Finite-difference Time-domain Simulation On Optical Transmission Properties Of Subwavelength Metal Structures

Surface plasmons (SPs) are important for potential applications in many fields, such asinformation, energy, medical treatment and so on. Especially for micro-nano opticaldevices, many prototype devices have been constructed. However, they are just the concepttype devices currently. Much research work remains to be launched. For example, tofurther research the physical mechanism of enhanced optical transmission viasubwavelength metal structures, to research the regulation mechanism of SPs devices andto realize dynamic control, to improve and explore new SPs devices. Based on strictclassical electromagnetic field theory and the Maxwell’s equations, finite-differencetime-domain (FDTD) method is carried out to study the optical filtering property of metalholes arrays and optical beam splitting property of metal nano-slits respectively. The mainwork is as follows：(1) The basic properties and novel effects of SPs are introduced and the basic theory offinite difference time domain method is derived. The algorithm and the program of bothdispersion FDTD and nonlinear FDTD are realized.(2)3-D Finite-difference time-domain method is employed to numerically calculate theoptical transmission properties of femtosecond optical pulses via a novel subwavelengthTai Chi shaped holes arrays structure. The results show that there are band pass filteringproperties of this structure in both visible wavelengths range and near infrared wavelengthsrange. The full-width at half-maximum of the narrow pass band in visible wavelengthsrange is nearly20nm. The position of transmittance peaks is mainly dependent on theperiod in the direction parallel to the incident pulse polarization and occurs red shifts whenthe period increases. By adjusting the light polarization direction can dynamic controlfiltering properties of Tai Chi shaped holes arrays.(3)2-D Finite-difference time-domain method is employed to numerically calculate the optical transmission properties of femtosecond optical pulses via metal nano-slits structurecontaining nonlinear materials. The number of output ports can be dynamically controlledby changing the intensity of incident light. The symmetric structure of three nanoslitspossesses1×2symmetric optical beam splitting properties when the incident lightintensity is8.3GW/cm2and the splitting angle is about64°; and possesses1×3symmetricoptical beam splitting properties when the incident light intensity is1.33GW/cm2.Thenumber of output ports distribution can be adjusted simply by changing the width, numberor order of the nanoslits.