Transactions in Optics and Photonics

A Review on Optical Beam Phase Correction Techniques for Ground to Space Free-Space Optical Communication

Abhishek Karambelkar — 2026-07-01

The Free Space Optical Communication (FSOC) links face significant challenges and issues resulting in an unattainable level of reliability and high performance due to phase distortions, scintillation, beam wandering, and atmospheric turbulence. In order to address these concerns, a comprehensive analysis of independent techniques to correct the optical beam steering and advanced compensation strategies is presented. For both terrestrial and ground to space FSOC applications, this assessment evaluates theoretical analyses, modelling studies, hardware implementations, and experimental demonstrations pertaining to the various optical beam phase correction methods. Adaptive optics, feedback-based beam steering, optical phase conjugation, non-mechanical phase correction methods and error correction techniques classify the various methods used for improving the optical beam performance. The comparative analyses in the reviewed studies indicate that traditional Adaptive Optics (AO) systems are very effective at weak and moderate turbulence levels but that neural network-based controllers perform better under rapidly changing or strong turbulence conditions. Furthermore, the use of hybrid schemes that employ various compensation mechanisms consistently resulted in increased link reliability and performance; however, the added level of complexity associated with hybrid schemes detracts from the overall efficiency of the system. This review provides a detailed analysis of the various state-of-the-art phase correction systems currently available, comparative performance data, and recent developments in the FSOC field.

How to Solve a Common Problem of Organic Luminescent Materials: Concentration Quenching of Luminescence

Alexander Kukhta — 2026-06-17

Concentration quenching is a common problem in organic luminescent materials, significantly reducing the efficiency of luminescent devices and luminescence-based tools. Although the mechanism of this phenomenon has been studied for a long time, it remains still not fully understood. It is a great challenge to find the most efficient ways to diminish or to overcome concentration quenching. This mini-review examines the progress made in biological and optoelectronic research to address this problem, mainly over the last decade. All known mechanisms of concentration quenching (except for light reabsorption and energy migration) are based on intermolecular interactions. Thus, to prevent or diminish concentration quenching of luminescence in organic molecules, one can only remove or reduce short-range interactions between the emitting molecules. Internal (adjusting the mutual orientation of the emitting molecules, designing molecules with bulky side chains, and sterically wrapping additional molecular parts, which results in increasing the distance between molecules) and external (host-guest systems, which isolate emitting molecules by means of creating a shielding barrier between them) tools for minimizing concentration quenching are considered. Shielding barriers can be obtained by doping and encapsulating molecules. Organic, metal-organic, and inorganic cages, organic, metal-organic, and inorganic frameworks, polymeric and inorganic nanoporous materials, as well as carbon and other nanomaterials, are being successfully developed for dye encapsulation. All the proposed tools have resulted in diminishing concentration quenching. However, for further progress in overcoming of concentration quenching, a series of new proposed approaches such as the synthesis of new sterically wrapped and Aggregation-Induced Emission (AIE) molecules, hyperfluorescent structures, and the embedding of luminescent molecules into organic, metal-organic, inorganic, and carbon-based cages as well as covalent organic and metal-organic frameworks are considered to be the most prospective, because they make it possible to apply the highest concentrations without essential luminescence quenching.

Role of Tunable Nonlinearities of Metamaterials on Tightly Focused Beam Generation

N. K. Hashim — 2026-06-17

MetaMaterials (MMs) offer strong tunability of optical properties, enabling diverse photonic applications. We investigate the role of tunable optical nonlinearities in the formation of Tightly Focused Beam (TFB). The system is described by a nonlinear Schrödinger equation, and modulation instability is analyzed both analytically and numerically to identify parameter regimes supporting localized beam formation. The dynamics of Gaussian and hollow Gaussian beams are further studied using numerical simulations, with emphasis on TFB generation. Results show that adjustable nonlinearities in MMs significantly enhance control over beam focusing characteristics. Notably, hollow Gaussian beams generate higher-intensity TFB clusters compared to standard Gaussian beams. These findings suggest potential applications in optical trapping and high-density data storage.