Suyu Li

Optimally enhanced optical emission in laser-induced air plasma by femtosecond double-pulse

In laser-induced breakdown spectroscopy, a femtosecond double-pulse laser was used to induce air plasma. The plasma spectroscopy was observed to lead to significant increase of the intensity and reproducibility of the optical emission signal compared to femtosecond single-pulse laser. In particular, the optical emission intensity can be optimized by adjusting the delay time of femtosecond double-pulse. An appropriate pulse-to-pulse delay was selected, that was typically about 50 ps. This effect can be especially advantageous in the context of femtosecond laser-induced breakdown spectroscopy, plasma channel, and so on.

Effect of sample position on collinear femtosecond double-pulse laser-induced breakdown spectroscopy of silicon in air

A femtosecond double-pulse laser was used to induce the plasma of silicon in air. The laser wavelength was 800 nm. The interpulse delay of the femtosecond double-pulse was from −20 ps to 100 ps. During the experiment, the spectral line was fixed at the wavelength of 288.157 nm. The emission intensity was observed to lead to a significant increase by choosing the proper sample position. The range of the sample position is from 5.17 mm to 5.27 mm. And, the best sample position for the higher laser fluence was different from the position for the lower laser fluence. At the higher laser fluence, the optimized emission intensity can be obtained at either side of the best focal position for all interpulse delays of the double-pulse. The phenomena can be explained by the nonlinear propagation of the femtosecond laser pulse in air. At the lower laser fluence, the best sample position will change from one side to both sides with the increase of the interpulse delay of the double-pulse. The results showed that the effect of the sample position can be especially advantageous in the context of femtosecond double-pulse laser-induced breakdown spectroscopy. The study will lead a further improvement in the applications of the femtosecond double-pulse laser.

Optical emission generated from silicon under dual-wavelength femtosecond double-pulse laser irradiation.

In femtosecond double-pulse laser-induced breakdown spectroscopy, collinear double-pulse performance is investigated experimentally using various laser wavelength combinations of 800 nm and 400 nm Ti: sapphire lasers. The induced plasma emission line collected by BK7 lenses is the Si (I) at 390.55 nm. The double-pulse time separation ranges from -300 ps to 300 ps. The line intensity is dependent on the time separation of the dual-wavelength femtosecond double-pulse, and its behavior is unlike that of single-wavelength femtosecond double-pulses. Optical emission intensity can be enhanced by selecting appropriate time separation between sub-pulses. This result is particularly advantageous in the context of femtosecond laser-induced breakdown spectroscopy.

Successful treatment of giant condyloma acuminatum with combination retinoid and interferon-γ therapy.

Giant condyloma acuminatum, or Buschke–Löwenstein tumour, is a unique variant of anogenital warts. It is characterized by locally aggressive behaviour but rarely metastasizes. Many treatment strategies such as radical surgery, radiation and chemotherapy have been used to treat it but their efficacy is often poor and the recurrence rates are high. We report a case of 16-year-old girl who was treated with oral retinoid combined with intramuscular interferon-γ. All lesions cleared within three months. During a follow-up period of more than two years, no recurrence has developed. This relatively painless, non-scarring treatment may represent a novel therapeutic option.

Influence of ambient pressure on the ablation hole in femtosecond laser drilling Cu.

The holes were drilled by femtosecond laser pulse (800 nm, 100 fs) on Cu sheets at different ambient pressures. The pressure range was from 1 Pa to atmospheric pressure. The number of pulses to drill through the target, the stable photodiode signal, and the hole diameter were obtained as functions of ambient pressure. The morphology of the hole was observed by a scanning electron microscope (SEM). The result showed that the ambient pressure had significant influence on the morphology of the hole.

Persistence of atomic spectral line on laser-induced Cu plasma with spatial confinement

This paper carries out the spatial confinement effect on laser-induced Cu breakdown spectroscopy in a cylindrical cavity via a nanosecond pulsed Q-switch Nd:YAG laser operating at a wavelength of 1064 nm. The temporal evolution of the laser-induced plasma spectroscopy is used to investigate the characteristics of spectral persistence. The atomic spectral persistence in plasma generated from Cu with spatial confinement is experimentally demonstrated, where the results indicate that the diameter of the confinement cavity plays a very important role in the persistence of an excited neutral Cu emission line, while the depth of the confinement cavity is almost independent of Cu (I) line persistence. As the diameter of the confinement cavity increases, the persistence of the Cu (I) line in the plasma grows longer under a certain limit. The likely reason for this phenomenon is that under spatial confinement, the reflected shockwave compresses the plasma and leads to an increase in the plasma temperature and dens...

Temperature effect on femtosecond laser-induced breakdown spectroscopy of glass sample

In this study, we observed the evolution of the spectral emission intensity of a glass sample with the increase of sample temperature, laser energy, and delay time in femtosecond laser-induced breakdown spectroscopy (fs-LIBS). In the experiment, the sample was uniformly heated from 22 °C to 200 °C, the laser energy was changed from 0.3 mJ to 1.8 mJ, and the delay time was adjusted from 0.6 μs to 3.0 μs. The results indicated that increasing the sample temperature could enhance the emission intensity and reduce the limits of detection, which is attributed to the increase in the ablated mass and the plasma temperature. And the spectral intensity increases with the increase of the laser energy and the delay time, however, the spectral line intensity no longer increases when the laser pulse energy and delay time reach a certain value. This study will lead to a further improvement in the applications of fs-LIBS.

Two sequential enhancements of laser-induced Cu plasma with cylindrical cavity confinement

This study was conducted to investigate spatial confinement effects in laser-induced Cu plasma via optical emission spectroscopy. Two sequential enhancement events of Cu atomic emission lines were observed. This phenomenon was attributed to the compressed plasma by the reflected shockwave facilitating a highly condensed plasma core area with high plasma temperature and a dense population of excited atoms.

A case of lues maligna in an AIDS patient

Lues maligna is a severe and rare manifestation of syphilis, also known as malignant syphilis or ulceronodular syphilis and mostly occurring in patients with HIV infection. In this report, we present a case of lues maligna in an AIDS patient. Our report shows the typical clinical features of lues maligna and the important association between lues maligna and HIV/AIDS. Although the clinical manifestations of lues maligna are complicated and severe, the response to the therapy of penicillin is excellent.

Influence of distance between focusing lens and target surface on laser-induced Cu plasma temperature

In this study, the influence of distance between the focusing lens and target surface on the plasma temperature of copper induced by a Nd:YAG laser was investigated in the atmosphere. The plasma temperature was calculated by using the Cu (I) lines (510.55 nm, 515.32 nm, and 521.82 nm). The Cu (I) lines were recorded under different lens-to-sample distances and laser pulse energies (15.8 mJ, 27.0 mJ, 43.4 mJ, 59.2 mJ, and 76.8 mJ). The results indicated that the plasma temperature depended strongly on the distance between the focusing lens and target surface. With the increase in the distance, the plasma temperature firstly rose, and then dropped. This could be attributed to the interaction between the tailing of the nanosecond laser pulse and the front portion of the plasma plume, the plasma shielding effect, and the expanding of the plasma. In addition, there was an interesting phenomenon that the plasma temperature and the emission intensity were not completely consistent with the change of the lens-to-...