Random nonlinear materials: application to ultrashort pulse characterization

In this research line, we study the nonlinear light propagation in a particular kind of optical materials exhibiting a random-sized distribution of nonlinear domains, with an inversion of the quadratic susceptibility sign. Such crystals provide frequency conversion processes over an unusually wide angular and frequency bandwidth, without need for angular or temperature tuning as in typically used nonlinear crystals. We implement these materials in a novel single-shot auto-correlation technique based on the analysis of the transversally emitted second harmonic signal. As novelty and unlike the other well-known auto- and cross-correlation schemes, this technique can be implemented for the temporal characterization of pulses over a very wide dynamic range (30 fs–1ps) and wavelengths (800–2200 nm), using the same device and without any critical angular or temperature alignment. In a different configuration, based on the d-scan technique, we also can obtain a complete characterization of the ultrashort pulses (time duration, chirp parameter, and phase). On the other side, we analyze the spatial distribution of the nonlinear signal emitted by these crystals, which gives information about the disordered composition of the material itself. The combination between experimental studies and simulations provide a nondestructive tool for the material characterization. This line has generated a European Patent on “Optical system and method for ultrashort pulse characterization” (14-7325 EPO/PCT IB2016000087) together with the University of Salamanca and the company Sphere S.A., Portugal.

Involved Researchers: J. Trull, C. Cojocaru, R. Vilaseca, K. Staliunas.

PhD Students: B. Wang

Former group members: Vito Roppo

Collaborations: Wieslaw Krolikowski and Yan Sheng (Laser Physics Centre, Australian National University, Canberra, Australia), Íñigo Sola (University of Salamanca, Spain), Luis Roso (Spanish Center for Pulsed Lasers, Salamanca, Spain), Helder Crespo (University of Oporto, Portugal), Rosa Romero (Sphere S.A., Portugal).

Light and sound waves in crystals, structured media and metamaterials” (conceptual part).

Scientific coordinator: K. Staliunas, J. Trull.

Funding Agency: Ministerio de Economía y Competitividad.

Participants: M. Botey, C. Cojocaru, R. Herrero, J. Trull, R. Vilaseca, A. Perego, S. Kumar, W. Ahmed, B. Wang, Hossam Selim.

Project ref. No.: FIS2015-65998-C2-1-P.

Start/Ends dates: 01/01/2016 - 31/12/2018 (36 month).

Partners: UPC, Spain (global coordinator); UPV Gandia, Spain (subproject 2).

Nonlinear effects in modulated photonic structures: metal-dielectric and graphene-based nanostructures and random nonlinear media.

Scientific coordinator: C. Cojocaru

Funding Agency: RDECOM – US Army.

Participants: J. Trull, R. Vilaseca, B. Wang.

Project ref. No.: W911NF-16-1-0563.

Start/Ends dates: 09/2016 - 02/2018 (18 month).