Electrically tunable optical refractive index of a WS2 film on a SiC substrate

For applications in portable electronic devices and machine vision, a small sized focus-tunable lens or lens system is highly desired. Materials with electrically tunable optical refractive indices are required in these fields. A functional material consisting of a WS₂ thin film on a SiC substrate was synthesized and reported in our investigation. A 15-nm-thick WS₂ film was deposited on an n-doped SiC substrate (7.37 × 10¹⁹ cm ^{− 3}) by pulsed laser deposition. The optical refractive index of the WS₂ / SiC material was found to be electrically tunable. The value of the effective optical refractive index ranged from 4.03 to 5.84, which implies a 44.9% variation in the refractive index change, at a wavelength of 460 nm under an applied external DC voltage modulated in the range of 0 to 7 V. We also found experimentally that the focal length of the plane lens was tunable from 184 to 156 mm at a wavelength of 650 nm with the applied voltage ranging from 0 to 7 V. Our investigation presents a new way to modulate the refractive index and make the compact focus-tunable lens design convenient.