Yuanqin Xia

Solid state dye lasers based on LDS 698 doped in modified polymethyl methacrylate.

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 lasers 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.

Highly photostable solid-state dye lasers based on mixed pyrromethene 567 and coumarin 500

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 lasers based on copolymers of methyl methacrylate and 2-hydroxyethyl acrylate doped with pyrromethene 567 dye

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.

Femtosecond laser field induced modifications of electron-transfer processes in Ne+-He collisions

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.

Solid-state dye lasers based on polymethyl methacrylate modified with methanol

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.

Generation of tunable coherent XUV harmonic emission from Xe at low pressure

We report the harmonic spectral properties of Xe at low gas pressure and the significant amount of redshift and blueshift of the harmonic spectra. Different amounts of harmonic frequency shift are obtained by adjusting the gas pressure and peak laser intensity; namely, by varying the ionization of the gas medium. The observed blueshift shows that nondiabatic effects in the ionized gas medium play a major role, while the observed redshift toward higher gas pressure is attributed to the decrease in electron density effects due to the defocusing and electron–ion recombination. We demonstrate the possibility of coherently tuning the soft x-ray source by taking advantage of the frequency shift of harmonics.

High pulse energy output from tunable solid-state dye laser based on MPMMA doped with PM567

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.

Highly efficient and photostable solid-state dye lasers doped with PM567 with the addition of Tinuvin770

Solid-state dye samples based on polymethyl methacrylate (PMMA) doped with pyrromethene 567 (PM567) with the addition of Tinuvin770 were prepared. The effects of a light stabilizer and concentration on the laser performances of the solid state dye PM567, including spectra properties, slope efficiency and photostability were investigated. The highest slope efficiency 66.6% was obtained in the sample (PM567:Tinuvin770 = 2.0:0.5). The addition of Tinuvin770 resulted in a dramatic enhancement of photo-stability. Pumping the samples at a rate of 5 Hz with a pulse energy as high as 100 mJ (the pump energy density was 0.26 J/cm2), the output energy dropped to half of its initial value after approximate 149500 shots and the normalized photostability reached 97.2 GJ/mol in the sample (PM567:Tinuvin770 = 2:5). All results have shown that a high efficient and photostable solid-state dye laser with the addition of Tinuvin770 can be obtained.

Tunable narrow linewidth laser output from PM567 doped nematic liquid crystal under holographic pumping

LC cell injected the mixture of dye pyrromethene 567 (PM567) and nematic liquid crystal (NLC) by capillary action was prepared. Holographic pumping with a Nd:YAG laser (532 nm, 1 Hz, 10 ns) to form gain distributed feedback in the cell, tunable laser output from the cell was investigated. Through changing the intersection angles of the two coherent light beams from 46° to 50°, the tuning range we obtained is about 37 nm (550–587 nm). Additionally, the FWHM of the laser under such experimental setup was less than 0.1 nm even without the resonant cavity, and the threshold of the laser was about 26 μJ, which was very low as we known.

Calculations of laser induced quadrupole–quadrupole collisional energy transfer in Xe–Kr

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.