High Performance Optical Systems Research Articles

Desensitization design of freeform off-axis TMA optical systems with configuration selection

The off-axis three-mirror anastigmatic (TMA) optical system has the advantages of eliminating all primary aberrations, having no aperture obscuration, no chromatic aberration, and good environmental adaptability, making it essential in high-performance optical instruments. Freeform surfaces, with their rich degrees of freedom (DOFs) in mathematical representation, positively affect the image quality and sensitivity of optical systems. When applied correctly to off-axis TMA optical systems, they can achieve fast F-numbers, large fields of view (FOVs), and long focal lengths. There are dozens of configurations for off-axis TMA optical systems, and freeform surfaces can be combined in numerous ways within these systems. This paper first analyzes the sensitivity of off-axis TMA optical systems with different configurations, selects the configuration with the lowest sensitivity, and combines it with a low sensitivity freeform surface combination to achieve high-performance freeform off-axis TMA optical systems with low sensitivity.

Local slope tolerance model for optical surfaces with distortion as the evaluation criterion

Ultra-precision imaging systems support cutting-edge scientific exploration and technological innovation. The continuous development of optical freeform and aspheric surface technology offers new possibilities for high-performance optical systems but also presents significant manufacturing challenges. In this paper, we derive and discuss in detail the impact of surface manufacturing errors on the image point positions of optical systems. The analysis reveals that among the manufacturing errors, the surface slope error is the primary factor driving positional changes in image points. Based on these insights, a local slope tolerance model using distortion as the evaluation criterion is proposed. This model specifies the slope error requirements at each point on the surface, ensuring the optical system's distortion meets the acceptable threshold during manufacturing. The model’s effectiveness is validated through an off-axis three-mirror freeform optical system and a Cassegrain aspheric optical system.

Infantry Weapon Systems Used by Special Operations Forces to Carry Out Assigned Missions

Abstract Special Operations Forces (SOF) operate in dynamic, challenging environments, requiring accurate and versatile infantry weapon systems to effectively perform their assigned missions. This article provides a comprehensive review of the diverse range of infantry weapon systems used by SOF units in different theatres of operations. Through a synthesis of empirical data, operational perspectives and expert analysis, the study aims to elucidate the critical role of specialised weaponry in increasing the success rate of SOF missions. The analysis covers a broad spectrum of weapon platforms, each tailored to meet distinct mission requirements. In addition, the article explores the integration of advanced technologies into weapon construction, such as high-performance optical systems, silencers and other modular accessories, which enhance the lethality, accuracy and stealth capabilities of special forces units.

Radiofrequency and optical satellite link budgeting calculator

Abstract Satellite communications represent one of the most widely used communication systems nowadays. From the 50’s of 20th century up to the present, the demand for satellite services has increased rapidly, so the need to design and implement reliable, up-to-date systems that meet the needs of users is increasingly imperative. Technological progress also implies a better use of the radio spectrum and the incorporation of benefits in terms of transmission performance. Traditionally, satellite systems have been implemented in the range corresponding to radio frequency, and more recently, special attention has been paid to the exploration of the spectrum corresponding to optical communications, due to the superior benefits that it offers, despite the set of challenges that its implementation represents. Such advances demand the greatest certainty of operation even from the conception and design stage of the transmission system, since satellite communications are not prone to constant changes and maintenance. The calculation process known as link budget is a tool present in the design of any wireless communications system, and its results determine the efficiency and reliability of the design. However, due to the large number of manufacturers and operators, as well as considering the novelty of using high-performance optical systems, it is difficult to stick to a single method or even to point out one as totally reliable and simple to use. With the purpose of expediting the calculation of link budgets, there are various computational tools that allow this process to be carried out. However, these tools carry the problem of poor compatibility, differences and a low degree of reliability and ease of use. In the present work, the construction and use of a web application is proposed that includes the link budget calculation process for both radio and optical satellite systems, flexible, simple, user-friendly, compatible, and mainly, abode to standardised and documented models for provide reliability and accuracy.

Electrically tunable dual-channel absorber based on a graphene integrated slanted grating cavity

In this paper, we propose a tunable dual-channel absorber based on a monolayer of graphene combined with a slanted grating. A single-channel perfect absorption of a monolayer graphene structure at 850 nm was initially achieved in a Fabry-Perot cavity resonance. The absorption rate of graphene was enhanced by nearly 24.5 times. Furthermore, the symmetry of the grating is broken to excite the quasi-bound states in the continuum (quasi-BICs) resonance mode, resulting in another absorption channel at 878.8 nm, thus achieving a perfect dual-channel absorber. The absorption half-width and absorption wavelength can be adjusted by tuning the grating thickness and the electro-optical effect of the DAST material. Furthermore, adjusting the polarization angle of the incident light enables the transition between single- and dual-channel absorbers. The proposed device has potential applications in the fields of high-performance graphene-based optoelectronic devices and optical switching systems.

Self-powered graphene/4H-SiC nanowire array-based ultraviolet photodetectors with fast response time and low dark current for promising wireless ultraviolet communication

Self-powered ultraviolet photodetectors (UV PDs) capable of detecting UV light signals without using an external power supply have become particularly attractive because of their high sensitivity, consistent optical response, ultra-small size, low energy consumption, and long-term robustness for the future. Here we reported a self-powered UV PDs coupling of two-dimensional (2D) single-layer graphene and one-dimensional (1D) 4H-SiC nanowire arrays. The fabricated PDs can feature an ultra-high on-off ratio of 6301 at 0 V and the 2D-1D architectural exhibits a low dark current of ∼4 pA, an ultra-fast response of 4.89 ms. The high performance was associated with the formed heterojunction between the 2D graphene and 1D 4H-SiC nanowire array and the high carrier mobility of the graphene. Moreover, the 2D-1D PDs with a large switching ratio and ultra-fast response time can be beneficial to achieve efficient, real-time, and accurate information transmission under 275 nm UV light, shedding some light on the development of high-performance wireless optical communication systems.

Analysis of satellite-to-ground quantum key distribution with adaptive optics

Future quantum communication infrastructures will rely on both terrestrial and space-based links integrating high-performance optical systems engineered for this purpose. In space-based downlinks in particular, the loss budget and the variations in the signal propagation due to atmospheric turbulence effects impose a careful optimization of the coupling of light in single-mode fibers required for interfacing with the receiving stations and the ground networks. In this work, we perform a comprehensive study of the role of adaptive optics (AO) in this optimization, focusing on realistic baseline configurations of prepare-and-measure quantum key distribution, with both discrete and continuous-variable encoding, and including finite-size effects. Our analysis uses existing experimental turbulence datasets at both day and night time to model the coupled signal statistics following a wavefront distortion correction with AO, and allows us to estimate the secret key rate for a range of critical parameters, such as turbulence strength, satellite altitude and ground telescope diameter. The results we derive illustrate the interest of adopting advanced AO techniques in several practical configurations.

Design and research of high-performance optical bus control system

Design and research of high-performance optical bus control system

Scattering characteristics of various nodular defects in a dichroic beam splitter.

Dichroic beam splitters are widely used in multi wavelength laser systems, and their scattering loss affects the signal-to-noise ratio and performance of the system. In this study, we investigate forward and backward scattering induced by nodular defects in a dichroic beam splitter. The seed size, seed position, and geometric constants of nodules exhibited distinct effects on the scattering characteristics. The modeling and simulation provide valuable insights into the relationship between the structural parameters of nodules and their scattering characteristics, offering practical guidance for various high-performance optical multilayer coatings and systems.

Investigation of surface imperfection in freeform optics with high-order XY polynomial design

Freeform surfaces find potential applications in optics but pose new challenges for manufacturing and functional testing. A basic description of such surfaces is observed in terms of surface spatial frequencies which have been altered as a result of evolution in the fabrication of optics. While mid-spatial-frequency (MSF) errors arising from manufacturing and metrology processes are well documented, our investigation reveals that such errors originate not only during these stages but also during the surface construction at the design phase, particularly for high-order XY polynomial optical surfaces. The presence of MSF errors can significantly affect the performance of high-performance optical systems across various applications. The study discussed in this paper focuses on the relationship between the resolution of the design dataset of freeform surfaces with high-order polynomials and the subsequent surface imperfections in the production of precision optics. The main contributions of this investigation are the identification of MSF errors at surface construction of the design phase and the control over the MSF errors in design dataset using the 2nd-order Gaussian filtration which will bridge the gap between freeform optics design and ultra-precision manufacturing.

Fabry-Perot Bragg grating nanoresonator with ultrahigh intrinsic Q based on low-loss silicon nitride.

Photonic integrated circuits based on ultralow loss silicon nitride waveguides have shown significant promise for realizing high-performance optical systems in a compact and scalable form factor. For the first time, we have developed a Fabry-Perot Bragg grating nanoresonator based on silicon nitride on silicon dioxide platform with an ultra-high intrinsic quality factor of 19.3 million. By combining the introduction of tapered grating between cavity and periodic Bragg grating, increasing the width of cavity to multi-mode region and optimized annealing strategy for Si3N4 film, the propagation loss is reduced to around 0.014 dB/cm. Fabry-Perot Bragg grating nanoresonator can be easily implemented in a simple straight waveguide occupying a minimal amount of space. Therefore, it is a key component to build a high performance photonic integrated circuit for many applications.

Integrated barium titanate electro-optic modulators operating at CMOS-compatible voltage.

We propose monolithically integrated electro-optical modulators based on thin-film x-cut barium titanate that exhibit large modulation bandwidth and operate at voltages compatible with complementary metal-oxide-semiconductor technology. The optical and radio frequency parameters of the modulator are systematically simulated, calculated, and optimized, respectively. Our simulation includes the evaluation of single-mode conditions, the separation distance between the electrode edge and the waveguide edge, bending loss, optical field distribution, and half-wave voltage-length product for optical parameters, and characteristic impedance, attenuation constant, radio frequency effective index, and -3d B modulation bandwidth for radio frequency parameters. By engineering both the microwave and photonic circuits, we have achieved high electro-optical efficiencies and group-velocity matching simultaneously. Our numerical simulation and theoretical analysis show that the half-wave voltage-length product was 0.48V·cm, and the -3d B modulation bandwidths with a device length of 5mm and 10mm were 262GHz and 107GHz, respectively. Overall, our study highlights the potential of the proposed modulators for low driving voltage and high-performance optical communication systems.

General design algorithm for stray light suppression of a panoramic annular system.

In this work, a universal algorithm for designing a panoramic annular lens (PAL) system free from stray light is proposed. The impact of a given stray light path to the optical system could be estimated without running a full stray light analysis process, which allows designers to eliminate troublesome stray light paths by optimizing lens parameters at an early stage of optical design. A 360° ×(40°-100°) PAL system is designed and implemented to verify the proposed method. Simulation shows that the point source transmittance (PST) decreases by 2 orders of magnitude at a specific field-of-view (FoV) range after optimizing the system. Experimental results show perfect consistency with the simulation predictions, which indicate that two types of stray light are totally eliminated in the demonstrated system. This stray light analysis and suppression method provides a promising approach for the research and development of ultra-wide angle high performance optical systems.

Multifunctional interface between integrated photonics and free space

The combination of photonic integrated circuits and free-space metaoptics has the ability to untie technological knots that require advanced light manipulation due to their conjoined ability to achieve strong light–matter interaction via wave-guiding light over a long distance and shape them via large space-bandwidth product. Rapid prototyping of such a compound system requires component interchangeability. This represents a functional challenge in terms of fabrication and alignment of high-performance optical systems. Here, we report a flexible and interchangeable interface between a photonic integrated circuit and the free space using an array of low-loss metaoptics and demonstrate multifunctional beam shaping at a wavelength of 780 nm. We show that robust and high-fidelity operation of the designed optical functions can be achieved without prior precise characterization of the free-space input nor stringent alignment between the photonic integrated chip and the metaoptics chip. A diffraction limited spot of ∼3 μm for a hyperboloid metalens of numerical aperture 0.15 is achieved despite an input Gaussian elliptical deformation of up to 35% and misalignments of the components of up to 20 μm. A holographic image with a peak signal-to-noise ratio of >10 dB is also reported.

The nonlinear effects and applications of gain doped whispering-gallery mode cavities

Whispering-gallery mode (WGM) cavities formed by dielectric structures have attracted intensive interest in various fields. The high-quality factor and smaller mode volume associated with the optical modes have inspired experiments in nonlinear optics, nanophotonics, and quantum information science. Moreover, they are also used in optical biosensors and other significant applications. To further reduce the material loss of the resonator, optical gain materials, such as erbium and ytterbium, are doped into the dielectric structure to increase the nonlinear effect and enhance the interaction between light and matter. Here in this review, we outline the most recent advancements in gain-doped optical WGM microcavities. Moreover, we introduce the dynamics of the gain in WGM resonators, the integration of gain media into WGM microcavities with various shapes, and the fabrication and applications of the gain microcavities. Also, the applications of the gain cavity based on the whispering-gallery mode have been introduced, e.g., ultra-sensitive sensors, low-threshold lasers, and high-performance optical systems.

Four-channel CWDM transmitter chip based on thin-film lithium niobate platform

Multi-lane integrated transmitter chips are key components in future compact optical modules to realize high-speed optical interconnects. Thin-film lithium niobate (TFLN) photonics have emerged as a promising platform for achieving high-performance chip-scale optical systems. Combining a coarse wavelength-division multiplexing (CWDM) devices using fabrication-tolerant angled multimode interferometer structure and high-performance electro-optical modulators, we demonstrate monolithic on-chip four-channel CWDM transmitter on the TFLN platform for the first time. The four-channel CWDM transmitter enables high-speed transmissions of 100 Gb/s data rate per wavelength channel (i.e., an aggregated date rate of 400 Gb/s).

Local tolerance and quality evaluation for optical surfaces

The manufacture of high-precision surfaces is the foundation of building high-performance optical systems. For over 50 years, the tolerance for optical surfaces has been specified by the root-mean-square (rms) or peak-to-valley (PV) value over the entire surface geometry. However, different regions on optical surfaces do not contribute equally to image quality and, thus, can tolerate different levels of errors. A global tolerance described by a single or few parameters cannot precisely provide the manufacturing requirements of each region on the surface, which may result in unnecessary accuracy specifications for surfaces. Furthermore, the components with the same PV or rms figure errors can produce different imaging qualities; however, this difference cannot be distinguished by the conventional figure of merit. To address these problems, a framework that includes a local tolerance model and a quality merit function for optical surfaces is proposed. The local tolerance model can provide an accurate tolerance for each region on the surface so the targeted wave aberration requirements are met during components manufacturing. More importantly, the proposed merit function closely ties the surface figure error to imaging performance, e.g., the findings can explain that the component with lower geometric accuracy may produce better imaging quality. This framework provides new insights into optical design, manufacture, and metrology and especially paves the way for the manufacture of high-precision large-aperture systems.

Binary image classification using collective optical modes of an array of nanolasers

Recent advancements in nanolaser design and manufacturing open up unprecedented perspectives in terms of high integration densities and ultra-low power consumption, making these devices ideal for high-performance optical computing systems. In this work, we exploit the symmetry properties of the collective modes of a nanolaser array for a simple binary classification task of small digit images. The implementation is based on a 8 × 8 nanolaser array and relies on the activation of a collective optical mode of the array—the so-called “zero-mode”—under spatially modulated pump patterns.

A wide-field and high-resolution lensless compound eye microsystem for real-time target motion perception

Optical measurement systems suffer from a fundamental tradeoff between the field of view (FOV), the resolution and the update rate. A compound eye has the advantages of a wide FOV, high update rate and high sensitivity to motion, providing inspiration for breaking through the constraint and realizing high-performance optical systems. However, most existing studies on artificial compound eyes are limited by complex structure and low resolution, and they focus on imaging instead of precise measurement. Here, a high-performance lensless compound eye microsystem is developed to realize target motion perception through precise and fast orientation measurement. The microsystem splices multiple sub-FOVs formed by long-focal subeyes, images targets distributed in a panoramic range into a single multiplexing image sensor, and codes the subeye aperture array for distinguishing the targets from different sub-FOVs. A wide-field and high resolution are simultaneously realized in a simple and easy-to-manufacture microelectromechanical system (MEMS) aperture array. Moreover, based on the electronic rolling shutter technique of the image sensor, a hyperframe update rate is achieved by the precise measurement of multiple time-shifted spots of one target. The microsystem achieves an orientation measurement accuracy of 0.0023° (3σ) in the x direction and 0.0028° (3σ) in the y direction in a cone FOV of 120° with an update rate ~20 times higher than the frame rate. This study provides a promising approach for achieving optical measurements with comprehensive high performance and may have great significance in various applications, such as vision-controlled directional navigation and high-dynamic target tracking, formation and obstacle avoidance of unmanned aerial vehicles.

Flat-top filter using slanted guided-mode resonance gratings with bound states in the continuum

The attribute of bound states in the continuum (BICs) for highly efficient flat-top filter by using a slanted guided-mode resonance (GMR) grating is developed in this work. By introducing a slanted angle θ, the fully symmetric grating is broken to transform the dark BICs into bright quasi-BICs mode. Theoretical analysis based on the finite-different time-domain method is applied to evaluate the filtering performances. It is found that the GMR and quasi-BICs peaks combine at θ=31.4°, and the flat-top filtering response is realized at the central wavelength of 1550 nm under normal incidence. Moreover, the linewidth-tunable and central wavelength-tunable spectral response can be varied according to the change in the coupling strength of the GMR grating by changing the structural parameters such as period, fill factor and refractive index of the grating. It is the first report of a flat-top filter designed by combining GMR and quasi-BICs. The proposed structure shows promise for application in high-performance optical communication systems.