Patent ID: 7889343
Filing Date: 2011-02-15
Classification: G01N

Abstract:
1. Method of optical detection of nano-objects in a refractive medium, comprising the following steps: (a) illuminating at least one of (i) the nano-objects and (ii) the refractive medium with a first coherent electromagnetic wave which is periodically amplitude modulated, so as to cause an absorption of electromagnetic energy and induce a modulated variation of the refractive index of the refractive medium by increasing the temperature, according to a specified temperature and refractive index profile, in an area in the vicinity of the nano-object; (b) simultaneously with step (a), forming a probe wave by illuminating the nano-object with a second coherent electromagnetic wave; (c) generating an emerging probe wave by diffusion of the formed probe wave in the area by the temperature and refractive index profile, the emerging probe wave having at least one intensity component amplitude modulated by a beat at the modulation frequency of the first electromagnetic wave; and (d) detecting in the emerging probe wave the intensity component amplitude modulated by a beat, making it possible to distinguish and represent the non-object in the refractive medium, wherein step (a) comprises: generating a first laser beam forming the first coherent electromagnetic wave forming a heating wave; and focusing the first modulated laser beam on the nano-objects in the refractive medium, wherein step (b) comprises: generating a second laser beam, forming the probe wave; focusing the second modulated laser beam on at least one of the nano-objects in the refractive medium; and superimposing the heating wave and the probe wave on a common optical path formed between a dichroic mirror and a single common objective for the step of focusing the second modulated laser beam, wherein step (a) further comprises linearly polarizing the first laser beam in a first direction, and step (b) further comprises linearly polarizing the second laser beam in a second direction, the probe wave being linearly polarized in the second direction; and wherein after step (c), further comprising step (e) of linearly polarizing the emerging probe wave in a third direction orthogonal to the second direction, and between steps (e) and (d), further comprising step (f) of separating by polarization separation the emerging probe wave linearly polarized in the third direction and the probe wave polarized in the second direction, so as to deliver only the emerging probe wave linearly polarized in the third direction.