Optics research receives a boost through new water-based optical device


Scientists have published a study in OSA Continuum where they have revealed insights about the mechanism of Pockels effect in a new type of light modulator.

According to researchers behind the study, Pockels effect has only been observed in only a special type of crystal, which is costly and hence difficult to use. However, they observed such an effect in the top layer of water when it is in contact with an electrode, showing a glimmer of hope for scientists trying to create simple optical devices. Although the Pockels coefficient (a measure of the Pockels effect) was an order of magnitude greater, it turned out that because this effect was generated only in the thin interfacial layer, this called for a highly sensitive detector.

Scientists created a setup with a transparent electrode on a glass surface in water, and an electric field was applied to it. The interfacial layer (also called the electric double layer or EDL) is only a few nanometers thick and shows different electrochemical properties than the rest of the water. It is also the only part of water where Pockels effect can be observed under an electric field. The scientists used the concept of total reflection to create a large angle at the interface between water and electrode. They observed that when light travels through the electrode and enters the EDL, changes in the refractive index of both layers can modify the reflected signal.

Since the refractive index in the transparent electrode is larger than for both water and glass (1.33 and 1.52, respectively), the amount of light reflected at both ends increases, thereby causing a more enhanced Pockels effect. This was important because a large, more enhanced signal would mean that even low-sensitivity devices could be used to measure it. Moreover, because the experimental setup is not complex, consisting of only a transparent electrode dipped in water containing electrolytes, this method is much simpler to use. Not to mention, water is an inexpensive medium, resulting in a low-cost process overall.

This new method of modulating light serves as a better alternative to existing ones, especially owing to advantages like low cost and easier detection. Not only this, Prof Tokunaga and his team believe that by uncovering new mechanisms of light modulation, their study will open doors for more advanced research in this field.