Biochip device

1. A biochip device for excitation by an excitation light having a wavelength, the biochip device comprising:

a multimode waveguide that is a plate of material having a refractive index, with a thickness in a range supporting multiple light-propagating modes at the excitation wavelength, the multimode waveguide having a top face and a bottom face, the multimode waveguide having a portion carrying chromophore elements emitting fluorescence in response to the excitation light by guided waves having an evanescent portion, the chromophore elements being used to detect molecular attachments; and

a light-diffusing element configured to diffuse the excitation light incoming from a direction out of the plane of the waveguide into the waveguide in a plurality of modes propagating inside the waveguide in the plane of the waveguide as guided waves and having a disordered spatial distribution of refractive index, the light-diffusing element diffusing the excitation light into the waveguide from another portion of the waveguide to the portion carrying the chromophore elements, the light-diffusing element being a light diffusing structure provided in the waveguide or on the waveguide, or being modifications of the waveguide,

the light diffusing structure comprising one of non-uniform metal or dielectric particles or colloidal particles positioned in the waveguide or on the top face or the bottom face of the waveguide, microcavities formed within the waveguide, and a layer of polytetrafluoroethylene on the waveguide,

the modifications being one of non-stoichiometric compounds and local phases of the waveguide being different from the phase of remaining portions of the waveguide.

2. The device according to claim 1 , further comprising an index-matching layer disposed on the top face or the bottom face of the waveguide, the index-matching layer having a refractive index smaller than the refractive index of the waveguide material.

3. The device according to claim 2 , further comprising, a means for absorbing light, the index-matching layer interposed between the top face or the bottom face of the waveguide and the means for absorbing light, the index-matching layer and the means for absorbing light together eliminating guided modes from the waveguide.

4. The device according to claim 3 , wherein the index-matching layer is carried by the waveguide and is located between the light-diffusing structure and said portion of the waveguide carrying the chromophore elements.

5. The device according to claim 4 , wherein means for absorbing is disposed on the index-matching layer.

6. The device according to claim 2 , a means for deflecting light placed on the index-matching layer.

7. The device according to claim 6 , wherein the means for deflecting comprises a prism.

8. The device according to claim 3 , wherein said waveguide has a thickness e and a guided mode having the greatest effective index reflecting inside the waveguide has a reflection angle θ, and

the index-matching layer and the absorption layer extend over a distance that is longer than 2×e×tanθ.

9. The device according to claim 2 , wherein the index-matching layer extends upstream from the portion carrying the chromophore elements and in part within said portion.

10. The device according to claim 1 , wherein the waveguide is a wedge waveguide that has top and bottom faces and a side edge connecting the top and bottom faces, the top and bottom faces diverging from each other from a point going from the light-diffusing structure to downstream from the portion of the biochip device carrying the chromophore elements, the side edge being opposite the point.

11. The device according to claim 2 , further comprising a hybridizing chamber disposed on the top face of the waveguide and surrounding the portion of the waveguide carrying the chromophore elements and a hybridizing fluid contained in said chamber,

wherein the refractive index of the index-matching layer is greater than or equal to the greatest refractive index of said hybridizing chamber and said hybridizing fluid.

12. The device according to claim 11 , wherein the value of the refractive index of the index-matching layer lies in the range n=1.30 to n=1.45.

13. The device according to claim 1 , wherein the non-uniform metal or dielectric particles are particles in a resin or polymer matrix having a refractive index that is less than that of the diffusing particles by at least 0.5.

14. The device according to claim 1 , wherein the light-diffusing structure comprises the microcavities that are sized from 0.1 μm to 40 μm.

15. The device according to claim 1 , wherein the light-diffusing structure is the non-uniform metal or dielectric particles, and

the non-uniform metal or dielectric particles are deposited on one of the faces of the waveguide and comprise fluorophore material that responds to light excitation by generating fluorescent light that propagates in the waveguide in the form of waves having an evanescent portion.

16. The device according to claim 15 , wherein the fluorophore material comprises quantum dots, organic fluorophores, or rare earth or luminescent ions.

17. The device according to claim 6 , wherein said waveguide has a thickness e and a guided mode having the greatest effective index reflecting inside the waveguide has a reflection angle θ, and

the index-matching layer and the absorption structure extend over a distance that is longer than 2×e×tanθ.

18. The device according to claim 1 , wherein the light-diffusing structure that is one of the non-uniform metal or dielectric particles or the polytetrafluoroethylene is formed by a layer deposited on one of the faces of the waveguide.

19. The device according to claim 13 , wherein said matrix is made of an acrylic resin or of a glycerophthalic resin.

20. The device according to claim 13 , wherein said matrix is a fluoropolymer matrix.