MESURE OPTIQUE DE CONSTANTES PIÉZOÉLECTRIQUES À L'AIDE D'UNE SONDE INTERFÉROMÉTRIQUE HÉTÉRODYNE

Plusieurs constantes piézoélectriques de cristaux (SiO2, LiNbO3) et de polymères (PVDF) ont été déterminées par mesure, avec un interféromètre hétérodyne, de la déformation de l'échantillon. Le déplacement minimum détectable avec cet instrument est de 10-3 Å, la précision des mesures est de 5%. L'influence de la liaison avec le support sur le déplacement de la surface libre d'une plaquette a été établie et vérifiée expérimentalement. La valeur généralement admise du module d11 du quartz (2,31 x 10-12 m/V) a été confirmée. Pour le niobate de lithium, dont la valeur de d33 est controversée, nous avons trouvé d33= 9,5 x 10-12 m/V. Dans le cas du PVDF, la méthode conduit à une constante d33 (13,6 x 10-12 m/V) plus de deux fois plus faible que celle indiquée par le fabricant.Piezoelectric constants of crystals (SiO2, LiNbO3) and polymers (PVDF) have been determined using an optical heterodyne interferometer to measure the strain. With this set-up, the minimum detectable displacement is 10-3 Å and the accuracy is 5%. The effect of the bonding to the support has been analysed and experimentally checked. The well established value of modulus d11 of quartz (2.31 x 10-12 m/V) has been confirmed. For LiNbO3 the contorversial value of d33 was determined as 9.5 x 10-12 m/V. For PVDF, the method leads to a constant d33 (13.6 x 10-12 m/V) more than two times smaller than the figure given by the manufacturer

Development of large aperture elements for active and adaptive optics

Large-aperture elements for laser active and adaptive optics are investigated in collaboration within IOP AcSci CR, FEng CTU and 5M. A bimorph deformable mirror for high-power lasers based on a lightweight structure with a composite core is currently in development. In order to realize a sufficiently large working aperture we are using new technologies for production of core, bimorph actuator and DM reflector. Detailed simulation of components and structure is validated by measurement and testing. A research of DM actuation and response of a complicated mirror structure needed for an accurate control of a deformation is performed. Testing of samples and subscale measurements are currently performed, measurement of a complete structure is in preparation

Development of large aperture elements for active and adaptive optics

Large-aperture elements for laser active and adaptive optics are investigated in collaboration within IOP AcSci CR, FEng CTU and 5M. A bimorph deformable mirror for high-power lasers based on a lightweight structure with a composite core is currently in development. In order to realize a sufficiently large working aperture we are using new technologies for production of core, bimorph actuator and DM reflector. Detailed simulation of components and structure is validated by measurement and testing. A research of DM actuation and response of a complicated mirror structure needed for an accurate control of a deformation is performed. Testing of samples and subscale measurements are currently performed, measurement of a complete structure is in preparation

Surface modification of copper using high intensity, 10(15)W/cm(2), femtosecond laser in vacuum

A study of copper target surface modification with high intensity (10(15)W/cm(2), fluence of similar to 300 J/cm(2)) Ti:sapphire laser, operating at 800 nm wavelength and pulse duration of 60 fs is presented. The Cu surface variations were studied in vacuum ambience. The copper target specific surface changes and phenomena observed are: (i) creation of craters (with extra-low diameters); (ii) formation of periodic surface structures especially expressed at the reduced intensity; (iii) presence of the clean surface in the irradiated zone (mainly absence of the oxide(s)), and (iv) occurrence of plasma in front the surface, emitting predominantly X-ray radiation (soft and hard). It can be concluded from this study that the reported laser intensities can effectively be applied for copper surface modification. The appearance of plasma in front of the target, irradiating in the X-ray/UV region, offers additional effect of surface purification facilitating contaminant-free conditions which is highly important for specific applications, e.g. in microelectronics. Generally, femtosecond laser surface modification of copper is non-contact and very rapid compared to traditional modification methods. (C) 2012 Elsevier B.V. All rights reserved

Titanium surface modification using femtosecond laser with 10(13)-10(15) W/cm(2) intensity in vacuum

The response of titanium surface irradiated with high intensity (10(13) - 10(15) W/cm(2)) Ti:sapphire laser was studied in vacuum. Most of the reported investigations were conducted with nano- to femtosecond lasers in gas atmospheres while the studies of titanium surface interacting with femtosecond laser in vacuum are scarce. The laser employed in our experiment was operating at 800 nm wavelength and pulse duration of 60 fs in single pulse regime. The observed surface changes and phenomena are (1) creation of craters, (2) formation of periodic surface structures at the reduced intensity, and (3) occurrence of plasma in front the target. Since microstructuring of titanium is very interesting in many areas (industry, medicine), it can be concluded from this study that the reported laser intensities can effectively be applied for micromachining of the titanium surface (increasing the roughness, formation of parallel periodic surface structures etc.)

Development of large aperture elements for active and adaptive optics

Large-aperture elements for laser active and adaptive optics are investigated in collaboration within IOP AcSci CR, FEng CTU and 5M. A bimorph deformable mirror for high-power lasers based on a lightweight structure with a composite core is currently in development. In order to realize a sufficiently large working aperture we are using new technologies for production of core, bimorph actuator and DM reflector. Detailed simulation of components and structure is validated by measurement and testing. A research of DM actuation and response of a complicated mirror structure needed for an accurate control of a deformation is performed. Testing of samples and subscale measurements are currently performed, measurement of a complete structure is in preparation