Broadband star coupler
An optical device. In some embodiments, the optical device includes a first interface; a second interface; a first plurality of waveguides, at the first interface; a second plurality of waveguides, at the second interface; and a free propagation region. A first waveguide of the first plurality of waveguides has a width at least 20% greater than a second waveguide of the first plurality of waveguides.
1. An echelle grating, comprising:
a first interface;
a second interface;
a plurality of output waveguides, at the first interface;
one or more input waveguides, at the second interface; and
a free propagation region connecting the plurality of output waveguides and the one or more input waveguides,
a first waveguide, of the plurality of output waveguides, having a first width,
a second waveguide, of the plurality of output waveguides, having a second width,
the first width being at least 5% greater than the second width,
the echelle grating being configured:
when light is received at a first wavelength in only a third waveguide, of the one or more input waveguides, to direct the light at the first wavelength to the first waveguide; and
when light is received at a second wavelength in only the third waveguide, to direct the light at the second wavelength to the second waveguide, and
a ratio of the first width to the second width being within 10% of a ratio of the first wavelength to the second wavelength.
2. The echelle grating of claim 1 , wherein a trench between the first waveguide and a waveguide, of the plurality of output waveguides, adjacent to the first waveguide has a width less than 1 micron.
3. The echelle grating of claim 2 , wherein the width of the trench is less than 700 nm.
4. The echelle grating of claim 2 , wherein each trench between a pair of adjacent waveguides of the plurality of output waveguides has a width less than 1 micron.
5. The echelle grating of claim 4 , wherein each trench between a pair of adjacent waveguides of the plurality of output waveguides has a width less than 700 nm.
6. An echelle grating, comprising:
a first interface;
a second interface;
a plurality of output waveguides, at the first interface;
one or more input waveguides, at the second interface; and
a free propagation region connecting the plurality of output waveguides and the one or more input waveguides,
a first waveguide, of the plurality of output waveguides, having a first width,
a second waveguide, of the plurality of output waveguides, having a second width,
the first width being at least 5% greater than the second width,
the echelle grating being configured:
when light is received at a first wavelength in only a third waveguide, of the one or more input waveguides, to direct the light at the first wavelength to the first waveguide; and
when light is received at a second wavelength in only the third waveguide, to direct the light at the second wavelength to the second waveguide, and
a ratio of the first width to the second width being within 10% of a ratio of the first wavelength to the second wavelength
the first width being selected such that a first field pattern, at a grating of the echelle grating, corresponding to a fundamental mode of the first waveguide, includes, within a range of angles subtended by the grating of the echelle grating, at least 99% of the power of the first field pattern.
7. The echelle grating of claim 6 , wherein the second width is selected such that a second field pattern, at the grating of the echelle grating, corresponding to a fundamental mode of the second waveguide, includes, within a range of angles subtended by the grating of the echelle grating, at least 99% of the power of the second field pattern.