Manipulating guided wave radiation with integrated geometric metasurface

Metasurfaces have manifested unprecedented capabilities in manipulating light by subwavelength unit cells, facilitating the miniaturization and multifunctions of optical systems. On the other hand, lithium niobate on insulator (LNOI) technology is revolutionizing the integrated photonics, enabling multifunctional devices and applications. Yet the optical interface for coupling and manipulation is not sufficient and versatile. Here, we developed a geometric metasurface interface for LNOI waveguide and demonstrated several on-chip integrated devices for free space light field manipulations. By decorating waveguides with subwavelength optical antennas, we manipulated the guided waves into desired wavefronts in space, achieved complex free-space functions, such as focusing, multichannel vortex beam generation, and holography. Our architecture goes beyond the conventional gratings and enriches the functionalities of metasurface, which would open up a new perspective for future versatile guided-wave driven optical devices.

Modern Types of Axicons: New Functions and Applications

Axicon is a versatile optical element for forming a zero-order Bessel beam, including high-power laser radiation schemes. Nevertheless, it has drawbacks such as the produced beam’s parameters being dependent on a particular element, the output beam’s intensity distribution being dependent on the quality of element manufacturing, and uneven axial intensity distribution. To address these issues, extensive research has been undertaken to develop nondiffracting beams using a variety of advanced techniques. We looked at four different and special approaches for creating nondiffracting beams in this article. Diffractive axicons, meta-axicons-flat optics, spatial light modulators, and photonic integrated circuit-based axicons are among these approaches. Lately, there has been noteworthy curiosity in reducing the thickness and weight of axicons by exploiting diffraction. Meta-axicons, which are ultrathin flat optical elements made up of metasurfaces built up of arrays of subwavelength optical antennas, are one way to address such needs. In addition, when compared to their traditional refractive and diffractive equivalents, meta-axicons have a number of distinguishing advantages, including aberration correction, active tunability, and semi-transparency. This paper is not intended to be a critique of any method. We have outlined the most recent advancements in this field and let readers determine which approach best meets their needs based on the ease of fabrication and utilization. Moreover, one section is devoted to applications of axicons utilized as sensors of optical properties of devices and elements as well as singular beams states and wavefront features.

High-Efficiency, Wide Working Bandwidth Antenna Based on SOI Platform for Optical Phased Array

A novel structure of a subwavelength surface optical antenna for optical phased array is proposed in this paper. An asymmetric vertical grating structure is applied to achieve high emission efficiency (73% at 1550 nm). Optical antennas with large fabrication tolerances can also maintain a wide working bandwidth of 1 dB between 1350 and 1850 nm. The far-field scanning characteristics of 16-channel optical phased array are investigated in this study by employing the proposed antenna. The results show that the background suppression without considering side lobes caused by the antenna arrangement is −24.5 dB when the phase difference is 0 and when the scan range is as large as ±14.8° × 73.6°.

Carbon Nanotube Far Infrared Detectors with High Responsivity and Superior Polarization Selectivity Based on Engineered Optical Antennas

Single-wall carbon nanotube (SWCNT) thin films are promising for sensitive uncooled infrared detection based on the photothermoelectric effect. The SWCNT film is usually shaped into a belt and diversely doped to form a p-n junction at the center. Under the illumination of a focused incident light, the temperature gradient from the junction to the contacts leads to photoresponse. When the SWCNTs are aligned in one direction, the photoresponse becomes polarization selective. Although a typical bowtie antenna can improve the responsivity and polarization extinction ratio by deep-subwavelength light focusing, the absolute absorptance of the junction region is only 0.6%. In this work, the antenna was engineered for a higher light coupling efficiency. By integrating a bottom metal plane at a specific distance from the SWCNT film and optimizing the antenna geometries, we achieved ultra-efficient impedance matching between the antenna and the SWCNTs, thus the absorptance of the junction region was further enhanced by 21.3 times and reached 13.5%, which is more than 3 orders of magnitude higher than that of the device without the engineered antenna. The peak responsivity was further enhanced by 19.9 times and responsivity reached 1500 V/W at 1 THz. The resonant frequency can be tuned by changing the size of the antenna. Over the frequency range of 0.5 THz to 1.5 THz, the peak responsivity was further enhanced by 8.1 to 19.9 times, and the polarization extinction ratio was enhanced by 2.7 to 22.3 times. The highest polarization extinction ratio reached 3.04 × 105 at 0.5 THz. The results are based on the numerical simulations of the light and the thermal fields.

Three-dimensional plasmonic nano-router via optical antennas

A three-dimensional (3D) nanoscale optical router is a much-desired component in 3D stacked optical integrated circuits. However, existing 3D routers based on dielectric configurations suffer from large footprints and nanoscale routers based on plasmonic antennas only work in a 2D in-plane scene. Here, we propose and experimentally demonstrate cross-layered all-optical 3D routers with nanoscale footprints. Optical slot antenna pairs are used to realize the routing of plasmonic signals between different layers for arbitrary direction in a broadband wavelength range. The routers are also integrated with waveguide directly for exploring further applications. Based on these router elements, a 3D network of optical butterfly interconnection is demonstrated for multi-directional all-optical data communication. The proposed configuration paves the way for optical cross-layer routing on the nanoscale and advances the research and applications for 3D plasmonic circuits with high integration density in the future.

A Design Approach of Optical Phased Array with Low Side Lobe Level and Wide Angle Steering Range

In this paper, a new design approach of optical phased array (OPA) with low side lobe level (SLL) and wide angle steering range is proposed. This approach consists of two steps. Firstly, a nonuniform antenna array is designed by optimizing the antenna spacing distribution with particle swarm optimization (PSO). Secondly, on the basis of the optimized antenna spacing distribution, PSO is further used to optimize the phase distribution of the optical antennas when the beam steers for realizing lower SLL. Based on the approach we mentioned, we design a nonuniform OPA which has 1024 optical antennas to achieve the steering range of ±60°. When the beam steering angle is 0°, 20°, 30°, 45° and 60°, the SLL obtained by optimizing phase distribution is −21.35, −18.79, −17.91, −18.46 and −18.51 dB, respectively. This kind of OPA with low SLL and wide angle steering range has broad application prospects in laser communication and lidar system.

Optical Nanoantennas for Photovoltaic Applications

In the last decade, the development and progress of nanotechnology has enabled a better understanding of the light–matter interaction at the nanoscale. Its unique capability to fabricate new structures at atomic scale has already produced novel materials and devices with great potential applications in a wide range of fields. In this context, nanotechnology allows the development of models, such as nanometric optical antennas, with dimensions smaller than the wavelength of the incident electromagnetic wave. In this article, the behavior of optical aperture nanoantennas, a metal sheet with apertures of dimensions smaller than the wavelength, combined with photovoltaic solar panels is studied. This technique emerged as a potential renewable energy solution, by increasing the efficiency of solar cells, while reducing their manufacturing and electricity production costs. The objective of this article is to perform a performance analysis, using COMSOL Multiphysics software, with different materials and designs of nanoantennas and choosing the most suitable one for use on a solar photovoltaic panel.

Nanoantenna modelling for their further use as data transmitter-receiver devices on 3-d integral circuits

This article describes the application of optical nanocomponents for their further use in computer and information systems. it was revealed It was found on the basis of the analysis that the improvement of existing nanocomponents will allow to realize their full potential, as well as to find the use of nanoantennas in the field of creating communication lines on device boards as devices for receiving and transmitting data. Nanoantennas are promising devices that are already successfully used in modern microscopy devices. However, recently, optical antennas have begun to be applied in devices used in other areas of human life. As a result, the use of this technology can lead to an increase in the speed and volume of data transfer between the components of the integrated circuit. This, in turn, will increase the quality and speed of calculations in complex equations. A modeling technology has been proposed, and calculations of the necessary geometric parameters have been made, which will be suitable for the goals set by this work. On the basis of the proposed technology, four models that meet the required parameters have been developed. Calculations of the created three-dimensional models of nanoantennas have been performed. As a result of the study, a model has been identified that has the most balanced parameters suitable for its further use as the main device for receiving and transmitting data on three-dimensional integrated circuits.