Fluorescent chemical sensors have been widely exploited for the detection and quantification of trace explosives. Their
performances are mainly dependent on the sensitive material. Fluorescent organic materials are very efficient in terms of
sensitivity, selectivity and response time but their degradation is a major drawback. Sol-gel materials offer a much longer
life span, especially in the case of inorganic sensitive coatings. The elaboration of sol-gel sensitive films is detailed in
this paper. Two examples of sol-gel fluorescent sensitive materials are presented: a hybrid organic-inorganic film and an
Subsurface cracks in fused silica optics are known to be damage initiators under laser irradiation. Each step of optic
production, from sawing to polishing, creates its own type of cracks. An efficient optic manufacturing process requires
that each production step removes cracks from the previous step. The extent of cracks has to be measured for each
production step. We review and compare different subsurface damage (SSD) characterization techniques applied to
ground and fine ground fused silica samples.
Recent works have shown that for low contaminants level, damage density is independent of the amount of
contaminants. In these conditions, sub-surface defects (cracks), generated along the optical process, is considered as the
main source of damage. Hence, efforts have been made to improve SSD measurement in order to improve its suppression
during industrial process. We have developed a method to measure SSD depth which is detailed in this presentation. This
method is based on successive acid etching steps. The principle is to establish contamination level (ICP-AES
measurement) as a function of etched thickness of SiO<sub>2</sub>. The experimental setup has been specially designed to minimize
contaminations, reduce hydrofluoric acid quantities and to ease the etch rate determination. SSD depth is given by the
asymptotic impurities. This method has been applied to a grinded fused silica intentionally doped in barium tracer.
Results have been successfully compared to other characterization techniques such as MRF dimpling or empirical law
correlating SSD and surface roughness.
During the development of the laser megajoule (LMJ), a high power laser facility dedicated to DT fusion, CEA has made
important efforts to understand and improve laser induced damage threshold of fused silica optics at the wavelength of
351 nm. For several years, with various industrials and academics partners, we have focused on optimizing the grinding,
lapping and polishing processes to increase materials performance. In this paper, we describe our efforts in various
fields: subsurface damage characterization, lapping process simulation, diamond grinding and lapping machine
instrumentations, ... Our concern is to control and manage the material removal at each step of the process in order to
reduce the cracks region extension and thus to diminish the damage density.