Ultrahigh modulation enhancement in all-optical THz modulators integrated with gold nanobipyramids

Abstract

Optical regulation strategy with the aid of hybrid materials can significantly optimize the performance of terahertz devices so as to be used in the real world. Gold nanobipyramids (AuNBPs) with synthetical tunability to the nearinfrared band show strong local electric field enhancement, which improves the optical coupling at the interface and benefits the modulation performance of all-optical devices. Here we design AuNBPs-integrated terahertz modulators with multiple structured surfaces and indicate that introducing AuNBPs can effectively enhance their modulation depths. In particular, an ultrahigh modulation enhancement with one order of magnitude can be achieved in the AuNBPs hybrid metamaterials accompanied with the multifunctional modulation characteristics. Applying the coupled Lorentz oscillator model, the theoretical calculation suggests that the optical regulation with AuNBPs originates from increased damping rate and higher coupling coefficient under pump excitation. With the help of excellent modulation enhancement in the AuNBPs integrated metastructures, a prototype of novel spatial light modulator is constructed. As a novel terahertz photonic device with the low-power consumption and multifunctionality, this modulator is promising for the potential application in spatial and frequency selective imaging.