Echelle grating demux/mux in SiN

Patent metadata

Field	Value
Publication number	US-10317621-B2
Application number	US-201815885544-A
Country	US
Kind code	B2
Filing date	Jan 31, 2018
Priority date	Jan 31, 2017
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

In an example, an Echelle grating wavelength division multiplexing (WDM) device includes a first waveguide, a slab waveguide, multiple second waveguides, an Echelle grating, and a metal-filled trench. The first waveguide includes either an input waveguide or an output waveguide. The multiple second waveguides are optically coupled to the first waveguide through the slab waveguide. The multiple second waveguides include multiple output waveguides if the first waveguide includes the input waveguide or multiple input waveguides if the first waveguide includes the output waveguide. The Echelle grating includes multiple grating teeth formed in the slab waveguide. The metal-filled trench forms a mirror at the grating teeth to reflect incident light from the first waveguide toward the multiple second waveguides or from the multiple second waveguides toward the first waveguide.

First claim

What is claimed is:

1. An Echelle grating wavelength division multiplexing (WDM) device, comprising:
a first waveguide comprising an input waveguide or an output waveguide;
a slab waveguide;
multiple second waveguides optically coupled to the first waveguide through the slab waveguide, the multiple second waveguides comprising multiple output waveguides if the first waveguide comprises the input waveguide or multiple input waveguides if the first waveguide comprises the output waveguide;
an Echelle grating that includes multiple grating teeth formed in the slab waveguide; and
a metal-filled trench that forms a mirror at the grating teeth to reflect incident light from the first waveguide toward the multiple second waveguides or from the multiple second waveguides to the first waveguide, wherein:
the metal-filled trench comprises a trench defined by a toothed wall formed by the slab waveguide and a toothed wall formed by a cladding material and spaced apart from the toothed wall formed by the slab waveguide; and
the slab waveguide comprises silicon nitride (SiN) and the cladding material comprises silicon dioxide (SiO2).

2. The Echelle grating WDM device of claim 1 , wherein the metal-filled trench comprises tungsten.

3. The Echelle grating WDM device of claim 1 , wherein the mirror has a broadband reflectivity of at least 70%.

4. The Echelle grating WDM device of claim 3 , wherein the mirror has the broadband reflectivity of at least 70% in a wavelength range of at least 1271 nanometers (nm) to 1340 nm.

5. The Echelle grating WDM device of claim 1 , wherein at least the slab waveguide and the metal-filled trench are formed in a back end of line (BEOL) process of a complementary metal-oxide-semiconductor (CMOS) fabrication process used to form the Echelle grating WDM device.

6. The Echelle grating WDM device of claim 1 , wherein the Echelle grating and the metal-filled trench are encapsulated at least 240 nanometers (nm) below a top surface of a silicon (Si) photonic integrated circuit (PIC) that includes the Echelle grating and the metal-filled trench.

7. The Echelle grating WDM device of claim 6 , wherein the Echelle grating and the metal-filled trench are encapsulated 240 nm to 600 nm below a top surface of the Si PIC in which the Echelle grating WDM device is formed.

8. The Echelle grating WDM device of claim 7 , wherein the grating teeth have a pitch less than 300 nanometers.

9. An Echelle grating demultiplexer (demux), comprising:
an input waveguide;
a slab waveguide;
multiple output waveguides optically coupled to the input waveguide through the slab waveguide;
an Echelle grating formed in a silicon nitride (SiN) layer of a silicon (Si) photonic integrated circuit (PIC), the Echelle grating including multiple grating teeth formed in the slab waveguide, the multiple grating teeth having a pitch of less than 300 nanometers (nm); and
a broadband mirror located at the multiple grating teeth and encapsulated at least 240 nm below a top surface of the Si PIC.

10. The Echelle grating demux of claim 9 , wherein the broadband mirror comprises a metal-filled trench formed in the SiN layer between a cladding material and the multiple grating teeth of the Echelle grating and the slab waveguide.

11. The Echelle grating demux of claim 10 , wherein:
the metal-filled trench comprises a trench defined by a toothed wall formed by the slab waveguide and a toothed wall formed by the cladding material and spaced apart from the toothed wall formed by the slab waveguide; and
the slab waveguide comprises SiN and the cladding material comprises silicon dioxide (SiO2).

12. The Echelle grating demux of claim 9 , wherein the broadband mirror comprises tungsten.

13. The Echelle grating demux of claim 9 , wherein the broadband mirror comprises a mirror with a reflectivity of at least 70% over a wavelength range of at least 70 nm.

14. The Echelle grating demux of claim 9 , wherein the multiple output waveguides comprise multiple Si waveguide photodetectors.

15. The Echelle grating demux of claim 9 , further comprising multiple contact pads coupled to the multiple Si waveguide photodetectors.

16. A method to form a silicon (Si) photonic integrated circuit (PIC) that includes an Echelle grating demultiplexer (demux) or multiplexer (mux) in a complementary metal-oxide-semiconductor (CMOS) fabrication process, the method comprising:
forming a Si substrate, a buried oxide (BOX) layer above the Si substrate, and a Si layer with one or more active devices above the BOX layer in a front end of line (FEOL) process of the CMOS fabrication process; and
forming above the Si layer one or more dielectric and metallization layers, including a silicon nitride (SiN) layer, in a back end of line (BEOL) process of the CMOS fabrication process, including:
forming a SiN slab waveguide in the SiN layer;
forming an Echelle grating with multiple grating teeth in the SiN slab waveguide;
forming a trench separating the multiple grating teeth in the SiN slab waveguide from a dielectric cladding material in the SiN layer; and
forming a mirror in the trench.

17. The method of claim 16 , wherein forming the mirror in the trench includes filling the trench with a metal.

18. The method of claim 17 , wherein filling the trench with the metal includes filling the trench with a same metal used in the BEOL process to also make one or more metallized pillars that individually provide electrical access between a top of the Si PIC and the one or more active devices.

19. The method of claim 16 , wherein forming the mirror in the trench includes filling the trench with tungsten.

20. The method of claim 16 , wherein forming the one or more dielectric and metallization layers, including the SiN layer, in the BEOL process of the CMOS fabrication process, includes forming one or more metallized pillars that extend from a top to a bottom of the one or more dielectric and metallization layers, and wherein the mirror includes a metal filled in the trench within at least one of a same one or more dielectric and metallization layers as the one or more metallized pillars.

Assignees

• Finisar Corp

Inventors

• Mahgerefteh Daniel

Classifications

• G02B6/124

  Geodesic lenses or integrated gratings · CPC title

• G02B6/12007

  forming wavelength selective elements, e.g. multiplexer, demultiplexer · CPC title

• G01J3/0259

  Monolithic · CPC title

• G01J3/1809

  Echelle gratings · CPC title

• G02B6/1203

  using mounting means, e.g. by using a combination of materials having different thermal expansion coefficients · CPC title