| Popis: |
All-optical switches offer advanced control over the amplitude, phase, and/or polarization of light at ultrafast timescales using optical pulses as both the carrying signal and the control. Limited only by material response times, these switches can operate at terahertz speeds which is essential for technology-driven applications, such as all-optical signal processing and ultrafast imaging, as well as for fundamental studies, such as frequency translation and novel optical media concepts such as photonic time crystals. In conventional systems, the switching time is determined by the relaxation response of a single active material, which is generally challenging to adjust dynamically. This work demonstrates that the zero-to-zero response time of an all-optical switch can instead be varied through the combination of so-called “fast” and “slow” materials in a single device. When probed in the epsilon-near-zero (ENZ) operational regime of a material with a slow response time, namely, plasmonic titanium nitride, the proposed hybrid switch exhibits a relatively slow, nanosecond response time. The response time then decreases as the probe wavelength increases reaching the picosecond time scale when the hybrid device is probed in the ENZ regime of the faster material, namely, aluminum-doped zinc oxide. Overall, the response time of the switch is shown to vary by two orders of magnitude in a single device and can be selectively controlled through the interaction of the probe signal with the constituent materials. The ability to adjust the switching speed by controlling the light-matter interactions in a multi-material structure provides an additional degree of freedom in the design of all-optical switches. Moreover, the proposed approach utilizes “slower” materials that are very robust and allow to enhance the field intensities while “faster” materials ensure an ultrafast dynamic response. The proposed control of the switching time could lead to new functionalities and performance metrics within key applications in multiband transmission, optical computing, and nonlinear optics. |
