Announcing the world’s first 40G silicon laser modulator!

In this blog, I would like to share with you our recent breakthrough in Silicon Photonics research at Photonics Technology Lab of Intel, a laser modulator that encodes optical data at 40 billion bits per second. Here I am holding a packaged device:

[click here for more pics of the modulator and the research team]

As you may know, a photonic integrated circuit (PIC) could provide a cost-effective solution for optical communication and future optical interconnects in computing industry. PICs on silicon platforms have attracted particular interest because of silicon’s low cost and high volume manufacturability. Competition in this arena is intense as many players in both academia and industry have been aggressively pursuing research into completely integrated CMOS photonics. The DARPA-initiated Electronic & Photonic Integrated Circuits (EPIC) program has also been supporting several Universities and startups to develop capabilities in this area.

One of the key components needed for silicon PICs is the high-speed silicon optical modulator, which is used to encode data on optical beam. Today’s commercially available optical modulators at 10 Gbps are based on more exotic electro-optic materials such as lithium niobate and III-V compound semiconductors. These devices have deployed at speeds up to 40 Gbps. Our goal to achieve similar performance in silicon has been very challenging, because crystalline silicon does not exhibit the linear electro-optic (Pockels) effect used to modulate light in these materials. Engineers are forced to rely on the free-carrier plasma dispersion effect, in which silicon’s refractive index is changed when the density of free carriers (electrons/holes) is varied, to modulate light in silicon.

In 2004, we published in Nature the first silicon modular to reach gigahertz speeds, 50x times faster than previous attempts in silicon. Since then, we scaled the device to 10Gbps, brining silicon modulation speed to a level comparable to most commercial devices. In January 2007, we designed and fabricated a new type of silicon optical modulator scalable to >>10 Gbps and demonstrated data transmission at 30 Gbps (see Optics Express, 22 January 2007, pp. 660-668). The modulator still relies on the free-carrier effect, but its high speed is the result of a unique device design with traveling-wave drive scheme.

This is the new chip on the right. With a similar device configuration, the modulator performance has been further improved by better device packaging to reduce the parasitic effect, better traveling-wave electrode with lower RF attenuation, and better modulator termination circuitry. In the conference of

Integrated Photonics and Nanophotonics Research and Applications, Salt Lake City, Utah, July 9-11, 2007, I presented our world record results in a silicon modulator to a small group of scientists. We have finally reached the goal of data transmission at 40 Gbps speed, matching the fastest devices deployed today using other materials.


The Intel modulator is based on a Mach-Zehnder interferometer with a reverse-biased pn junction in each of the arms (Figure 1a). When a reverse voltage is applied to the junction, free carriers – electrons and holes resulting from the n- and p-dopants – are pulled out of the junction, changing its refractive index via the free-carrier effect. The intensity of the light transmitted through the Mach-Zehnder interferometer is modulated by modulating the phase difference between the interferometer’s two arms. This modulation can be very fast, because free carriers can be swept out of the junction with a time of approximately 7 ps. The modulator speed is thus limited by the parasitic effects such as RC time constant limit.


To minimize the RC constant limitation, Intel researchers adopted a traveling-wave drive scheme allowing electrical and optical signal co-propagation along the waveguide. The traveling-wave electrode which is based on a coplanar waveguide was designed to match the velocity for both optical and electrical signals, while keeping the RF attenuation small. To operate the traveling-wave modulator, the RF signal is fed into the transmission line using a commercially available driver from the optical input side and the transmission line is terminated with an external resistor (see Fig. 1a). After packaging the modulator on a printed circuit board, the researchers demonstrated that the modulator has a 3 dB bandwidth of ~30 GHz (Fig. 2a) and data transmission capability up to 40 Gbps (Fig. 2b).

The high-speed silicon modulator could find use in various future applications. For example, a highly integrated silicon photonic circuit may provide a cost effective solution for the future optical interconnects within computers and other devices. With the demonstration of the 40 Gbps silicon modulator and the electrically pumped hybrid silicon laser, it will become possible to integrate multiple devices on a single chip (Fig. 3) that can transmit terabits of aggregate data per second in the near future – truly enabling tera-scale computing.


You are welcomed to submit comments.


43 Responses to Announcing the world’s first 40G silicon laser modulator!

  1. German Jimenez says:

    Your presentation is quite interesting. I have a couple of questions, though. It looks like there is a huge effort to match existing market capabilities by using silicon instead of the industry standard. What is the cost advantage of Silicon (is it 0.5x, 0.1x cheaper?). Is there a chance this technology will actually exceed current standards of data transferring?
    Congratulations for your accomplishment.

  2. George says:

    Very impressive stuff. Very well explained.
    I’m not a circuit designer but have been working with I/O designers long enough to know their first question when I/O speed is quoted: to what distance can the transmission support the rate of 40G/s (on a board: what is the trace length limit for the output driver)?

  3. I’ve been following the laser modulator stories in Circuit for a while. It’s nice to see the transmission speeds increasing. When will it be available commercially? Are there any plans to further increase the modulator’s throughput? Or to send 64-bit data in paralell? Imagine a 40 giga-WORD per second data stream!

  4. Mick Flanigan says:

    This is really amazing! I am sure the lab has been working very hard for many years, being very dilligent in working through the test process many times over! It is great to see all your hard work is paying off! When can I put one in my home?

  5. Sameer says:

    First of all congratulations on this tremendous breakthrough!!
    In your post you mentioned: “a photonic integrated circuit (PIC) could provide a cost-effective solution for optical communication and future optical interconnects in computing industry”
    Since I work in CPUs right now, I am interested in knowing how close are we in solution for optical interconnects? This would give us a tremendous boost in energy efficiency and performance.

  6. Achieving 40Gb/s using a silicon laser modulator is a significant milestone for silicon photonics in that we’ve matched the data transmission speed records set by the fastest III-V optical devices available today. We see silicon photonics at the heart of future, low cost optical interconnects for tera-scale computing. Congratulations to the team on this achievement.

  7. dc++ says:

    That is so gross, i knew that Intel have great scientists, but photonics is a great advance in the Intel’s development

  8. Kalpesh Mistry says:

    First of all congrate’s to whole team who has given a successful device. I was shocked to hear this type of fastest modulator is invented in today’s fastest moving world.
    Really it sounds great that the data transmission is increasing from 10Gbps to 30Gbps that means we are gaining 30% speed. That’s really good.
    Hope to found this device available soon in market!

  9. Philip says:

    Great work! Very impressive…
    A friendly reminder to Dr. Liu: 40Gbs should be 400 billion bits per sec, right?

  10. Bob Sundahl says:

    A major breakthrough! And much more convenient than lithium niobate. It would seem that the next item needed would be a similar detector, with a low delay time. Or would this technology be used for non-synchronous systems?

  11. Daanish says:

    Niice this will help make fast computers cheaper ans will help in communication technoligies and further our quest for better and more efficient technoligies.

  12. Julie says:

    Wonderful, the concept sounds – and design looks great. I’d like to evaluate it’s workability for some particular emerging industry applications.
    Feel free to contact me, if you are able to sign an NDA.
    Julie Mikalson,
    Progressive Strategies,
    Portland, Oregon

  13. Ryan Barone says:

    Was the cost associated with this worth it? It would have been a lot easier and most likely more cost-effective if we had used this money to better the technology that we already know is capable of reaching these speeds. This is amazing, no doubt, but we’ve kinda set ourselves back a little bit by focusing on trying to beat a record rather than advancing.

  14. Igal says:

    Ansheng, congratulations to you and the PTL team for those great achivments and to the FAB8 team for make it happen.

  15. RJFlash says:

    Awesome! Well done accomplishing the new technology. I’ve read about this on, and it is true. Photon based data-chips. This may, one day replace electron based chips…?? Light waves in a chip!! cooooool!

  16. jose luis says:

    man i am impressive what can do the human mind. I know there is no limit to the people who think that the progress is here, i hope this will be used correctly and serve to the world.
    congratulations and i hope you continue working and researching. Bye

  17. blue_eye says:

    a laser modulator that encodes optical data at 40 billion bits per second
    it is mean transmation or what ??

  18. Stacy says:

    Dr. Liu (and others on this blog),
    Can anyone here answer a question for me? Is there any electro-optic device that can phase modulate light at Ghz frequencies and produce modulation indeces of 1000 or more for infrared light? I have only been able to find phase modulators with modulation index 3 to 4 orders of magnitude smaller. Thanks!

  19. PiONER says:

    Фантастика ! Наука идет вперед !
    Я даже представить не могу…что нас ждет в
    2050 году.

  20. lianxi jia says:

    i have asked for a presentation from you, thanks for your help, ago.
    i have a question about the swept time of the carrier, what’s the key factor to determine this parameter, the configuration of the waveguides or the traveling-wave elecrode?

  21. Philippe Velha says:

    How big are your modulators?
    Do you think it is possible to reduce the size of modulators?
    In D-WDM an UD-WDM standards the needs are about of more than a thousand chanels. So modulators have to be very tiny to be integrated in a single chip. The use of microcavities to made these modulators could be a suitable solution. What do you think about that?

  22. Dimo4ka says:

    Niice this will help make fast computers cheaper ans will help in communication technoligies and further our quest for better and more efficient technoligies.

  23. farhan says: name is farhan ahemd.i’m an electronics student and much interested in research about latset technology.would you please send me more detail of silicon photonics and other latest research technology.
    thank you,

  24. Anderson Liu says:

    You are the pride of the Chinese people! Hope we can see it in the market in the near feature.

  25. Wesley says:

    i’m 16 and in high school, but i have been working on an optical pc due to the faster speeds. this has potential, but will take years to be available commercially, and a fully optical pc would take a vast amount of power.

  26. Alfred says:

    Very good!!!
    The market is making the 100 Gbps polymer modulators, please check out Will the silicon modulator be able to match that in the future? If not, what are the major limiting factors?

  27. DR.R.C.CHHIPA says:

    Basically ,materials, their processing , concurrently invent new materials.Further metal alkoxides as precurssors to various advanced technological materials are responsible for that .New and more advancet technology can be developed by controlled material

  28. Fiber Optic Converter says:

    40G!!!!!!This is really amazing!!!! It is great to see all your hard work is paying off! Thanks for your contribution to the fiber optic laser industry.