D. Murra

Soft x-ray submicron imaging detector based on point defects in LiF

The use of lithium fluoride (LiF) crystals and films as imaging detectors for EUV and soft-x-ray radiation is discussed. The EUV or soft-x-ray radiation can generate stable color centers, emitting in the visible spectral range an intense fluorescence from the exposed areas. The high dynamic response of the material to the received dose and the atomic scale of the color centers make this detector extremely interesting for imaging at a spatial resolution which can be much smaller than the light wavelength. Experimental results of contact microscopy imaging of test meshes demonstrate a resolution of the order of 400nm. This high spatial resolution has been obtained in a wide field of view, up to several mm2. Images obtained on different biological samples, as well as an investigation of a soft x-ray laser beam are presented. The behavior of the generated color centers density as a function of the deposited x-ray dose and the advantages of this new diagnostic technique for both coherent and noncoherent EUV so...

Spontaneous and stimulated emission in the thresholdless microlaser

High gain and virtual zero threshold have been recognized to be distinctive properties of the microlaser since its original proposal and realization by our laboratory in 1988. These properties are investigated both theoretically and experimentally. They are found to be determined by the synergy of several quantum-statistical processes that take place in the condition of extreme field confinement provided by the peculiar Casimir-type topology of the optical microcavity. The determination of the microcavity mode structure leads to a detailed study of the process of spontaneous emission (SpE), its merging with stimulated emission, and the consequent anomalous onset of the collective atomic behavior at low excitation levels. A microlaser excitation threshold of ~50 pJ has been determined experimentally with a molecular Oxazine microlaser excited by a femtosecond source. The relevance in atomic dynamics of the processes of SpE inhibition—enhancement, mode competition, fluorescence loss, interatomic transverse Bose correlations, and periodic excitation—is investigated both theoretically and experimentally. A discussion of the overall process in terms of a second-order phase transition in a nonequilibrium statistical problem is given. The extension of the microlaser dynamics to other quantum systems, such as the microscopic parametric oscillator, and to Raman and Compton scattering is considered.

Point defects in lithium fluoride by EUV and soft X-rays exposure for X-ray microscopy and optical applications

The extreme ultraviolet radiation emitted by a laser-plasma source or by a capillary discharge laser is applied to the generation of luminescent patterns in lithium fluoride. This novel technique is able to produce colored patterns with high spatial resolution on large (more than 10 cm/sup 2/) areas in a short exposure time compared with other irradiation methods like the electron beam writing. The potentials of this technique for applications in photonics are commented. This work reviews the activity performed during the past four years at the ENEA Frascati Center and at LAquila University, Italy. Preliminary images of microradiography or X-ray contact microscopy using lithium fluoride as an imaging detector are presented. The advantages of this new detector compared with photographic films or with photoresists are discussed.

Picosecond pulse generation in the thresholdless optical microlaser

Picosecond optical pulses have been generated in different kinds of thresholdless dye microlaser operating in high‐Q plane microcavities at high pumping rate. The temporal behavior of the system is studied by means of a simple rate equation analysis. It is shown that the buildup time of the output pulse is independent of the cavity finesse. The experiment has been performed by means of a temporally resolved up‐conversion technique. A buildup time of the pulse of 3 ps, together with a rise time of 1.5 ps have been measured. These results correspond to a predictable response frequency of 300 GHz.

Beam homogenization: theory, modeling, and application to an excimer laser beam

An innovative approach is presented for modelling laser beam homogenization by means of the integration method. The numerical results are compared with experimental data, and the influence of the measurement technique is discussed.

Invisible marking system by extreme ultraviolet radiation: The new frontier for anti-counterfeiting tags

We present a marking technology which uses extreme ultraviolet radiation to write invisible patterns on tags based on alkali fluoride thin films. The shape of the pattern is pre-determined by a mask (in the case of contact lithography) or by a suitable mirror (projection lithography). Tags marked using this method offer a much better protection against fakes than currently available anti-counterfeiting techniques. The complexity and cost of this technology can be tailored to the value of the good to be protected, leaving, on the other hand, the specific reading technique straightforward. So far, we have exploited our invisible marking to tag artworks, identity cards, electrical components, and containers of radioactive wastes. Advantages and limits of this technology are discussed in comparison with the anti-counterfeiting systems available in the market.

Flat-top shaped laser beams: reliability of standard parameters

We present experimental results of reshaping and making uniform the spatial energy distrubution of raw beams respectively emitted by a low-coherence excimer laser and by a highly coherent diode pumped Nd-YAG laser. We used an optical system which is able to homegenize bad beams having strong local intensity spikes, and to modulate almost continously the spot size of the homogenized beam along one or both axes in a fixed target plane. We have evaluated the results using the standard parameters described in the document of the International Organization for Standardization ISO 13694. We found that the reliability of the results is dependent both on teh experimental setup and on the definition of edge steepness and plateau uniformity of the quoted ISO document. Here we propose an amendment to the definition of these standard parameters that could improve their reliability.

A novel light beam homogeniser

We introduce a new optical system that is able to simultaneously make homogeneous the spatial energy distribution and vary the spot size of any light beam, including beams having strong local intensity fluctuations, without replacement of lenses and without changing the total length of the optical system. This homogeniser technology includes a software to design the optimum optical system to achieve the wished output beam performance, as well as to know how the beam shape changes when changing the position of each optical element. In this paper, we present the design software and the experimental results achieved with our technology applied to a large volume excimer laser.

Electronic solar compass for high precision orientation on any planet

A compact, fully automatic electronic solar compass has been developed at the ENEA Frascati Laboratories. The compass is inspired to ``camera obscura sundials like those inside churches. Sun ephemerides are calculated using an approximate but effective analytical solution of Keplers laws, where the Earth (or other planets) orbit main parameters are introduced. The instrument is light, cheap and it has an accuracy better than 1 arcmin. Some examples of application of the device as well as the possibility to use it on Mars are presented.

Characterisation and Mitigation of Ions and Particulate Emitted by Sources for Extreme Ultraviolet Lithography

Laser produced plasmas are widely used as extreme ultraviolet (EUV) and soft X-ray radiation sources in many different fields. Lithography is one of the most challenging applications of the EUV spectral region (5-50u2009nm). The worldwide importance of EUV lithography (EUVL) is basically due to its potential to extend optical projection lithography to higher resolution in integrated circuit manufacturing, thanks to the shorter wavelength and to the availability of high reflectivity normal incidence mirrors. In addition to the huge technological and financial effort carried out by international consortia to raise EUVL at the industrial level, less expensive laboratory-scale facilities have been built up to perform component testing and metrology. Within a national project on nanotechnologies at the ENEA Research Centre in Frascati a micro exposure tool (MET) has been designed and developed for projection lithography, exploiting the facility EGERIA (extreme ultraviolet radiation generation for experimental research and industrial applications). EGERIA is a EUV/soft X-ray laser produced plasma source equipped with a high efficiency debris mitigation system (DMS).