Oliver Sale

Bio: Oliver Sale is an academic researcher from University of North Texas. The author has contributed to research in topics: Photonics & Photonic crystal. The author has an hindex of 3, co-authored 5 publications receiving 28 citations.

Holographic fabrication of graded photonic super-quasi-crystals with multiple-level gradients.

Abstract: Photonic quasi-crystals and photonic crystals with certain degrees of disorder can have a broadband light–matter interaction. In this paper, we present the holographic fabrication of graded photonic super-quasi-crystals through pixel-by-pixel phase pattern engineering using a spatial light modulator. Using the same phase pattern arranged in a decagon, we have fabricated graded photonic super-quasi-crystals with five-fold symmetry and multiple levels of gradients and graded photonic super-crystals with rectangular unit super-cells, depending on the Fourier filter. Although a certain degree of disorder was incorporated in the quasi-crystals, we still observed the golden ratio in the diameters of the diffraction rings of the fabricated quasi-crystals, indicating five-fold symmetry. Using direct pixel-by-pixel phase engineering, the same laser projection system, consisting of an integrated spatial light modulator and a reflective optical element, can be used for the fabrication of graded photonic super-crystals with various symmetries. The multi-level gradient effects on the optical properties of an organic light-emitting diode were simulated. When the cathode of an organic light-emitting device is patterned in the graded photonic super-crystals, a light extraction efficiency up to 76% in the visible range can be achieved.

Holographic Fabrication and Optical Property of Graded Photonic Super-Crystals with a Rectangular Unit Super-Cell

Abstract: Recently developed graded photonic super-crystals show an enhanced light absorption and light extraction efficiency if they are integrated with a solar cell and an organic light emitting device, respectively. In this paper, we present the holographic fabrication of a graded photonic super-crystal with a rectangular unit super-cell. The spatial light modulator-based pixel-by-pixel phase engineering of the incident laser beam provides a high resolution phase pattern for interference lithography. This also provides a flexible design for the graded photonic super-crystals with a different ratio of length over the width of the rectangular unit super-cell. The light extraction efficiency is simulated for the organic light emitting device, where the cathode is patterned with the graded photonic super-crystal. The high extraction efficiency is maintained for different exposure thresholds during the interference lithography. The desired polarization effects are observed for certain exposure thresholds. The extraction efficiency reaches as high as 75% in the glass substrate.

Broadband light-matter interaction due to resonance cavities in graded photonic super-crystals

Abstract: In this paper, we report the formation of resonance cavities within graded photonic super-crystals (GPSCs) with unit cells formed via a near-uniform central region with eight side graded regions. The graded regions in the GPSCs have several photonic band gaps, whereas the uniform region has one photonic band gap. The different locations of the photonic band gaps form a central cavity and eight surrounding side cavities with more cavities at the boundary of the corresponding uniform and graded regions. The quality-factor of the cavities in the boundary regions has been calculated to be as high as 5.8×105. The central and side cavities have a relatively low-quality factor. Broadband light-matter interaction has been observed in the simulation of transmission through the GPSC. When the thickness of the GPSC is out of resonance with the central cavity mode, the dip in the transmission through the GPSC is shallow and narrow. When the thickness of the GPSC is in-resonance with the central cavity mode, a wide and deep transmission dip is observed in the wavelength range in the photonic band gap of the graded regions. This indicated that the coupling of in-plane resonance in the central region with the Fabry-Perot resonance in the GPSC is occurring.

Holographic fabrication of octagon graded photonic supercrystal and potential applications in topological photonics

Abstract: Novel optical properties in graded photonic super-crystals can be further explored if new types of graded photonic super-crystals are fabricated. In this paper, we report holographic fabrication of graded photonic super-crystal with eight graded lattice clusters surrounding the central non-gradient lattices through pixel-by-pixel phase engineering in a spatial light modulator. The prospect of applications of octagon graded photonic super-crystal in topological photonics is discussed through photonic band gap engineering and coupled ring resonators.

Photonics in nature and bioinspired designs: sustainable approaches for a colourful world

Abstract: Biological systems possess nanoarchitectures that have evolved for specific purposes and whose ability to modulate the flow of light creates an extraordinary diversity of natural photonic structures. In particular, the striking beauty of the structural colouration observed in nature has inspired technological innovation in many fields. Intense research has been devoted to mimicking the unique vivid colours with newly designed photonic structures presenting stimuli-responsive properties, with remarkable applications in health care, safety and security. This review highlights bioinspired photonic approaches in this context, starting by presenting many appealing examples of structural colours in nature, followed by describing the versatility of fabrication methods and designed coloured structures. A particular focus is given to optical sensing for medical diagnosis, food control and environmental monitoring, which has experienced a significant growth, especially considering the advances in obtaining inexpensive miniaturized systems, more reliability, fast responses, and the use of label-free layouts. Additionally, naturally derived biomaterials and synthetic polymers are versatile and fit many different structural designs that are underlined. Progress in bioinspired photonic polymers and their integration in novel devices is discussed since recent developments have emerged to lift the expectations of smart, flexible, wearable and portable sensors. The discussion is expanded to give emphasis on additional functionalities offered to related biomedical applications and the use of structural colours in new sustainable strategies that could meet the needs of technological development.

Ultra-fast all-optical 2-to-4 decoder based on a photonic crystal structure

Abstract: In this paper, a photonic crystal structure based on nonlinear cavities has been proposed to improve the time response of a 2-to-4 decoder. The structure includes an array of chalcogenide rods with an air gap in which the spatial period of rods is 500 nm. The radius of the fundamental rods is assumed to be 125 nm, which results in a photonic bandgap of 1092–1724 nm at TM mode. Three cavities, including the nonlinear rods with a Kerr coefficient of 10−14m2/W, drop the incoming waves concerning the amount of optical intensity. The finite-difference time-domain method was used to calculate the components of the electric and magnetic fields throughout the structure. The time analysis of the device shows the rise time is equal to 200 fs, which is less than one for the previous structures. The area of 110µm2 and the margins of 4% and 88% for logics 0 and 1 are other advantages of the proposed structure. Based on the obtained results, it was proven that the performance of the 2-to-4 photonic crystal-based decoder has been improved by this work.

Ultra-fast all-optical full-adder based on nonlinear photonic crystal resonant cavities

Abstract: In this paper, a new photonic crystal-based full-adder for the summation of three bits has been proposed. For realizing this device, three input waveguides are connected to the main waveguide. An optical power splitter is placed at the end of this waveguide. Concerning the amount of optical intensity inside this waveguide, two nonlinear resonant cavities transmit the waves toward the correct ports. When the cavities do not drop the optical waves, the splitter guides them toward the output ports. The maximum delay time of the presented structure is around 0.5 ps and shows the fastest response among the reported works. This improvement is obtained due to using the resonant cavities. The time analysis results in a maximum working frequency of 2 THz. Also, designing the structure in 93 µm2 demonstrates that it is more compact than the previous works. The normalized low and high margins are obtained around 10% and 85%, respectively. So, the proposed device is capable of considering optical processing circuits.

Holographic Fabrication and Optical Property of Graded Photonic Super-Crystals with a Rectangular Unit Super-Cell

Abstract: Recently developed graded photonic super-crystals show an enhanced light absorption and light extraction efficiency if they are integrated with a solar cell and an organic light emitting device, respectively. In this paper, we present the holographic fabrication of a graded photonic super-crystal with a rectangular unit super-cell. The spatial light modulator-based pixel-by-pixel phase engineering of the incident laser beam provides a high resolution phase pattern for interference lithography. This also provides a flexible design for the graded photonic super-crystals with a different ratio of length over the width of the rectangular unit super-cell. The light extraction efficiency is simulated for the organic light emitting device, where the cathode is patterned with the graded photonic super-crystal. The high extraction efficiency is maintained for different exposure thresholds during the interference lithography. The desired polarization effects are observed for certain exposure thresholds. The extraction efficiency reaches as high as 75% in the glass substrate.