Phys.org   March 11, 2024 Researchers in Japan constructed a tunable Fabry–Perot interferometer (FPI) by controlling the effective refractive index of pitch-variable subwavelength gratings (PV-SWGs) that were incorporated into an FP cavity. The period of the PV-SWG could be varied to change the effective refractive index and shift the optical resonant frequency of the FPI. Compared with conventional methods that tune the optical resonance by adding fillers or deforming the cavity, the  FPI obtained a higher transmission and quality factor (Q-factor) for the transmittance peak, and its resonant frequency could be shifted by simply stretching the PV-SWG. According to the researchers […]