FREE subscription
Subscribe for free to receive each issue of Semiconductor Today magazine and weekly news brief.
































22 January 2007


Innolume develops quantum-dot SOAs

Innolume GmbH of Santa Clara, CA, USA (formerly NL Semiconductor until changing its name last week) says it has developed GaAs-based semiconductor optical amplifiers (SOAs) for the 1.3 micron spectral range. Innolume’s proprietary quantum-dot (QD) technology platform has previously been used to develop mode-locked lasers, broadband lasers, and high-power lasers, for which it produces wafers and devices at NL’s former headquarters in Dortmund, Germany.

The SOA is a key building block in wavelength division multiplexing (WDM) communications networks - it boosts optical signals which have attenuated over long distances traveled through fiber. However, the current quantum-well based technology faces significant challenges in optimal operation at ultrahigh speeds (100Gb/s and beyond). The unique properties of quantum dots, such as extremely fast gain recovery, have long-since had the potential to enable optimal operation at ultrahigh speeds, but until now the basic parameters of QD-based SOAs, such as net gain and gain saturation, have remained lower compared to commercially available InP-based quantum-well SOAs, says Innolume.

Innolume’s 1.3 micron SOA is based on an AlGaAs/GaAs laminated structure grown on a GaAs substrate and incorporates a highly efficient an InAs/InGaAs quantum-dot active region. The SOA relies on tilted-stripe AR/AR ridge-waveguide design which ensures stable single-spatial-mode operation, reduced optical feedback and suppression of the spontaneous emission intensity. It is housed in a standard 14-pin butterfly package with two single-mode pigtails and integrated thermoelectric cooler.

Using the technology, Innolume says it has demonstrated a significant improvement in the operation of QD-based SOAs: fiber-to-fiber small-signal gain as high as 25 dB and saturation output power at -3dB in excess of 10 dBm.

“The discrete nature of electronic states in QDs provides the opportunity to accumulate a significant amount of charge carriers in the excited state while simultaneously keeping the ground state in the saturation regime,” says Dr Alexey Kovsh, Innolume’s chief technology officer Laser Technology. “In addition, QDs exhibit a relaxation time of only a few hundred femtoseconds ­ so these two properties together give us a strong expectation of patterning-free linear amplification of signals into the Terabit per second range. Furthermore, pronounced spectral hole burning, which is a unique property of QD devices, leads to significantly enhanced cross gain modulation, enabling effective wavelength conversion even at these ultra high speeds,” he adds.

“We have brought QD parameters for amplification and wavelength conversion for SOAs to a level sufficient to fully exploit in the coming generation of ultrahigh-speed communication networks,” claims Kovsh.

See related item:

NL adds silicon photonics capabilities and changes name to Innolume