Self-collimation Of Light Research Articles

Tunable optical nonlinearity and self-collimation of light in food dye solutions

Food dyes are widely used in scientific research apart from the food colorant industry. In this work, we investigate nonlinear propagation of optical beams in food dye solutions of different colors, experimentally observing tunable nonlinearity and self-collimating effects of optical beams during propagation. We discuss possible mechanisms leading to optical nonlinearity by numerical simulation and theoretical analysis of the optical forces, and show that the nonlinearity in such solutions is mainly attributed to the thermo-optic effects. In addition, with appropriately mixed food dye solutions, we observe that nonlinear response arises at otherwise inactive wavelengths, leading to coupling of two self-collimated beams of different wavelengths. These results illustrate the possibility of employing low-cost food dye solutions for optical limiting and switching applications.

Tunable Optical Nonlinearity and Self-Collimation of Light in Food Dye Solutions

Tunable Optical Nonlinearity and Self-Collimation of Light in Food Dye Solutions

Design of mesoscopic self-collimating photonic crystals under oblique incidence.

Mesoscopic Photonic Crystals (MPhCs) are composed of alternating natural or artificial materials with compensating spatial dispersion. In their simplest form, as presented here, MPhCs are composed by the periodic repetition of a MPhC supercell made of a short slab of bulk material and a short slab of Photonic Crystal (PhCs). Therefore, MPhCs present a multiscale periodicity with a subwavelength periodicity within each PhC slab and with a few-wavelength periodicity for its supercell. Thanks to this mesoscopic structure, MPhCs allow the self-collimation of light, through a mechanism called mesoscopic self-collimation (MSC), along both directions of high symmetry and directions oblique with respect to the MPhCs slab interfaces. Here, we propose a new design method useful for conceiving MPhCs that allow MSC under oblique incidence, avoiding in-plane scattering and ensuring propagation via purely guided modes, without out-of-plane radiation losses. In addition, the proposed method allows a systematic search for optimal MSC structures, which also simultaneously satisfy the impedance matching condition at MPhC interfaces, thus reducing the effect of multiple reflections between bulk-PhC interfaces. The proposed design method has the advantage of an extreme analytical simplicity and it allows direct design of oblique-incidence MPhC structures. Its accuracy is validated through Finite Difference Time Domain simulations and the MSC performances of the designed structures are evaluated, in terms of angular direction, beam waist, overall transmittance, and through discussion of a Figure of Merit that accounts for residual beam curvature. This simple yet powerful method can pave the way for the design of advanced MSC-based photonic interconnects and circuits that are immune to crosstalk and out-of-plane losses.

Bio-inspired spatially variant photonic crystals for self-collimation and beam-steering applications in the near-infrared spectrum

The self-collimation of light through Photonic Crystals (PCs) due to their optical properties and through a special geometric structure offers a new form of beam steering with highly optical control capabilities for a range of different applications. The objective of this work is to understand self-collimation and bending of light beams through bio-inspired Spatially Variant Photonic Crystals (SVPCs) made from dielectric materials such as silicon dioxide and common polymers used in three-dimensional printing like SU-8. Based upon natural PCs found in animals such as butterflies and fish, the PCs developed in this work can be used to manipulate different wavelengths of light for optical communications, multiplexing, and beam-tuning devices for light detection and ranging applications. In this paper, we show the optical properties and potential applications of two different SVPC designs that can control light through a 90-degree bend and optical logic gates. These two-dimensional SVPC designs were optimized for operation in the near-infrared range of approximately 800–1000 nm for the 90-degree bend and 700–1000 nm for the optical logic gate. These SVPCs were shown to provide high transmission through desired regions with low reflection and absorption of light to prove the potential benefits of these structures for future optical systems.

Analysis of interference between two optical beams in a quasi-zero electric permittivity photonic crystal superlattice

A quasi-zero-average-index photonic crystal structure has been recently demonstrated by using the concept of complementary media. It consists of dielectric photonic crystal superlattices with alternating layers of negative index photonic crystals and positive index dielectric media. This photonic crystal structure has unique optical properties, such as phase-invariant field and self-collimation of light. In particular, the nanofabricated superlattices can be used in chip-scale optical interconnects and interferometers with quasi-zero-average phase difference. However, in potential interconnect applications, crosstalk between neighboring signals needs to be avoided. In this article, we study simulations of the interference of propagating electromagnetic waves in a quasi-zero electric permittivity photonic crystal superlattice. The simulations here are restricted to TM modes, with the main electric field along the vertical direction.

Compact Mach-Zehnder interferometer based on self-collimation of light in a silicon photonic crystal

We demonstrate a compact silicon photonic crystal Mach-Zehnder interferometer operating in the self-collimation regime. By tailoring the photonic band structure such as to produce self-collimated beams, it is possible to design beam splitters and mirrors and combine these to a 20 x 20 microm(2) format. With transmission spectroscopy we find a pronounced unidirectional optical output, the output ratio being as high as 25 at the self-collimation wavelength. Furthermore, the self-collimated beams and the unidirectionality are clearly observed in real space using near-field and far-field optical microscopy. Interpretation of the optical data is strongly supported by different types of simulations.

Self-collimation of light in disordered left-handed metamaterials

Transmission of light through a left-handed slab is studied theoretically. The slab consists of randomly distributed electric and magnetic scatterers. In a practical realization these could be wire and split ring resonators forming a disordered metamaterial. Enhanced transmission close to the middle of the slab is demonstrated. It is explained canalization of source image through self-collimated channels. Existence of self-collimated channels localized on the surface of the slab is demonstrated and a possibility of sub-wavelength imaging by such a system is discussed.

Self-Collimation of Light over Millimeter-Scale Distance in a Quasi-Zero-Average-Index Metamaterial

Inspired by the concept of complementary media, we experimentally demonstrate that an engineered metamaterial made of alternating, stripe layers of negatively refracting (photonic crystals) and positively refracting (air) materials strongly collimates a beam of near-infrared light. This quasi-zero-average-index metamaterial fully preserves the beam spot size throughout the sample for a light beam traveling through the metamaterial a distance of 2 mm-more than 1000 times the input wavelength lambda=1.55 microm. These results demonstrate the first explicit experimental verification of optical antimatter as proposed by Pendry and Ramakrishna [J. Pendry and S. Ramakrishna, J. Phys. Condens. Matter 15, 6345 (2003)10.1088/0953-8984/15/37/004], using two complementary media in which each n(eff)=-1 layer appears to annihilate an equal thickness layer of air.

Self-collimation of light in three-dimensional photonic crystals

We calculate three-dimensional (3D) dispersion relations of woodpile and inverse opal photonic crystals. Inspecting the iso-frequency surfaces of the four lowest-order bands at appropriate frequencies we identify regions where self-collimation of light may be expected. These predictions are verified by means of finite-difference time-domain calculations both for high- and low-index photonic crystals.