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Exchanges around Femtosecond Laser Applications in Glasses

Final Report Summary - E-FLAG (Exchanges around Femtosecond Laser Applications in Glasses)

1. Publishable summary

Towards on demand low cost optical components in glasses

Mastering femtosecond laser interaction in glasses
The project is to master femtosecond laser – glassy materials interaction in the view to achieve applications from a newly appearing technology i.e. 3D direct shaping of optical properties in transparent materials by means of femtosecond laser. The interaction of this kind of laser with transparent samples is such that refractive index change can be as large as +/-10-2 (and sometimes more) in most transparent materials (amorphous or crystals), the linear birefringence can be as large as 10-2 (a unique feature, mainly limited to silica glasses), the attenuation can be lower than 1dB/cm (to be improved) but the writing speed can be as large as 1 cm/s! And, on top of that, this is made locally in 3D due to high non-linear interaction resulting in a lateral resolution around 1-5microns. These features lead to think to tremendous progress in photonics with such a flexible tool. Generally speaking, we think that we will be able to show the possibility for achieving adapted optical small components to transform any beam characterized by a set of parameters in its section like where corresponds to a point in the beam cross section, is the wave vector at this point, is the polarization vector and I is the intensity, into any other one having different set of parameters.

3D optical properties shaping in transparent materials
Scientific and technical locks are clearly identified. 3D integrated optical devices are becoming in the realization of future telecommunication system, micro-optics and for optical memories, and will be a technological breakthrough. Most of the classical methods of elaboration are combination of lithography and dry etching. However, these methods are rather complicated and costly in 3D as they require a numbers of steps. Most photonic components have larger sizes hardly compatible with the degree of integration of their counterparts in microelectronics or in the prospect of applications in the field of biophotonics. Femtosecond direct writing opens an unprecedented gateway to overcome these locks. Nowadays, it is already possible to achieve a few devices, including Bragg gratings and 3D waveguides, but the goals of our project, based on the asymmetry induced in silica-based glasses, go further and are planning to produce new structures and therefore the new original devices in 3D such as volume Bragg gratings, Fresnel lenses with radial birefringence, axicons, beam shaper, non-uniform retardation plates, and more generally birefringent optical structures. They have enormous potential in the field of micro-optics, optical communications, high power lasers, data storage systems, the image creations, and so on…

Main results: The damage created in silica are such that a high birefringence can be observed. It is formed by a network of spaced nanoplans of about 300 nm and 20 nm thick. We have determined the nature of these nanoplans which are formed of porous matter due to decomposition of the silica. Another striking result is the production of monocrystalline wire of LiNbO3 in a Li2O-Nb2O5-SiO2 glass matrix by femtosecond irradiation. This wire is formed by moving the laser in the glass volume and without thermal assistance. These results pave the way for applications in the field of optics for information processing as the realization of optical switches or routers. The results obtained in the framework of the ANR FLAG also allowed us to obtain a share of new contracts (RTRA Triangle de la Physique and a European contract entitled e-FLAG). In the continuity of the FLAG project we have entered into pre- maturation in the context of the "innovation - entrepreneurship - prematurity" call coordinated by the FCS of the Paris-Saclay IDEX 2014. This project will produce prototypes of birefringent optical components by femtosecond laser. Also new opportunities such as long-term storage of data and the development of low cost optical components for infrared imaging could be considered.

In terms of scientific production, e-FLAG project resulted in 25 publications in international journals, 5 invited lectures, 40 acts of international conferences with peer review, 2 book chapters written on invitation and one patent.

FLAG project is an international research project coordinated by ICMMO (UMR8182 CNRS-University Paris Sud). With the ANR-blanc 2009-2014 (FLAG), we formalized the fundamental core at the root of this project. With the support of the Essonne French Department (ASTRE procedure) and Idex Paris Saclay (Pré-maturation) we have completed our project by imparting it a direction towards innovations (inclusion of 2 companies in the network). Finally, the FP7-IRSES 2010-2014 program (e-FLAG) has given an international dimension to the project promoting exchanges with the world leaders: ORC-Southampton (UK), Jena (Germany) and Macquarie University (Australia) and the University of Sydney (Australia).