Binary-phase zone plate arrays for the generation of uniform focal profiles

Abstract

The generation of uniform focal intensity profiles is important for a number of applications, including laser-plasma interaction experiments. We report on a focusing system that uses a novel binary-phase optic capable of producing efficient two-dimensional uniform top-hat intensity optical and x-ray profiles.

Measuring the Equation of State with Lasers

“…For our direct-drive experiments we used phase zone plates (PZPs) to smooth the beam [10]. PZPs comprise an array of Fresnel lens, where each lens imparts a random dephasing of o or π to break down the spatial coherence of the laser beam, thereby giving a smoothing effect similar to that produced by the more com mon technique of optical smoothing (e.g., that based on random phase plates).…”

“…Despite the fact that equations of state of matter at high pressures are of great interest for several fields of modern phys ics, notably astrophysics and inertial con finement fusion, models for the behaviour of materials at pressures above 10 Mbar have not been validated experimentally. Moreover, the regime of applicability of the limiting case of the Thomas-FermiDirac model which is expected to describe equations of state at extremely high pres sure remains unknown.…”

Shock dynamics induced by double-spot laser irradiation of layered targets

“…Smoothing techniques (such as phased zone plates [1][2][3], random phase plates [4], kinoform phase plates [5], smoothing by spectral dispersion [6], induced spatial incoherence [7]) have dramatically improved our control on laser implosions and laser--plasma interactions. However, there still remains an issue of non-uniformity at very early times, called 'laser imprint' problem [8][9][10][11][12], which may affect compression uniformity at later times and in particular infl uence the development of the Rayleigh-Taylor instability [13].…”

<title>Large-aperture kinoform phase plates in fused silica for spatial beam smoothing on Nova and the Beamlet lasers</title>

“…Although easy to fabricate and currently in routine use in many fusion laboratories 2 , the binary RPPs do not meet the ICF requirements stated above since the far-field intensity profile is restricted to essentially an Airy function containing only 84% (an upper limit) of the energy inside the central spot. Approaches using lenslet arrays (refractive or diffractive) 3,4 have limited use since they operate in the quasi-far-field and have a short depth of focus.…”