We applied the principles of photonic crystal devices to the millimeter wave portion of the electromagnetic spectrum. For the lens, we have observed their collimation and imaging ability both shown in the amplitude and phase. The results described in the report shown that the diffractive photon crystal lens is a perspective candidate to subwavelength focus lens in different area of applications, including microscopy, lens array element, etc.

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Subwavelength Diffractive Photonic Crystal Lens

An exact solution to compute the band gap in phononic crystals

Based upon developed radial FDTD-method, used for solution of Maxwell equations in cylindrical coordinates and implemented in Matlab-7.0 environment, we simulated focusing of the annular Gaussian beam with radial polarization by conical microaxicon with numerical aperture 0.60. It is shown that the area of focal spot (defined as area where intensity exceeds half of its maximum) can be 0.096λ 2 , and focal spot diameter equals to 0.35λ.

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Sharp focus area of radially-polarized gaussian beam propagation through an axicon

Gain mediums attract much attention due to their excellent amplification characteristics. However, the potential applications of gain mediums are severely limited because of the requirement of a high external energy to excite the media, thereby compensating for the ohmic loss. In this paper, we developed a theoretical model by numerically solving the coupled Maxwell’s equations and semiclassical electronic rate equations using the finite-difference time-domain method. In the model, the active gain medium is represented by a four-level atomic system, and the atoms are pumped with a homogeneous pumping rate. Then, we investigated the loss compensation with the synergetic effects of gain mediums and extraordinary optical transmission (EOT) phenomena caused by the excitation of the surface plasmon polariton. With the proposal of a novel gain/metal/gain structure that is patterned to be a periodic subwavelength hole array, the self-consistent process of EOT phenomena coupled to the gain medium enables full compensation of the ohmic loss under a much lower pumping rate. This paper not only presents a novel structure but also provides deep insight into the interaction between nanostructures and gain mediums.

Coupling of Gain Medium and Extraordinary Optical Transmission for Effective Loss Compensation

A novel passband microstrip filter exploiting the continuous pattern technique is proposed. This new structure is obtained by modulating the microstrip width by means of a "butterfly wing" layout. This novel configuration gives a narrow transition band and a good high frequency signal rejection. The experiment results show excellent agreement with the numerical ones.

A continuous varying impedance passband microstrip filter exploiting a butterfly wing shape

The paper deals with the modeling, based on the Finite Difference Time Domain method, of active one- and two- dimensional photonic crystals. The onset of laser oscillation is observed by simulating the active substance as having a negative frequency-dependent Lorentzian-shaped conductivity so including into Maxwell's equations an electric current density. Particular attention is devoted to the implementation of uniaxial perfectly matched layer absorbing boundary conditions for the simulation of infinitely extending structures having gain features. Laser behaviour is simulated as a function of various parameters; the threshold wavelengthand conductivity are evaluated as the wavelengthand conductivity where the transmittance diverges. Moreover, the properties of the active two-dimensional photonic band gap structures are given in terms of a Q quality factor which increases by increasing the crystal size and strongly depends on the lattice shape. For the square lattice, when the crystal size increases from N =2t oN = 8 the Q-factor increases by about an order of magnitude (from 0.027 to 0.110) for TE polarization while for TM polarization it decreases from 0.025 to 0.022. At last the Q-factor pertaining to the chess-board lattice, to parity of other parameters, assumes greater values and already for N = 4, it reaches the values obtained for the 16 × 8 square lattice, for bothTE and TM polarizations.

https://www.jpier.org/PIER/pier39/12.0211251.Dorazio.PSPP.pdf

V. De Palo

Papers

Finite difference time domain modeling of light amplification in active photonic band gap structures