US-12619120-B2 - Photodetector with split inputs

Abstract

The present disclosure describes photodetectors with multiple inputs and methods of operating photodetectors with multiple inputs. An apparatus includes a substrate, an optical absorber, an optical device, and a tuner. The optical absorber is positioned on the substrate. The optical device produces a first optical signal and a second optical signal from an optical signal received at a first port of the optical device and directs the first optical signal and the second optical signal to the optical absorber. The tuner adjusts a first phase of the first optical signal and a second phase of the second optical signal such that a reflection of the first optical signal from the optical absorber destructively interferes with a reflection of the second optical signal from the optical absorber at the first port.

Inventors

• Rajat Sharma
• Donald B. Adams
• Attila Mekis
• Gianlorenzo Masini

Assignees

• CISCO TECHNOLOGY, INC.

Dates

Publication Date

20260505

Application Date

20230418

Claims (20)

1. 1 . An apparatus comprising: a substrate; an optical absorber positioned on the substrate; a set of metal contacts arranged on the optical absorber and along a line that divides the optical absorber into a first portion and a second portion; an optical device arranged to: produce a first optical signal and a second optical signal from an optical signal received at a first port of the optical device; direct the first optical signal through the first portion of the optical absorber without intersecting the line; and direct the second optical signal through the second portion of the optical absorber without intersecting the line; and a tuner arranged to adjust a first phase of the first optical signal and a second phase of the second optical signal such that a reflection of the first optical signal from the optical absorber destructively interferes with a reflection of the second optical signal from the optical absorber at the first port.
2. 2 . The apparatus of claim 1 , wherein the optical device comprises a second port, and wherein the reflection of the first optical signal constructively interferes with the reflection of the second optical signal at the second port.
3. 3 . The apparatus of claim 2 , further comprising a photodiode arranged to detect the reflection of the first optical signal and the reflection of the second optical signal at the second port.
4. 4 . The apparatus of claim 3 , wherein the tuner adjusts the first phase of the first optical signal based at least in part on the reflection of the first optical signal and the reflection of the second optical signal detected by the photodiode at the second port.
5. 5 . The apparatus of claim 1 , wherein the optical device comprises at least one of a directional coupler, a y-splitter, or a multi-mode interferometer.
6. 6 . The apparatus of claim 1 , wherein the optical device comprises a first waveguide and a second waveguide, wherein the first waveguide directs the first optical signal to the optical absorber, and wherein the second waveguide directs the second optical signal to the optical absorber.
7. 7 . The apparatus of claim 6 , wherein the tuner adjusts the first phase of the first optical signal by applying thermal energy to the first waveguide.
8. 8 . The apparatus of claim 6 , wherein the tuner adjusts the first phase of the first optical signal by adjusting a physical dimension of the first waveguide.
9. 9 . The apparatus of claim 6 , wherein the tuner adjusts the first phase of the first optical signal by injecting, accumulating, or depleting carriers in the first waveguide.
10. 10 . The apparatus of claim 1 , wherein the set of metal contacts comprises a first set of metal, and wherein the apparatus further comprises: a second set of metal contacts arranged along a surface of the substrate such that the second set of metal contacts are positioned between a first edge of the optical absorber and a first edge of the substrate along an axis that is perpendicular to the line.
11. 11 . The apparatus of claim 10 , further: a third set of metal contacts arranged along a surface of the substrate such that the third set of metal contacts are positioned between a second edge of the optical absorber and a second edge of the substrate along the axis that is perpendicular to the line.
12. 12 . A method comprising: producing, by an optical device, a first optical signal and a second optical signal from an optical signal received at a first port of the optical device; and directing, by the optical device, the first optical signal through a first portion of an optical absorber without intersecting a line along which a set of metal contacts are arranged to divide the optical absorber into the first portion and a second portion; directing, by the optical device, the second optical signal through the second portion of the optical absorber without intersecting the line; and adjusting, by a tuner, a first phase of the first optical signal and a second phase of the second optical signal such that a reflection of the first optical signal from the optical absorber destructively interferes with a reflection of the second optical signal from the optical absorber at the first port.
13. 13 . The method of claim 12 , wherein the optical device comprises a second port, and wherein the reflection of the first optical signal constructively interferes with the reflection of the second optical signal at the second port.
14. 14 . The method of claim 13 , further comprising detecting, by a photodiode, the reflection of the first optical signal and the reflection of the second optical signal at the second port.
15. 15 . The method of claim 14 , wherein the tuner adjusts the first phase of the first optical signal based at least in part on the reflection of the first optical signal and the reflection of the second optical signal detected by the photodiode at the second port.
16. 16 . The method of claim 12 , wherein the optical device comprises at least one of a directional coupler, a y-splitter, or a multi-mode interferometer.
17. 17 . The method of claim 12 , wherein the optical device comprises a first waveguide and a second waveguide, wherein the first waveguide directs the first optical signal to the optical absorber, and wherein the second waveguide directs the second optical signal to the optical absorber.
18. 18 . The method of claim 17 , wherein the tuner adjusts the first phase of the first optical signal by applying thermal energy to the first waveguide.
19. 19 . The method of claim 17 , wherein the tuner adjusts the first phase of the first optical signal by adjusting a physical dimension of the first waveguide.
20. 20 . The method of claim 17 , wherein the tuner adjusts the first phase of the first optical signal by injecting, accumulating, or depleting carriers in the first waveguide.

Description

TECHNICAL FIELD Embodiments presented in this disclosure generally relate to photodetectors. More specifically, embodiments disclosed herein include a photodetector with split inputs. BACKGROUND Photodetectors convert optical signals into electrical signals. The photodetectors may include an optical absorber through which optical signals pass. The optical signals separate electrical carriers in the optical absorber, generating electrical signals. BRIEF DESCRIPTION OF THE DRAWINGS So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate typical embodiments and are therefore not to be considered limiting; other equally effective embodiments are contemplated. FIG. 1 illustrates an example system. FIG. 2 illustrates an example optical absorber in the system of FIG. 1. FIG. 3 illustrates an example optical absorber in the system of FIG. 1. FIG. 4 illustrates an example implementation of the system of FIG. 1. FIG. 5 illustrates an example implementation of the system of FIG. 1. FIG. 6 illustrates an example implementation of the system of FIG. 1. FIG. 7 illustrates an example implementation of the system of FIG. 1. FIG. 8 illustrates an example implementation of the system of FIG. 1. FIG. 9 is a flowchart of an example method performed in the system of FIG. 1. FIG. 10 illustrates an example system. FIG. 11 illustrates an example implementation of the system of FIG. 10. FIG. 12 illustrates an example implementation of the system of FIG. 10. FIG. 13 illustrates an example implementation of the system of FIG. 10. FIG. 14 is a flowchart of an example method performed in the system of FIG. 10. To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially used in other embodiments without specific recitation. DESCRIPTION OF EXAMPLE EMBODIMENTS Overview The present disclosure describes photodetectors with multiple inputs and methods of operating photodetectors with multiple inputs. According to an embodiment, an apparatus includes a substrate, an optical absorber, an optical device, and a tuner. The optical absorber is positioned on the substrate. The optical device produces a first optical signal and a second optical signal from an optical signal received at a first port of the optical device and directs the first optical signal and the second optical signal to the optical absorber. The tuner adjusts a first phase of the first optical signal and a second phase of the second optical signal such that a reflection of the first optical signal from the optical absorber destructively interferes with a reflection of the second optical signal from the optical absorber at the first port. According to another embodiment, a method includes producing, by an optical device, a first optical signal and a second optical signal from an optical signal received at a first port of the optical device and directing, by the optical device, the first optical signal and the second optical signal to an optical absorber. The method also includes adjusting, by a tuner, a first phase of the first optical signal and a second phase of the second optical signal such that a reflection of the first optical signal from the optical absorber destructively interferes with a reflection of the second optical signal from the optical absorber at the first port. According to another embodiment, an apparatus includes an optical device and a tuner. The optical device produces a first optical signal and a second optical signal from an optical signal received at a first port of the optical device. The tuner adjusts a first phase of the first optical signal and a second phase of the second optical signal such that a reflection of the first optical signal destructively interferes with a reflection of the second optical signal at the first port. Example Embodiments Photodetectors convert optical signals into electrical signals. The photodetectors may include an optical absorber (e.g., a germanium on silicon optical absorber) through which optical signals pass. The optical signals create free electrical carriers (e.g., electrons and holes) in the optical absorber, generating electrical signals. Some photodetectors include metal contacts on a top surface of the optical absorber. These metal contacts may interact with optical signals passing through the optical absorber beneath the metal contacts, resulting in responsivity loss. Additionally, the optical absorber may reflect some of the optical signals, which can create interference and degrade link performance. The present disclosure describes a photodetector with m