High dynamic range laser pulse contrast measurement with a optical clipping of plasma

Summary form only given. High dynamic range measurements of optical pulse contrast are of great interest for high energy laser pulse characterization. With a device alone, one would either measure the main pulse peak with no information the pedestal or measure the pedestal while saturating or even damaging the detector with the main pulse. Therefore, to measurement the pedestal without damaging the device, one effectively needs to let the pedestal through while substantially attenuating the main pulse. Laser induced breakdown in transparent media provides a shuttering effect to any light arriving after the plasma generated by the main pulse. A plasma shutter can serve as a peak reduction device to prevent any photodetector from being saturated or damaged by the intense pulse peak while it is measuring the low energy pedestal or prepulse. The temporal profiles of two beams were obtained using comparison method, and then the energy reduction factor was acquired. The two beams, one passing through a transparent medium is clipped by laser induced plasma, and the other transmits with a delay line, come into a set of photoelectricity conversion component and oscillograph in simultaneously. It is shown that the transmitted pulse energy reduction factor is 12 to 14 with the 1.06 μm 1 ns laser pulse, a 100 mm focal length lens, a 100 μm thick fused silica plate, and a pinhole of 80 μm radius to ensure that the entire aperture area is from the plasma shuttered focal plane. Changing the thickness of the fused silica plate and the radius of the aperture pinhole respectively shows no impact on the energy reduction factor. The energy reduction factor increases while the energy of input beam enhances and the trailing edge of the clipped pulse gradually falls faster. The temporal profile of original laser pulse was reconstructed by profile stitching at the point of energy reduction.