Since todays Internet traffic is more and more concentrated in hyperscale datacenters,1 new concepts for shortrange optical communication systems with high modulation bandwidth, high temperature stability, and low energy consumption are urgently needed. Birefringent spin-lasers, in particular spin-controlled vertical-cavity surface-emitting lasers (spin-VCSELs), are a novel type of ultrafast laser devices which promise to serve as ultrafast transmitters for the next generation of optical communication systems. While current-driven intensitymodulated VCSELs are state-of-the-art laser devices for short-range communication, their modulation bandwidth is limited to values below 40 GHz.2, 3 Recently, we were able to demonstrate that modulating carrier spin and light polarization in spin-VCSELs instead of carrier density and light intensity in conventional devices enables ultrafast polarization dynamics and a modulation bandwidth of more than 200 GHz.4 This high modulation bandwidth was achieved by increasing the resonance frequency of the coupled carrier spin-photon system by implementing high values of birefringence to the cavity of 850 nm GaAs/GaAlAs VCSELs. Here, we show experimental results for the intensity and polarization dynamics in highly birefringent spin-VCSELs as a function of bias current, birefringence, and temperature and demonstrate the capability of spin-VCSELs for ultralow energy consumption and high temperature stability. Furthermore, we present first results on polarization dynamics in 1.3 μm VCSELs for potential long-range communication systems and discuss novel concepts for future integrated and electrically pumped devices.
In this paper, we present the design and manufacturing of photonic-crystal long-wavelength VCSELs. They were
developed to provide a high-performance low-cost alternative to Fabry-Perot and DFB lasers for 2.5 Gbps applications
within the intermediate range access network. The paper covers photonic-crystal long-wavelength device design,
manufacturing process, DC and AC characteristics, as well as reliability studies. The addition of photonic-crystal
structures to the long-wavelength vertical-cavity surface-emitting lasers allows us to increase the oxide diameter. This
reduces the series resistance as well as the thermal resistance resulting in increased single-mode output-power and an
enhanced high-temperature performance of our devices.
We report on a new coherent phenomenon in semiconductor microcavities at polariton selective resonance excitation by two femtosecond pulses, propagating along k2 and k1, associated with exciton gratings, travelling in lateral direction ± (k2 - k1). Diffracted polaritons experience a frequency shift as observed in nondegenerate spectrally resolved transient four-wave mixing experiments.
The dynamics of excitonic transitions in semiconductors have been investigated by degenerate four-wave mixing experiments. We have studied the coherence, interference and dephasing of free, bound and localized excitons in bulk semiconductors and of quasi-2D excitons in quantum well structures. The influence of inhomogeneous broadening is investigated and compared with quantum interference in a continuum of states. The nature of four-wave mixing beats in a system of bound excitons and biexcitons is discussed.
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