Matrix formulation of the Gaussian expansion of coherent multiple beams in arbitrary dimensions.

Modeling the propagation of beams along laser beamlines is very challenging due to the multidimensional and multiscale configuration of the problem. Spatio-temporal couplings are particularly difficult to address with conventional numerical methods. Here we derive the Wigner function of a sum of Gaussian beams by calculating the multidimensional Fourier transform of the intercorrelation function of the fields. The matrix formulation allows for a simple propagation of the Wigner function in the framework of matrix optics. The relevancy of this approach is assessed by applying this model to one-dimensional and multidimensional configurations and by studying the influence of spatio-temporal couplings when considering propagation and dispersion by a diffraction grating.

Wigner matrix formalism for phase-modulated signals.

Laser beams can carry multi-scale properties in space and time that ultimately impact their quality. The study of their evolution along complex optical sequences is of crucial interest, especially in high-intensity laser chains. For such analysis, results obtained with standard numerical methods strongly depend on the sampling. In this paper, we develop an analytic model for a sinusoidal phase modulation inside a sequence of first-order optics elements based on the Wigner matrix formalism. A Bessel decomposition of the Wigner function gives pseudo-Wigner functions that obey the general ABCD matrix law transformation without approximations and sampling considerations. Applied to a Gaussian beam, explicit expressions are obtained for the projections of the Wigner function in the sub-spaces and give a powerful tool for analyzing the laser beam properties. The formalism is established in the spatial and temporal domains and can be used to evaluate the impact of the phase noise on the beam properties and is not limited to small modulation depths. For the sake of illustration, the model is applied to the Talbot effect with the analysis of the propagation in the spatial and phase-space domains. A comparison with full numerical calculations evidences the high accuracy of the analytic model that retrieves all the features of the diffracted beam.

Modeling of the petawatt PETAL laser chain using Miró code.

Miró software has been used intensively to simulate the Laser Megajoule (LMJ) with the treatment of amplification, frequency conversion, and both temporal/spatial smoothing of the beam for nanosecond pulses. We show that the software is able to model most relevant aspects of the petawatt PETAL laser chain in the subpicosecond regime, from the front-end to the focal spot with a broadband treatment of the amplification and compression stages, including chromatism compensation in the laser chain, segmentation and recombination of the beams on the second compression stage, and focusing by an off-axis parabola.

1.15 PW-850 J compressed beam demonstration using the PETAL facility.

The Petawatt Aquitaine Laser (PETAL) facility was designed and constructed by the French Commissariat à l'énergie atomique et aux énergies alternatives (CEA) as an additional PW beamline to the Laser MegaJoule (LMJ) facility. PETAL energy is limited to 1 kJ at the beginning due to the damage threshold of the final optics. In this paper, we present the commissioning of the PW PETAL beamline. The first kJ shots in the amplifier section with a large spectrum front end, the alignment of the synthetic aperture compression stage and the initial demonstration of the 1.15 PW @ 850 J operations in the compression stage are detailed. Issues encountered relating to damage to optics are also addressed.

Experimental demonstration of a synthetic aperture compression scheme for multi-Petawatt high-energy lasers.

We present the experimental demonstration of a subaperture compression scheme achieved in the PETAL (PETawatt Aquitaine Laser) facility. We evidence that by dividing the beam into small subapertures fitting the available grating size, the sub-beam can be individually compressed below 1 ps, synchronized below 50 fs and then coherently added thanks to a segmented mirror.

[Prognostic value of cytofluorometry in bladder tumors]. / Intérêt pronostique de la cytofluorométrie dans les tumeurs vésicales.

Bladder lavage fluid was examined using flow-cytometry (FCM) in 112 patients with transitional cell carcinoma seen over 30 months. FCM investigates the entire mucosa, furnishes indications as to the possible existence of dysplasia or carcinoma in situ, and thus provides for a more accurate evaluation of the evolutive potential of the "bladder disease". FCM consists in the automated assay of the DNA content of epithelial cells. The test is positive when "tumorous" diploid or aneuploid cells are demonstrated. The diagnostic sensitivity of FCM is comparable to that of cytologic diagnosis on bladder lavage specimens, but FCM has the additional advantage of detecting those patients at high risk for disease progression by measurement of the DNA index. Grade 1 and 2 tumors are diploid in 70% of patients, against only 14% for grade 3 tumors and carcinomas in situ. Follow up of 25 grade 2 patients and determination of the recurrence index clearly establishes the prognostic significance of the degree of tumorous ploidy. Furthermore, the effectiveness of endovesical chemotherapy can be monitored using FCM measurement of the aneuploidy index.

Comparative flow DNA analysis of different cell suspensions in breast carcinoma.

This study compared three methods of dissociation of breast lesions for DNA flow cytometry. Eleven benign lesions and 66 cancers were dissociated using mechanical, Ficoll, or enzymatic methods. DNA flow analysis showed that the DNA index did not vary from one method of dissociation to another. All benign lesions were diploid and 67% of all cancers were aneuploid. Enzymatic dissociation gave a lower percentage of aneuploid cells with a diminution of the proportion of cells in the G2 + M phase (13.2% enzymatic against 17.6% Fi-coll); on the other hand, it provided cell populations of greater viability than the other methods (32.6% enzymatic, 17.2% Fi-coll; P less than 0.01). The mechanical and Ficoll suspensions did not differ significantly when they were analyzed on the basis of their DNA content and their cellular viability. When compared with mechanical preparation, Ficoll suspension showed a lower recovery of tumor cells, but this inconvenience was compensated for by a more homogeneous aspect where the contribution of aggregates and debris was clearly lessened. Therefore, this study led us to choose Ficoll suspension for subsequent flow analysis of breast tumors.