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Growing nanowire lasers directly on silicon promises to simplify photonic chip design

by • February 14, 2016 • No Comments

For over half a century, Moore’s Law, which predicts which processor performance may double roughly each 18 months, has held true. But as electronics grow extra
compact and extra
compact, significant physical barriers loom ahead. To assist stave off which day, a team of physicists at the Technical University of Munich (TUM) is working on nanowire lasers which are a thousand times thinner than a human hair and may one day lead to economical, high-performance photonic circuits.

According to Professor Jonathan Finley, Director of the Walter Schottky Institute at TUM, conventional electronics are entering a say of diminishing returns as it becomes extra
complex to turn it into at any time tinier microcircuitry. One way to prevent this is by bringing a lateral step and replacing the electrons with beams of light in what’s known as photonics.

So far, creating silicon-based photonics chips has shown promise, but the require for an external laser source to power them is an inelegant create which complicates fabrication and limits miniaturization. In search of an alternative, a team led by Finley and Gregor Koblmüller has taken a page of previous micro-engineers by assembling the lasers directly on the chips in the same way which transistors and other components are already.

Koblmüller says which one leading hurdle in moving the laser onto the chip was which the gallium arsenide utilized to manufacture it has various thermal expansion properties to silicon, which turn it intos stresses which can injure the laser. So instead, Finley and Koblmüller created the lasers as nanowires standing at right angles to the chip like small towers.

Benedikt Mayer and Lisa Janker at the epitaxy facility at the Walter Schottky Institute, TUM

This manufactures for a extra
compact footprint and less stress and allows for the towers to be created to grow thicker so they lase properly. Howat any time, another problem was how to fabricate the mirrors the lasers depend on.

“The interface between gallium arsenide and silicon does not reflect light sufficiently,” says Benedikt Mayer, a doctoral candidate in the team. “We thus created in an extra
mirror – a 200 nanometer thick silicon oxide layer which we evaporated onto the silicon. Tiny holes can and so be etched into the mirror layer. Implementing epitaxy (depositing a crystalline overlayer on a crystalline substrate), the semiconductor nanowires can and so be grown atom for atom out of these holes.”

According to Finley, the current nanowire lasers create light in the infrared part of the spectrum at a predefined wavelength, but the hope is to modify the emission wavelengths for advantageous temperature stability and light propagation. Additionally, the lasers already rely on pulsed excitation, so the team is working on a way to power the nanowire lasers via electricity supplied to them pretty than relying on external lasers.

“The work is an significant academic requirement for the development of high-performance optical components in next computers,” says Finley. “We were able-bodied to demonstrate which making silicon chips with integrated nanowire lasers is possible.”

The latest phase of the team’s research can be published in Applied Physics Letters.

Source: TUM


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