Nonlinear Dynamics in Semiconductor Lasers - Abstract
Bimberg, Dieter
The rapidly growing demand for higher data rates e.g. in optical access networks, backplane, memory/CPU or chip to chip interconnects requires novel ultra-high bit rate sources and amplifiers, which are more energy efficient per bit than anything presently existing. Otherwise in a few decades our raw electricity production will be completely consumed by communication systems. Quantum dot (QD) based photonic devices are not only promising but deployed now for networks at 1.3?µm wavelength. Mode-locked QD-lasers used as optical comb generators operating in the 5?160 GHz range for high frequency applications in future beyond 100 G Ethernet systems benefit from the low alpha factor, the linearity of the pulse chirp and the broad spontaneous emission spectrum of the QD gain medium. Pulse widths down to 0.7?ps and frequency multiplexed operation up to 160 Gbit/sec were demonstrated. Semiconductor optical amplifiers (SOAs) are essential for access networks. QD-SOAs at 1.3?µm show ultrafast gain dynamics and pattern effect free amplification both theoretically and experimentally. QD-based SOAs for wavelength conversion at 40 Gbit/s and beyond are much superior to standard QW-SOAs. Conversion at 50 Gbit/s has been demonstrated. InGaAs/GaAs-based VCSELs are enabling devices for short distance interconnects at wavelengths between 850 and 1300 nm. InGaAs quantum wells and/or stacked ?submonolayer growth quantum dots? (SML-QDs) are used as active medium in these VCSELs. SML-QD based VCSELs exhibit an excellent temperature stability, which is one requirement to avoid gain saturation under strong electrical pumping for high photon densities and high bandwidth operation. The devices emitting at 980 nm show open eyes for 38?Gbit/s up to 85 °C and 49 Gbit/s operation at -14°C [3]. At 850 nm we demonstrated open eyes with good S/N ratio up to 40 Gbit/s. Such lasers show now a record low power dissipation of 59 fJ/bit at 25 Gbit/s at 25 Gbit/s.This number is equivalent to 59 mW/Tbit and thus below the magical limit of 100 mW/Tbit required by the ITRS roadmap for 2015. Electro-optical resonance modulation of VCSELs with a monolithically integrated electro-optical modulator allow intrinsic modulation bandwidth beyond 50 GHz and might allow datacom beyond 100 Gbit/s with one single device with still increased energy efficiency. Chip to chip and on-chip interconnects are in need of emitters or transceivers integrated with the Si chip, with much reduced surface as compared to present VCSELs. Metal clad vertical cavity surface emitting lasers (MCVCSELs) on Si have the requested unique features and advantages not found for conventional VCSELs. Such devices show CW room-temperature single-mode operation beyond 10 µW.Their size can be scaled down to a few hundred nm, which will allow large scale integration of 104 of them on Si for 100 Tbit/s interconnects.