Dynamic optical buffer using coupled resonators

The high speed of light makes it difficult to confine it to a small area. Therefore, it is difficult to realize an optical memory that can retain information in the form of photons. In this study, we have developed two silicatroid micro optical resonators (i.e., light confinement containers), which are tiny glass elements that can confine and read light. We have coupled the two resonators. We have achieved this behavior by coupling two resonators.

Another operation required to realize optical memory is the ability to read out light at arbitrary times. Since the device is coupled to a tapered optical fiber, it is possible to confine and retrieve light by dynamically adjusting the coupling. This is similar to opening and closing the lid of a container. To achieve this operation, the C2 resonator shown in the figure below is used as a gate, and the light can be confined and read out by matching or shifting the wavelength of the resonator with that of C1.

Similar devices have been realized using photonic crystals, but the retention time has been extended to 20 nanoseconds by using silica micro-optical resonators, which have high fundamental performance for confining light.

The light readout operation is shown in the graph below. The pink area indicates that the control light is on, during which the gate is closed. When the control light is turned off, light can be extracted, and the figure below shows that light can be confined for 20 nanoseconds. 20 nanoseconds is about 6 meters in a vacuum, which means that light can be confined in a container of only 100 micrometers.