Method and system for optical detection of nano-objects in a light refracting medium

Device for optical detection of nano-objects in a refractive medium, comprising:

• means for generating a periodically amplitude modulated first coherent electromagnetic wave and for illuminating at least one of (i) the nano-objects and (ii) the refractive medium with the first wave 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;
• means for generating a second coherent electromagnetic wave and for illuminating the nano-object with the second coherent electromagnetic wave simultaneously with illuminating at least one of (i) the nano-objects and (ii) the refractive medium with the first wave, thereby forming a probe wave, to generate, by diffusion of this probe wave in the area by the temperature and refractive index profile, an emerging probe wave having at least one intensity component amplitude modulated by a beat at the modulation frequency of the first electromagnetic wave;
• and
• means for detecting, in the emerging wave, the intensity component amplitude modulated by a beat, making it possible to distinguish and represent the nano-object in the refractive medium,
• wherein the means for illumination by a first coherent electromagnetic wave comprises:
• means for generating a first laser beam forming the first coherent electromagnetic wave forming a heating wave;
• and
• means for focusing the first modulated laser beam on the nano-objects in the refractive medium,
• wherein the means for simultaneous illumination of the nano-object by a second electromagnetic wave comprises:
• means for generating a second laser beam, forming the probe wave;
• and
• means for focusing the second modulated laser beam on at least one of the nano-objects in the refractive medium,
• wherein the heating wave and the probe wave are superimposed by means of a dichroic mirror, on a common optical path formed between this dichroic mirror and a single common objective forming the focusing means,
• wherein, for the detection in the emerging probe wave of the intensity component amplitude modulated by a beat, by reflection, the device additionally comprises:
• means for linearly polarizing the first laser beam in a first direction;
• means for linearly polarizing the second laser beam in a second direction, the probe wave being linearly polarized in the second direction;
• means for linearly polarizing the emerging probe wave in a third direction orthogonal to the second direction;
• and
• means for polarization separation placed on the optical path common to the emerging probe wave linearly polarized in the third direction and to the probe wave polarized in the second direction, the separator means making it possible to deliver only the emerging probe wave linearly polarized in the third direction.