Bricked sub-wavelength periodic waveguide, modal adapter, power divider and polarisation splitter that use said waveguide

A modal adapter for wave transverse electric mode (TE) and transverse electric mode (TM),

• the modal adapter using a periodic waveguide, the periodic waveguide comprising:
• a substrate on which there is arranged a plurality of blocks of a core material arranged in a periodic manner with a period ‘Λz’ in a propagation direction, and a cover material, arranged between and on the plurality of blocks, there being first blocks of width ‘ax’ and second blocks of width ‘bx’, alternating on the substrate perpendicularly to the propagation direction according to a period ‘Λx’, and the second blocks being shifted a distance ‘dz’ in the propagation direction with respect to the first blocks,
• the modal adapter comprising
• a first zone of conversion from a conventional waveguide to a sub-wavelength, SWG, waveguide of the same width as the conventional waveguide and with a period in longitudinal direction ‘Λz’, wherein the waveguide (SWG) comprises bars of core material alternating with a central bridge of core material, the bars and the central bridge being arranged on a substrate, and wherein the central bridge progressively decreases in width until it disappears,
• a second zone of conversion of the SWG waveguide resulting from the first zone into the periodic waveguide, wherein the shift ‘dz’ of the second blocks varies from an initial value equal to zero to a final value.

A device comprising:

• at least one input waveguide,
• at least a first output waveguide,
• at least a second output waveguide,
• a multi-mode interference device comprising a periodic waveguide in its central part,
• at least a first modal adapter, arranged between the at least one input waveguide and the multimode interference device, and
• at least a second modal adapter, arranged between the multimode interference device and at least one of the first and second output waveguides;
• wherein the periodic waveguide comprises
• a substrate on which there is arranged a plurality of blocks of a core material arranged in a periodic manner with a period ‘Λz’ in a propagation direction, and a cover material, arranged between and on the plurality of blocks, there being first blocks of width ‘ax’ and second blocks of width ‘bx’, alternating on the substrate perpendicularly to the propagation direction according to a period ‘Λx’, and the second blocks being shifted a distance ‘dz’ in the propagation direction with respect to the first blocks, and
• wherein the at least the first modal adapter and the at least the second modal adapter each comprise a modal adapter type, the modal adapter type comprising:
• a first zone of conversion from a conventional waveguide to a sub-wavelength, SWG, waveguide of the same width as the conventional waveguide and with a period in longitudinal direction ‘Λz’, wherein the waveguide (SWG) comprises bars of core material alternating with a central bridge of core material, the bars and the central bridge being arranged on a substrate, and wherein the central bridge progressively decreases in width until it disappears, and
• a second zone of conversion of the SWG waveguide resulting from the first zone into the periodic waveguide, wherein the shift ‘dz’ of the second blocks varies from an initial value equal to zero to a final value.