Damage threshold measurements on EUV optics using focused radiation from a table-top laser produced plasma source

Abstract

We present first damage threshold investigations on EUV mirrors and substrate materials using a table-top laser produced plasma source. A Schwarzschild objective with Mo/Si multilayer coatings for the wavelength of 13.5 nm was adapted to the source, generating an EUV spot of 5 microm diameter with a maximum energy density of approximately 6.6 J/cm(2). Single-pulse damage tests were performed on grazing incidence gold mirrors, Mo/Si multilayer mirrors and mirror substrates, respectively. For gold mirrors, a film thickness dependent damage threshold is observed, which can be partially explained by a thermal interaction process. For Mo/Si multilayer mirrors two damage regimes (spot-like, crater) were identified. Fused silica exhibits very smooth ablation craters, indicating a direct photon-induced bond breaking process. Silicon shows the highest damage threshold of all investigated substrate and coating materials. The damage experiments on substrates (fused silica, silicon, CaF(2)) were compared to excimer laser ablation studies at 157 nm.

Damage mechanisms of MoN/SiN multilayer optics for next-generation pulsed XUV light sources

“…They are widely used in "front-line" experiments like XUV time resolved holography as a part of the imaging system [8], as diffraction limited XUV beam focusing optics for warm dense matter creation [9,10] and as a part of the delay line for one color pump and probe studies on XUV transmission of solids [11]. Recently, the single shot damage mechanism in one type of these optical coatings -the Mo/Si multilayerwas studied [12,13] at the FLASH (Free-electron LASer in Hamburg) facility (providing fs XUV pulses) and using an XUV plasma source at the Laser Lab Goettingen, Germany (with ns pulse duration). Melting of amorphous Si layers followed by diffusion of Mo atoms into the molten Si and subsequent molybdenum silicide formation was proved to be the leading damage mechanism in these multilayers.…”

Mo/Si multilayer-coated amplitude-division beam splitters for XUV radiation sources

“…The 13.5 nm wavelength was chosen as it is one of the most common available wavelengths at XUV sources [e.g. plasma-based lasers (Barkusky et al, 2010), high-harmonic generation (Chen et able expertise on ML coatings coming from lithography research. The coatings were deposited by electron-beam evaporation in an UHV background of $ 1 Â 10 À8 mbar, with post-deposition smoothing of the Si layers using low-energy ion treatment.…”

EUV damage threshold measurements of Mo/Si multilayer mirrors

“…The experimental setup used for the measurements was described already previously [9]. It includes a laser-based EUV source and a separated optics chamber connected to this source (cf.…”

“…However, only very few ablation [4][5][6] and damage threshold studies at a wavelength of 13.5 nm are available up to now for these optical elements [7,8]. Barkusky et al [9] investigated EUV induced single pulse damage thresholds of grazing-incidence mirrors, Mo/Si multilayer mirrors and mirror substrate materials as fused silica, silicon and CaF 2 , presenting first damage threshold data for nanosecond pulse durations.…”