K.A. Williams

158-microJ pulses from a single-transverse-mode, large-mode-area erbium-doped fiber amplifier.

We report the amplification of 10-100-pJ semiconductor diode pulses to an energy of 158 microJ and peak powers >100 kW in a multistage fiber amplifier chain based on a single-mode, large-mode-area erbium-doped amplifier design. To our knowledge these results represent the highest single-mode pulse energy extracted from any doped-fiber system.

Long-wavelength monolithic mode-locked diode lasers

A detailed study of the design issues relevant to long-wavelength monolithic mode-locked lasers is presented. Following a detailed review of the field, we have devised a validated travelling wave model to explore the limits of mode-locking in monolithic laser diodes, not only in terms of pulse duration and repetition rate, but also in terms of stability. It is shown that fast absorber recovery is crucial for short pulse width, that the ratio of gain to absorption saturation is key in accessing ultrashort pulses and that low alpha factors give only modest benefit. Finally, optimized contact layouts are shown to greatly enhance pulse stability and the overall operational success. The design rules show high levels of consistency with published experimental data.

Integrated optical 2 /spl times/ 2 switch for wavelength multiplexed interconnects

A highly compact integrated optical switch is proposed and demonstrated for broadband optical switching applications. Routing of 8 /spl times/ 10 Gb/s data channels is demonstrated using a low-cost 1250-Mb/s control scheme. The advantages of lossless operation, broad optical bandwidth, and nanosecond switching times are leveraged. Multichannel wavelength is exploited for reduced latency, enhanced capacity, and functionality, while retaining compatibility with existing off-the-shelf electronics and transceiver technology. The requirements for optical header processing, wavelength translation, and optical buffering are avoided. Low-penalty multiwavelength transmission is demonstrated for a highly compact sub-mm/sup 2/ amplifying 2 /spl times/ 2 switch. Pattern dependent gain and amplified spontaneous emission are minimized to facilitate 0.0-0.4 dB penalty. Mitigation techniques compatible with the architecture are deployed to reduce the penalty under adverse operating conditions. Control schemes are proposed and demonstrated to facilitate 8 /spl times/ 10 Gb/s optically switched networking.

Design of high-brightness tapered laser arrays

The design of a high-power low-divergence low-astigmatism tapered-waveguide laser array is described. A two-dimensional beam propagation model is used for the first time to optimize a tapered-waveguide laser, which includes full thermal and spatiotemporal descriptions to allow detailed assessment of the major waveguiding effects on the output beam. This allows limits to the far-field performance to be addressed and compared with experimental data.

Fabrication-tolerant active-passive integration scheme for vertically coupled microring resonator

The large-scale photonic integration of microring resonators in three dimensions made possible by recent developments in vertical coupling and wafer bonding technology is shown to be sensitive to lateral mask misalignment for the ring and bus waveguides introduced during the fabrication process. For a typical 20-/spl mu/m radius, vertically coupled microring calculations reveal a linear relationship between deviation in the coupling coefficient and lateral misalignment. A coupling coefficient reduction of 50% is predicted for a lateral misalignment of 0.3 /spl mu/m, which is typical for an alignment accuracy limited by the current state-of-the-art mask alignment process. The use of a wide multimode bus waveguide is proposed to ameliorate this alignment sensitivity. The mode-expanded bus waveguide, together with its physically wider structure, reduces the dependence of modal overlap and coupling length on precise alignment, resulting in significantly relaxed fabrication tolerance. Deviation of coupling coefficient decreases by an order of magnitude for the new ring coupler geometry, where a sole reduction of 5% is obtained for the same amount of misalignment. The implications of the proposed structure are subsequently investigated for microring laser performance. The differential slope efficiency is shown to be at least five times less sensitive to lateral misalignment for the proposed structure within a small misalignment regime. This readily adaptable coupler geometry based on existing vertical coupling architectures is transferable to any fabrication scheme with multiple waveguide layers coupled vertically, and is of particular importance to microring resonators with small radii.

Performance and scalability of a single-stage SOA switch for 10/spl times/10 gb/s wavelength striped packet routing

This letter reports successful routing of 10/spl times/10 Gb/s multiwavelength optical packets using single-stage semiconductor optical amplifier switches. Performance under switching is assessed with up to ten wavelengths with particular emphasis being placed on the limit of operation. A 15.2-dB power margin is demonstrated which allows at least eight port connections with a commercially available 0-dBm output 10-Gb/s transmitter and -21-dBm sensitivity receiver.

SWIFT: a testbed with optically switched data paths for computing applications

This paper reports the implementation of SWIFT, designed to enable testing of novel network architecture for optical interconnects, optical devices, and real world applications. We describe the design and implementation of the testbed using semisynchronous timing and multiple wavelength striping.

Self-configuring intelligent control for short reach 100Gb/s optical packet routing

An advanced control architecture is proposed which recognizes and configures new connections, automatically performs calibration and initiates the routing of 100 Gb/s data packets. The scheme is proposed for high capacity, low overhead, short reach networking.

Optical Local Area Networking Using CWDM

This paper describes the current status of Coarse Wavelength Division Multiplexing (CWDM), and then progresses to discuss how it may evolve in networking applications in the future. As WDM can enhance not only transmission but also networking systems, the paper reports a potentially low cost WDM based access node architecture, particularly suited for routing optical data packets on nanosecond timescales. The scheme is cascadable and involves the use of a simple semiconductor optical amplifier (SAO) based add-drop switch. Preliminary results concerning the operation of the add-drop switches under multi-wavelength operation are reported.

Gain-switched dynamics of tapered waveguide bow-tie lasers: experiment and theory

A large signal dynamic beam propagation model has been developed to describe the gain-switched operation of GaAs-AlGaAs double tapered waveguide bow-tie laser diodes. Good agreement is demonstrated between experiment and theory, highlighting the role of nonuniform carrier depletion and transverse mode spatial hole-burning in limiting peak pulse powers on picosecond time scales.