No abstract

In this study, we present an all-optical reflection modulator for the 2 µm communication band exploiting a nanogear-array metasurface and phase-change-material G e 2 S b 2 T e 5 (GST). The reflectance of the structure can be manipulated by altering the phase of GST by employing optical stimuli, and this paper provides details on the optical and opto-thermal modeling techniques of GST. A numerical investigation reveals that the metastructure exhibits a conspicuous changeover from ∼ 99 % absorption to very poor interaction with the operating light depending on the switching states of the GST, ending up with 85% modulation depth and only 0.58 dB insertion loss. Due to noticeable differences in optical responses, we can demonstrate a high extinction ratio of 28 dB and a commendable figure of merit of 49, so far the best modulation performance in this wavelength window, to our knowledge. In addition, real-time tracking of reflectance during phase transition manifests high-speed switching expending low energy per cycle, of the order of sub-nJ. Hence, given its overall performance, the device will be a paradigm for optical modulators for upcoming 2 µm communication technology.

We report a refractive index sensor comprising of unique T grating on top of periodic nano-cavities. The sensor has two resonant modes sensitive to different regions of the structure with low inter-region interference, hence allows simultaneous detection of two different analytes or more accurate detection of a single analyte. The sensor also provides a self-referencing feature for a broad range of refractive index, from 1.3 to 1.5. Using the FDTD method, the sensitivities of 801.7 nm RIU -1 and 1386.8 nm RIU -1 have been recorded for the two modes respectively. The versatility of the structure makes the sensor a prominent candidate for biochemical and other sensing applications.