Selective response of Nitinol substrate using Bragg reflector structures

The aim of this work is to elaborate low stress dichroic filters intended for the control of shape memory alloys deformation (SMA). This deformation has been performed by the use of laser sources (658 nm and 785 nm, for this preliminary study) in order to heat different samples of SMA. The two dichroic filters have been elaborated using a Bragg reflector structure with the choice of the materials discussed considering the superelastic behaviour of the substrate. The presented structure was made up of the stack of two materials, the amorphous hydrogenated silicon (a-Si:H) and the amorphous polymethacrylic acid (a-pMAA), deposited on glass substrate with the order: (a-Si:H a-pAM)3 a-Si:H. Finally the dichroic filters have been tested with success: the deformation of shape memory alloy has been observed and the filters show a high stability towards laser irradiation.