Abstract
A novel tunable plasmonic demultiplexer is proposed and numerically investigated by finite element method (FEM). It consists of two half-nanodisk cavities and two sets of E7 liquid crystal arrays which are side-coupled to three metal-dielectric-metal (MDM) waveguides. The demultiplexer can split the input lights into two parts corresponding to port1 (1310 nm) and port2 (1550 nm). The Q-factors of port1 and port2 are 54.6 and 36, and the crosstalk values are −20.7 dB and −29.9 dB, respectively. Obviously, both channels have high Q-factors and low crosstalk value. Moreover, the E7 liquid crystal arrays play a key role in the whole structure, which makes the output power adjustable proportionally by adjusting the applied voltage. This novel feature greatly enriches the function of our demultiplexer. Using the electronical tunable birefringence characteristic of liquid crystal and its arrays structure paves a new way to realize practical on-chip plasmonic system, which can be widely used not only in demultiplexers but also in nanosensors, optical splitters, filters, optical switches, nonlinear photonic and slow-light devices.
Highlights
Surface plasmon polaritons (SPPs) excited at the interface between metal and dielectric have bigger propagation constant and smaller wavelength at the same frequency
A novel tunable plasmonic demultiplexer is proposed and numerically investigated by finite element method (FEM). It consists of two half-nanodisk cavities and two sets of E7 liquid crystal arrays which are side-coupled to three metal-dielectric-metal (MDM) waveguides
There are two common coupling types in MDM demultiplexers – one is that the resonators are directly side-coupled to one bus waveguide between the input and output ports [16], the other is that the input waveguide, output waveguide and resonators are all coupled through a gap [14], [15], [17]
Summary
Surface plasmon polaritons (SPPs) excited at the interface between metal and dielectric have bigger propagation constant and smaller wavelength at the same frequency. The closest one to our wavelength range is reference [6], whose classic performance parameter is C = −9.05 dB, Q = 15.6 for 1310 nm and C = −15.49 dB, Q = 21 for 1550 nm They all tend to have the same defect that the output power of each port only varies with the input power, and the output power ratio between each output port cannot adjust. The output power modulation part is made up of two vertical output waveguides, each of which side-coupled an array of E7 liquid crystal. By adjusting the applied voltage from 1 V to 60 V, it can be specified any output power ratio through these two output ports This is attributed to the elaborate design that the alignment orientation of the two sets of E7 liquid crystal arrays is perpendicular. Our study on the characteristics of liquid crystal arrays provides a powerful theoretical guidance for all-optical integration systems and ultracompact plasmonic devices
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