On-chip magnetic-free optical multi-port circulator based on a locally linear parity-time symmetric system.

This paper introduces a new type of magnetic-free optical circulator without utilizing a Faraday rotator, polarization beam splitter, and magneto-optic material for the first time, to the best of our knowledge. The designed circulator operates linearly and relies on the parity-time symmetric (PTS) system. The property of the non-Hermitian system (the linear PTS system) plays the key role in the suggested optical circulator so that it can simultaneously support N-ports. The proposed device is integrated, broadband, and operates in the optical telecommunication frequency band. A great value of isolation rate of 47 dB is achieved. The proposed circulator can pave the way for optical integrated circuits and optical networks.

Wideband and low-dispersion engineered slow light using liquid infiltration of a modified photonic crystal waveguide.

We present a wideband and low-dispersion slow-light photonic crystal waveguide with a large normalized delay-bandwidth product that can be exploited in many ultra-compact all-optical devices, such as modulators and switches. The proposed new approach is based on infiltrating optical fluid into the first and second rows of the shifted air holes adjacent to the line-defect waveguide in a hexagonal lattice of photonic crystal. The simulation results show that the normalized delay-bandwidth product can be enhanced to a large value of 0.469 with a wide bandwidth operation of 36.8 nm in the C-band frequency optical communication window. Furthermore, by means of two-dimensional finite-difference time-domain calculations, the low-dispersion slow-light propagation is demonstrated by simulating the temporal Gaussian pulse width broadening.

Designing Switchable Phononic Crystal-Based Acoustic Demultiplexer.

We present the design procedure for switchable acoustic demultiplexers based on a fluid-fluid phononic crystal (PnC) platform. It consists of a T-shaped PnC waveguide coupled to two output waveguide ports through two dissimilar point-defect cavities. The PnC platform consists of a periodic array of infinitely long rods of water (inclusions) embedded in mercury background. The waveguides are made by the removal of a row or a column of inclusions from the PnC, while the fluid in one of the two dissimilar cavities is methyl nonafluorobutyl ether (MNE) and in the other is ethyl nonafluorobutyl ether (ENE). The difference in the sound velocity in MNE and ENE provides an adequate difference in the dissimilar cavities resonant modes, required for the demultiplexing functionality of the designed structure. The different dependences of the sound velocities in these two fluids on temperature have also enabled the switching of the multiplexed channel, simply by appropriately changing the cavities temperature.

A 2×2 spatial optical switch based on PT-symmetry.

We show a PT-symmetric coupler having an arm with a tunable gain and a no-loss arm when appropriately designed to possess reciprocal behavior, unlike its rivals having a fixed gain/loss arm, can perform as a tunable 2×2 spatial optical switch. The degree of the tunability equals the ratio of the coupler's length to the total coupling length.