2012
DOI: 10.1063/1.3684242
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Optimizing conversion efficiency and reducing ion energy in a laser-produced Gd plasma

Abstract: We have demonstrated an efficient extreme ultraviolet (EUV) source at 6.7 nm by irradiating Gd targets with 0.8 and 1.06 μm laser pulses of 140 fs to 10 ns duration. Maximum conversion efficiency of 0.4% was observed within a 0.6% bandwidth. A Faraday cup observed ion yield and time of flight signals for ions from plasmas generated by each laser. Ion kinetic energy was lower for shorter pulse durations, which yielded higher electron temperatures required for efficient EUV emission, due to higher laser intensit… Show more

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Cited by 48 publications
(26 citation statements)
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“…In order to increase the energy CE from the incident laser energy to the interested wavelength emission energy with the defined bandwidth, it is important to suppress not only the reabsorption by assurance of the plasma is optically thin but also plasma hydrodynamic expansion loss, while maintaining a plasma electron temperature of T e = 100−120 eV [6,17]. Lateral expansion of the plasma causes kinetic energy losses, which reduce the energy available for radiation and is particularly important for small focal spot diameters [6].…”
Section: Characteristics Of the Gd Plasmas For Beuv Source Applicationsmentioning
confidence: 99%
See 1 more Smart Citation
“…In order to increase the energy CE from the incident laser energy to the interested wavelength emission energy with the defined bandwidth, it is important to suppress not only the reabsorption by assurance of the plasma is optically thin but also plasma hydrodynamic expansion loss, while maintaining a plasma electron temperature of T e = 100−120 eV [6,17]. Lateral expansion of the plasma causes kinetic energy losses, which reduce the energy available for radiation and is particularly important for small focal spot diameters [6].…”
Section: Characteristics Of the Gd Plasmas For Beuv Source Applicationsmentioning
confidence: 99%
“…Optically, thin plasmas provide more efficient sources. Therefore, systematic LPP UTA source studies with up-to-date intense picosecond pulse lasers [17] or middle infrared laser, such as the CO 2 laser [14], are needed to determine available light source wavelengths for future applications.…”
Section: Introductionmentioning
confidence: 99%
“…Applications, such as EUV generation, would benefit from picosecond lasers of high beam quality and average power from 100 W to more than 1 kW at a 1-100-kHz repetition rate [26]. Another application interesting for the industrial market that would profit from lasers of these parameters is processing of carbon fiber-reinforced plastics [27].…”
Section: Kilowatt-class Picosecond Thin-disk Lasersmentioning
confidence: 99%
“…Such choice of fuel and driver was shown to be the most practical option for a number of reasons; highest possible conversion efficiency (CE) in a range of 3-6% (at 2−% bandwidth at 13.5 nm) among the low−environmental−haz− ard candidate materials [20,21]; technical feasibility of EUV collection optics with substantial reflectivities around the 13.5 nm [22]; sufficiently small size of the EUV emitting plasma thanks to the focusability of a driv− ing laser beam; low debris production when combined with a 10.6−micron wavelength provided by a CO 2 laser driver [23][24]; and finally the viability of required multi− −kW laser power output of mentioned CO 2 lasers [25][26] allowing for a power scalability. The LPP source principle is also a promising route to a shorter wavelength range of 6.Xnm using Gd as a fuel and is presently an area of active research efforts [27,28].…”
Section: Introductionmentioning
confidence: 99%