Structure of a micronanostructure optical wave guide for controlling birefringence

Optical waveguide structure, comprising:

• a supporting substrate,
• an optical waveguide located on a surface of the supporting substrate, the optical waveguide comprising at least one guide layer having a refractive index n1 intended to guide an optical wave in a direction of propagation parallel to the surface of the guide layer,
• wherein the said at least one guide layer comprises at least one zone having a birefringence of value B, the said zone comprising voids provided in the thickness of the guide layer, the voids being filled with a fluid or material having a refractive index n2 which is not the same as n1 and being organised in at least two parallel rows, each row being in a plane essentially perpendicular to the surface of the guide layer and essentially parallel to the direction of propagation of the optical wave, each row extending over a distance equal to or longer than the wavelength of the optical wave which is to be propagated within the guide layer,
• the width of the voids being equal to or less than one tenth of the wavelength of the optical wave intended to be propagated within the guide layer, the width of a void being the maximum distance between the two opposite edges of a particular void present in a plane perpendicular to the direction of propagation of the optical wave,
• each void within one row being at a distance from an adjacent void equal to or less than one tenth of the wavelength of the optical wave intended to be propagated within the guide layer,
• the width of the voids in relation to the distance separating two adjacent voids in two adjacent rows and the refractive index n2 of the fluid or material filling the voids being selected on the basis of the birefringence value B which it is desired to obtain according to the following formula:
• B
• =
• 1
• ff
• n
• H
• ,
• TE
• 2
• +
• (
• 1
• -
• ff
• )
• n
• B
• ,
• TE
• 2
• -
• n
• H
• ,
• TM
• 2
• ×
• ff
• +
• n
• B
• ,
• TM
• 2
• ×
• (
• 1
• -
• ff
• )
• ff being the filling factor for the material of refractive index n1 and having a value between 0 and 1, the values 0 and 1 being excluded,
• nH,TE and nH,TM being the effective refractive indices of the TE mode and the TM mode respectively of the guide layer of higher refractive index,
• nB,TE and nB,TM being the effective refractive indices of the TE mode and the TM mode respectively of the fluid or material filling the voids of lower refractive index.