Since the first seeding of an OFI soft x-ray laser in 2004, we progressed towards the full characterization of the output
beam. The final is to be able to deliver to users well-known beam. Temporal as well as spatial parameters have been
measured for different conditions of amplification. We observed a strong enhancement of the spatial coherence due to
the amplification process with a far-field pattern exhibiting an airy-like shape. The gain zone having strong discontinuity
behaves like a hard pinhole. Spatial filtering has been also observed on the wave front (δ/5 root-mean-square, rms,
before seeding and δ/20 rms after amplification). Temporal coherence has been studied thanks to the use of a Fourier-
Transform spectrometer. Spectral widths, δδ/δ, around 10-5 have been measured for different plasma lengths or gas pressures. Departure from Gaussian shape has been clearly observed on the spectral line for some cases.
We present a full optimization of the high harmonics wave-front thanks to the use of a soft x-ray Hartmann sensor. The
sensor was calibrated using high harmonics source with a λ/50 accuracy. We observed relatively good high harmonics
wave-front, two times the diffraction-limit, with astigmatism as the dominant aberration for any interaction parameters.
By slightly clipping the unfocused beam, it is possible to produce a diffraction-limited beam containing about 90% of the
incident energy. The influence of high harmonic generation parameters was also studied in particularly the influence of
the infra-red wave-front. In particular we studied the correlation between the infrared wave-front use to create high
harmonics and the high harmonic wave-front. We also report wave-front measurements of a high order harmonic beam
into an x-ray laser plasma amplifier at 32.8 nm.
Among X-ray and extreme ultraviolet light sources able to produce shorter and shorter, coherent and intense pulses, High
order harmonics generated in rare gases are currently the unique way to generate attosecond pulses. However, the
manipulation and transport of attosecond pulses require the development of dedicated optics for reaching specific
characteristics in terms of amplitude but also in terms of spectral phase control. We present here a multilayer design for
chirp compensation of attosecond pulses. We also present an application of these multilayers mirrors for attosecond train
pulse holography experiment with high harmonics. This experience took benefit of both temporal and spatial phase
properties of high harmonics. A resolution of 750 nm has been achieved by using a 350 as train pulse for the reference
wave constituted of four consecutive harmonics (λ=28 nm to λ=41 nm). This new method will allow making ultra fast
movies with attosecond resolution of transient phenomena with quasi-3D resolution.
In the race towards attosecond (as) pulses for which high order harmonics generated in rare gases are the best candidates, both the Harmonic spectral range and spectral phase have to be controlled. We present in this proceeding four mirrors numerically optimized and designed to compensate for the intrinsic Harmonic chirp recently discovered and which is responsible for a temporal broadening of the pulses. They are capable of compressing the duration down to 100 as. We present the fabrication of those aperiodic multilayers and show the measurement of reflectivity, which prooves that those multilayers are in agreement with the specifications and so let us think that they will be able to compress attosecond high harmonics trains.
The recent development of high numerical aperture (NA) EUV optics such as the 0.3-NA Micro Exposure Tool (MET) optic has given rise to a new class of ultra-high resolution microexposure stations. Once such printing station has been developed and implemented at Lawrence Berkeley National Laboratory’s Advanced Light Source. This flexible printing station utilizes a programmable coherence illuminator providing real-time pupil-fill control for advanced EUV resist and mask development.
The Berkeley exposure system programmable illuminator enables several unique capabilities. Using dipole illumination out to sigma=1, the Berkeley tool supports equal-line-space printing down to 12 nm, well beyond the capabilities of similar tools. Using small-sigma illumination combined with the central obscuration of the MET optic enables the system to print feature sizes that are twice as small as those coded on the mask. In this configuration, the effective 10x-demagnification for equal lines and spaces reduces the mask fabrication burden for ultra-high-resolution printing. The illuminator facilitates coherence studies such as the impact of coherence on line-edge roughness (LER) and flare. Finally the illuminator enables novel print-based aberration monitoring techniques as described elsewhere in these proceedings.
Here we describe the capabilities of the new MET printing station and present system characterization results. Moreover, we present the latest printing results obtained in experimental resists. Limited by the availability of high-resolution photoresists, equal line-space printing down to 25 nm has been demonstrated as well as isolated line printing down to 29 nm with an LER of approaching 3 nm.
Metrology of XUV beams and more specifically X-ray laser (XRL) beam is of crucial importance for development of applications. We have then developed several new optical systems enabling to measure the x-ray laser optical properties. By use of a Michelson interferometer working as a Fourier-Transform spectrometer, the line shapes of different x-ray lasers have been measured with an unprecedented accuracy (δλ/λ~10-6). Achievement of the first XUV wavefront sensor has enable to measure the beam quality of laser-pumped as well as discharge pumped x-ray lasers. Capillary discharge XRL has demonstrated a very good wavefront allowing to achieve intensity as high 3*1014 Wcm-2 by focusing with a f = 5 cm mirror. The measured sensor accuracy is as good as λ/120 at 13 nm. Commercial developments are under way.