Free-Space Indium Tin Oxide Electro-Optic Transmission Modulator

Free-space electro-optic modulators provide control over the transverse transmission of an incident beam and are essential elements in metrology, sensing, and free-space communication. We present a novel modulator that leverages the free-carrier dispersion effect in indium tin oxide in combination with a plasmonic grating to achieve significant amplitude modulation with the potential to locally modify the optical signal at micrometer scales and high operation speeds. Subwavelength optical confinement and good spatial overlap of both grating resonance plasmonic modes and electrostatic fields created by the gold grating enable a notable modulation depth (∼0.5%) within a sub-10 nm active layer at the free-space wavelength of 1.55 μm. Due to the wide resonance formed by a plasmonic grating, broadband operation over 100 nm is demonstrated. Our monolithic indium tin oxide electro-optic platform enables a wide range of cost-effective light modulation applications that demand smaller footprints, faster operation, and higher robustness than in currently available state-of-the-art spatial light modulators.