Performance Of Optical System Research Articles

Scalable fabrication approach and fill factor optimization for single pixel microlens arrays

Microlenses are a suitable approach to improve the performance of optical systems. An important optical efficiency determining parameter is the fill factor, which describes the relation of the lens area to the total optical active area. In this work, an optimization of the fill factor by optimizing the fabrication process steps is presented. The approach here is the use of i-line waferstepper lithography in combination with thermal reflow of photoresist and subsequent 1:1 pattern transfer in the lens material by reactive ion etching. For this method, the fill factor is determined by the minimum lens gap and, thus, the optical efficiency is strongly limited by the resolution limit of the i-line waferstepper lithography (350 nm). The goal of this investigation is to achieve the lowest possible lens gap even below the stepper-based resolution limit by optimizing each single process step without developing a new approach. The final result of the optimization was a fill factor improvement of 15%.

Performance of free-space optical coherent detection systems under imprecise channels with nonzero boresight pointing errors

Performance of free-space optical coherent detection systems under imprecise channels with nonzero boresight pointing errors

Integration of Metrology in Grinding and Polishing Processes for Rotationally Symmetrical Aspherical Surfaces with Optimized Material Removal Functions

Aspherical surfaces, with their varying curvature, minimize aberrations and enhance clarity, making them essential in optics, aerospace, medical devices, and telecommunications. However, manufacturing these surfaces is challenging because of systematic errors in CNC equipment, tool wear, measurement inaccuracies, and environmental disturbances. These issues necessitate precise error compensation to achieve the desired surface shape. Traditional methods for spherical optics are inadequate for aspherical components, making accurate surface shape error detection and compensation crucial. This study integrates advanced metrology with optimized material removal functions in the grinding and polishing processes. By combining numerical control technology, computer technology, and data analysis, we developed CAM software (version 1) tailored for aspherical surfaces. This software uses a compensation correction algorithm to process error data and generate NC programs for machining. Our approach automates and digitizes the grinding and polishing process, improving efficiency and surface accuracy. This advancement enables high-precision mass production of rotationally symmetrical aspherical optical components, addressing existing manufacturing challenges and enhancing optical system performance.

Characterization of the Small Robotic Telescope Instrument and Implementation at ITERA Lampung Astronomical Observatory

As time has passed, the technological advances used to run these telescope systems have become faster, more reliable, and more user-friendly. Institut Teknologi Sumatera (ITERA) has installed a small robotic telescope at the Meteorology–Climatology–Geophysics Observing Station in collaboration with an ASTELCO System. The telescope system is designed to make fully robotic observations and can operate in both interactive and unattended robotic modes. This study's primary focus is on the OZT-ALTS telescope robotic system with the optical system using triplet apochromatic lens technology manufactured by LZOS with a focal ratio of f/8 refractor design. The telescope mount is a German Equatorial (NTM-500 manufactured by ASTELCO) with a direct drive system with an absolute encoder, and it allows fully programmable tracking speeds with a typical slewing speed of 20°/sec and a tracking accuracy range of 0.3–1.0 arcsec. For the process of collecting moon observation images, we use Manta G-031B. The OZT-ALTS robotic telescope is now contributing to monitoring crescent moon observation and astronomical studies. This paper presents the scientific motivation behind the OZT-ALTS robotic telescope and the facility's specifications and unique features. Furthermore, we present to characterize the result of the hardware OZT-ALTS robotic telescope system to increase the mechanical and optical performance of the telescope system based on the in-situ test observations. Based on the result, setting the Gain on the camera at 3.5 e-/ADU is the limit for the CCD to produce good-quality output images by utilizing the entire dynamic range without saturation. We also present an example of the science we have performed with the OZT-ALTS robotic telescope. The OZT-ALTS can observe young crescent moon events in the daylight after implementing the CLAHE technique to enhance contrast objects. On the other hand, the OZT-ALTS can also observe WASP-16b and WASP-34b exoplanets by using the transit method to analyze the decreasing light curve when a planet passes between a star and its observer.

The possibilities of using adaptive optics in modern ophthalmology

Until recently, the assessment of individual retinal cells was possible only with the help of histological examination, since such retinal imaging methods as scanning laser ophthalmoscopy and optical coherence tomography had low resolution to obtain images of structures at the cellular level, which was mainly due to aberrations caused by the optics of the eye. Adaptive optics technology has improved the performance of optical systems by correcting optical wavefront aberrations. Adaptive optics allows noninvasively visualizing the retina at the microscopic level in vivo, providing the opportunity to analyze individual structures such as photoreceptors, blood vessels, nerve fibers, ganglion cells and a lattice plate. Adaptive optics imaging in patients with diabetic retinopathy makes it possible to accurately determine the spatial distribution of cones, a decrease in which is associated with the presence of diabetic retinopathy and an increase in the severity of the disease. The detection of differences in cone distribution density between the control group and patients with diabetes mellitus without clinical signs of diabetic retinopathy may contribute to its early diagnosis, as well as a deeper understanding of the consequences of changes in the photoreceptor apparatus. Adaptive optics imaging methods are able to identify disorders of photoreceptor cells and assess the degree of progression of age-related macular degeneration, which definitely expands diagnostic capabilities at the early stages of its detection. Assessment of the condition of nerve fiber bundles through the use of Adaptive optics helps to identify changes associated with glaucoma, and also provides the ability to visualize details that cannot be evaluated using optical coherence tomography. Adaptive optics imaging allows you to directly measure the wall of retinal vessels and the diameter of their lumen. The ratio of wall thickness to vessel lumen and the cross-sectional area of the vessel wall directly reflect the remodeling process and can be used for the purpose of early diagnosis and monitoring of hypertension.

Investigating performance of optical communication system with FSO/OWC channel

Abstract In recent years, the evolution of optical wireless communication (OWC) system has emerged as a viable alternative to radio frequency communication. These technologies provide an effective solution for addressing the need for point-to-point communication, offering benefits such as higher bandwidth, faster data rates, no licensing requirements, low power usage, quick and simple installation, enhanced security, and resistance to electromagnetic interference. In this article, we analyze two wireless optical communication systems: one using an FSO channel and the other using an OWC channel. The analysis focuses on range and quality factor as performance metrics. We examine the performance of one-to-many Tx/Rx FSO/OWC channel under three different atmospheric conditions: clear weather, haze, and fog, using eye diagrams. The system analysis includes mathematical models for the received optical power and the pointing error. Additionally, we investigate the impact of spatial diversity on the performance of FSO/OWC channel with configurations of 1 × 1, 2 × 2, 4 × 4, and 8 × 8. Our findings indicate that the 8 × 8 FSO/OWC configurations yield better results compared to other configurations and the OWC channel performs well over long distances up to 110 km, while the FSO channel is more suitable for short range communication up to 37 km.

Design and performance estimation of a novel solar multiplate mirror concentration PVT system based on nanofluid spectral filter

This paper presents the design and performance evaluation of a novel solar multiplate mirror concentration photovoltaic and thermal (MPVT) system using ethylene glycol/indium tin oxide liquid spectral filter (LSF). The LSF is prepared, and the test results show that its average spectral transmissivity and average spectral absorptivity are 69.2 % and 30.8 %. Optical characteristics and operation performance of the MPVT system are evaluated, and parametric interaction analysis is also carried out to reveal the relationships of optical and structural parameters of the MPVT system. The results indicate that the MPVT system is technically feasible and has acceptable adaptability on solar tracking error. The decrease in LSF flow channel width and increase in LSF flow channel installation height can increase the concentration ratio. The electric power and photoelectric efficiency of the photovoltaic module are 818.2 W and 29.07 %. The thermal and exergy efficiencies of the MPVT system are 23.88 % and 32.81 %. By increasing the inlet LSF flow velocity and ambient temperature or decreasing the inlet LSF temperature properly, the thermal performance of the MPVT system can be improved. But the effects of the three parameters on the exergy efficiency of the MPVT system are all relatively small.

BER and outage throughput analysis of DPIM/DHPIM coded QPSK-OFDM based outdoor optical wireless communications

With the growing demand for fast and reliable communication systems, particularly in outdoor environments, it is essential to investigate advanced encoding techniques. Digital Pulse Interval Modulation (DPIM) and Dual Header Pulse Interval Modulation (DHPIM) emerge as promising alternatives to traditional line coding methods, providing enhanced spectral efficiency and resistance to signal disruptions. This paper presents the performance of a Quadrature Phase-Shift Keying (QPSK) Orthogonal Frequency Division Multiplexing (OFDM)-based Optical Wireless Communication (OWC) system using these advanced encoding schemes. The analysis includes simulation results on QPSK-OFDM-based transmitter design, free space optical channel modeling based on Gaussian and log-normal distribution atmospheric turbulence, and recovery of input digital stream using the mentioned line coding techniques. The results demonstrate optimal bit error rate (BER) values for the QPSK-OFDM-based OWC system. The primary innovation of this research lies in the encoding schemes and their performance in outdoor optical wireless communication systems under turbulent conditions. Through extensive simulations and analysis, detailed insights into the bit error rate and outage throughput characteristics of DPIM/DHPIM coded QPSK-OFDM are provided, offering a unique perspective on the performance of these schemes in real-world scenarios. The findings not only highlight the optimal BER values achievable with the QPSK-OFDM-based OWC system but also offer insights into the system's ability to overcome transmission challenges under various atmospheric conditions.

Improved performance of three mirror anastigmat telescope with freeform surface: Optical design, testing and validation aspects

"In this paper, the optical design of a Three Mirror Anastigmat (TMA) Telescope is modified by substitution of a convex freeform secondary and optimization carried out to obtain improved performance. The proposed convex freeform surface is precisely manufactured using the bonnet polishing technique and tested with a sub-aperture stitched algorithm, meeting the specified surface accuracy requirements. Further, to validate the design, the realized secondary freeform optic is tested in conjunction with primary and tertiary optics in the conceived TMA configuration. The telescope system performance is established using a double-pass interferometric test setup. The modified design enhances the telescope system's performance in the extended field of view (FoV) from ±2.5° to ±3.5° across the track and from ±0.4° to ±0.6° along the track. Measured performance results demonstrate an average modulation transfer function (MTF) of 0.56 and an average Strehl ratio of 0.64 at all field points. The effective focal length of the system is computed to be 975 mm. In summary, the proposed freeform surface significantly improves the optical system performance within the available real estate of the envisaged space telescope system."

Vortex inverted pin beams: mitigation of scintillations in strong atmospheric turbulence.

We recently introduced a new class of optical beams with a Bessel-like transverse profile and increasing beam width during propagation, akin to an "inverted pin." Owing to their specially engineered distribution, these beams have shown remarkable performance in atmospheric turbulence. Specifically, inverted pin beams (PBs) were found to have a reduced scintillation index as compared to collimated or focused Gaussian beams as well as other types of pin beams especially in moderate to strong turbulence. In this work, we demonstrate that inverted pin beams carrying orbital angular momentum (OAM) can further suppress intensity scintillations in moderate to strong irradiance fluctuation conditions. Our results can be useful in improving the performance and link availability of free-space optical communication systems.

Robust phase extraction from complex signals/fringe patterns for optical communications in 5G and beyond through continuous wavelet ridge technique

AbstractThe rapid progress in high‐precision optical instruments necessitates sophisticated image processing techniques for extracting vital information from generated images. Most of these instruments output images comprising RGB pixels. Deciphering these pixel values into phase information poses a significant challenge, especially in the presence of background noise. This study focuses on utilizing Two‐Dimensional Continuous Wavelet Transforms (2‐D CWT) for analyzing fringe patterns with varying noise levels and fringe alignments, crucial for high‐precision optical systems pivotal in enhancing the performance and reliability of optical communication systems in advanced 5G networks. The simulation results demonstrate that 2‐D CWT efficiently extracts phase information from complex and highly noisy fringes while requiring less computational time. Furthermore, the algorithm effectively handles noise disturbances with a commendable degree of accuracy, ensuring robust performance in 5G‐enabled optical systems critical for supporting ultra‐high‐speed data transmission and low‐latency communication requirements. This research contributes to optimizing image analysis techniques for 5G optical systems, facilitating their integration into next‐generation communication networks.

Simulative analysis of carrier suppressed return to zero based symmetrical compensated optical link

Abstract Optical communication systems provide high data rates to fulfil users’ demands. In addition, the modulation format is essential to the system’s transmission quality and spectral efficiency. Furthermore, the effects of chromatic dispersion, which impair the performance and quality of transmitted signals, are mitigated using dispersion compensation techniques. In optical communication systems, dispersion compensation techniques are essential for preserving signal quality, increasing transmission distances, improving system performance, and offering network designers flexibility. These methods seek to improve signal quality and enable transmission at longer distances by reducing or eliminating the distortion brought on by dispersion. This paper uses a symmetrical compensation technique to analyze the performance of the CSRZ modulation format-based optical communication system. The research is conducted within a communication range of 150–350 km. The system is evaluated in terms of input power, filter order, and filter depth. The results indicate that the proposed system performed better at an input power of 4 dBm using a third-order filter and 60 dB filter depth.

Performance Analysis of Hybrid Optical OFDM Schemes in terms of PAPR, BER and Spectral Efficiency using Various PAPR Reduction Methods

Orthogonal Frequency Division Multiplexing (OFDM) is an extremely important technique for transmitting data in both optical wireless and optical fiber communication. Optical wireless systems are limited to transmitting real and positive values to the optical transmitter, since they rely only on the intensity of a signal to convey information. Consequently, traditional OFDM is not suitable for direct implementation in optical systems. Various altered OFDM schemes have been examined to counteract multipath distortion, such as DC-biased optical OFDM (DCO-OFDM), asymmetrically clipped optical OFDM (ACO-OFDM), asymmetrically clipped DC biased optical OFDM (ADO-OFDM) and layered asymmetrically-clipped optical OFDM (LACO-OFDM) technique to improve the bit error rate (BER) performance and spectral efficiency of optical system. This article explores ways for reducing Peak-to-Average Power Ratio (PAPR). A mathematical model is formulated to account for clipping and Selective Mapping (SLM), as well as channel noise, in all of these approaches for received signal. LACO-OFDM has been determined to be a superior option when compared to other techniques. LACO-OFDM, a recently developed technique, demonstrates excellent performance in terms of PAPR, BER, and spectral efficiency. The simulation results demonstrate that the LACO-OFDM approach has greatly enhanced the spectral efficiency in comparison to previous approaches.

Plasmon-induced electron transportation in heterostructure N-rGO/NiFe-LDH@Au with enhanced photoelectrochemical water oxidation

Facile design and fabrication of an ideal heterointerface model is considered as a significant advancement towards photoelectrochemical (PEC) water splitting efficiency. Here, we detail the incorporation of plasmonic Au nanoparticles into N-doped reduced graphene oxide/NiFe-layered double hydroxide (N-rGO/NiFe-LDH) interface by cost-effective coprecipitation-photoreduction method and photoelectrode assemblage via drop casted technique for enhanced PEC water oxidation. Au nanoparticles efficiently harvest the light energy upon plasmonic excitation and transfer the energy towards contacted NiFe-LDH and N-rGO, thereby promoting PEC performances. In comparison to N-rGO/NiFe-LDH, the as-obtained N-rGO/NiFe-LDH@Au composite exhibits 1.46 fold times enhancement in photocurrent density (5.7 mA/cm2 at 1.23 V vs RHE) and considerable cathodic shift of 20 mV at onset potential of 0.18 V for PEC water oxidation. Additionally, N-rGO/NiFe-LDH@Au exhibits incident photon to current conversion efficiency (IPCE) of 10 % and better photostability of more than 6 h for boosted water splitting. The incorporation of Au nanoparticles significantly augmented the photoactivity as apparent from the photocurrent density assessment. The improved PEC performance of N-rGO/NiFe-LDH@Au photoelectrode is accredited to the surface plasmon resonance (SPR) induced electron transfer process and heterostructure configuration holding numerous defect sites for smooth charge transportation. This fabrication approach is quite a simplistic method to enlarge the optical behavior and effective performance of the PEC system and also provide guidance to assemble other sophisticated materials suitable for the energy conversion process.

On the performance of a hybrid optical communication system: MGDM–FSO for challenging environments

On the performance of a hybrid optical communication system: MGDM–FSO for challenging environments

Multi-Perspective Heterodyne Digital Holography For High-Speed Imaging Of Density Fluctuations In Supersonic Flow

Density fluctuation measurements with high spatio-temporal resolution provide meaningful insights into the dynamics of turbulent structures in shear layers, boundary layers, and disturbances that influence the transition to turbulence. The current contribution presents a new multiple perspective digital holographic imaging technique that aims to resolve high-frequency density fluctuations with spatial discrimination along the line of sight. A key element of the proposed method is the generation of a beamlet array of varying view angles that is spatially overlapped within the measurement zone. We present the first experimental realization of this approach using a 7-element hexagonally packed fly’s eye lens array and analyze results for a pair of mutually perpendicular and axially offset sonic jets. The experimental apparatus also incorporates heterodyne detection with a heterodyne frequency set to 1/4 of the imaging frame rate. The optical system performance is evaluated for a crossing jet flow and key design considerations for the multi-perspective optical system are discussed.

Low-complexity MLSE for coherent optical fiber transmission systems with symbol correlation.

This study demonstrates the effectiveness of a simplified maximum likelihood sequence estimation (MLSE) approach in enhancing the performance of coherent optical fiber transmission systems, particularly under conditions of linear and nonlinear symbol correlation. To counter the high complexity of traditional MLSE in high-speed systems, we introduce what we believe to be a novel simplification method. This approach replaces the conventional channel impulse response (CIR) convolution with a look-up table (LUT) and simplifies the Euclidean distance (ED) calculations. Additionally, we provide a detailed analysis of algorithmic operations, complementary metal oxide semiconductor (CMOS) transistor count, and power consumption across various technology nodes. The proposed simplified MLSE scheme has the potential to reduce implementation complexity to approximately 5% of the conventional approach. The proposed low-complexity approach was verified with both simulations and experiments. The results show that the performance loss is less than 0.3 dB in Q-factors for both linear and nonlinear bandwidth-constrained transmission scenarios.

Influence of Eu, Gd and Lu dopants on the properties of TiO2: A first-principles study

The present study investigates the electronic structure, magnetic properties, and optical performance of anatase TiO2 and pure TiO2 systems with the addition of rare earth elements RE (Eu/Gd/Lu). Using first-principles calculations based on density-functional theory, we explore the effects of RE doping on these systems. Our calculations reveal that the structural stability remains intact under the conditions of RE doping. The total magnetic moment is determined to be 2.987 μB, 6.052 μB, and 0 μB for Eu, Gd, and Lu-doped TiO2 respectively. Furthermore, the band gap of Eu/Gd/Lu-doped TiO2 decreases significantly to 1.91eV, 1.8eV, and 1.88eV, leading to a lower energy requirement for electron transition, as compared to the initial energy band gap of 2.31eV. The incorporation of rare earth elements also results in an increase in the number of valence and conduction band energy levels near the Fermi level, primarily influenced by orbital electrons in the 4f layer of the rare earth elements. Additionally, our findings demonstrate a remarkable shift towards the red region in the absorption spectrum of the Eu-TiO2 system, accompanied by a relatively long photocarrier lifetime. These characteristics suggest its potential as a photocatalyst with enhanced performance. Overall, this research provides valuable theoretical insights towards the development and synthesis of novel TiO2 photocatalysts.

Benefits of flexibility in current and future IM-DD based TDM-PON [Invited

Due to continuously emerging high bandwidth applications, research and standardization of time division multiplexed passive optical networks (TDM-PONs) have focused on increasing the peak bitrate. However, increasing the bitrate while supporting the stringent optical power budget of a PON becomes increasingly challenging because of the larger chromatic dispersion penalties as well as reduced receiver sensitivity when the bitrate of the intensity modulation with direct-detection (IM-DD) based PON is increased. Also, increasing bitrate generally causes higher power consumption, which leads to more challenging thermal designs and misalignment with environmental targets. In this paper we give an overview of flexible concepts that can help achieve the required optical power budget and support reduced power consumption of a future IM-DD based TDM-PON. We demonstrate that a flexible PON can provide an increased overall throughput or an extended reach and power budget with the use of flexible modulation formats, probabilistic and geometric shaping, and flexible rate forward error correction (FEC). Another dimension of flexibility in the form of a configurable optical distribution network (ODN) is described and its merits and challenges are discussed. Flexible concepts based on interleaving of FEC codewords can align signal processing like FEC decoding and the protocol processing closer to the user-rate of an optical network unit (ONU), which leads to reduced power consumption. Flexibility based on multiple channels based on wavelength multiplexing or spatial multiplexing enables optimization of the power consumption to the amount of traffic on the PON. Several flexible concepts have already been adopted in the PON standards. We highlight flexible gain FEC for upstream 50G PON, the transmitter dispersion eye closure (TDEC) metric, and the flexible split-ratio ODN for power saving. Flexible modulation has not been adopted yet in PON standards, but it is expected that flexibility is more and more needed to support the performance, cost effectiveness, and power conservation of future optical access systems.

Development and validation of a collaborative robotic platform based on monocular vision for oral surgery: an in vitro study.

Surgical robots effectively improve the accuracy and safety of surgical procedures. Current optical-navigated oral surgical robots are typically developed based on binocular vision positioning systems, which are susceptible to factors including obscured visibility, limited workplace, and ambient light interference. Hence, the purpose of this study was to develop a lightweight robotic platform based on monocular vision for oral surgery that enhances the precision and efficiency of surgical procedures. A monocular optical positioning system (MOPS) was applied to oral surgical robots, and a semi-autonomous robotic platform was developed utilizing monocular vision. A series of vitro experiments were designed to simulate dental implant procedures to evaluate the performance of optical positioning systems and assess the robotic system accuracy. The singular configuration detection and avoidance test, the collision detection and processing test, and the drilling test under slight movement were conducted to validate the safety of the robotic system. The position error and rotation error of MOPS were 0.0906 ± 0.0762mm and 0.0158 ± 0.0069degrees, respectively. The attitude angle of robotic arms calculated by the forward and inverse solutions was accurate. Additionally, the robot's surgical calibration point exhibited an average error of 0.42mm, with a maximum error of 0.57mm. Meanwhile, the robot system was capable of effectively avoiding singularities and demonstrating robust safety measures in the presence of minor patient movements and collisions during vitro experiment procedures. The results of this in vitro study demonstrate that the accuracy of MOPS meets clinical requirements, making it a promising alternative in the field of oral surgical robots. Further studies will be planned to make the monocular vision oral robot suitable for clinical application.