The Transmittance, Transmittance Wavefront, and Laser Induced Damage Properties of Thin Fluoride Polymer Films May Be Used as Short Pulse Laser Debris Shields

Shufan Chen,Yu Fang,Xuan Luo,Chuanqun Huang,Xiaodong Jiang,Weidong Wu

doi:10.1155/2016/1367537

Abstract

Debris mitigation which pollutes and even damages the optical elements is a major challenge for all high-peak-power lasers system. In order to solve the problem, we employed some preliminary research. In this work, first, the film optical properties of fluorinated ethylene propylene (FEP), perfluoroalkoxy copolymer (PFA), and ethane-tetrafluoroethylene copolymer (ETFE) were investigated with respect to their possible application as laser debris shields. The results indicate that three of the polymer films have high transmittance at 355 nm, especially in FEP film, the transmittance of which at 355 nm is near to 94%. The transmittance wavefront and the laser that induce damage of FEP film were investigated further. The result indicates that the wavefront error of FEP film (with a diameter of 90 mm) is about 0.33λ. The damage test was performed by a 355 nm neodymium:yttrium aluminum garnet (Nd:YAG) laser with a 9.3 ns pulse duration, and it was found that the highest nondamage fluence for FEP film is 10.35 J/cm2. Through a demonstration experiment, it was testified that the FEP film can prevent large amount of metal fractions and the FEP film can be used as the debris shields indeed.

Highlights

In inertial confinement fusion (ICF) experiments, when the target is bombarded by laser, amount of target debris will be generated
We found that the laser induced damage of the fluoride polymer film can be divided into three processes (Figure 4)
Second process: when the laser energy density increased to certain range, the structure of polymer film begins to change and the glow spots turn up, but no obvious holes can be observed

Summary

Introduction

In inertial confinement fusion (ICF) experiments, when the target is bombarded by laser, amount of target debris will be generated. The laser target debris is consisting of a small amount of metal vapor, droplets of liquid metal, and massive solid projectiles. This debris will pollute and even damage the optical elements. Even the researchers of Sandia have done excellent work on the polymer film debris shield, but they only care about the Z-Petawatt FOA with the working wavelength of 1054 nm. The polymer film can be used at 1054 nm, but it is inapplicable to National Ignition Facility (NIF) for the working wavelength of which tripled laser is about 355 nm and the three kinds of polymer film including nitrocellulose, Mylar, and polyimide all have obvious absorption at 355 nm.

Experimental

Result and Discussion

Conclusions