US-12625397-B2 - Low voltage traveling wave electro-absorption modulator for high bandwidth operation

Abstract

Systems and methods are described herein for an electro-absorption modulator (EAM) device. An example EAM device comprises an optical waveguide comprising a waveguide core configured to facilitate a propagation of an optical signal therethrough; a segmented traveling wave electrode structure comprising electrode segments disposed on the optical waveguide; and an electrical transmission line operatively coupled to the electrode segments via conducting bridges, wherein the electrical transmission line is configured to facilitate a propagation of an electrical signal therethrough, wherein the electrode segments are configured to overcome bandwidth and extinction ratio constraints of a lumped EAM.

Inventors

• Moshe B. Oron
• Oren Steinberg
• Isabelle Cestier
• Elad Mentovich
• Timothy De Keulenaer

Assignees

• MELLANOX TECHNOLOGIES, LTD.

Dates

Publication Date

20260512

Application Date

20230313

Claims (20)

1. 1 . An electro-absorption modulator (EAM) device comprising: an optical waveguide comprising a waveguide core configured to facilitate a propagation of an optical signal therethrough; a segmented traveling wave electrode structure comprising electrode segments disposed on the optical waveguide; and an electrical transmission line operatively coupled to the electrode segments via conducting bridges, wherein the electrical transmission line is configured to facilitate a propagation of an electrical signal therethrough, wherein dimensions of the optical waveguide and the electrode segments are defined by using the product of a dynamic extinction ratio slope (ERS), a bandwidth of the EAM device, and a width of the optical waveguide.
2. 2 . The EAM device of claim 1 , wherein the optical waveguide comprises alternating active sections and passive sections.
3. 3 . The EAM device of claim 2 , wherein each electrode segment is disposed on a corresponding active section.
4. 4 . The EAM device of claim 2 , wherein the optical waveguide further comprises a continuous multi-quantum well (MQW) layer stack, wherein portions of the MQW layer stack disposed in the active sections have an energy gap defining an active energy gap value, and portions of the MQW layer stack disposed in the passive sections have an energy gap defining a passive energy gap value, wherein the passive energy gap value is greater than the active energy gap value to maintain low insertion loss.
5. 5 . The EAM device of claim 2 , wherein: a length of each electrode segment is within a range of about 25 microns to about 90 microns, a width of the optical waveguide is within a range of about 0.8 microns to about 1.8 microns, a thickness of an intrinsic region of the optical waveguide is within a range of about 0.22 microns to about 0.35 microns, and an electrode filling factor associated with the EAM device is within a range of about 0.25 to about 0.5.
6. 6 . The EAM device of claim 5 , wherein a minimum number of active sections required to meet an extinction ratio requirement for optical link operation is 2.
7. 7 . The EAM device of claim 5 , wherein the EAM device meets a bandwidth requirement associated with XDR optical links or GDR optical links, wherein the bandwidth requirement of XDR optical links is 60 GHz, and the bandwidth requirement of GDR optical links is 120 GHz.
8. 8 . The EAM device of claim 1 , wherein the EAM device is monolithically integrated along with a laser source on a same chip.
9. 9 . The EAM device of claim 1 , wherein the EAM device is configured for operation by an RF source in a direct drive modulation mode, wherein the RF source is a Serializer-Deserializer (SerDes) transmitter.
10. 10 . The EAM device of claim 1 , wherein the optical waveguide comprises at least a ridge waveguide or a buried heterostructure (BH) waveguide.
11. 11 . The EAM device of claim 1 , wherein the electrode segments and the electrical transmission line are configured to provide velocity matching between the electrical signal and the optical signal.
12. 12 . The EAM device of claim 1 , wherein the electrical transmission line is a microstrip transmission line.
13. 13 . The EAM device of claim 1 , wherein: the electrical transmission line has a width within a range of about 3 microns to about 10 microns and a thickness within a range of about 1.0 microns to about 3 microns; an insulating spacer layer associated with the electrical transmission line, wherein the insulating spacer layer has a thickness within a range of about 4.5 microns to about 7 microns; and a resulting unloaded electrical transmission line impedance within a range of about 60Ω to about 130Ω.
14. 14 . An electro-absorption modulator (EAM) device comprising: an optical waveguide comprising alternating active sections and passive sections, wherein the optical waveguide is configured to facilitate a propagation of an optical signal therethrough; a segmented traveling wave electrode structure comprising electrode segments disposed on the waveguide; and an electrical transmission line operatively coupled to the electrode segments via conducting bridges, wherein the electrical transmission line is configured to facilitate a propagation of an electrical signal therethrough, wherein the EAM device is configured for operation by an RF source in a direct drive modulation mode, wherein the RF source is a Serializer-Deserializer (SerDes) transmitter that is configured to supply the electrical signal at a driving voltage of 0.45V, and wherein dimensions of the optical waveguide and the electrode segments are defined by using the product of a dynamic extinction ratio slope (ERS), a bandwidth of the EAM device, and a width of the optical waveguide.
15. 15 . The EAM device of claim 14 , wherein: a length of each electrode segment is within a range of about 25 microns to about 90 microns, a width of the waveguide is within a range of about 0.8 microns to about 1.8 microns, a thickness of an intrinsic region of the waveguide is within a range of about 0.22 microns to about 0.35 microns, and an electrode filling factor associated with the EAM device is within a range of about 0.25 to about 0.5.
16. 16 . The EAM device of claim 15 , wherein the EAM device meets a bandwidth requirement associated with XDR optical links or GDR) optical links, wherein the bandwidth requirement of XDR optical links is 60 GHz, and the bandwidth requirement of GDR optical links is 120 GHz.
17. 17 . The EAM device of claim 14 , wherein the waveguide comprises at least a ridge waveguide or a buried heterostructure (BH) waveguide.
18. 18 . A method of generating an optical output signal using an electro-absorption modulator (EAM) device, the method comprising: receiving, from a laser source, a continuous wave (CW) light via an optical waveguide, wherein the optical waveguide comprises a segmented traveling wave (S-TW) electrode structure comprising electrode segments disposed thereon, wherein the optical waveguide comprises alternating active sections and passive sections, wherein each electrode segment is disposed on a corresponding active section; receiving, from a radio frequency (RF) source, an electrical signal having a driving voltage of about 0.45V via an electrical transmission line, wherein the electrical transmission line is operatively coupled to the electrode segments via conducting bridges; generating, using the EAM device, an optical output signal based on at least the CW light; and transmitting the optical output signal via the optical waveguide to an external circuit, wherein dimensions of the optical waveguide and the electrode segments are defined by using the product of a dynamic extinction ratio slope (ERS), a bandwidth of the EAM device, and a width of the optical waveguide.
19. 19 . The method of claim 18 , wherein the EAM device meets a bandwidth requirement associated with XDR optical links or GDR optical links, wherein the bandwidth requirement of XDR optical links is 60 GHz, and the bandwidth requirement of GDR optical links is 120 GHz.
20. 20 . The method of claim 18 , wherein the EAM device is monolithically integrated along with the laser source on a same chip.

Description

TECHNOLOGICAL FIELD Example embodiments of the present disclosure relate to traveling wave electro-absorption modulators (TW-EAM) and, more particularly, to a low voltage TW-EAM design for high bandwidth operation. BACKGROUND Next generation optical links, such as XDR optical links and GDR optical links are often used in large networks, such as those in the telecommunications and financial industries, where the data needs to be transferred quickly and securely. Such optical links require optical modulators, such as Mach-Zehnder modulators (MZMs) and electro-absorption modulators (EAMs), that modulate an optical beam to encode data into the data stream. However, the 3 dB modulation bandwidth of conventional EAMs is significantly less than the high bandwidth requirement of XDR and GDR optical links. Applicant has identified a number of deficiencies and problems associated with current designs of optical modulators for high bandwidth operation. Through applied effort, ingenuity, and innovation, many of these identified problems have been solved by developing solutions that are included in embodiments of the present disclosure, many examples of which are described in detail herein. BRIEF SUMMARY Systems, methods, and computer program products are provided for low voltage traveling wave electro-absorption modulator (TW-EAM) for high bandwidth operation. In one aspect, an electro-absorption modulator (EAM) device is presented. The EAM device comprises: an optical waveguide comprising a waveguide core configured to facilitate a propagation of an optical signal therethrough; a segmented traveling wave electrode structure comprising electrode segments disposed on the optical waveguide; and an electrical transmission line operatively coupled to the electrode segments via conducting bridges, wherein the electrical transmission line is configured to facilitate a propagation of an electrical signal therethrough, wherein the electrode segments are configured to overcome bandwidth and extinction ratio constraints of a lumped EAM. In some embodiments, the optical waveguide comprises alternating active sections and passive sections. In some embodiments, each electrode segment is disposed on a corresponding active section. In some embodiments, the optical waveguide further comprises a continuous multi-quantum well (MQW) layer stack, wherein portions of the MQW layer stack disposed in the active sections have an energy gap defining an active energy gap value, and portions of the MQW layer stack disposed in the passive sections have an energy gap defining a passive energy gap value, wherein the passive energy gap value is greater than the active energy gap value to maintain low insertion loss. In some embodiments, a length of each electrode segment is within a range of about 25 microns to about 90 microns, a width of the optical waveguide is within a range of about 0.8 microns to about 1.8 microns, a thickness of an intrinsic region of the optical waveguide is within a range of about 0.22 microns to about 0.35 microns, and an electrode filling factor associated with the EAM device is within a range of about 0.25 to about 0.5. In some embodiments, a minimum number of active sections required to meet an extinction ratio requirement for optical link operation is 2. In some embodiments, the EAM device meets a bandwidth requirement associated with XDR optical links or GDR optical links, wherein the bandwidth requirement of XDR optical links is 60 GHz, and the bandwidth requirement of GDR optical links is 120 GHz. In some embodiments, the EAM device is monolithically integrated along with a laser source on a same chip. In some embodiments, the EAM device is configured for operation by an RF source in a direct drive modulation mode, wherein the RF source is a Serializer-Deserializer (SerDes) transmitter. In some embodiments, the optical waveguide comprises at least a ridge waveguide or a buried heterostructure (BH) waveguide. In some embodiments, the electrode segments and the electrical transmission line are configured to provide velocity matching between the electrical signal and the optical signal. In some embodiments, the electrical transmission line is a microstrip transmission line. In some embodiments, the electrical transmission line has a width within a range of about 3 microns to about 10 microns and a thickness within a range of about 1.0 microns to about 3 microns; an insulating spacer layer associated with the electrical transmission line, wherein the insulating spacer layer has a thickness within a range of about 4.5 microns to about 7 microns; and a resulting unloaded electrical transmission line impedance within a range of about 60Ω to about 130Ω. In another aspect, an electro-absorption modulator (EAM) device is presented. The EAM device comprises an optical waveguide comprising alternating active sections and passive sections, wherein the optical waveguide is configured to facilitate a propagation of an optical sign