Waveguide, waveguide production method, and polarisation splitter using said waveguide

Abstract

The invention relates to a waveguide and a polarisation splitter based on said waveguide, in which a rotation of an angle greater than zero is applied to a plurality of sections of a core material and a plurality of sections of a covering material, thereby achieving an independent control of the refractive indices of a zero-order transverse electric mode and a zero-order transverse magnetic mode. This document also describes a manufacturing method of said waveguide which allows the birefringence of the light that passes through the waveguide.

What is to be claimed is: 
     
         1 . A polarisation splitter comprising:
 a first waveguide comprising a first plurality of sections of a core material and a first plurality of sections of a covering material alternately arranged in a periodic way with a period smaller than a wavelength of a light guided through the first waveguide;   a second waveguide with at least a second portion thereof adjacently arranged at a distance from at least a first portion of the first waveguide, the second waveguide comprising a second plurality of sections of a core material and a second plurality of sections of a covering material alternately arranged in a periodic way with a period smaller than the wavelength of the light guided through the second waveguide; and   a central structure arranged between at least the first and second portions of the first and second waveguides, the central structure comprising a third plurality of sections of a core material and a third plurality of sections of a covering material alternately arranged in a periodic way with a period smaller than the wavelength of the light guided through the central structure;   wherein the first and second pluralities of sections of core material and the first and second pluralities of sections of covering material respectively have constant geometric properties at least throughout the length of the first and second portions of the first and second waveguides;   wherein interfaces defined between each section of core material and each section of covering material of at least one of the first, second and third pluralities of sections of core material and the respective plurality of sections of covering material form an angle greater than zero with respect to a plane perpendicular to a propagation direction of the light guided by at least one of the first and second waveguides.   
     
     
         2 . The polarisation splitter of  claim 1 , wherein the angle is selected such that a first effective index of a zero-order transverse electric mode is different from a second effective index of a zero-order transverse magnetic mode. 
     
     
         3 . The polarisation splitter of  claim 1 , wherein the angle is selected such that a first effective index of a zero-order transverse electric mode is equal to a second effective index of a zero-order transverse magnetic mode. 
     
     
         4 . The polarisation splitter of  claim 1 , wherein the first waveguide comprises a first modal adapter at an input of the first waveguide, the first modal adapter comprising a plurality of sections of core material and sections of covering material arranged in an alternated and periodic way with a period smaller than the wavelength of the light guided through the first modal adapter. 
     
     
         5 . The polarisation splitter of  claim 4 , wherein the first and second waveguides comprise second and third modal adapters, respectively, at respective outputs of the first and second waveguides, each of the second and third modal adapters comprising a plurality of sections of core material and sections of covering material arranged in an alternated and periodic way with a period smaller than the wavelength of the light guided through the second and third modal adapters, respectively. 
     
     
         6 . The polarisation splitter of  claim 5 , wherein the sections of core material of at least one of the first, second and third modal adapters have a variable width. 
     
     
         7 . The polarisation splitter of  claim 1 , wherein the interfaces of the first plurality of sections of core material and the first plurality of sections of covering material form the angle greater than zero. 
     
     
         8 . The polarisation splitter of  claim 1 , wherein the interfaces of at least one of the second and third pluralities of sections of core material and the respective plurality of sections of covering material form the angle greater than zero. 
     
     
         9 . The polarisation splitter of  claim 1 , wherein a duty cycle of the central structure is different from a duty cycle of one or both of the first and second waveguides. 
     
     
         10 . The polarisation splitter of  claim 9 , wherein the first waveguide has a same duty cycle as the second waveguide. 
     
     
         11 . A polarisation splitter comprising:
 a first waveguide, the first waveguide comprising a plurality of sections of a core material and a plurality of sections of a covering material alternately arranged in a periodic way with a period smaller than a wavelength of a light guided through the waveguide;   a subwavelength grating, SWG, structure adjacent to at least a portion of the first waveguide, the SWG structure comprising a plurality of sections of a core material and a plurality of sections of a covering material alternately arranged in a periodic way with a period smaller than a wavelength of the light guided through the central structure; and   a second waveguide with at least a portion thereof adjacent to the SWG waveguide, the second waveguide comprising a plurality of sections of a core material and a plurality of sections of a covering material alternately arranged in a periodic way with a period smaller than the wavelength of the light guided through the waveguide;   wherein interfaces defined between each section of core material and each section of covering material of the plurality of sections of core material of the second waveguide or SWG structure and the plurality of sections of covering material of the second waveguide or SWG structure form an angle greater than zero with respect to a plane perpendicular to a propagation direction of the light guided by at least one of the first and second waveguides;   wherein the plurality of sections of core material and the plurality of sections of covering material of at least one of the first and second waveguides have constant geometric properties throughout at least part of a length thereof.   
     
     
         12 . The polarisation splitter of  claim 11 , wherein the angle is selected such that a first effective index of a zero-order transverse electric mode is different from a second effective index of a zero-order transverse magnetic mode. 
     
     
         13 . The polarisation splitter of  claim 11 , wherein the angle is selected such that a first effective index of a zero-order transverse electric mode is equal to a second effective index of a zero-order transverse magnetic mode. 
     
     
         14 . The polarisation splitter of  claim 11 , wherein the first waveguide comprises a first modal adapter at an input of the first waveguide and a second modal adapter at an output of the first waveguide, the first and second modal adapters each comprising a plurality of sections of core material and sections of covering material arranged in an alternated and periodic way with a period smaller than the wavelength of the light guided through the first modal adapter. 
     
     
         15 . The polarisation splitter of  claim 14 , wherein the second waveguide comprises a third modal adapter at an output of the second waveguide, the third modal adapter comprising a plurality of sections of core material and sections of covering material arranged in an alternated and periodic way with a period smaller than the wavelength of the light guided through the third modal adapter. 
     
     
         16 . The polarisation splitter of  claim 11 , wherein at least the interfaces of the plurality of sections of core material and the plurality of sections of covering material of the SWG structure form the angle greater than zero. 
     
     
         17 . The polarisation splitter of  claim 16 , wherein the interfaces of the plurality of sections of core material and the plurality of sections of covering material of the second waveguide form the angle greater than zero. 
     
     
         18 . The polarisation splitter of  claim 11 , wherein a duty cycle of the central structure is different from a duty cycle of one or both of the first and second waveguides. 
     
     
         19 . A polarisation splitter comprising:
 a first waveguide, the first waveguide comprising a plurality of sections of a core material and a plurality of sections of a covering material alternately arranged in a periodic way with a period smaller than a wavelength of a light guided through the waveguide; and   a second waveguide with at least part of a length thereof adjacent to the SWG waveguide, the second waveguide comprising a plurality of sections of a core material and a plurality of sections of a covering material alternately arranged in a periodic way with a period smaller than the wavelength of the light guided through the waveguide;   wherein interfaces defined between each section of core material and each section of covering material of the plurality of sections of core material and the plurality of sections of covering material of either the first waveguide or the second waveguide form an angle greater than zero with respect to a plane perpendicular to a propagation direction of the light guided by the first waveguide;   wherein the plurality of sections of the core material and the plurality of sections of the covering material of at least one of the first and second waveguides have constant geometric properties throughout at least part of a length thereof.   
     
     
         20 . The polarisation splitter of  claim 19 , further comprising a third waveguide with at least part of a length thereof adjacent to the second waveguide; wherein an end of the second waveguide or the third waveguides is adapted to output a zero-order transverse magnetic mode when zero-order transverse electric and magnetic modes are inputted at an end of the first waveguide.