Silicon waveguide having polarization insensitive and temperature insensitive phase delay

An apparatus, comprising:

• a section of a first waveguide configured to receive an input signal at a first initial point, wherein said section of said first waveguide having a length between said first initial point and a first end point;
• a first polarization rotator located within said section of said first waveguide, wherein said first polarization rotator is located at a first distance from said first initial point of said section of said first waveguide;
• a section of a second waveguide configured to receive said input signal at a second initial point, wherein said section of said second waveguide having said length between said second initial point and a second end point;
• a second polarization rotator located within said section of said second waveguide, wherein said second polarization rotator is located at a second distance from said second initial point of said section of said second waveguide;
• a middle section of said first waveguide propagates a first polarization mode and a middle section of said second waveguide propagates a second polarization mode, wherein a length of said middle section is defined by a relative distance between said first distance and said second distance and is selectable to achieve a desired phase delay of an output signal from said first waveguide and an output signal from said second waveguide;
• a first 3dB coupler coupled to said first waveguide at said first initial point and coupled to said second waveguide at said second initial point;
• and
• a second 3dB coupler coupled to said first waveguide at said first end point, and coupled to said second waveguide at said second end point.

A method comprising:

• receiving an input signal at a first initial point of a first section of a first waveguide, wherein said first section of said first waveguide comprises a length between said first initial point and a first end point;
• rotating a polarization on said input signal at a first polarization rotator located within said first section of said first waveguide, wherein said first polarization rotator is located at a first distance from said first initial point of said first section of said first waveguide;
• receiving said input signal at a second initial point of a second section of a second waveguide, wherein said second section of said second waveguide comprises said length between said second initial point and a second end point;
• and
• rotating a polarization on said input signal at a second polarization rotator located within said second section of said second waveguide, wherein said second polarization rotator is located at a second distance from said second initial point of said second section of said second waveguide;
• wherein a relative distance between said first distance and said second distance is configured to achieve a desired phase delay of an output signal from said first waveguide and an output signal from said second waveguide, and
• a first portion defined between said first initial point and the location of an input to the first polarization rotator and a second portion defined between the location of an input to the second polarization rotator and said second end point have a same polarization and phase of respective signals.