All-fiber bidirectional optical modulator derives from the microfiber coated with ITO electrode

Abstract

A cheap, compact, and simply prepared all-fiber bidirectional optical modulator based on the Pockels effect of water and the band population effect was first, to the best of our knowledge, proposed and demonstrated. The transparent conductive oxide indium-tin-oxide (ITO) was coated on the surface of a nonadiabatic microfiber and first used as a modulating electrode on the microfiber. The device was realized by just submerging the microfiber in water. With supplying an electric field perpendicular to the interface between the microfiber and water, the refractive index was modulated in the electric double layer near the tapered region of the microfiber, under the Pockels effect of water. Subsequently, the interference spectrum was modulated. Meanwhile, the intensity of the light was modulated due to the band population effect in the space-charge layer. In this Letter, the proposed all-fiber optical modulator can realize simultaneous bidirectional modulation of the phase and intensity of output light. Experimentally, the maximum phase shift and the extinction ratio were 4.38 nm and 4.87 dB at 1550 nm, respectively. Significantly, the work used the Pockels effect of water and the band population effect to realize an all-fiber optical modulator, showing great potential in the optical phase modulators, optical switches, and electric field sensors.

Nanoscale Adsorption, Assembly, and Deionization Dynamics Recorded by Optical Fiber Sensors

“…Thus, this change affects the sensitive SPR and is manifested as a fast change in the spectral wavelength. Since a negative potential value is applied, a blueshift in the resonant wavelength λ SPR related to the orientation of water molecules is observed (Figure d), and the results are in agreement with those of a previous report . With the step from −1.0 to 0 V, in the reverse direction, this behavior also occurs.…”

“…Since a negative potential value is applied, a blueshift in the resonant wavelength λ SPR related to the orientation of water molecules is observed (Figure 3d), and the results are in agreement with those of a previous report. 43 With the step from −1.0 to 0 V, in the reverse direction, this behavior also occurs. When the experiment is performed in deionized water, similar results are obtained (Figure S9).…”

“…This intuitive behavior is attributed to the optical Pockels effect within the EDL in aqueous solution at the electrode−solution interface. 43 When an electric field is applied to the aqueous surroundings adjacent to the optical fiber, its effective RI undergoes a rapid change due to the anomalous properties of water molecules. Thus, this change affects the sensitive SPR and is manifested as a fast change in the spectral wavelength.…”

“…With the step from 0 V to −1.0 V, the spectrum shifts with a relatively fast speed that exceeds that of the temporal preset autosave interval (1 s) of the spectrometer. This intuitive behavior is attributed to the optical Pockels effect within the EDL in aqueous solution at the electrode–solution interface . When an electric field is applied to the aqueous surroundings adjacent to the optical fiber, its effective RI undergoes a rapid change due to the anomalous properties of water molecules.…”

Interfacial Pockels Effect of Solvents with a Larger Static Dielectric Constant than Water and an Ionic Liquid on the Surface of a Transparent Oxide Electrode

“…2022, 12, 2454 2 of 12 an order of magnitude larger [13] than that of the electro-optic crystal LiNbO 3 [14,15], which has been put to practical use. In a series of subsequent studies, it was reported that the Pockels effect at the solid-liquid interface is relatively large even in hydrogenbonding solvents, such as alcohols [16], that it is small in water at the interface of noble metal electrodes, such as platinum and silver [17,18], and that an optical modulator with a practical level of signal magnitude is possible using the Pockels effect in water at the transparent electrode interface [19,20]. In the observation of the Pockels effect, an electrolyte is dissolved in the solvent to make it conductive and form an EDL, and it is known that the effect does not depend on the type of electrolyte ion [12,16].…”