Generación de ondas de polarización cruzada: estudio teórico, experimental y nuevas aplicaciones

La tesis doctoral que se presenta en este libro se centra en el estudio teórico y experimental del efecto no lineal conocido como generación de ondas de polarización cruzada (Cross Polarized Wave Generation, XPWG). El fenómeno no lineal que se produce en cristales cúbicos m3m consiste en la generación de un pulso de femtosegundo cuyo eje de polarización es ortogonal al del pulso incidente. Este fenómeno se utiliza habitualmente como método de mejora del contraste de pulsos de alta intensidad. En particular, la tesis doctoral muestra la construcción de un código numérico capaz de resolver la ecuación no lineal de Schrödinger (NLSE) y que se aplica a la propagación de pulsos de femtosegundo a través de materiales capaces de producir el efecto XPWG. A partir de este código de simulación se exploran nuevas aplicaciones. En particular se muestra la capacidad de construir pulsos cuya polarización varía localmente a lo largo del espacio y del tiempo. Además se realiza un estudio teórico de la capacidad del XPWG para producir pulsos aislados de attosegundo. Finalmente se presentan cálculos numéricos y medidas experimentales que muestran la posibilidad de utilizar este efecto no lineal en sistemas de caracterización de pulsos como el D-Scan

Ultraintense Femtosecond Magnetic Nanoprobes Induced by Azimuthally Polarized Laser Beams

We report a novel scheme to generate laser-induced, ultrafast, intense (Tesla scale), spatially isolated, magnetic fields. Three-dimensional particle-in-cell simulations show that a femtosecond azimuthally polarized infrared vector beam, aimed at a conducting circular aperture, produces an intense axially polarized tip-shaped femtosecond magnetic field, extending over micrometer distances and being isolated from the electric field. Our results are backed up by an analytic model, demonstrating the underlying physics and guiding for optimal parameters. In particular, we find the conditions under which the magnetic nanoprobe is substantially enhanced, reaching 4 T when driven by a 1011 W/cm2 laser field, which reflects a selective enhancement by a factor of ∼6. Our scheme offers a promising tool to control, probe, and tailor magnetic nanodomains in femtosecond time scales through pure magnetic interaction by using structured laser beams.The authors thank Luis López, Eduardo Martı́nez, and Victor J. Raposo for fruitful discussions. The authors thank the support from Ministerio de Economı́a y Competitividad (FIS2015-71933- REDT), Xunta de Galicia/ FEDER (ED431B 2017/64 and ED431E 2018/08), and Ministerio de Ciencia, Innovación y Universidades (EQC2018-0041 17-P). C.H.-G. acknowledges support from a 2017 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation. C.H.-G., E.C.J., and L.P. acknowledge support from Junta de Castilla y León (SA046U16, SA287P18) and Ministerio de Economı́a y Competitividad (FIS2016-75652-P). M.B. is funded by the FPU grant program of MECD. The authors acknowledge the OSIRIS Consortium, consisting of UCLA and IST (Lisbon, Portugal) for the use of OSIRIS, for providing access to the OSIRIS framework

Physical and Quality of Life Changes in Elderly Patients after Laparoscopic Surgery for Colorectal Cancer-A Prospective Cohort Study

Background—The incidence of colorectal cancer is increasing among elderly people, where postoperative complications are frequent. Methods—We evaluated postoperative physical and quality of life changes in elderly patients undergoing laparoscopic surgery for colorectal cancer. A prospective cohort study was performed in 31 colorectal cancer patients ≥60 years who were scheduled for laparoscopic surgery due to colorectal cancer. Outcomes were measured one month preoperative (T1), three days postoperative (T2) and one month postoperative (T3). Results—The largest early postoperative (from T1 to T2) declines were observed for isometric knee extension strength (33.1%), 30 s Chair Stand Test (27.9%) and handgrip strength (16.9%). Significant reductions in quality of life measured with the QLQ-C30 summary score and the EQ 5D index score were found between T1–T3 and T1–T2, respectively. Conclusions—A decline in isometric knee extension strength, 30 s Chair Stand Test, handgrip strength and quality of life is evident in elderly patients in the days following laparoscopic surgery for colorectal cancer. Preoperative values are recovered one month after surgery for all the outcomes, except for isometric knee extension, which should receive especial attention