Method and system for a low-loss optical Y-junction power splitter

1. A method for communication, the method comprising:

in a semiconductor die having an optical source assembly comprising a semiconductor laser bonded to a top surface of the semiconductor die above a grating coupler, and first, second, and third optical Y-junctions, the optical Y-junctions each comprising an input waveguide, two output waveguides of continuous widths, a taper region and a step feature, the input waveguide and the taper region including a smooth transition between the input waveguide and the taper region and the step feature being between the taper region and the two or more output waveguides, wherein said continuous widths of the two output waveguides define a splitting ratio of the Y-junctions:

communicating a continuous wave (CW) optical signal from the optical source assembly to the grating coupler;

receiving the optical signal in the input waveguide of the first Y-junction from the grating coupler;

communicating optical signals to each of the two output waveguides of the first Y-junction with optical powers defined by the splitting ratio;

communicating the optical signals from the output waveguides of the first Y-junction to input waveguides of the second and third Y-junctions;

communicating four optical signals from the second and third Y-junctions to four optical modulators in said semiconductor die; and

modulating said four optical signals using said optical modulators based on electrical signals coupled to said optical modulators.

2. The method according to claim 1 , wherein the semiconductor die comprises a photonically-enabled integrated circuit.

3. The method according to claim 1 , wherein the semiconductor die comprises silicon.

4. The method according to claim 1 , wherein the semiconductor die comprises a complementary-metal oxide semiconductor (CMOS) photonics die.

5. The method according to claim 1 , wherein the step feature extends in a direction perpendicular to an axis of the two output waveguides.

6. The method according to claim 1 , wherein a fourth optical Y-junction is part of a Mach-Zehnder interferometer.

7. The method according to claim 1 , wherein an insertion loss of the first, second, and third Y-junctions is less than 0.2 dB.

8. A system for communication, the system comprising:

a semiconductor die having an optical source assembly comprising a semiconductor laser bonded to a top surface of the semiconductor die above a grating coupler, and first, second, and third optical Y-junctions, each of the optical Y-junctions comprising:

an input waveguide;

two output waveguides of continuous widths;

a taper region, the input waveguide and the taper region including a smooth transition between the input waveguide and the taper region; and

a step feature between the taper region and the two output waveguides, wherein said continuous widths of the two output waveguides define a splitting ratio of the Y-junctions,

the semiconductor die being operable to:

receive a continuous wave (CW) optical signal from the optical source assembly via the grating coupler;

receive the optical signal in the input waveguide from the grating coupler;

communicate optical signals to each of the two output waveguides of the first Y-junction with optical powers defined by the splitting ratio;

communicate the optical signals from the output waveguides of the first Y-junction to input waveguides of the second and third Y-junctions;

communicate four optical signals from the second and third Y-junctions to four optical modulators in said semiconductor die; and

modulate said four optical signals using said optical modulators based on electrical signals coupled to said optical modulators.

9. The system according to claim 8 , wherein the semiconductor die comprises a photonically-enabled integrated circuit.

10. The system according to claim 8 , wherein the semiconductor die comprises silicon.

11. The system according to claim 8 , wherein the optical Y-junctions are operable to receive an optical signal in the input waveguide and communicate substantially equal power optical signals to each of the two output waveguides.

12. The system according to claim 8 , wherein the semiconductor die comprises a complementary-metal oxide semiconductor (CMOS) photonics die.

13. The system according to claim 8 , wherein the step feature extends in a direction perpendicular to an axis of the two output waveguides.

14. A system for communication, the system comprising:

a semiconductor die having first, second, and third optical Y-junctions and an optical source assembly comprising a semiconductor laser, the optical source assembly coupled to a top surface of the semiconductor die above a grating coupler, each of the optical Y-junctions comprising:

an input waveguide;

two output waveguides of continuous widths;

a notch between the output waveguides;

a taper region, the input waveguide and the taper region including a smooth transition between the input waveguide and the taper region; and

a step feature between the taper region and the two output waveguides, wherein said continuous widths of the two output waveguides define a splitting ratio of the Y-junctions,

the semiconductor die being operable to:

receive continuous wave (CW) optical signal from the optical source assembly via the grating coupler;

receive the optical signal in the input waveguide of the first Y-junction from the grating coupler;

communicate optical signals to each of the two output waveguides of the first Y-junction with optical powers defined by the splitting ratio;

communicate the optical signals from the output waveguides of the first Y-junction to input waveguides of the second and third Y-junctions;

communicate four optical signals from the second and third Y-junctions to four optical modulators in said semiconductor die; and

modulate said four optical signals using said optical modulators based on electrical signals coupled to said optical modulators.