We report the design and realization of a high-performance InGaAsP/lnP multiple quantum-well waveguide phase modulator based on the quantum confined Stark effect. Use of the quaternary InGaAsP for the well material enabled a high phase-modulation efficiency to be obtained with a low intensity modulation throughout the 1.5-1.55 μm fiber band. A 180° phase modulation of TE polarized light was obtained in a 4 mm long device under 5 V bias with just 0.6 V at 1.49 μm wavelength and 0.9 V at 1.55μm wavelength. The phase shift increased quadratically with applied bias, in accordance with theory, giving a total phase shift of 1100° (TE) and 830° (TM) at 1.4 μm at 6 V, with 500° (TE) and 400° (TM) at 1.55μm. The refractive index change associated with the measured phase shift was found to have an approximate inverse-square dependence on the energy detuning from the exciton resonance. The intensity modulation associated with the phase modulation was very low. At 1.49 μm, there was just 0.7 cm-1 measured excess loss for TE light, with 1.6 cm-1 for TM light. This excess loss decreased at longer wavelengths and vanished at around 1.54 μm. No optical intensity dependence was discernible up to the maximum cavity power of 10? W/m2. Device speed was limited to −1 GHzby RC charging times.
Recent work on the development of integrated optical devices for nonlinear switching and processing has focused on the performance of Mach Zehnder1 and directional coupler2 switches. However previous research into optical fibres has identified the potential of the birefringent polarisation gate3 which is known to have better stability against external fluctuation than interferometric gates based on independent optical paths.
Femtosecond optical switching is demonstrated in a nonlinear semiconductor birefringent waveguide. Optically induced polarization rotation increases the normalised gate transmission by a factor of 44.
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