Rm Osgood

Fast and low-power thermooptic switch on thin silicon-on-insulator

We have designed and fabricated Mach-Zehnder interferometer thermooptic switches using a wafer-bonded thin-silicon-on-insulator materials system. The thermally switched devices use single-mode strip waveguides with dimensions 0.26/spl times/0.6 /spl mu/m/sup 2/, operating at a wavelength of /spl lambda/=1.55 /spl mu/m. Useful device characteristics include a low switching power, 50 mW, and a fast rise time of <3.5 /spl mu/s. These results demonstrate the potential of this high-index-contrast materials system for the design of fast and low-power thermooptic switches and as an active element in photonic integrated circuits.

Self-phase-modulation in submicron silicon-on-insulator photonic wires

We measure the transmission of ps-pulses through silicon-on-insulator submicron waveguides for excitation wavelengths between 1400 and 1650 nm and peak powers covering four orders of magnitude. Self-phase-modulation induced spectral broadening is found to be significant at coupled peak powers of even a few tens of mW. The nonlinear-index coefficient, extracted from the experimental data, is estimated as n(2) ~ 5*10(-18) m(2)/W at 1500 nm. The experimental results show good agreement with model calculations that take into account nonlinear phase shift, first- and second order dispersion, mode confinement, frequency dispersion of n(2), and dynamics of two-photon-absorption-generated free carriers. Comparison with theory indicates that an observed twofold increase of spectral broadening between 1400 and 1650 nm can be assigned to the dispersion of n(2) as well as first order- rather than second-order dispersion effects. The analysis of pulse broadening, spectral shift and transmission saturation allows estimating a power threshold for nonlinearity-induced signal impairment in nanophotonic devices.

Ultrahigh-Bandwidth Silicon Photonic Nanowire Waveguides for On-Chip Networks

An investigation of signal integrity in silicon photonic nanowire waveguides is performed for wavelength-division-multiplexed optical signals. First, we demonstrate the feasibility of ultrahigh-bandwidth integrated photonic networks by transmitting a 1.28-Tb/s data stream (32 wavelengths times 40-Gb/s) through a 5-cm-long silicon wire. Next, the crosstalk induced in the highly confined waveguide is evaluated, while varying the number of wavelength channels, with bit-error-rate measurements at 10 Gb/s per channel. The power penalty of a 24-channel signal is 3.3 dB, while the power penalty of a single-channel signal is 0.6 dB. Finally, single-channel power penalty measurements are taken over a wide range of input powers and indicate negligible change for launch powers of up to 7 dBm.

Observation of zeroth-order band gaps in negative-refraction photonic crystal superlattices at near-infrared frequencies.

We present the first observations of zero-n bandgaps in photonic crystal superlattices consisting of alternating stacks of negative index photonic crystals and positive index dielectric materials in the near-infrared. Guided by ab initio three-dimensional numerical simulations, the fabricated nanostructured superlattices demonstrate the presence of zero-order gaps in remarkable agreement with theoretical predictions across a range of different superlattice periods and unit cell variations. These volume-averaged zero-index superlattice structures present a new type of photonic band gap, with potential for complete wavefront control for arbitrary phase delay lines and open cavity resonances.

Dynamics of dual-frequency solitons under the influence of frequency-sliding filters, third-order dispersion, and intrapulse Raman scattering

We analyze the structure of the optical field emerging from a superposition of two soliton-like pulses with different frequencies and arbitrary phase-shift between them, and show that the optical output contains either symmetric or antisymmetric two-soliton states. Furthermore, we study numerically the dynamics of these emerging two-soliton states under the influence of perturbative effects that are important for optical communications systems: frequency-sliding filters, third-order dispersion, and intrapulse Raman scattering.

Spontaneous Raman scattering in a silicon wire waveguide

We report spontaneous Raman scattering at 1550nm in an SOI strip waveguide with cross-sectional area 0.1µm2. The tight optical confinement permits efficient Raman conversion for small coupled pump powers (1435nm) of <50mW.

Semidiscrete solitons in arrayed waveguide structures with Kerr nonlinearity

We construct families of optical semidiscrete composite solitons (SDCSs), with one or two independent propagation constants, supported by a planar slab waveguide, cross-phase-modulation coupled to a periodic array of stripes. Both structures feature the cubic nonlinearity and support intrinsic modes with mutually orthogonal polarizations. We report three species of SDCSs, odd, even, and twisted ones, the first type being stable. Transverse motion of phase-tilted solitons, with potential applications to beam steering, is considered also.

Dispersion Engineering in Silicon Photonic Wires Using Thin Si 3 N 4 Conformal Dielectric Coating

We investigate numerically dispersion engineering in silicon photonic wires using conformal Si3N4coatings. We analyze the impact of coating thickness upon the group-velocity-dispersion and effective waveguide nonlinearity, and show broadband four-wave-mixing gain in engineered waveguides.

Novel optical and thermal modeling for modelocked VCSELs

We develop a new approach based on the finite-difference time-domain (FDTD) method for simulating dynamics of modelocked VCSELs. Our FDTD model, transcends the limitation of a widely used traveling-wave technique, and can be used to determine both the sub-wavelength spatial features of the optical field, as well as its temporal dynamics on a sub-cycle time-scale. The thermal effects are included through coupled lattice and plasma temperature equations. The material response is incorporated via the effective Bloch equations. A VCSEL with gain and saturable absorber is simulated and stable modelocking obtained. Fine features of the pulses spatial profile are also studied.