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Y2O3:Tm3+, Yb3+ was prepared by nanosecond pulsed laser irradiation. The X-ray diffraction pattern shows that the material produced by laser irradiation is amorphous, which presents strong blue upconversion emission under the excitation of 976 nm diode laser. The relative intensity of the blue emission to the infrared one is linearly dependent on the pump power and is an order of magnitude higher than that of the bulk material. The analyses of rate equations and the time-resolved spectroscopic results indicate that the enhancement of the blue upconversion is attributed to the longer lifetime of the levels of the Tm3+ and Yb3+ ions.

Solid-state dye samples based on modified copolymers of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) with methanol doped with PM567 were first prepared. The volume proportions of methanol have great effects on the laser's characteristics including spectra, lasing output and thermal properties. The highest slope efficiency of 64.25% was achieved in the sample MP (MMA:HEMA = 85:15 + 10% methanol). Pumping the samples at a repetition rate of 5 Hz with a pulse energy as high as 100 mJ (the fluence was 0.26 J/cm 2 ), the maximum lifetime of 278,000 shots was obtained in the sample MP (MMA:HEMA = 85:15 + 15% methanol), and the corresponding normalized photostability reached 180.7 GJ/mol. The obtained ten-shots damage thresholds were as high as 6.7 J/cm 2 . The results indicate that the laser properties of solid-state dyes can be greatly enhanced by using modified copolymers of MMA and HEMA with methanol as solid hosts.

Tunable solid-state dye laser sample based on modified polymethyl methacrylate (MPMMA) with methanol co-doped with pyrromethene 567 (PM567) and Coumarin 440 (C440) was prepared. Tunable dye laser output wavelength from 546 to 594 nm was obtained in an oscillator-amplifier configuration. With the input seed laser energy being about 1.5 mJ, the highest dye laser output energy reached 113.9 mJ, and the corresponding conversion slope efficiency was 51.39%. To the best of our knowledge, the tuning range and narrow linewidth dye output energy is the best under the same condition so far. The linewidth for the seed laser and amplified laser were measured with the result of less than 0.2 nm. With the amplified medium being pumped at a repetition rate of 10 Hz with a pulse energy as high as 120 mJ (the fluence was 0.42 J/cm2), the laser output energy dropped to half of its initial value after approximate 43000 pulses.

We study amplified spontaneous emission of Pyrromethene-650-doped nematic liquid crystal deposited onto quartz and glass substrates. We prepare samples with different dye-doped concentrations pumped with a Nd:YAG laser at 532 nm. With an applied electric field, a tuning range of the amplified spontaneous emission of more than 20 nm was realized in each sample due to changing the effective refractive index of the nematic-liquid-crystal layer caused by the reorientation of nematic-liquid-crystal molecules. We show that there exist a threshold voltage and a saturation voltage for all the samples. With the increase in the dye-doped concentration, the peak wavelength of the amplified spontaneous emission has a red shift of about several nanometers.

Solid-state dye samples based on modified polymethyl methacrylate with methanol (MPMMA) doped with pyrromethene 567 (PM567) were first prepared. The effects of volume percentage of methanol on the laser performances of the samples, including spectra properties, slope efficiency and photostability were studied. The highest slope efficiency 66.39% was obtained in the sample (MMA:methanol = 16:4). Pumping the samples at a repetition rate of 5 Hz with a pulse energy as high as 100 mJ (the fluence was 0.26 J/cm2), the output energy dropped to half of its initial value after approximate 156720 shots and the corresponding normalized photostability reached 101.86 GJ/mol in the sample (MMA:methanol = 17:3). Our results indicate that it can obtain a high slope efficiency and good photostability for a solid-state dye laser using MPMMA as solid hosts.

We report the phase-matched high-harmonic generation from N2 driven by kHz femtosecond laser pulses. By varying the position of the laser focus in the gas tube, we observe the radiation of different harmonics. Our results provide a potential source for studying ultrafast molecular dynamics.

Based on the four-state model of laser-induced collisional energy transfer, the cross section of the collisional energy transfer in the Sr-Ca system is obtained. Various factors, including field intensity, relative speed, and temperature, which influence the collisional cross section, are discussed for illustrating the features of the Sr-Ca laser-induced collisional energy transfer (LICET) process. The calculated results show that the LICET spectral profiles obviously become narrower when the laser field intensity increases. The collision cross section rises with laser intensity and tends to saturate. In the vicinity of the spectral profile center, the cross section at fixed laser detuning becomes smaller as the relative speed and system temperature increase. The results indicate that the intermediate states strongly affect the spectral profile of LICET.

Solid-state dye sample based on modified polymethyl methacrylate (MPMMA) co-doped with pyrromethene 597 (PM597), and coumarin 460 (C460) were prepared. A frequency-doubled pulsed Nd:YAG laser is used to pump solid-state dye sample, and the narrow linewidth dye laser of 94.4 mJ was obtained at 582 nm in an oscillator-amplifier configuration. Using a beta-BaB2O4 (BBO) crystal to frequency double the dye laser into ultraviolet (UV), a tuning range from 279 to 305 nm was demonstrated from a single doped PM597 dye. To the best of our knowledge, the UV tuning range is the best under the same condition so far. The conversion slope efficiency from solid dye laser to UV laser was 8.9% and the highest UV laser output energy reached 6.94 mJ at 291 nm.

Ultrafine Y2O3: Pr, Yb nanoparticles were produced by femtosecond pulsed laser ablation. Scanning and transmission electron microscope analyses indicated that these spherical particles have a diameter of about 10 nm with a narrow size distribution and no visible coalescence. These nanoparticles show much improved upconversion intensity compared to nanoparticles prepared by the sol–gel method and a new 510 nm emission band was observed. The time-resolved spectra indicated that the samples prepared by the laser method have longer decay time in spite of the smaller size, resulting from the exclusion of chemical residues, which lead to the enhancement of upconversion intensity.

We study laser performance with two laser dyes, Pyrromethene 567 and Rhodamine 610, co-doped into modified poly(methyl methacrylate) (MPMMA). We achieve a more than 37 nm wide tunable range. We obtain a narrowband-laser slope efficiency of 27.24%, which is almost as high as a broadband-output slope efficiency of 36.6%. To the best of our knowledge, the narrowband slope efficiency is the highest under the same conditions so far. The narrowband laser linewidth obtained is far less than 0.3 nm. All our results indicate that high laser performance can be achieved using two dyes co-doped into MPMMA.

We study the characteristics of a xenon-lamp-pumped dye (PM567) laser with different molar concentrations, inner diameters of the glass tube, resonators, and condenser cavities. The experimental setup uses ordinary industrial products without any special design. We study the dependences of the laser-output energy and other laser characteristics on the configurations of the resonator and the components used. We succeed in obtaining an output energy efficiency with respect to the electrical stored energy of 0.433% and a slope efficiency of 0.498%.

The two-photon absorption (TPA) characteristics of PMMA discs doped with three different dyes were studied using an fs-pulsed Ti-Sapphire laser as the pump source, and employing the open-aperture Z -scan technique. TPA cross-sections obtained for PMMA doped with the dyes PM597, DCM and rhodamine 6G–rhodamine B (co-doped) were found to be equal to 24.7, 33.3 and 32.3 GM, respectively (1 GM=10 −50 cm 4 s phot −1 mol −1 ). Furthermore, two-photon fluorescence was measured for the samples containing DCM and rhodamine 6G–rhodamine B (co-doped). Compared to the one-photon fluorescence spectrum, the peaks in the two-photon fluorescence spectrum were red shifted and the extent of red shift increased with increasing doping concentration. We have also observed that the red shift in the two-photon fluorescence peak of the samples in the solid form is much larger than that in the solution state. This phenomenon could be explained by a twisted intra-molecular charge transfer model.

Solid-state dye samples based on polymethyl methacrylate (PMMA) co-doped with pyrromethene 567 (PM567) and coumarin 500 (C500) were prepared. The effects of C500 concentration on the performances of the solid state dye mediums, including spectra property, slope efficiency and photostability were studied. The highest slope efficiency 64.25% was obtained in the sample (PM567: C500 = 2: 8). Pumping the samples at a rate of 5Hz with a pulse energy as high as 100 mJ (the fluence was 0.26 J/cm2), the output energy dropped to half of its initial value after approximate 116130 pulses and the normalized photostability reached 75.48 GJ/mol in the sample (PM567: C500 = 2: 1). Our results have shown that it is possible to obtain a high-efficiency with a long-lifetime for a solid-state dye laser co-doped with PM567 and C500.

Solid-state dye laser samples based on copolymers of methyl methacrylate (MMA) and 2-hydroxyethyl acrylate (HEA) doped with pyrromethene 567(PM567) were prepared. The highest slope efficiency 46.4% was obtained. With pump repetition rate of 10 Hz and intensity of 0.1 J/cm2, the output energy of the sample based on P (MMA: HEA 16:4) remained up to 82.10% of its initial value after approximate 100000 shots. To our knowledge, the achieved photostability is the best under the same condition so far. Compared with the sample based on the monopolymer, the slope efficiency and photostability of copolymer-based solid-state dye samples were both enhanced. The results indicate that the high laser performance using solid-state dye samples based on copolymers of MMA with HEA as solid hosts can be achieved.

Tunable solid-state dye laser samples based on poly methyl methacrylate (PMMA) doped with PM567 and PM580 were prepared and the laser performances for them were studied in this letter. With pump repetition rate of 1 Hz and incident intensity of 0.1 J/cm2, more than 30 nm wide tunable range had all been achieved using the two samples, and the highest slope efficiency of 52.08% was obtained in the sample PM567. To the best of our knowledge, the efficiency is the highest under the same condition so far. The linewidth for the laser was measured with the result of less than 0.2 nm. All results indicate that the high laser performance using tunable solid-state dye lasers based on PMMA doped with PM dyes can be achieved.

Summary The origination of observed X-ray emissions are identified through looking for atomic spectra database lines data. From this observed ion stages, the peak intensity of femtosecond laser over a length of 3 mm of the gas cell can be deduced. We mainly present results of an experiment in which X-rays from an optical-field ionized (OFI) plasma driven by different polarized 34-mJ, 105-fs, 10-Hz Ti: sapphire laser system are generated under well-controlled conditions in a low-pressure gas cell (a gas cell filled with 0.266 KPa of Nitrogen) and in high gas density of the gas cell (a gas cell filled with 1.33 KPa of Nitrogen). Using Nitrogen as the medium, from X-rays emitted under well-controlled conditions of low-density plasmas driven by different laser polarization, we show many important features of the OFI process (the electron temperature for linear and circular light polarization, the generated ionization stages). From X-ray emissions at high gas density by different laser polarization, because of non-OFI process effects such as electron heating, collisional ionization and ionization defocusing, there is different optimum gas density value of the gas cell for different emitting spectrum line. The spectral line in which originated from C-like N ion show more intensity with linear than with circular polarization. The spectral line in which originated from B-like N ion gives a little more intensity with circular than with linear polarization. At the same time, we discuss and analyze that physical mechanisms may be responsible for these influences of laser polarization on X-rays emission from low-density and high-density optical-field ionized plasmas in Nitrogen.

A frequency stabilization approach is introduced for the microsecond pulse sodium beacon laser using an intra-cavity tilt- and temperature-tuned etalon based on a computer-controlled feedback system connected with a fast high-precision wavelength meter. The frequency stability of the sodium beacon lasers is compared with and without feedback loop controlling. The output wavelength of the laser is locked to the sodium D-2 alpha absorption line (589.159 nm) over 12 h with the feedback loop controlling technology. As a result, the sodium laser guide star is successfully observed by the telescope of National Astronomical Observatories at Xinglong. This approach can also be used for other pulses and continuous-wave lasers for the frequency stabilization.

A high-pulse-energy high-beam-quality tunable Ti:sapphire laser pumped by a frequency-doubled Nd:YAG laser is demonstrated. Using a fused-silica prism as the dispersion element, a tuning range of 740–855 nm is obtained. At an incident pump energy of 774 mJ, the maximum output energy of 104 mJ at 790 nm with a pulse width of 100 μs is achieved at a repetition rate of 5 Hz. To the best of our knowledge, it is the highest pulse energy at 790 nm with pulse width of hundred micro-seconds for an all-solid-state laser. The linewidth of output is 0.5 nm, and the beam quality factor M 2 is 1.16. The high-pulse-energy high-beam-quality tunable Ti:sapphire laser in the range of 740–855 nm can be used to establish a more accurate and consistent absolute scale of second-order optical-nonlinear coefficients for KBe2BO3F2 measured in a wider wavelength range and to assess Miller's rule quantitatively.

Femtosecond time-resolved coherent anti-Stokes Raman spectroscopy is utilized to measure the premixed methane/oxygen/nitrogen flame temperature at atmospheric-pressure. The procedure for fitting theoretical spectra to experimental spectra is explained. The experimental results show good agreements with theoretical ones and present a good repeatability. Laser parameters are very important for accurate temperature measurements. The effects of laser parameters on temperature measurements are discussed. Laser parameters in our discussion are shown as follows. Laser pulse shape is hyperbolic secant and Lorentz, respectively. The delay time between the pump and Stokes is from -40 fs to +40 fs. The central wavelength of the pump/probe pulses is from 650 nm to 700 nm. Pulse duration is from 40 fs to 120 fs. In 2000 K, variations of delay time between the pump and Stokes pulses lead to less than 5% error and while variations of the other three parameters lead to less than 1.5% error. Timing jitter is added to the pump/probe pulses and Stokes pulses. In 2000 K, the results indicate that timing jitter of 10% lead to less than 2% error for temperature measurements. In the higher temperature measurement, the impact of laser parameters’ error is greater.

We experimentally study high harmonic generation from elliptically polarized femtosecond laser pulses. The harmonic intensity as a function of laser ellipticity is measured. We show that the atomic ellipticity dependence is stronger than the molecular dependence.

We report the femtosecond time-resolved CARS in BBO crystal, ethanol, cresyl violet 670 and pyrromethene 650 using the various degrees of freedom such as the timing, polarization and wavelengths of the laser pulses.

Two LICET transitions in Cs-Sr systems are suggested and the results of numerical calculations of the transition probability and collisional crosssection are obtained respectively from our four-level model and the conventional three-level model. Comparisons of these results prove the theoretical prediction that if the frequency difference ω21, is comparable to ω43, the three-level theory has great error in describing the LICET transition, while the four-level theory can describe all cases of LICET process perfectly.

Solid-state dye samples based on modified polymethyl methacrylate with methanol (MPMMA) co-doped with pyrromethene 567 (PM567) and coumarin 460 (C460) were prepared. The effects of C460 concentration on the laser performances of the solid-state dye mediums, including spectra property, laser slope efficiency and photostability were studied. The highest laser slope efficiency of 66.66% was obtained in the sample (PM567:C460=2:10). When the samples were pumped at a repetition rate of 5 Hz with a pulse energy as high as 100 mJ (the fluence was 0.26 J/cm2), the laser output energy dropped to half of the initial value after approximate 398000 pulses in the sample (PM567:C460=2:2). Our results have shown that it can obtain a high-efficiency and long-lifetime solid-state dye laser under high pulse energy pump using MPMMA co-doped with PM567 and C460.

By combining the pulse molecular beam technique and time of flight mass spectrum, the multiphoton resonance ionization of Xe in the vicinity of 440 nm is studied. The dependence of resonant ionization on laser energy and source pressure of Xe was analyzed and discussed. The resonant ionization spectrum near 440 nm was obtained and the AC Stark effect was determined to be the major cause of asymmetric line broadening in the low pressure multiphoton ionization spectrum of xenon. The results show that spectrum broadening could be ascribed to cooperative effects from different laser energy and electric field.

Molecular wave functions are used to calculate the harmonic emission of diatomic molecules based on a time-dependent Schroedinger equation. Tunable effects are shown for both magnitudes and molecular-alignment-dependent properties of the harmonic emission with different electronic excited states or mixed states as the initial states. The calculated results are consistent with the experimental results of harmonic signals from N{sub 2} under different rotational temperatures and laser intensities. The molecular-alignment dependence of harmonic signals is rapidly weakened with increasing levels of electronic excited states. Especially when the initial state of N{sub 2} is the first electronic excited state, B{sup 3} PI{sub g}, the magnitudes of the 21st harmonic are significantly changed, and the molecular-alignment dependence of the harmonic shows reverse properties compared to those of the ground state, X{sup 1} SIGMA{sub g}{sup +}, which can be used to manipulate the harmonic emission.

Hyperspectral stimulated Raman scattering microscopy is deployed to measure single-membrane vibrational spectrum as a function of membrane potential. Using erythrocyte ghost as a model, quantitative correlation between transmembrane potential and Raman spectral profile was found. Specifically, the ratio between the area under Raman band at ∼2930 cm−1 and that at ∼2850 cm−1 increased by ∼2.6 times when the potential across the erythrocyte ghost membrane varied from +10 mV to −10 mV. Our results show the feasibility of employing stimulated Raman scattering microscopy to probe the membrane potential without labeling.

The ultrafast molecular vibrational dynamics in PMMA sheets is studied by femtosecond time-resolved coherent anti-Stokes Raman spectroscopy at room temperature. The C – H stretch modes at 2870 cm-1 and 3008 cm-1 in PMMA sheets are excited and detected. The coherence relaxation times and beat wavenumbers of the Raman modes are obtained.

High harmonic generation and its spectral properties are studied by using kHz tightly focused laser pulses in a Xe?He gas mixture. The cutoff region of harmonics in mixed gases is extended from H21 to H25. The results are attributed to the harmonic generation from the excited He atoms assisted by harmonic radiation from the Xe atoms. We illustrate that the pressure dependence of harmonic H19 shows a flat intensity profile in mixed gases. The results are explained by the harmonic H19 being moved from the cutoff region to a plateau region.

We demonstrate the presence of femtosecond laser induced charge transfer in Ne+-He collisions. Electron transfer in ion-atom collisions is considerably modified when the collision is embedded in a strong laser field with the laser intensity of ∼1015 W/cm2. The observed anisotropy of the He+ angular distribution confirms the prediction of early work that the capture probability varies significantly with the laser polarization angle.

A laser induced quadrupole–quadrupole collisional energy transfer system of Xe–Kr is proposed, and the three-level laser induced collisional energy transfer (LICET) model is presented. Calculating results show that the peak of the LICET profile moves to the red and the FWHM becomes narrower, obviously with the laser field intensity increasing, while the resulting spectra is shifted in frequency toward the blue and the full width at half peak of the profile becomes larger as the relative velocity increases. The spectrum of the quadrupole–quadrupole LICET in the Xe–Kr system has a wider tunable range in an order of magnitude than the dipole–dipole LICET spectra. A cross section of 3.36×10−15 cm2 is obtained, which indicates that the quadrupole–quadrupole LICET process also can be an effective way to transfer energy selectively from a storage state to a target state.

Solid-state samples based on modified polymethyl methacrylate (MPMMA) with methanol doped with the dye pyrromethene 650 (PM650) are prepared. The effects of a volume percentage of methanol on the laser characteristics of the sample, including spectra properties, slope efficiency, photostability and tunable properties, are investigated. The broadband dye laser output wavelength is around 655 nm and a highest slope efficiency of 32.23% is achieved. Pumping the samples at a repetition rate of 5 Hz with a pulse energy of as high as 100 mJ (the fluence is 0.26 J/cm2), the longest lifetime (168000 shots) is obtained in the sample (MMA:methanol=18:2), and the corresponding normalized photostability reaches 109.19 GJ/mol. When the sample (MMA:methanol=18:2) is placed in a Shoshan-type oscillator, the narrow-linewidth operation is a continuous tuning range (up to 64 nm). The results indicate that the laser characteristics of solid-state dyes can be greatly enhanced by using modified PMMA with methanol serving as the solid host.

By considering the relative velocity distribution function and multipole expansion interaction Hamiltonian, a three-state model for calculating the cross section of laser-induced quadrupole—quadrupole collisional energy transfer is presented. Calculated results in Xe—Kr system show that in the present system, the laser-induced collision process occurs for ~4 ps, which is much shorter than the dipole—dipole laser-induced collisional energy transfer (LICET) process. The spectrum of laser-induced quadrupole—quadrupole collisional energy transfer in Xe—Kr system has wider tunable range in an order of magnitude than the dipole—dipole LICET spectra. The peak cross section decreases and moves to the quasi-static wing with increasing temperature and the full width at half peak of the profile becomes larger as the system temperature increases.

Time-resolved resonance-enhanced coherent anti-Stokes Raman scattering (CARS) is applied to investigate molecular dynamics in gaseous iodine. 40 fs laser pulses are applied to create and monitor the high vibrational states of iodine at room temperature (corresponding to a vapor pressure as low as about 35 Pa) by femtosecond time-resolved CARS. Depending on the time delay between the probe pulse and the pump/Stokes pulse pairs, the high vibrational states both on the electronically ground states and the excited states can be detected as oscillations in the CARS transient signal. It is proved that the femtosecond time-resolved CARS technique is a promising candidate for investigating the molecular dynamics of a low concentration system and can be applied to environmental and atmospheric monitoring measurements.

A three-state model for calculating the cross section of laser-induced dipole-quadrupole collisional energy transfer in Sr-Ca system is presented. The motion equations for the probability amplitudes of the three intermediate states are obtained. The expression of the cross section is derived. Various factors including field intensity, relative speed, system temperature which influence the collisional cross section are discussed to illustrate the features of the dipole-quadrupole laser-induced collisional energy transfer (LICET)process. Calculating results show that the peak of the LICET profiles moves to the red, the tuning range of the profiles obviously becomes narrower with the laser field intensity increasing and a cross section of 1.25 × 10(-13)cm(2) at a laser intensity of 8.29 × 10(9)W/cm(2) is obtained. Our results indicate that dipole-quadrupole LICET process can be the effective way to transfer energy selectively from a storage state of arbitrary parity to a target state of arbitrary parity.

Broad band solid state dye lasers based on LDS 698 doped in modified polymethyl methacrylate (MPMMA) with laser wavelength about 650 nm were demonstrated. It was demonstrated that the fluorescence spectra of LDS 698 in solid host MPMMA displays an obvious blue shift about 50 nm comparing with that in ethanol solution. The dye concentration has great effect on the laser's performance including laser slope efficiency and lifetime. The lifetime increased dramatically with the increase of the LDS 698 concentration. With pump repetition rate of 10 Hz and intensity of 0.1 J/cm(2), the maximum lifetime 300,000 shots corresponding normalized photostability 102 GJ/mol was obtained with LDS 698 at 1.5 x 10(-4)mol/L.