Waveguide structure and optical system with waveguide structure

A resonator type semiconductor laser, the resonator comprising a waveguide structure comprising:

• a first waveguide region having a constant first width adapted to guide electromagnetic waves mode sustainably along its longitudinal axis;
• a second waveguide region adapted to guide electromagnetic waves mode sustainably along its longitudinal axis,
• wherein the longitudinal axis of the first waveguide region and the longitudinal axis of the second waveguide region form a common longitudinal axis of the waveguide structure, wherein a first end face of the first waveguide region and a first end face of the second waveguide region are aligned with each other, wherein a width of the first face of the second waveguide region corresponds to the first width, and a width of the second waveguide region widens along its longitudinal axis from the first face to a second face to a second width greater than the first width;
• and
• a grating having a plurality of webs and trenches, the grating being disposed along the common longitudinal axis in the second waveguide region;
• wherein the second waveguide region and the grating are adapted to guide electromagnetic waves in the second waveguide region along the common longitudinal axis in a mode-maintaining manner and to reflect them in a mode-maintaining manner;
• and the first waveguide region, the second waveguide region and the grating are adapted to guide electromagnetic waves in the first waveguide region and in the second waveguide region along the common longitudinal axis in a mode-maintaining manner and to reflect them in a mode-maintaining manner;
• wherein the first waveguide region, the second waveguide region, and the grating are adapted to cause a mode-maintaining reversal of direction for at least one transverse propagation mode of the first waveguide region excited at a second end face of the first waveguide region.

An optical system comprising a waveguide structure comprising:

• a first waveguide region having a constant first width adapted to guide electromagnetic waves mode sustainably along its longitudinal axis;
• a second waveguide region adapted to guide electromagnetic waves mode sustainably along its longitudinal axis,
• wherein the longitudinal axis of the first waveguide region and the longitudinal axis of the second waveguide region form a common longitudinal axis of the waveguide structure, wherein a first end face of the first waveguide region and a first end face of the second waveguide region are aligned with each other, wherein a width of the first face of the second waveguide region corresponds to the first width, and a width of the second waveguide region widens along its longitudinal axis from the first face to a second face to a second width greater than the first width;
• and
• a grating having a plurality of webs and trenches, the grating being disposed along the common longitudinal axis in the second waveguide region;
• wherein the second waveguide region and the grating are adapted to guide electromagnetic waves in the second waveguide region along the common longitudinal axis in a mode-maintaining manner and to reflect them in a mode-maintaining manner;
• and the first waveguide region, the second waveguide region and the grating are adapted to guide electromagnetic waves in the first waveguide region and in the second waveguide region along the common longitudinal axis in a mode-maintaining manner and to reflect them in a mode-maintaining manner;
• wherein the first waveguide region, the second waveguide region, and the grating are adapted to cause a mode-maintaining reversal of direction for at least one transverse propagation mode of the first waveguide region excited at a second end face of the first waveguide region.