The dynamic properties of ground- and excited-state emission in InAs/GaAs quantum-dot lasers operating close to 1.31 μm are studied systematically. Under low bias conditions, such devices emit on the ground state, and switch to emission from the excited state under large drive currents. Modification of one facet reflectivity by deposition of a dichroic mirror yields emission at one of the two quantum-dot states under all bias conditions and enables to properly compare the dynamic properties of lasing from the two different initial states. The larger differential gain of the excited state, which follows from its larger degeneracy, as well as its somewhat smaller nonlinear gain compression results in largely improved modulation capabilities. We demonstrate maximum small-signal bandwidths of 10.51 GHz and 16.25 GHz for the ground and excited state, respectively, and correspondingly, large-signal digital modulation capabilities of 15 Gb/s and 22.5 Gb/s. For the excited state, the maximum error-free bit rate is 25 Gb/s.

Recently a novel photonic integration technology, based on a thin InP-based membrane, is emerging. This technology offers monolithic integration of active and passive functions in a sub-micron thick membrane. The enhanced optical confinement in the membrane results in ultracompact active and passive devices. The membrane also enables approaches to converge with electronics. It has shown high potential in breaking the speed, energy and density bottlenecks in conventional photonic integration technologies. This paper explains the concept of the InP membrane, discusses the versatility of various technology approaches and reviews the recent advancement in this field.

Intimate integration of photonics with electronics is regarded as the key to further improvement in bandwidth, speed and energy efficiency of information transport systems. Here, a method based on wafer-scale polymer bonding is reviewed which is compatible with foundry-sourced high-performance InP photonics and BiCMOS electronics. We address challenges with respect to circuit architecture, co-simulation framework and interconnect technology and introduce our approach that can lead to broadband high-density interconnects between photonics and electronics. Recent proof-of-concept work utilizing DC-coupled driver connections to modulators, which significantly reduces the interconnect complexity, is summarized. Furthermore, cosimulation concepts based on equivalent circuit models are discussed with emphasis on the importance of impedance matching between driver and modulator. Finally, realizations of broadband interconnects and functional photonic building blocks after wafer bonding are highlighted to demonstrate the potential of this wafer-scale co-integration method.

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The intimate integration of photonics and electronics in transceivers facilitates energyefficiency, bandwidth acceleration and a route to radical miniaturization. We present and implement a wafer-to-wafer integration method which combines electronic and photonic foundry technologies.