Optical component operating in near-field transmission

1. A near-field detection optical component operating in transmission, characterized in that it includes at least one portion ( 11 b ) forming at least one grating ( 11 ) of diffraction microstructures ( 11 a ) succeeding one another over several periods (p), this grating ( 11 ) being capable of converting evanescent waves ( 16 ) which are established between the component and an object ( 12 ) located in the near field when it reflects or emits a radiation having a wavelength, into propagating waves ( 16 ′) by a diffraction effect during transmission, through the portion ( 11 b ) forming the grating ( 11 ) of diffraction microstructures ( 11 a ), the period (p) of the grating ( 11 ) being of the same order of magnitude as the wavelength of the radiation,

wherein the optical component further includes at least one portion ( 18 ) amplifying the evanescent waves ( 16 ) before their conversion, which cooperates with the portion ( 11 b ) forming the grating ( 11 ) of diffraction microstructures ( 11 a ).

2. The optical component according to claim 1 , wherein the period (p) of the grating ( 11 ) is smaller than the radiation wavelength.

3. The optical component according to claim 1 , wherein it has a lateral size (T) larger than several wavelengths of the radiation, or even substantially equal to about a hundred radiation wavelengths.

4. The optical component according to claim 1 , wherein in the period (p) of the grating verifies the relationship kx−k0<2π/p<kx+k0 with k0=2π/λ and kx being the transverse component of the evanescent waves emitted by the object.

5. The optical component according to claim 1 , wherein the period (p) of the grating verifies the relationship kx−2k0<2π/p<kx−k0 with k0=2π/λ and kx being the transverse component of the evanescent waves emitted by the object.

6. The optical component according to claim 1 , wherein the amplifying portion ( 18 ) is placed side-by-side with the portion ( 11 b ) forming the grating ( 11 ) of diffraction microstructures ( 11 a ).

7. The optical component according to claim 1 , wherein the amplifying portion ( 18 ) is made in a metal material based on gold, silver, platinum, aluminum, indium-antimony or in a semiconducting material.

8. The optical component according to claim 1 , wherein the amplifying portion ( 18 ) has a thickness (h) substantially smaller than the wavelength of the radiation.

9. The optical component according to claim 1 , wherein the amplifying portion ( 18 ) covers a face of the portion ( 11 b ) forming the grating ( 11 ) of diffraction microstructures ( 11 a ) on the opposite side from the diffraction microstructures ( 11 a ).

10. The optical component according to claim 1 , wherein the amplifying portion ( 18 ) and the portion ( 11 b ) forming the grating ( 11 ) of diffraction microstructures are made in a same material.

11. The optical component according to claim 1 , wherein it includes an alternating stack formed by at least one portion ( 11 b ) forming the grating of diffraction microstructures and by one or more amplifying portions ( 18 ) or else several portions ( 11 b ) each forming the grating of diffraction microstructures and at least one amplifying portion ( 18 ).

12. The optical component according to claim 1 , wherein the portion ( 11 b ) forming the grating of diffraction microstructures is made in an electrically conducting material and/or in a dielectric material.

13. The optical component according to claim 1 , wherein the grating ( 11 ) of diffraction microstructures includes protruding portions separated by recessed portions or solid portions separated by through-holes ( 20 ) or by solid electrically conducting portions separated by solid dielectric portions.

14. The optical component according to claim 1 , wherein the grating ( 11 ) of diffraction microstructures includes substantially circular and concentric corrugations.

15. The optical component according to claim 1 , wherein the grating ( 11 ) of diffraction microstructures is invariant under rotation.

16. The optical component according to claim 1 , wherein the portion ( 11 b ) forming at least one grating ( 11 ) of diffraction microstructures is period-modulated.

17. The optical component according to claim 1 , wherein the portion ( 11 b ) forming at least one grating of diffraction microstructures includes several gratings (R 1 , R 2 ) side-by-side with different periods (p 1 ′, p 2 ′).

18. The optical component according to claim 1 , wherein the portion ( 11 b ) forming at least one grating ( 11 ) of diffraction microstructures includes broken periodicity ( 19 ) in a central portion.

19. The optical component according to claim 18 , wherein the broken periodicity is solid or is a void.

20. The optical component according to claim 19 , wherein the void extends into the amplifying portion ( 18 ).

21. A near-field detection optical device wherein it includes an optical component according to claim 1 .

22. The near-field detection optical device according to claim 21 , wherein it includes a detector ( 17 ) placed downstream from the optical component for converted propagating waves ( 16 ′).

23. The detection device according to claim 21 , wherein it includes a solid immersion lens ( 21 ) placed downstream from the optical component ( 10 ), the solid immersion lens ( 21 ) being placed upstream from the detector ( 17 ) for converted propagating waves ( 16 ′) in the presence of the detector ( 17 ).

24. The detection device according to claim 21 , wherein this is a readout head or a read/write head on an optical information medium or a near-field optical microscope probe.