David Lee Weidman

Nonlinear optical susceptibilities of high‐index glasses

We report results of degenerate four‐wave mixing measurements of nonresonant nonlinearities in a variety of high‐index lead and bismuth containing oxide glasses and the chalcogenide As2S3. The third‐order nonlinear susceptibilities of the oxide glasses are found to scale with the heavy metal content. A lead‐bismuth‐gallate glass was identified with a nonresonant χ3 equal to 42±7×10−14 esu, which is approximately three times larger than that of any glass previously reported.

Enhanced-nonlinearity single-mode lead silicate optical fiber.

A single-mode lead silicate optical fiber has been fabricated to permit lower-power all-optical switching. The core glass has a nonlinear index of refraction eight times that of silica. The loss of the fiber is less than 2 dB/m. Over 177pi of phase shift was obtained, as measured by self-phase modulation, in a 29-cm length of fiber. At the 1-kW peak power level required to produce this large phase shift, two-photon absorption and stimulated Raman scattering did not significantly degrade the desired nonlinear behavior.

Synchronization of passively mode-locked erbium-doped fiber lasers and its application to optical communication networks

We synchronized two passively mode-locked erbium-doped fiber lasers using a phase lock loop with a large dynamic range and bandwidth, which is realized by using a novel acoustooptic-modulator-grating scheme. Cross-correlation of the two lasers shows the interlaser jitter is under 2 ps (same as the laser pulse width) for period as long as hours. To prove the quality of phase locking, we apply synchronized lasers in two all-optical network applications, one of which requires the lasers to have the same wavelength and the second requires the lasers to be at different wavelengths. In the single wavelength application, the synchronized lasers drive a cascade of two low-birefringence, polarization maintaining, optical logic gates with switching timing window of 4 and 5 ps, respectively. We obtain nonlinear transmission of /spl sim/50% at a switching energy of 8 pJ and contrast ratio of 16 dB, which are comparable performance as that obtained using a single laser. In the different wavelength application, we use 0.8 ps pulses to switch 2 ps pulses in a two-wavelength nonlinear optical loop mirror demultiplexer with timing window of 5.5 ps. Stable switching is reached at a efficiency as high as 90% at switching energy of 0.8 pJ, and a contrast ratio of 20 dB. Excellent agreement is found between the experimental data and the simulated results, which exclude the timing jitter.

Resonant ring fiber filters

We have studied structures where a concentric ring with an index higher than that of the cladding index is added to a conventional fiber core. The structure supports at least one additional symmetric mode with substantial power in the ring, besides the normal mode in the core. Within certain designed parameter regimes, the propagation constants of the lowest two symmetric modes cross at a certain wavelength. This is equivalent to saying that the LP01 mode can change from having more power in core to having more power in ring at a certain wavelength or vice versa. At this resonance, each of the two modes has substantial power in the core and the ring. This resonant nature of the structure creates a strong wavelength dependent mode field for LP01 and LP02 modes near the resonance wavelength. Filters based on this principle are demonstrated for the first time.

Optical waveguides from low-melting-temperature glasses with organic dyes

Polymers and, more recently, sol-gel glasses are generally regarded as the better hosts for optical devices which rely on organic dye molecules as the active component. Most traditional low melting temperature glasses are too easily attacked by water to be a serious alternative; however, a novel composition family based on SnF2 eliminates many of the shortcomings of other glasses with similar viscosity properties and they seem to have an affinity for dissolving many organic dye molecules. The properties of these glasses and the ongoing efforts to demonstrate the feasibility of fabricating guided wave structures are described.

High nonlinearity, low loss fiber for 1 pJ switching of 8-ps optical pulses

The nonlinear optical loop mirror (NOLM) configuration is shown. It consists of a central 50/50 achromatic fiber coupler for data input/output, two WDM Mach-Zehnder fiber couplers for add/drop of the control pulses and 2 km of the highly nonlinear fibre.