The optical nonlinearity in polycrystalline zinc selenide(ZnSe),excited with 775 nm,1 kHz femtosecond laser pulses was investigated via the nonlinear transmission with material thickness and the Z scan technique.The m...The optical nonlinearity in polycrystalline zinc selenide(ZnSe),excited with 775 nm,1 kHz femtosecond laser pulses was investigated via the nonlinear transmission with material thickness and the Z scan technique.The measured two photon absorption coefficientβwas intensity dependent,inferring that reverse saturated absorption(RSA)is also relevant dur-ing high intensity excitation in ZnSe.At low peak intensity I<5 GW cm^(-2),we findβ=3.5 cm GW^(-1) at 775 nm.The spec-tral properties of the broad blueish two-photon induced fluorescence(460 nm-500 nm)was studied,displaying self-ab-sorption near the band edge while the upper state lifetime was measured to be τ_(e)~3.3 ns.Stimulated emission was ob-served when pumping a 0.5 mm thick polycrystalline ZnSe sample within an optical cavity,confirmed by significant line narrowing fromΔλ=11 nm(cavity blocked)toΔλ=2.8 nm at peak wavelength λ_(p)=475 nm while the upper state life-time also decreased.These results suggest that with more optimum pumping conditions and crystal cooling,polycrystal-line ZnSe might reach lasing threshold via two-photon pumping atλ=775 nm.展开更多
As a new research area, laser surface wettability modification brings new applications for both laser and materials for industry. The picoseconds （10 ps） pulse laser surface micro-processing over alumina covered alu...As a new research area, laser surface wettability modification brings new applications for both laser and materials for industry. The picoseconds （10 ps） pulse laser surface micro-processing over alumina covered aluminium is researched. In the experiment, lO-ps laser pulse is employed and the energy threshold for different laser wavelength and repetition rate is measured. At the repetition rate of 5 kHz, the energy thresholds are： 1064 nm： 4.0 μJ/pulse, 532 nm： 2.8 μJ/pulse, and 355 nm： 4.2 #J/pulse. Picoseconds pulse laser is demonstrated feasible in surface scanning at industrial level.展开更多
文摘The optical nonlinearity in polycrystalline zinc selenide(ZnSe),excited with 775 nm,1 kHz femtosecond laser pulses was investigated via the nonlinear transmission with material thickness and the Z scan technique.The measured two photon absorption coefficientβwas intensity dependent,inferring that reverse saturated absorption(RSA)is also relevant dur-ing high intensity excitation in ZnSe.At low peak intensity I<5 GW cm^(-2),we findβ=3.5 cm GW^(-1) at 775 nm.The spec-tral properties of the broad blueish two-photon induced fluorescence(460 nm-500 nm)was studied,displaying self-ab-sorption near the band edge while the upper state lifetime was measured to be τ_(e)~3.3 ns.Stimulated emission was ob-served when pumping a 0.5 mm thick polycrystalline ZnSe sample within an optical cavity,confirmed by significant line narrowing fromΔλ=11 nm(cavity blocked)toΔλ=2.8 nm at peak wavelength λ_(p)=475 nm while the upper state life-time also decreased.These results suggest that with more optimum pumping conditions and crystal cooling,polycrystal-line ZnSe might reach lasing threshold via two-photon pumping atλ=775 nm.
文摘As a new research area, laser surface wettability modification brings new applications for both laser and materials for industry. The picoseconds （10 ps） pulse laser surface micro-processing over alumina covered aluminium is researched. In the experiment, lO-ps laser pulse is employed and the energy threshold for different laser wavelength and repetition rate is measured. At the repetition rate of 5 kHz, the energy thresholds are： 1064 nm： 4.0 μJ/pulse, 532 nm： 2.8 μJ/pulse, and 355 nm： 4.2 #J/pulse. Picoseconds pulse laser is demonstrated feasible in surface scanning at industrial level.
