Daniel Van Blerkom

Digital free-space optical interconnections: a comparison of transmitter technologies

We investigate the performance of free-space optical interconnection systems at the technology level. Specifically, three optical transmitter technologies, lead-lanthanum-zirconate-titanate and multiple-quantum-well modulators and vertical-cavity surface-emitting lasers, are evaluated. System performance is measured in terms of the achievable areal data throughput and the energy required per transmitted bit. It is shown that lead-lanthanum-zirconate-titanate modulator and vertical-cavity surface-emitting laser technologies are well suited for applications in which a large fan-out per transmitter is required but the total number of transmitters is relatively small. Multiple-quantum-well modulators, however, are good candidates for applications in which many transmitters with a limited fan-out are needed.

Small-signal-equivalent circuits for a semiconductor laser.

Passive electrical circuits whose voltage and current equations are exactly equivalent to the small-signal rate equations of a semiconductor laser are derived to model an electrically modulated laser (verified to be the same as that given in the literature), an optically modulated laser (i.e., a laser used as an optical amplifier), and a multimode laser. These circuits offer a fast and efficient simulation tool with little computational complexity in which the small-signal assumption (i.e., small modulation range) is neither violated nor insufficient for the simulation.

Heterogeneous integration of optoelectronic components

The heterogeneous integration of optoelectronic, electronic, and micro-mechanical components from different origins and substrates makes possible many advanced systems in diverse applications. Besides the monolithic integration approach, which is the basis for the success of todays silicon industry, various hybrid integration technologies have been explored. These include flip-chip bonding, micro-robotic placement, epitaxial lift-off and direct bonding, substrate removal and bonding, and several self-assembly methods. In this paper, we describe the results of our monolithic integration effort involving a 2 by 2 optoelectronic switching circuit and an 8 by 8 active-pixel sensor array on GaAs substrates, and a 16 by 16 spatial light modulator array produced by flip-chip bonding of III-V multi-quantum-well (MQW) modulators and silicon driver circuits. We also present our preliminary experimental results on the self-assembly of small inorganic devices coated with DNA polymers with self- recognition properties.

Free-Space Optical Interconnection: A Technology Comparison of Vertical-Cavity Surface-Emitting Lasers and Multiple-Quantum-Well Modulators

We evaluate current vertical-cavity surface-emitting laser (VCSEL) and multiple-quantum-well (MQW) modulator technologies for low-fanout system applications. Si-CMOS transimpedance receiver circuits are used in the comparison. The aggregate bandwidth per unit area is calculated from the bandwidth and the total on-chip power dissipation. The results indicate that the electrical power dissipation in the receiver circuits dominates at low operating frequencies. At high operating frequencies the receiver gain drops significantly, thus more electrical power is dissipated in the transmitter to provide more optical power to the receiver to satisfy the voltage requirement at the receiver output. In VCSEL based systems, the optical power is generated entirely on-chip. Thus, only VCSELs with low threshold current and low series resistance would be able to provide the same aggregate bandwidth as the MQW modulator based systems.