Comparison of Nitric Oxide Concentrations in μs-and ns-Atmospheric Pressure Plasmas by UV Absorption Spectroscopy

In this paper,an absorption spectroscopy measurement method was applied on two atmospheric pressure plasma sources to determine their production of nitric oxide.The concentrations are essential for evaluating the plasma sources based on the principle of the Dielectric Barrier Discharge（DBD）for applications in plasma medicine.The described method is based on a setup with an electrodeless discharge lamp filled with a mixture of oxygen and nitrogen.One of the emitted wavelengths is an important resonance wavelength of nitric oxide（λ = 226.2 nm）.By comparing the absorption behaviour at the minimum and maximum of the spectral absorption cross section of nitric oxide around that wavelength,and measuring the change in intensity by the absorbing plasma,the concentration of nitric oxide inside the plasma can be calculated.The produced nitric oxide concentrations depend on the pulse duration and are in the range of 180 ppm to 1400 ppm,so that a distance of about 10 cm to the respiratory tract is enough to conform to the VDI Guideline 2310.

Direct generation of a stable multi-beam pulsed 355 nm UV laser based on a micro-lens array

Multi-beam laser processing is a very popular method to improve processing efficiency. For this purpose, a compact and stable multi-beam pulsed 355 nm ultraviolet(UV) laser based on a micro-lens array(MLA) is presented in this Letter. It is worth noting that the MLA is employed to act as the spatial splitter as well as the coupling lens. With assistance of the MLA,the 1064 nm laser and 532 nm laser are divided into four sub-beams and focused at different areas of the third-harmonic generation(THG) crystal. As a result, the multi-beam pulsed 355 nm UV laser is successfully generated inside the THG crystal. The measured pulse widths of four sub-beams are shorter than 9 ns. Especially, the generated four sub-beams have good long-term power stability benefitting from the employed MLA. We believe that the generated stable multi-beam355 nm UV laser can meet the requirement of high-efficiency laser processing, and the presented method can also pave the way to generate stable and long-lived multi-beam UV lasers.