Dual-ring-modulated laser that uses push-pull modulation

Patent metadata

Field	Value
Publication number	US-9939663-B2
Application number	US-201715421300-A
Country	US
Kind code	B2
Filing date	Jan 31, 2017
Priority date	Oct 24, 2013
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

A dual-ring-modulated laser includes a gain medium having a reflective end coupled to a gain-medium reflector and an output end coupled to a reflector circuit to form a lasing cavity. This reflector circuit comprises: a first ring modulator; a second ring modulator; and a shared waveguide that optically couples the first and second ring modulators. The first and second ring modulators have resonance peaks, which are tuned to have an alignment separation from each other. During operation, the first and second ring modulators are driven in opposing directions based on the same electrical input signal, so the resonance peaks of the first and second ring modulators shift wavelengths in the opposing directions during modulation. The modulation shift for each of the resonance peaks equals the alignment separation, so the resonance peaks interchange positions during modulation to cancel out reflectivity changes in the lasing cavity caused by the modulation.

First claim

What is claimed is:

1. A dual-ring-modulated laser, comprising:
a gain medium having a reflective end coupled to an associated gain-medium reflector;
a reflector circuit comprising a first ring modulator, a second ring modulator, a shared waveguide that optically couples the first and second ring modulators together, wherein the first and second ring modulators have resonance peaks that are tuned to have an alignment separation from each other;
an input waveguide that couples the gain medium to the reflector circuit to create a lasing cavity;
a push-pull drive circuit that drives the first and second ring modulators in opposing directions based on the same electrical input signal, so that the resonance peaks of the first and second ring modulators shift wavelengths in the opposing directions during modulation, wherein the modulation shift for each of the resonance peaks substantially equals the alignment separation, so that the resonance peaks interchange positions during modulation to cancel out reflectivity changes in the lasing cavity caused by the modulation; and
at least one output, which is optically coupled to the lasing cavity.

2. The dual-ring-modulated laser of claim 1 , wherein the reflector circuit additionally comprises:
a first intermediate waveguide optically coupled to the first ring modulator;
a second intermediate waveguide optically coupled to the second ring modulator; and
an optical splitter, which splits an optical signal received from the input waveguide to produce a first optical signal that feeds into the first intermediate waveguide, and a second optical signal that feeds into the second intermediate waveguide;
wherein the first optical signal on the first intermediate waveguide is split through partial optical coupling with the first ring modulator to produce a first output component that provides a first output for the laser, and a first reflected component that circulates clockwise in the first ring modulator, passes through the shared waveguide, circulates clockwise in the second ring modulator, and returns through the second intermediate waveguide and the optical splitter to the gain medium; and
wherein the second optical signal on the second intermediate waveguide is split through partial optical coupling with the second ring modulator to produce a second output component that provides a second output for the laser, which is complementary to the first output, and a second reflected component that circulates counterclockwise in the second ring modulator, passes through the shared waveguide, circulates counterclockwise in the first ring modulator, and returns through the first intermediate waveguide and the optical splitter to the gain medium.

3. The dual-ring-modulated laser of claim 1 , wherein the reflector circuit additionally comprises:
a reflector; and
a reflector waveguide;
wherein the input waveguide is optically coupled to the first ring modulator, the first ring modulator is optically coupled to the second ring modulator through the shared waveguide, and the second ring modulator is optically coupled to the reflector though the reflector waveguide; and
wherein an optical signal from the gain medium traverses a path that passes through the input waveguide, circulates around the first ring modulator, passes through the shared waveguide, circulates around the second ring modulator, and passes through the reflector waveguide to the reflector, which reflects the light back down the path in a reverse direction to the gain medium.

4. The dual-ring-modulated laser of claim 3 , wherein an end of the input waveguide, which is opposite to an end coupled to the gain medium, provides an output for the laser.

5. The dual-ring-modulated laser of claim 1 ,
wherein the input waveguide is optically coupled to the first ring modulator;
wherein the gain-medium reflector comprises a reflector waveguide, which is connected to the reflective end of the gain medium and is optically coupled to the second ring modulator;
wherein the gain medium generates a first optical signal that passes through the input waveguide and is split through partial optical coupling with the first ring modulator to produce a first output component that provides a first output for the laser, and a first reflected component that circulates counterclockwise in the first ring modulator, passes through the shared waveguide, circulates counterclockwise in the second ring modulator, and returns through the reflector waveguide to the gain medium; and
wherein the gain medium generates a second optical signal that passes through the reflector waveguide and is split through partial optical coupling with the second ring modulator to produce a second output component that provides a second output for the laser, which is complementary to the first output, and a second reflected component that circulates clockwise in the second ring modulator, passes through the shared waveguide, circulates clockwise in the first ring modulator, and returns through the input waveguide to the gain medium.

6. The dual-ring-modulated laser of claim 1 , wherein the first and second ring modulators have different radii, which causes a Vernier effect that provides a combined tuning range that is larger than the gain bandwidth of the gain medium.

7. The dual-ring-modulated laser of claim 1 , wherein the gain-medium reflector comprises one of the following:
a reflective facet coupled to the reflective end of the gain medium so that the gain medium and the reflective facet form a reflective semiconductor optical amplifier (RSOA);
a waveguide loop mirror coupled to the reflective end of the gain medium; and
a distributed Bragg waveguide (DBR) mirror coupled to the reflective end of the gain medium.

8. The dual-ring-modulated laser of claim 1 , wherein the gain medium is located on a gain chip, which is separate from a semiconductor chip that includes the reflector circuit and other components of the dual-ring-modulated laser.

9. A system, comprising:
at least one processor;
at least one memory coupled to the at least one processor; and
an optical transmitter for communicating optical signals generated by the system, wherein the optical transmitter includes a dual-ring-modulated laser comprising:
a gain medium having a reflective end coupled to an associated gain-medium reflector;
a reflector circuit comprising a first ring modulator, a second ring modulator, a shared waveguide that optically couples the first and second ring modulators together, wherein the first and second ring modulators have resonance peaks that are tuned to have an alignment separation from each other;
an input waveguide that couples the gain medium to the reflector circuit to create a lasing cavity;
a push-pull drive circuit that drives the first and second ring modulators in opposing directions based on the same electrical input signal, so that the resonance peaks of the first and second ring modulators shift wavelengths in the opposing directions during modulation, wherein the modulation shift for each of the resonance peaks substantially equals the alignment separation, so that the resonance peaks interchange positions during modulation to cancel out reflectivity changes in the lasing cavity caused by the modulation; and
at least one output, which is optically coupled to the lasing cavity.

10. The system of claim 9 , wherein the reflector circuit additionally comprises:
a first intermediate waveguide optically coupled to the first ring modulator;
a second intermediate waveguide optically coupled to the second ring modulator; and
an optical splitter, which splits an optical signal received from the input waveguide to produce a first optical signal that feed

Assignees

• Oracle Int Corp

Inventors

• Luo Ying
• Lin Shiyun
• Krishnamoorthy Ashok V
• Bovington Jock T
• Zheng Xuezhe

Classifications

• G02F2201/34

  reflector · CPC title

• G02F2201/126

  push-pull · CPC title

• H01S5/0287

  Facet reflectivity · CPC title

• H01S5/0261

  Non-optical elements, e.g. laser driver components, heaters (H01S5/0265 takes precedence) · CPC title

• H01S5/1032

  Coupling to elements comprising an optical axis that is not aligned with the optical axis of the active region · CPC title