Efficient collinear third-harmonic generation in a single two-dimensional nonlinear photonic crystal

We propose novel multi-phase-matched process that starts with generation of a pair of symmetric second-harmonic waves. Each of them interacts again with the fundamental wave to produce two constructively interfering third harmonic waves collinear to the fundamental input wave.Comment: Summary of presentation at the IQEC/LAT-2002 conferenc

Non-linear wavelength selection for pattern-forming systems in channels

We present the first results of 2nd harmonic generation in a two dimensional Penrose pattern in lithium niobate. These results show the flexibility and potential for novel devices resulting from the additional degree of freedom compared to one dimensional periodic poling

Un ejemplo de aportación de la didáctica de la física a la enseñanza : los ejercicios cualitativos y los razonamientos funcionales

Didactic specialists use exercises as a resource for research, whereas for teachers they are resources for teaching and evaluating. In most cases the evaluative exercises are of a quantitave type and the didactic value of the exercises of a qualitative type is not clearly shown. Starting frorn the analysis of the answers to exercises on the same subject but of different types, the author shows how important qiialitative exercises are and how they can be used as resources for teaching and evaluating

Photonic quasicrystals for general purpose nonlinear optical frequency conversion

We present a general method for the design of 2-dimensional nonlinear photonic quasicrystals that can be utilized for the simultaneous phase-matching of arbitrary optical frequency-conversion processes. The proposed scheme--based on the generalized dual-grid method that is used for constructing tiling models of quasicrystals--gives complete design flexibility, removing any constraints imposed by previous approaches. As an example we demonstrate the design of a color fan--a nonlinear photonic quasicrystal whose input is a single wave at frequency $\omega$ and whose output consists of the second, third, and fourth harmonics of $\omega$, each in a different spatial direction

Urban Arrival Infrastructures between Political and Humanitarian Support: The 'Refugee Welcome' Mo(ve)ment Revisited

Maximilian Park in Brussels was the site of a makeshift refugee camp for three months in 2015 when the institutional reception system was unable to provide shelter for newly arriving asylum seekers. Local volunteers stepped in, formed a civic initiative and organized a reception area under the banner ‘Refugees Welcome!’ The civic platform which emerged claimed and asserted (existing) rights for one specific group, asylum seekers, exclusively, and thus did not challenge the exclusive migration regime nor demand transformation. While such a humanitarian approach risks reproducing the exclusive border regime and the inequalities it engenders, political support is a disturbing rupture in the name of equality that resists normative classifications and inaugurates transformation. This article maps out the complex dialectical interrelation between political and humanitarian support and argues that political implications can only be understood through longer-term research, emphasizing processes of transformation that have resulted from these moments of disruption. Therefore, the article revisits Maximilian Park two and four years after the camp and reveals how the humanitarian approach chosen in the camp sustainably transformed the park, adding arrival infrastructures beyond the institutional, and had an impact on how refugees were dealt with and represented. Concluding, the article suggests the notion of ‘solidary humanitarianism’ that providing supplies, meeting acute existential needs and simultaneously articulating political claims that demand structural transformation: the right to shelter, basic supply, presence, and movement for all in the city