Liquid crystals and plasmonic materials possess unique optical properties and have been actively investigated in various contexts. In particular, micro- and nano-structures such as photonic crystals and metamaterials that possess novel tunable and/or nonlinear optical properties have been demonstrated. Most reported experimental studies employ ac electric field induced director axis reorientation or temperature-controlled birefringence modification. These electro-optical tuning mechanisms are characterized by switching times ranging on the order of milliseconds under typical applied field strength as in conventional display device.
Nonlinear all-optical or self-action mechanisms, in which the desired changes in optical refractive indices or birefringence are generated by the light intensity itself, are clearly more preferable since they do not require any electrode, and the incident light can impinge at almost any desired angle. In this presentation, we give a critical review of the nonlinear optical responses of nematic liquid crystals (NLC) associated with short pulsed laser induced order parameter and birefringence modifications, and describe how the plasmonic particulates/nanostructures embedded in them could enhance the nonlinearities and provide ultrafast switching mechanism. Experimental studies conducted with absorbing as well as transparent nematic liquid crystals have demonstrated the feasibility of sub-microseconds – nanoseconds all-optical one-way switching of nanoseconds pulsed laser at various wavelengths spanning the entire visible – near infrared regime (400 nm - 1550 nm) . These effects may be useful for developing tunable metamaterials and other materials/structures impregnated with nematic liquid crystals; they could also be applied to realize faster-response version of many coherent optical image processing applications demonstrated previously with slower mechanisms.