摘要
In many optical applications,there is an increasing need for dynamically tunable optical elements that are able to shape the wavefront of light‘on demand’.In this work,an elastomeric easy-to-fabricate optical element whose transmission functions can be reversibly phase configured by visible light is demonstrated.The light responsivity of proper azopolymers incorporated within an elastomeric matrix is exploited to induce a light-controlled graded refractive index(GRIN)distribution within the bulk compound.The induced refractive index distribution is continuous and conformal to the intensity profile of the illumination at moderate power.A 100mW doubled-frequency Nd:YAG Gaussian beam focused to a 650μm waist is shown to induce a maximum relative refractive index change of~0.4%in the elastomeric matrix,with an approximately parabolic profile.The restoring characteristics of the elastomeric matrix enable full recovery of the initial homogeneous refractive index distribution within a few seconds when the incident laser is switched off.As an exemplary application,the configurable GRIN element is used in a microscope-based imaging system for light control of the effective focal length.
基金
from the Italian Flagship Project NANOMAX(Progetto Bandiera MIUR PNR 2011–2013).