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.
We synchronized two passively mode-locked erbiumdoped 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 lowbirefringence, polarization maintaining, optical logic gates with switching timing window of 4 and 5 ps, respectively. We obtain nonlinear transmission of 50% at a switching energy of 8 pJ and contrast ration 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.
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.
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