Robust free space board-to-board optical interconnect with closed loop MEMS tracking

We present a free-space optical interconnect system capable of dynamic closed-loop optical alignment using a microlens scanner with a proportional integral and derivative controller. Electrostatic microlens scanners based on combdrive actuators are designed and characterized with vertical cavity surface emitting lasers (VCSELs) for adaptive optical beam tracking in the midst of mechanical vibration noise. The microlens scanners are fabricated on silicon-on-insulator wafers with a bulk micromachining process using deep reactive ion etching. We demonstrate dynamic optical beam positioning with a 700 Hz bandwidth and a maximum noise reduction of approximately 40 dB. Eye diagrams with a 1 Gb/s modulation rate are presented to demonstrate the improved optical link in the presence of mechanical noise

Integrated receiver architectures for board-to-board free-space optical interconnects

In many computer and server communications copper cables and wires are currently being used for data transmission and interconnects. However, due to significant shortcomings, such as long transmission time, high noise level, unstable electrical properties, and high power consumption for cooling, researchers are increasingly turning their research interests toward alternatives, such as fiber optic interconnects and free-space optical communication technologies. In this paper, we present design considerations for an integrated receiver for high-speed free-space line-of-sight optical interconnects for distortion-free data transmission in an environment with mechanical vibrations and air turbulences. The receiver consists of an array of high-speed photodiodes for data communication and an array of quadrant photodiodes for real-time beam tracking in order to compensate for the beam misalignment caused by vibrations in servers. Different configurations for spatially positioning the quadrant and data photodiodes are discussed for 4×4 and 9×9 multielement optical detector arrays. We also introduce a new beam tracking device, termed the strip quadrant photodiodes, in order to accurately track highly focused optical beams with very small beam diameter

Integrated receiver architectures for board-to-board free-space optical interconnects

In many computer and server communications copper cables and wires are currently being used for data transmission and interconnects. However, due to significant shortcomings, such as long transmission time, high noise level, unstable electrical properties, and high power consumption for cooling, researchers are increasingly turning their research interests toward alternatives, such as fiber optic interconnects and free-space optical communication technologies. In this paper, we present design considerations for an integrated receiver for high-speed free-space line-of-sight optical interconnects for distortion-free data transmission in an environment with mechanical vibrations and air turbulences. The receiver consists of an array of high-speed photodiodes for data communication and an array of quadrant photodiodes for real-time beam tracking in order to compensate for the beam misalignment caused by vibrations in servers. Different configurations for spatially positioning the quadrant and data photodiodes are discussed for 4×4 and 9×9 multielement optical detector arrays. We also introduce a new beam tracking device, termed the strip quadrant photodiodes, in order to accurately track highly focused optical beams with very small beam diameter

Ensembles of indium phosphide nanowires: physical properties and functional devices integrated on non-single crystal platforms

A new route to grow an ensemble of indium phosphide single-crystal semiconductor nanowires is described. Unlike conventional epitaxial growth of single-crystal semiconductor films, the proposed route for growing semiconductor nanowires does not require a single-crystal semiconductor substrate. In the proposed route, instead of using single-crystal semiconductor substrates that are characterized by their long-range atomic ordering, a template layer that possesses short-range atomic ordering prepared on a non-single-crystal substrate is employed. On the template layer, epitaxial information associated with its short-range atomic ordering is available within an area that is comparable to that of a nanowire root. Thus the template layer locally provides epitaxial information required for the growth of semiconductor nanowires. In the particular demonstration described in this paper, hydrogenated silicon was used as a template layer for epitaxial growth of indium phosphide nanowires. The indium phosphide nanowires grown on the hydrogenerated silicon template layer were found to be single crystal and optically active. Simple photoconductors and pin-diodes were fabricated and tested with the view towards various optoelectronic device applications where group III–V compound semiconductors are functionally integrated onto non-single-crystal platforms

Ensembles of indium phosphide nanowires: physical properties and functional devices integrated on non-single crystal platforms

A new route to grow an ensemble of indium phosphide single-crystal semiconductor nanowires is described. Unlike conventional epitaxial growth of single-crystal semiconductor films, the proposed route for growing semiconductor nanowires does not require a single-crystal semiconductor substrate. In the proposed route, instead of using single-crystal semiconductor substrates that are characterized by their long-range atomic ordering, a template layer that possesses short-range atomic ordering prepared on a non-single-crystal substrate is employed. On the template layer, epitaxial information associated with its short-range atomic ordering is available within an area that is comparable to that of a nanowire root. Thus the template layer locally provides epitaxial information required for the growth of semiconductor nanowires. In the particular demonstration described in this paper, hydrogenated silicon was used as a template layer for epitaxial growth of indium phosphide nanowires. The indium phosphide nanowires grown on the hydrogenerated silicon template layer were found to be single crystal and optically active. Simple photoconductors and pin-diodes were fabricated and tested with the view towards various optoelectronic device applications where group III–V compound semiconductors are functionally integrated onto non-single-crystal platforms