WAVEGUIDE MODULATOR STRUCTURES

• US 20180046057A1
• Filed: 03/04/2016
• Published: 02/15/2018
• Est. Priority Date: 03/05/2015
• Status: Active Grant

• Current Assignee: Rockley Photonics Limited
• Original Assignee: Rockley Photonics Limited
• Inventors: YU, Guomin, ZILKIE, Aaron John
• Granted Patent: US 10,191,350 B2
• Time in Patent Office: Days
• CPC Class Codes: G02F 1/025 in an optical waveguide structure G02F1/017, G02F1/2257 take precedence
• CPC Class Codes: G02F 1/212 Mach-Zehnder type
• CPC Class Codes: G02F 1/2257 the optical waveguides being made of semiconducting material
• CPC Class Codes: G02F 2202/10 semiconductor
• CPC Class Codes: H04B 10/5053 using a parallel, i.e. shunt, combination of modulators

Abstract

A Mach-Zehnder waveguide modulator comprising a left arm including a left SiGe optical waveguide, and a right arm including a right SiGe optical waveguide; wherein each of the left and right optical waveguides comprises a junction region and a plurality of electrodes for providing a bias across the junction to enable control of the phase of light travelling through the junction regions via dispersion.

Claims

1. A Mach-Zehnder waveguide modulator comprising:

a left arm including a left SiGe optical waveguide, and a right arm including a right SiGe optical waveguide;

wherein each of the left and right optical waveguides comprises a junction region and a plurality of electrodes for providing a bias across the junction to enable control of the phase of light travelling through the junction regions via dispersion.

2. A Mach-Zehnder waveguide modulator according to claim 1, wherein the junction region of each of the left and right optical waveguides comprises a PIN junction region, the PIN junction formed from:

a first semiconductor region corresponding to either a p-doped region or an n-doped region;

a second semiconductor region corresponding to the other of the p-doped or n-doped region;

and a central SiGe waveguide region;

wherein the first semiconductor region of the left optical waveguide is integral with the first semiconductor region of the right optical waveguide in a region between the left and right arms, forming a common doped region; and

a plurality of electrodes configured to apply a forward bias across one or both of the PIN junctions to enable control of the phase of light travelling through the respective PIN junction region(s) via dispersion.

3. A Mach-Zehnder waveguide modulator according to claim 1, wherein the junction region of each of the left and right optical waveguides comprises a PIN junction region, the PIN junction formed from:

a first semiconductor region corresponding to either a p-doped region or an n-doped region;

a second semiconductor region corresponding to the other of the p-doped or n-doped region;

and a central SiGe waveguide region;

wherein the first semiconductor region of the left optical waveguide is electrically isolated from the first semiconductor region of the right optical waveguide by a central isolated region between the left and right arms, forming a common doped region; and

a plurality of electrodes configured to apply a forward bias across one or both of the PIN junctions to enable control of the phase of light travelling through the respective PIN junction region(s) via dispersion.

4. A Mach-Zehnder waveguide modulator according to claim 1, wherein the junction of each of the left and right optical waveguides comprises a PN junction, the PN junction formed from:

a first semiconductor region corresponding to either a p-doped region or an n-doped region;

a second semiconductor region corresponding to the other of the p-doped or n-doped region; and

a plurality of electrodes configured to apply a reverse bias across one or both of the PN junctions to enable control of the phase of light travelling through the respective PN junction region(s) via dispersion.

5. A Mach-Zehnder waveguide modulator according to claim 1, wherein:

one of the first or second semiconductor regions includes a vertical doped portion which extends along the side of the waveguide.

6. A Mach-Zehnder waveguide modulator according to claim 5, wherein the vertical doped portion only extends in the vertical direction along a portion of the side wall of the waveguide, such that the central SiGe waveguide region has a greater height than the vertical doped region.

7. A Mach-Zehnder waveguide modulator according to claim 6, wherein the vertical doped portion extends along the entire side of the waveguide.

8. A Mach-Zehnder waveguide modulator according to claim 5, wherein, for a given waveguide arm of the modulator, no more than one side of the waveguide comprises a vertically doped portion.

9. A Mach-Zehnder waveguide modulator according to claim 1, comprising:

an intervening lightly p-doped semiconductor region located between the p-doped semiconductor region and the central waveguide region;

wherein the intervening lightly p-doped semiconductor region has a lower dopant concentration than the p-doped semiconductor region.

10. A Mach-Zehnder waveguide modulator according to claim 1, comprising:

an intervening lightly n-doped semiconductor region located between the n-doped semiconductor region and the central waveguide region;

wherein the intervening lightly n-doped semiconductor region has a lower dopant concentration than the n-doped semiconductor region.

11. A Mach-Zehnder waveguide modulator according to claim 1, wherein:

the central waveguide is composed of SiGe and the doped semiconductor regions are composed of Si.

12. A Mach-Zehnder waveguide modulator according to claim 1, wherein:

the central waveguide region, the first semiconductor region, and the second semiconductor region are all composed of SiGe.

13. A Mach-Zehnder waveguide modulator according to claim 11, wherein:

the central waveguide region, the n-doped semiconductor region, the p-doped semiconductor region, the lightly p-doped semiconductor region, and the lightly n-doped semiconductor region are all composed of SiGe.

14. A Mach-Zehnder waveguide modulator according to claim 1, wherein the plurality of electrodes includes a common electrode located at the common doped region.

15. A Mach-Zehnder waveguide modulator according to claim 1 wherein, for each waveguide arm:

the first semiconductor region includes a first lateral portion extending laterally away from the waveguide wall on a first side of the waveguide;

the second semiconductor region includes a second lateral portion extending laterally away from the waveguide wall on a second side of the waveguide; and

the plurality of electrodes comprises;

a first electrode located directly on top of the first lateral portion; and

a second electrode located directly on top of the first lateral portion.

16. A Mach-Zehnder waveguide modulator according to claim 1, wherein the plurality of electrodes includes a plurality of lumped electrodes.

17. A Mach-Zehnder waveguide modulators according to claim 1, configured to operate in a push-pull mode.