We report that it is possible to create a fiber electret by having both internal electrodes of a twin-hole fiber at the same anodic potential, i.e., without the use of a contacted cathode electrode. We find that a stronger and more temperature-stable charge distribution results when the fiber core is subjected to an external field near zero. Negative charges from the air surrounding the fiber are sufficient for the recording of an electric field across the core of the fiber that is twice stronger than when one anode and one cathode electrode are used. The enhancement in stability and in the strength of the effective chi((2)) induced are a significant step towards the wider use of fibers with a second order optical nonlinearity.

No abstract

A twin-hole fiber was provided with Au-Sn alloy electrodes and thermally poled at 255 masculineC with 4.3 kV applied during 155 minutes. An electric field 6X107 V/m was recorded. The poled fiber was cleaved and etched, revealing that the depletion region overlapped the entire core, was wedge shaped and pointed towards the cathode. The recorded profile closely followed the spatial distribution of the poling field.

A fiber-coupled tunable Er-Yb:glass minilaser is presented with output power of 40 mW. The laser can be stepwise tuned in single-frequency operation from 1530 to 1560 nm by compressing a fiber Bragg grating that provides selective feedback. Constant output power (fluctuation < 0.8 dB) over the full tuning range is demonstrated. The relative intensity noise spectrum was measured to be < 150 dB/Hz for frequencies > 2 MHz.

Twin-hole fibers were provided with Au-Sn alloy electrodes and thermally poled at 255 degrees C. The evolution of the depletion layer was studied by etching fibers poled at varying poling temperatures. The electro-optic response was measured for different poling times. When the depletion region did not overlap the core the direction of the recorded field was opposite to the applied poling field. Poling for a longer time made the depletion region extend through the core and changed the sign of the recorded field.