The second harmonic light generated in crystals with a random distribution of nonlinear domains is usually emitted in a
broad range of directions. When the fundamental light has good coherence, the intensity of the second harmonic shows a
speckle pattern even when the crystal is transparent. We explain that with the interference at the detection point of the
second harmonic generated by the different domains. Using a phase-only spatial light modulator in the fundamental
beam, it is possible to concentrate the second harmonic intensity in one direction at the same time that the intensity is
reduced in the other directions. In our experiments we measured enhancements in the selected direction up of 700 times
over the average intensity in other directions.
In this work, we study how extraordinary electromagnetic transmission through an array of holes in a metallic film appears as a function of the number of holes and their distribution. In order to do that, we have used a theoretical formalism able to analyze the optical properties of finite collections of apertures placed at arbitrary positions in a metallic film. First, we analyze how the total transmission in a hexagonal 2D hole array evolves as the number of holes in the array is increased. Secondly, we study what is the minimal system showing extraordinary electromagnetic transmission. We find numerically that a linear chain of holes can be considered as the basic entity with extraordinary transmission properties.
When rows of cylinders are periodically removed from a hexagonal array of dielectric cylinders, a new two-dimensional (2D) photonic crystal (PC) arises. The new structure consists of a lattice of vacancies embedded in the initial hexagonal lattice. We called it Suzuki Phase because it remains similar structures discovered in the 60's by K. Suzuki studying alkali halides. A plane-wave algorithm as well as a 2D finite difference-time-domain method has been employed to study the photonic properties of this PC as a function of the filling fraction (f) in the case of high dielectric cylinders ((epsilon) equals 13.6) in air. For TM- modes, it is shown that in a certain range of f an isolated miniband appears in the gap of the initial hexagonal lattice. The miniband, which is created by the coupling of defect states, is described by a tight-binding formalism with two parameters. Also, the frequencies of the two possible vacancy defects in the SP have been obtained and their symmetry analyzed.
Transmission of light through linear defects in two-dimensional (2D) photonic crystals has been already successfully demonstrated in two ways: numerical simulations and experimental measurements. Recently, novel waveguides have been proposed in which the propagation of photons is performed via hopping due to overlapping between nearest-neighbors defect cavities. These waveguides are commonly referred to as coupled-cavity waveguides (CCW). In this work, we present a comprehensive analysis of the light transmission (TM modes) in CCW's created in hexagonal 2D photonic crystals made of high-index dielectric rods. Numerical simulations of the transmission are performed using a 2D Finite-Difference Time-Domain method. A plane wave algorithm and a simple one-dimensional (1D) tight-binding model are employed to describe the miniband which allows the light transport. It is shown that modifying the individual cavities along the CCW one can control the average frequency and the dispersion relation of the miniband. The results also show that this novel guiding method can be used to develop 1310nm/1550nm Coarse-WDM optical demultiplexers employing bended waveguides.
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