An ultrafast all-optical switching with the response time on the order of 10 fs is demonstrated in a three-dimensional opal polystyrene nonlinear photonic crystal by means of precise femtosecond pump-probe technique. The switching is realized by the shift in the photonic band gap under external optical pumping of 8 fs Ti:sapphire pulse laser with a peak pump power of 20.6 GW/cm2. The good performance of optical switching is attributed to the very strong and fast Kerr nonlinear optical response of the polystyrene material.
This article demonstrates theoretical design of ultracompact all-optical AND, NAND, OR, and NOR gates with two-dimensional nonlinear photonic crystal slabs. Compound Ag-polymer film with a low refractive index and large third-order nonlinearity is adopted as our nonlinear material and photonic crystal cavities with a relatively high quality factor of about 2000 is designed on this polymer slab. Numerical simulations show that all-optical logic gates with low pump-power in the order of tens of MW/cm2 can be achieved. These design results may provide very useful schemes and approaches for the realization of all-optical logic gates with low-cost, low-pump-power, high-contrast and ultrafast response-time.
We propose a new scheme on unidirectional surface plasmon-polariton (SPP) excitation with the following advantages: ultracompact size, working at arbitrary incidence angle and over a wide spectrum. The proposed structure utilizes a partially filled metallic slot with dielectric to realize unidirectional SPP excitation via direct field manipulation. We theoretically and numerically show that unidirectional SPP excitation with a ratio of 93% can be achieved by a structure with a 50 nm slot. The proposed structure keeps its functional capability over incident angles from -80° to 80°, and has a broadband working spectrum of more than 70 nm.
The achievement of ultrafast all-optical switching on chip is a fundamental issue of all-optical integration. A feasible and promising method for this is to combine semiconductor photonic crystals with highly nonlinear polymer materials to form the hybrid nonlinear photonic crystal. In this paper we numerically investigate the femtosecond dynamic response of all-optical switching based on the effect of band gap edge shift in one-dimensional (1D) semiconductor–polymer hybrid nonlinear photonic crystal (NPC) structures. Taking into account the Kerr relaxation time of the polymer and semiconductor materials simultaneously, the introduction of highly nonlinear polymer materials with femtosecond relaxation time can realize all-optical switching in the femtosecond range in spite of the low response speed of the semiconductor materials. The physical origin is the large and ultrafast response Kerr nonlinearity of the polymer materials and this is proved by examining the dependence of switching time on the relaxation speed of the polymer materials. The results can be extended to 2D and 3D NPC structures.
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