables compact, robust and chirped pulse amplification-free amplification with high power picosecond pulses.

We demonstrate a passively mode-locked fiber laser with excessive normal dispersion (ENDi)yielding 230 nJ pulses with 69 fs dechirped duration. Numerical simulation indicates the energy scalability to over $1\ \mu \mathrm{J}$ is possible.

First, micro-arc oxidation (MAO) TiO2 films have been prepared on pure titanium in a phosphate-based electrolyte, and then the Ag+/MAO-TiO2 composite films have been fabricated by Ag+ impregnation in this paper. The microstructure and composition of MAO-TiO2 films and Ag+/MAO-TiO2 composite films have been studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). The photocatalytic activity of both films was evaluated by photocatalytic decolorization of methylene blue (MB) in aqueous solution as a model pollutant under sunlight irradiation simulation with homemade ultraviolet–visible spectroscopy (UV–vis). The results showed that the photocatalytic activity of MAO-TiO2 films increased with increasing the applied voltage and concentration in a certain scope. The morphology of Ag+/MAO-TiO2 composite films were of significantly difference and superior photocatalytic activity compared to the MAO-TiO2 film. Also, Ag+ impregnation was able to enhance the photocatalytic efficiency of MAO-TiO2 film.

The physical process of forming a modified region in soda-lime glass was investigated using 1 kHz intense femtosecond laser pulses from a Ti: sapphire laser at 775 nm. Through the modifications induced by the femtosecond laser radiation using selective chemical etching techniques, we fabricated reproducible and defined microstructures and further studied their morphologies and etching properties. Moreover, a possible physical mechanism for the femtosecond laser modification in soda-lime glass was proposed.

We describe a semi-analytical approach for modeling fibers which guide THz radiation in a porous core by the photonic bandgap effect due to a honeycomb cladding of air holes. These porous-core honeycomb bandgap THz fibers (PCHBTFs) are modeled as equivalent step-index fibers (SIFs). The effective core index of the SIFs can be solved analytically as that of the fundamental space-filling mode of the triangular lattice comprising the porous core. The cladding index is taken as that of the bandgap edge with the lower index and is computed numerically. The validity of the analogy between PCHBTFs with SIFs is established by comparing the mode profiles, mode number, mode indices, and the fraction of mode power in the core obtained for a 19-cell core multimode THz fiber by the semi-analytical theory with results by finite element method. The subtle difference in mode degeneracy of the PCHBTFs and SIFs is briefly discussed. The semi-analytical theory also predicts that a seven-cell core PCHBTF is effectively single mode with higher-order modes pushed close to the bandgap edge.

Investigations are performed to explore high-repetition-rate femtosecond laser ablation effects on the physical and chemical properties of poly(methyl methacrylate) (PMMA). A scanning electron microscopy (SEM) is used to characterize the morphology change in the laser-ablated regions. The infrared and Raman spectroscopy reveals that the fundamental structure of the PMMA is altered after laser ablation. We demonstrate the cumulative heating is much greater during high-repetition-rate femtosecond laser ablation, supporting a photothermal depolymerization mechanism during the ablation process.

We characterize the relative intensity noise (RIN) and relative timing jitter (RTJ) between the signal and pump pulses of optical parametric amplifiers (OPAs) seeded by three different seed sources. Compared to a white-light continuum (WLC) seeded- and an optical parametric generator (OPG) seeded OPA, the narrowband CW seeded OPA exhibits the lowest root-mean-square (RMS) RIN and RTJ of 0.79% and 0.32 fs, respectively, integrated from 1 kHz to the Nyquist frequency of 1.25 MHz. An improved numerical model based on a forward Maxwell equation (FME) is built to investigate the transfers of the pump and seed’s noise to the resulting OPAs’ intensity and temporal fluctuation. Both the experimental and numerical study indicate that the low level of noise from the narrowband CW seeded OPA is attributed to the elimination of the RIN and RTJ coupled from the noise of seed source, being one of the important contributions to RIN and timing jitter in the other two OPAs. The approach to achieve lower level of noise from this CW seeded OPA by driving it close to saturation is also discussed with the same numerical model.

We characterize, for the first time, relative intensity noise and timing jitter properties of the OPG output pulses based on the balanced optical cross-correlator technique, which is in a fairly good agreement with numerical simulation.

We demonstrate experimentally a passively relative carrier-envelope phase (CEP)-locking, broadly tunable and robust laser source which is based on narrowband cw injection seeding of a two stage femtosecond optical parametric amplifier (OPA).

We report dispersive waves generation in an argon-filled anti-resonant nodeless fiber pumped by ultrashort pulses centered at different wavelengths. The conversion efficiency can be as high as 16% with a bandwidth below 10 nm.

We demonstrate a simple sub-femtosecond precision timing jitter measurement method for mode-locked lasers based on the time scaling effects of asynchronous optical sampling.

We demonstrate a simple passive method to generate broadband chirped super-Gaussian pulses from high-gain ytterbium-doped fiber amplification system without obvious bandwidth degradation. By use of the inherent gain shaping effect of fiber amplifiers, pulses can recover the initial Super-Gaussian profile and bandwidth with large gain and optical signal-to-noise ratio (OSNR). In this method, fiber amplifier itself works as a spectral filter with flexible transmission profiles and gain, which can be optimized by pump power and fiber length. A spectrally resolved numerical model with amplified spontaneous emission (ASE) is developed for broadband ytterbium-doped double-clad fiber pulse amplifiers. In a proof-of-principle two-stage amplification system, with a shorter fiber preamplifier working in the gain-narrowing region as a pre-shaper, broadband Super-Gaussian pulses resemble themselves after the second amplification stage with the largest total gain and OSNR. Experimental results quantitatively confirm the numerical predictions. The proposed gain shaping method also provides a new way to compensate the pulse deformation and bandwidth narrowing in high-gain fiber chirped pulse amplification systems.

We demonstrate nonlinear propagation of femtosecond laser pulses in an all-solid photonic bandgap fiber. A supercontinuum from 560 to 1470 nm is generated from this fiber with an average power of 2 W. Spectral broadening not only occurs within the first bandgap, where the pump laser lies, but it also emits a phase-matched dispersive wave in a different propagation mode within the adjacent bandgap. Energy transfers across the intergap attenuation region with simultaneous mode conversion in the nonlinear process. The intermodal Cherenkov radiation generated across two bandgaps by the perturbed Raman solitons can enrich the nonlinear process in the all-solid photonic bandgap fiber.

We demonstrate 14.3-attosecond timing jitter [integrated from 10 kHz to 94 MHz offset frequency] optical pulse trains from 188-MHz repetition-rate mode-locked Yb-fiber lasers. In order to minimize the timing jitter, we shorten the non-gain fiber length to shorten the pulsewidth and reduce excessive higher-order nonlinearity and nonlinear chirp in the fiber laser. The measured jitter spectrum is limited by the amplified spontaneous emission limited quantum noise in the 100 kHz - 1 MHz offset frequency range, while it was limited by the relative intensity noise-converted jitter in the lower offset frequency range. This intrinsically low timing jitter enables sub-100-attosecond synchronization between the two mode-locked Yb-fiber lasers over the full Nyquist frequency with a modest 10-kHz locking bandwidth. The demonstrated performance is the lowest timing jitter measured from any free-running mode-locked fiber lasers, comparable to the performance of the lowest-jitter Ti:sapphire solid-state lasers., Comment: 7 pages, 8 figures, 1 table

Ultrafast fiber lasers exhibit high broadband gain per pass, superior thermo-optical properties, and excellent beam quality, making them very suitable for practical use. For simplicity and efficiency, advanced mode-locked oscillator designs which can compete with the amplifier systems are always favorable. Here, we demonstrate a high-peak-power Mamyshev oscillator based on single-polarization, large-mode-area photonic crystal fibers. Using properly arranged filters, the fiber oscillator directly emits pulses with 9 W average power at 8 MHz repetition rate, corresponding to a single-pulse energy exceeding 1 μJ. The pulses are dechirped to 41 fs outside the cavity, leading to a record oscillator peak power as high as 13 MW. With such unprecedented performance, the proposed single-stage oscillator should be very attractive for various applications.

We report a hybrid femtosecond laser system based on a femtosecond Yb-doped fiber laser and a Yb-doped potassium gadolinium tungstate (Yb:KGW) regenerative amplifier. To match the central wavelength of the seed source, a Yb:KGW crystal is used in the regenerative amplifier for Np polarization. We study and optimize the dynamics of nonlinear amplification to alleviate the gain narrowing effect. With optimization, the system can output 270 fs pulses with 21 μJ pulse energy at a 60 kHz repetition rate.

Fluoropolymer/TiO2 nanocomposite coatings have been prepared successfully in this paper. For the improvement of TiO2 nanoparticles dispersion and increasing the possibility of the interactions between nanoparticles and fluoropolymer matrix, the surface of TiO2 nanoparticles was modified with KH550 silane coupling agent. The microstructure and properties such as self-cleaning, surface hydrophobicity, ultraviolet and corrosion resistance were investigated by means of Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectra (XPS), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), self-cleaning test, contact angle measurement, UV spectrophotometer and electrochemical measurement system. The results showed that KH550-modified TiO2 nanoparticles are of good dispersive capacity in organic solvent, and they can improve the self-cleaning property, surface hydrophobicity, ultraviolet resistance, as well as corrosion resistance of the fluoropolymer/TiO2 nanocomposite coatings effectively. Also, the optimal reaction temperature and the mass percentage of KH550 to TiO2 have been obtained.

A novel cluster-small-core tellurite microstructured optical fiber (MOF) which possesses high nonlinearity and supports high-power transmission in the small core is presented in the paper. When the light is coupled to the input end of this MOF, a large effective mode area can be obtained. At the odd times of coupling length, the light will be coupled to the central single core and the intensity in central single core will increase by nearly 7-fold. Therefore, the MOF not only has the same nonlinearity coefficient with the central single core, but also can support high-power beam transmission. It effectively decreases the likelihood of breaking the input end of single-core MOF when directly pumped with high-power beam.

We demonstrate a wavelength-tunable source of high-energy sub-100 fs light pulses where all the key components, including a master oscillator, an amplifier, and a tunable frequency shifter, are based on photonic-crystal fibers (PCFs). Soliton self-frequency shift in a specifically designed all-solid photonic band-gap fiber with an effective mode area of 110 mm 2 is used in this system to transform a 1040 nm, 50 MHz, 100 fs amplified output of a large-mode-area ytterbium-doped PCF oscillator–amplifier system into sub-100 fs, 6.4 nJ light pulses smoothly tunable within the range of wavelengths from 1160 to 1260 nm. & 2012 Published by Elsevier B.V.