Opto-Thermally Tunable Axicon-Like Device Based on PDMS-Au Bilayers

A simple method to build up a reflective axicon-like structure is proposed based on the localized swelling of a PDMS-gold bilayer heated by a tightly focused pump laser source. When the distorted reflective surface is illuminated by a probe beam, the theoretical modeling and the experimental tests put in evidence the formation of virtual foci with tens mu textm diameter with a depth of focus to 103 mm. Other than being tunable in a flexible and simple way, the reflecting device is wavelength independent and completely reconfigurable with up to 207.3 W/mm2 pump power densities. As the width of the apical region is triggered by the dimension of the pump focal spot, the device is taylorable for miniaturized systems.