Left picture shows a cylindrically confined Pb-glass plasma at surrounding air pressure of 2 Torr. The Nd-YAG laser of fundamental wavelength and energy of 80 mJ was used in this work. The right picture represents a copper plasma generated using fundamental Nd-YAG laser at helium gas at 15 Torr.
Pictures on the first line show plasma modulated by combination of upper and lower wires when a TEA CO2 laser pulse of 750 mJ was focused onto zinc plate at 2 Torr. The second line shows V-shaped emission structure induced by a needle placed at three different positions, 3, 5 and 10 mm from the zinc plate.
Photograph of the plasma when a Nd-YAG laser of energy 120mJ was focused on the black acrylic sample at 2 Torr (most left side) for free expansion palsma and (second from left side) for modulated plasma when a needle (diameter 2mm) was placed parallel to the sample surface, approximately 3 mm away, and without intercepting the laser beam. Filters (Sigma Koki SCF-50S-48Y Yellow and Sigma Koki CCF-50S-500C Blue) were placed in front of the camera.
Photograph of the plasma when a Nd-YAG laser of 120mJ was focused on the black acrylic sample at 2 Torr (third from left side) for free expansion plasma and (most right side) for modulated plasma when a needle (diameter 2mm) was placed to the sample surface, approximately 3 mm away, and without intercepting the laser beam. A special sharp red band pass filter, from 650 nm to 666 nm, was used (Sigma Koki, VPF-25C-10-50-65630) in front of the camera lens. The red emission is due to the emission of hydrogen line (H I 656.2 nm)
A Photograph of the helium gas plasma and zinc target plasma when the laser light was tightly focused to a position 5 mm above the zinc surface in a helium gas of 760 Torr.