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This paper describes a high-pulse-energy frequency-doubled ultraviolet dye laser operating at a repetition rate of 500 Hz. The pump source is a laser-diode side-pumped Q-switched Nd:YAG laser with a pulse energy of 29 mJ at 532 nm. A master oscillator power amplifier is employed to amplify the output pulse of the dye laser to 8.1 mJ at 566 nm, and by frequency doubling with BBO crystal a pulse energy of 1.7 mJ at 283 nm is achieved with a pulse width of 8 ns. This is more than four times the largest reported pulse energies generated by other fixed-frequency dye lasers when operating at repetition rates of more than 1 kHz. The conversion efficiency and stability of dye laser are discussed, which show the potential for high-speed laser diagnostics in the fields of combustion and turbulent flow detection. [ABSTRACT FROM AUTHOR]

Spectrally dispersed femtosecond time-resolved coherent anti-Stokes Raman spectroscopy is applied to study the ultrafast vibrational dynamics in ethanol at room temperature. The anti-Stokes intensities were monitored as a function of delay time and wavenumber. By simply changing the timing of the laser pulses, the vibrational dynamics between the excited Raman transitions in ethanol molecules can be tracked and detected. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Micro-structured surface on diamond is widely used in microelectronics, optical elements, MEMS and NEMS components, ultra-precision machining tools, etc. The efficient micro-structuring of diamond material is still a challenging task. In this article, the influence of the focus position on laser machining and laser micro-structuring monocrystalline diamond surface were researched. At the beginning, the ablation threshold and its incubation effect of monocrystalline diamond were determined and discussed. As the accumulated laser pulses ranged from 40 to 5000, the laser ablation threshold decreased from 1.48 J/cm 2 to 0.97 J/cm 2 . Subsequently, the variation of the ablation width and ablation depth in laser machining were studied. With enough pulse energy, the ablation width mainly depended on the laser propagation attributes while the ablation depth was a complex function of the focus position. Raman analysis was used to detect the variation of the laser machined diamond surface after the laser machining experiments. Graphite formation was discovered on the machined diamond surface and graphitization was enhanced after the defocusing quantity exceeded 45 µm. At last, several micro-structured surfaces were successfully fabricated on diamond surface with the defined micro-structure patterns and structuring ratios just by adjusting the defocusing quantity. The experimental structuring ratio was consistent with the theoretical analysis. [ABSTRACT FROM AUTHOR]

A 500 kHz burst-mode YVO 4 /Nd:YVO 4 1064 nm laser oscillator with a burst duration of 1 ms and a burst energy of 45.0 mJ was presented. The acousto-optically Q-switched frequency could be varied from 10 kHz to 500 kHz, resulting in 10–500 sub-pulses per burst. At the pulse repetition rate of 500 kHz, the maximum single pulse energy reached 90.0 μJ with a pulse width of 37.8 ns, corresponding to a peak power of 2.4 kW. The beam quality factor of burst-mode laser at 500 kHz was measured to be M2=1.6. The burst-mode YVO 4 /Nd:YVO 4 laser could be acted as a master oscillator for further power scaling. [ABSTRACT FROM AUTHOR]