Andrew G. Kirk

Enhanced SPR sensitivity using periodic metallic structures

A sinusoidal silver grating is used to create a six-fold enhancement of the SPR response compared to a flat surface. The grating parameters are chosen to create a surface plasmon bandgap and it is shown that the enhancement of the sensitivity to bulk sample index occurs when operating near the bandgap. The Kretschmann configuration is considered and the Boundary Element Method is used to generate the dispersion curves.

256-channel bidirectional optical interconnect using VCSELs and photodiodes on CMOS

Two-dimensional parallel optical interconnects (2-D-POIs) are capable of providing large connectivity between elements in computing and switching systems. Using this technology we have demonstrated a bidirectional optical interconnect between two printed circuit boards containing optoelectronic (OE) very large scale integration (VLSI) circuits. The OE-VLSI circuits were constructed using vertical cavity surface emitting lasers (VCSELs) and photodiodes (PDs) flip-chip bump-bonded to a 0.35-/spl mu/m complementary metal-oxide-semiconductor (CMOS) chip. The CMOS was comprised of 256 laser driver circuits, 256 receiver circuits, and the corresponding buffering and control circuits required to operate the large transceiver array. This is the first system, to our knowledge, to send bidirectional data optically between OE-VLSI chips that have both VCSELs and photodiodes cointegrated on the same substrate.

Optical interconnects at the chip and board level: challenges and solutions

This paper discusses short-distance optical interconnects for general-purpose distributed digital systems. We describe the technology required to optically interconnect elements that are distributed across multiple packaging layers. This includes chips on a board, boards in a backplane, and shelves within a bay. The focus of this paper will be on technology capable of supporting high-data-rate, two-dimensional, optical communication using two-dimensional parallel optical interconnects.

Enhanced SPR response from patterned immobilization of surface bioreceptors on nano-gratings

In this report, nano-gratings with guided adsorption of biomolecules are investigated as new transducer elements or biointerfaces for surface plasmon resonance biosensor technologies. SPR biosensors are of particular interest due to the interaction between the electromagnetic fields and periodic nano-structures. In this article, sensitivity enhancement is demonstrated for a surface plasmon resonance interface, in a Kretschmanns configuration, featuring nano-gratings combined with nano-patterned immobilization of surface bioreceptors. The fabrication of this enhanced biointerface is demonstrated using a combination of metal lift-off and self-assembled monolayers. Rigorous coupled-wave analyses point to an increase in SPR angular response for the immobilization of surface bioreceptors onto areas of the nano-corrugated surface exhibiting high electromagnetic field intensity. Experimental measurements of the immobilization of anti-TNF-alpha antibody as a model bioreceptor using an imaging-SPR technique show a 3 times increase in angular resonance response from nano-grating surfaces with functionalized mesas compared to a planar surface or to a uniformly functionalized nano-grating surface. Furthermore, results also show an increased detection of TNF-alpha due to the increased accessibility to the adsorbed bioreceptors on the nano-gratings.

Interconnection of a two-dimensional array of vertical-cavity surface-emitting lasers to a receiver array by means of a fiber image guide

The implementation of a 10-channel parallel optical interconnect consisting of a two-dimensional array of vertical-cavity surface-emitting lasers, a 1.35-m fiber image guide, and a metal-semiconductor-metal receiver array is described. Transmission rates of 250 Mbits/s per channel are demonstrated with an optical cross talk of less than -27 dB and a loss of -3 dB. Coupling issues associated with image guides are analyzed and discussed.

512-channel vertical-cavity surface-emitting laser based free-space optical link

A vertical-cavity surface-emitting laser based bidirectional free-space optical interconnect has been implemented to interconnect two printed circuit boards. A total of 512 clustered channels with a density of 2844 channels/cm2 are transmitted over a distance of 83 mm. The optical interconnect is a combination of refractive microlenses and diffractive minilens relays.

Single rolled-up InGaAs/GaAs quantum dot microtubes integrated with silicon-on-insulator waveguides.

We report on single rolled-up microtubes integrated with silicon-on-insulator waveguides. Microtubes with diameters of ~7 μm, wall thicknesses of ~250 nm, and lengths greater than 100 μm are fabricated by selectively releasing a coherently strained InGaAs/GaAs quantum dot layer from the handling GaAs substrate. The microtubes are then transferred from their host substrate to silicon-on-insulator waveguides by an optical fiber abrupt taper. The Q-factor of the waveguide coupled microtube is measured to be 1.5×10(5), the highest recorded for a semiconductor microtube cavity to date. The insertion loss and extinction ratio of the microtube are 1 dB and 34 dB respectively. By pumping the microtube with a 635 nm laser, the resonance wavelength is shifted by 0.7 nm. The integration of InGaAs/GaAs microtubes with silicon-on-insulator waveguides provides a simple, low loss, high extinction passive filter solution in the C+L band communication regime.

Free-space optical link with spatial redundancy for misalignment tolerance

Free-space optical interconnects can provide high bandwidth with no physical contact, but suffer from poor tolerances to misalignment. In order to obtain high misalignment tolerances, we propose the use of an active alignment scheme in conjunction with an optimized optical design. The active alignment scheme uses a redundant set of optical links and the active selection of the best link. The optical design maximizes the alignment tolerances between the two boards to /spl plusmn/1 mm of lateral and /spl plusmn/1/spl deg/ of angular misalignment for a target data rate of 1.25 Gb/s.

Design rules for highly parallel free-Space optical interconnects

Recently, a number of successful free-space chip-to-chip and board-to-board optical interconnects have been demonstrated. Here, we present some of the design rules that can be derived as a result of this work and also as a result of numerical and theoretical analyzes. We draw a number of conclusions. In the area of optoelectronic very large scale integration (VLSI) design, we suggest that differential electrical and optical transceiver designs provide the best performance. In the area of optical design, we present scaling and system partitioning laws for clustered optical relays and determine the interconnect distances at which microlens or macrolens systems are more suitable. We also show that the ease with which two modules can be aligned can be related to the optical invariant of the system and is, thus, a function of the size of the detector and the numerical aperture of the detector optics. Finally, we show that when multiple optical components must be aligned, very high individual component tolerances are required if the system as a whole is to have a high chance of success.

Beam analysis by fractional Fourier transform

A method of spatial modal decomposition for optical beams by fractional Fourier transform, and its practical implementation with reduced complexity by use of modal interleavers, are discussed.