Status of optical coatings for the national ignition facility

NIF optical materials and fabrication technologies: an overview

“…• New laser glass compositions [21] , better glass property characterization [22][23][24][25][26][27][28][29] , advanced glass processing technology [30][31][32][33][34] and continuous optical glass melting methods [35] • Novel glass asphere and flat fabrication technologies using state-of-the-art deterministic figuring methods [5,36,37] • 10× faster KDP/DKDP crystal growth methods [38][39][40] with a better scientific understanding of the growth process [41][42][43][44][45][46] and novel high-capacity precision crystal finishing machines. • Laser damage resistant dielectric mirrors and polarizers manufactured to stringent multi-wavelength reflection and transmission specifications [7,10,11,[47][48][49][50][51][52][53][54][55] • Environmentally stable, laser damage-resistant, sol-gel anti-reflection coatings [14,[56][57][58][59] • Novel diffractive grating and continuous phase plate design and fabrication metho...…”

“…These mirrors are used to transform the 2-dimensional, planar geometry of the 192 output beams from the main laser into the 3dimensional spherical configuration required for target illumination. These mirrors also use HfO 2 /SiO 2 multi-layer stacks but the designs vary somewhat to account for the different use angles [10,11] .…”

Optical coatings for large facilities

“…As an example, the National Ignition Facility (NIF) -which is equipped with 192 laser beams and has been in operation since March 2009 -includes several thousands of large optics (1 m scale): mirrors, polarizers and transport mirrors, the size of which are compatible with the 40 × 40 cm2 beams and also smaller optics. 9 Ambitious laser projects have been implemented around the world and we give hereafter a quick overview of these projects for which large optics are required: Facility in Oxfordshire, United Kingdom is constituted with 8 beams of 2.5 kJ each (~2 ns) pulse infrared neodymium glass laser. Vulcan is also capable of operating in frequency doubled mode where it can deliver about 1 kJ to a target at 532 nm in 2 ns pulses.…”

<title>The National Ignition Facility: the world's largest optics and laser system</title>

“…• New laser glass compositions [12] and advanced optical glass melting methods [17,18] • Novel glass asphere and flat fabrication technologies using state-of-the-art deterministic figuring methods [15,19,20] • 10x faster KDP/DKDP crystal growth methods and novel high-capacity precision crystal finishing machines [15,21] • Laser damage resistant dielectric mirrors and polarizers manufactured to stringent multi-wavelength reflection and transmission specifications [22][23][24][25] • Environmentally stable, laser damage-resistant, sol-gel anti-reflection coatings [15,26] • Novel diffractive grating and continuous phase plate design and fabrication methods.…”

“…In this section we focus on new methods developed for NIF to improve the laser damage resistance of glasses and polished glass surfaces. (Note that similar work is also on-going to improve the damage resistance of optical coatings [22][23][24][25] and non-linear crystals (KDP and DKDP) [21,32] To better understand laser-induced damage in optical glasses requires an understanding of (1) the mechanisms for light interaction with bulk glass and glass surfaces at high intensity and short pulse length (fs to ns), (2) the chemistry and physics of glass surfaces as modified by finishing ("polishing"), (3) glass fracture and fracture analysis, and (4) optical radiation-induced defect formation in glass across a broad range of energies. Some key findings related to the specific application of optical glasses on NIF are summarized in the following sections.…”