A silicon chip with integrated laser and optical grating offers new possibilities for telecommunications

Aug 09, 2011 By Lee Swee Heng
Bright prospects
An ark-shaped diffraction grating is used to selectively reflect light from a laser back into the device. The photo also shows the waveguides used to channel light back and forth. Credit: A*STAR Research

(PhysOrg.com) -- Silicon is an ideal platform for integrated photonic circuits because the material is cheap and readily available. Silicon chips with an integrated laser source capable of emitting light at a specific wavelength are particularly useful in telecommunications. Unfortunately, silicon is a material with high optical loss, which often degrades the output power and performance of the laser source.

Yongqiang Wei at the A*STAR Data Storage Institute and co-workers have now fabricated a silicon chip that integrates not only a , but also an optical grating that provides optical gain and ensures that the laser outputs light at wavelengths near 1,550 nm—the standard operating for devices.

The transmission of large amounts of data through an optical fiber is based on laser beams of different wavelengths that are sent through the fiber all at the same time. For such multi-channel operation, however, the lasers need to be tuned to precise wavelengths to avoid cross-talk. This can be achieved with an optical grating.

So far, integrating a laser and an optical grating into a silicon chip has been challenging. The laser is typically made from several thin layers of different semiconductor materials, while the optical grating itself is etched out of silicon. Everything has to be precisely aligned, and the conventional way to achieve this is to grow the laser on a separate semiconductor chip. “The whole process takes more than 50 steps and requires the surface roughness of the silicon wafer to be extremely low, less than 0.3 nanometers,” says Wei.

In the new device, a light source is placed between a mirror and a curved optical grating (pictured). The grating acts like a selective mirror that only reflects light at a specific wavelength back into the laser. This creates an optical cavity that only allows lasing action at a specific wavelength, providing the precision necessary for telecommunications applications. The researchers tested their device and found that it has good performance, emitting light with optical power of 2.3 milliwatts—about the same power as a laser pointer—at a highly specific wavelength.

“The integration of multiple lasers and optical gratings on a single chip will be our next challenge,” says Wei. “Also, for practical applications, we plan to scale up our single-wavelength lasers by utilizing the same grating structure for a broader range of wavelengths in order to integrate multiple sources on the chip.” The new device marks a major step toward the realization of commercial telecommunications devices integrated on a single .

Explore further: 'Dressed' laser aimed at clouds may be key to inducing rain, lightning

More information: Wang, Y. et al. Silicon/III-V laser with super-compact diffraction grating for WDM applications in electronic-photonic integrated circuits. Optics Express 19, 2006–2013 (2011). doi:10.1364/OE.19.002006

Related Stories

New architecture for optical fiber networks proposed

Feb 24, 2011

The household demand for increased internet bandwidth has grown tremendously because of the popularity of data-intensive internet activities such as movie streaming. Conventional copper telephone lines struggle ...

Optical Atomic Clock: A long look at the captured atoms

Feb 05, 2008

Optical clocks might become the atomic clocks of the future. Their "pendulum", i.e. the regular oscillation process which each clock needs, is an oscillation in the range of the visible light. As its frequency is higher than ...

Tiny spectrometer offers precision laser calibration

May 11, 2007

A tiny device for calibrating or stabilizing precision lasers has been designed and demonstrated at the National Institute of Standards and Technology. The prototype device could replace table-top-sized instruments ...

Recommended for you

Robotics goes micro-scale

Apr 17, 2014

(Phys.org) —The development of light-driven 'micro-robots' that can autonomously investigate and manipulate the nano-scale environment in a microscope comes a step closer, thanks to new research from the ...

High power laser sources at exotic wavelengths

Apr 14, 2014

High power laser sources at exotic wavelengths may be a step closer as researchers in China report a fibre optic parametric oscillator with record breaking efficiency. The research team believe this could ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

windjammer
not rated yet Aug 13, 2011
You produce that at a reasonable cost and add WDM and mulitple colors and you have one excellent backplane or a compute system.

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...