We present a spectral phase-only shaping technique allowing to generate arbitrary temporal shapes and demonstrate its use for ultrafast ytterbium-based laser sources. This technique is based on the introduction of a nonlinear chirp that is determined solely by the input spectral intensity and the target temporal intensity. We describe its working principle and experimentally demonstrate the generation of triangle-shaped pulses at the output of a laser source, which delivers 150 μ J, sub-200 fs pulses at 150 kHz. These pulses are then passed through a nonlinear multipass cell to observe wavelength shifting via self-phase modulation. A spectral tunabibility of 14 nm is achieved around the input central wavelength of 1034 nm.
This study investigates the effects of laser-induced contamination (LIC) on ultraviolet (UV) laser beam propagation in the sub-picosecond regime. Using a sub-picosecond UV laser source operating at 343 nm with 30 W of mean power at 800 kHz, we examine the influence of prolonged UV exposure on the degradation of beam quality. The experiments are carried out on calcium fluoride (CaF 2 ) substrates, where contamination deposits are induced by high-power UV radiation under ambient air. We characterize the chemical composition, physical structure, and optical properties of the deposit. A numerical model is developed to simulate the influence of a phase defect corresponding to the LIC deposit and to estimate its impact on beam quality by calculating M 2 and beam intensity distribution. This study highlights the challenges posed by contamination when using high-power ultraviolet laser sources, particularly in industrial, and space applications.
La léiomyomatose péritonéale disséminée est une maladie bénigne, méritant d’être connue des radiologues afin de la différencier d’une maladie maligne qui engendrerait une prise en charge plus invasive. Nous rapportons le cas d’une patiente de 46 ans, asymptomatique, adressée pour bilan de masses abdominopelviennes découvertes fortuitement. Le bilan radiologique (IRM et scanner) identifiait des masses multiples, bien limitées, avec des caractéristiques de signal évocatrices de bénignité : hypersignal T2, hyposignal T1, absence de contingent hémorragique ou de restriction de la diffusion, rehaussement identique à celui du myomètre. Le diagnostic anatomopathologique obtenu à partir d’une biopsie réalisée par voie percutanée a permis d’identifier une prolifération cellulaire musculaire lisse évocatrice d’une léiomyomatose péritonéale disséminée, et de réfuter le diagnostic de sarcome ou autre tumeur maligne à tropisme péritonéal. La patiente reçoit depuis un traitement médical qui permet le contrôle de la maladie.Disseminated peritoneal leiomyomatosis is a benign disease, worth being known to radiologists in order to differentiate it from a malignant disease which would lead to a more invasive treatment. We report the case of a 46-year-old asymptomatic patient referred for assessment of abdominopelvic masses discovered incidentally. The radiological assessment (MRI and CT-scanner) identified multiple, well-defined masses, with signal characteristics suggestive of benignity: T2 hypersignal, T1 hyposignal, absence of haemorrhagic contingent or diffusion restriction, enhancement identical to that of the myometrium. The pathological diagnosis obtained from a biopsy performed percutaneously identified smooth muscle cell proliferation suggestive of disseminated peritoneal leiomyomatosis and refuted the diagnosis of sarcoma or other malignant tumours with peritoneal tropism. The patient has since received medical treatment that allows the control of the disease.
