Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Making the big step from electronics to photonics by modulating a beam of light with electricity

20.05.2005


Much of our electronics could soon be replaced by photonics, in which beams of light flitting through microscopic channels on a silicon chip replace electrons in wires. Photonic chips would carry more data, use less power and work smoothly with fiber-optic communications systems. The trick is to get electronics and photonics to talk to each other.Now Cornell University researchers have taken a major step forward in bridging this communication gap by developing a silicon device that allows an electrical signal to modulate a beam of light on a micrometer scale.


Cornell Nanophotonics Group - Scanning electron microscope image of the ring coupled to the waveguide with a zoom-in picture of the coupling region. Copyright © Cornell University


Cornell Nanophotonics Group - Schematic layout of the ring resonator based modulator. The inset shows a cross-section of the ring. Copyright © Cornell University



Other electro-optical modulators have been built on silicon, but their size is on the order of millimeters, too large for practical use in integrated circuit chips. (a micrometer, or micron, is one millionth of a meter, or one thousandth of a millimeter.) Smaller modulators have been made using compound semiconductors such as gallium arsenide, but silicon is preferable for its ability to be integrated with current microelectronics.

The work is described in a paper published in the May 19, 2005, issue of Nature by Michal Lipson, Cornell assistant professor of electrical and computer engineering, and her research group.


Their modulator uses a ring resonator -- a circular waveguide coupled to a straight waveguide carrying the beam of light to be modulated. Light traveling along the straight waveguide loops many times around the circle before proceeding. The diameter of the circle, an exact multiple of a particular wavelength, determines the wavelength of light permitted to pass. For the experiments reported in Nature, the ring used was 12 microns in diameter to resonate with laser light at a wavelength of 1,576 nanometers, in the near infrared.

The ring is surrounded by an outer ring of negatively doped silicon, and the region inside the ring is positively doped, making the waveguide itself the intrinsic region of a positive-intrinsic-negative (PIN) diode. When a voltage is applied across the junction, electrons and holes are injected into the waveguide, changing its refractive index and its resonant frequency so that it no longer passes light at the same wavelength. As a result, turning the voltage on switches the light beam off.

The PIN structure has been used previously to modulate light in silicon using straight waveguides. But because the change in refractive index that can be caused in silicon is quite small, a very long straight waveguide is needed. Since light travels many times around the ring resonator, the small change has a large effect, making it possible to build a very small device.

In tests, the researchers found that the device could completely interrupt the propagation of light with an applied voltage of less than 0.3 volts. The researchers note in their paper that devices using a PIN configuration have been relatively slow in switching but that the ring resonator configuration also eliminates this problem. Tests using a pulse-modulated electrical signal produced an output with a very similar waveform to the input at up to 1.5 gigabits per second.

The Nature paper is titled "Micrometer-scale Silicon Electro-Optic Modulator." Co-authors are Cornell graduate students Qianfan Xu and Bradley Schmidt and postdoctoral researcher Sameer Pradhan, now at Intel Corp.

Bill Steele | EurekAlert!
Further information:
http://www.cornell.edu

More articles from Power and Electrical Engineering:

nachricht Fraunhofer ISE Supports Market Development of Solar Thermal Power Plants in the MENA Region
21.02.2018 | Fraunhofer-Institut für Solare Energiesysteme ISE

nachricht New tech for commercial Lithium-ion batteries finds they can be charged 5 times fast
20.02.2018 | University of Warwick

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>