Kevin N. Moser, Marc R. Bourgeois, Elliot K. Beutler
et al.
Optical chirality density is a measure of the local handedness of electromagnetic fields. Like energy density, it may be absorbed or scattered through the interaction between light and matter. Here, we utilize the conservation of optical chirality to connect the parity and time-reversal symmetries of the intrinsic excitational eigenmodes of a material to those of their associated electromagnetic eigenfields as dictated by Maxwell's equations. To make this connection explicit, we theoretically examine the Born-Kuhn (BK) system, composed of a pair of plasmonic nanorods of variable separation, as a prototypical material model that is both geometrically chiral in its static structure and truly excitationally chiral in its eigenexcitations and eigenfields. By relaying optical chirality metrics of the BK eigenfields back to their underlying sourcing material degrees of freedom, we derive a unique mechanical chirality measure that is related to, but distinct from, other pseudoscalar metrics recently discussed in the literature. Beyond analysis in the absence of sources, we further derive optical chiral extinction, scattering, and absorption cross sections under external drive and discuss their rigorous connection to more common circular dichroism measurements as well as their limitations in comparison to eigenfield chirality metrics. Lastly, we investigate the conversion of achiral linearly polarized light into chiral elliptically polarized light through interaction with the BK system, illustrating the conservation of optical chirality in the interaction between light and matter through an analytically tractable example.
Achieving spatiotemporal control of light at subwavelength and subcycle scales is an important milestone in the development of new photonic materials and technologies. Ultrafast spatiotemporal light modulation currently relies on electronic interband and intraband transitions that yield pronounced refractive index changes but typically suffer from slow, picosecond response times due to carrier relaxation. Here we show that by leveraging resonant light-matter interactions in a high-quality factor metasurface it is possible to use the optical Kerr effect, a weaker, but instantaneous optoelectronic polarization effect, to achieve ultrafast, reconfigurable light modulation with unprecedented spatial and temporal control. By the subwavelength all-optical tuning of the refractive index of the dielectric metasurface unit cells, we experimentally demonstrate pulse-limited beam steering with a 74-fs response time at angles up to $\pm $13° in the near-infrared. The steering originates from the Kerr effect with a background contribution arising from slower two-photon-excited free carrier absorption. Additionally, we observe spatial back-action, linear frequency conversion, and demonstrate arbitrary ultrafast spatial light modulation in two dimensions. Our findings open the possibility of realizing new ultrafast physics in metastructures with applications in signal processing, pulse shaping, and ultrafast imaging.
Chengnian Huang, Zhihao Lan, Menglin L. N. Chen
et al.
The PT-symmetric waveguides have been frequently discussed in the photonics community due to their extraordinary properties. Especially, the study of power transmission is significant for switching applications. The aim of this study is to extract the mode power transmission parameters based on the coupled mode equations and analyze the power properties of the PT-symmetric system. The equations relying on the coupled mode theory are constructed according to the two different orthogonality relations between the original and adjoint system. The results matching well with the finite difference simulations demonstrate the validity of our method, while the conventional coupled mode theory fails. The power properties in the PT-symmetric and PT-broken phases are also observed. Furthermore, a new integration is implemented from which the conserved quantity is defined and extracted, which reflects the Hamiltonian invariant of the system. Our method fully incorporates the properties of complex modes and allows the study of the power transmission properties based on the orthogonality relations, which is also applicable to other types of non-Hermitian optical systems. This work provides a new perspective for the power analysis of PT-symmetric waveguides and is helpful to design the switching devices.
Rispandi, Cheng-Shane Chu, Abdulfatah Abdu Yusuf
et al.
A new design of ratiometric optical oxygen sensors demonstrates considerable potential for applications across medical, environmental, and industrial fields. These sensors are recognized for their high sensitivity, specificity, and resistance to interference from external environmental variables. This research introduces an innovative fabrication method using silicone-based 3D printing technology to develop such sensors. The approach integrates a silicone matrix with oxygen-sensitive dyes, specifically platinum(II) meso‑tetrakis(pentafluorophenyl)porphyrin (PtTFPP) or tris(4,7-diphenyl-1,10-phenanthroline), Ru(dpp)₃²⁺, along with reference dyes such as Rhodamine 110 or 7-amino-4-trifluoromethyl coumarin, which are unaffected by oxygen. These phosphorescent compounds are blended into the silicone medium by manual stirring. Using a 405 nm LED as the excitation source, it was verified that the emission spectra of the sensing and reference dyes do not overlap, allowing reliable oxygen detection via a ratiometric method. The effectiveness of the sensors is evaluated by comparing the intensity ratio IN₂/IO₂, where IN₂ and IO₂ correspond to the luminescent outputs in nitrogen and oxygen atmospheres, respectively. The sensors embedded with PtTFPP and Ru(dpp)₃²⁺ show linear Stern–Volmer behavior, with sensitivity values of about 69 and 12, respectively. Furthermore, the PtTFPP-based sensor exhibits response times of 41 s and 64 s for oxygen increase and decrease transitions, respectively, while the Ru(dpp)₃²⁺-based sensor records 45 and 68 s for the same changes. This ratiometric sensing approach enhances detection sensitivity and response consistency, minimizing variations caused by fluctuations in light source intensity or fiber optics. Combining ratiometric oxygen sensing with 3D-printed silicone structures provides a robust foundation for developing next-generation oxygen sensor technologies with improved capabilities. The silicone matrix's biocompatible nature and the sensor components' high performance are a significant step toward integrating additive manufacturing and optical sensing in developing reliable, miniaturized biomedical sensors for future healthcare technologies.
The mechanisms of material removal and structural transformation under laser radiation differ significantly between single-crystal diamond (SCD) and nanocrystalline diamond (NCD). This study employs atomic simulations to investigate the material removal mechanisms and structural transformation behaviors of SCD and NCD when subjected to laser irradiation. We analyze the effects of temperature and stress changes induced by laser radiation on structural transformations, revealing the driving mechanism behind graphitization transitions. Specifically, the thermal–mechanical coupling effect induced by lasers leads to graphitization in SCD, while in NCD, due to the stress concentration effects at the grain boundaries, graphitization preferentially occurs at these boundaries. The material removal processes for both SCD and NCD are attributed to thermal stress concentrations in the regions where the laser interacts with the diamond surface. This investigation provides a theoretical foundation for a more profound understanding of the behavior of diamond materials during laser irradiation.
Fiber optic biosensors (FOBs) have gained attention as powerful tools for detecting neuromarkers due to their high sensitivity, rapid response, and ability to be used in complex biological environments. These sensors utilize techniques such as surface plasmon resonance (SPR) and fluorescence spectroscopy, enabling the identification of biomolecules at low concentrations. Neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and multiple sclerosis (MS) pose significant health problems due to their progressive nature and the need for early detection. Biomarkers such as amyloid beta (Aβ), tau protein, α-synuclein, and neurofilament light chain (NFL) play a crucial role in the diagnosis and monitoring of these diseases. Fiber optic sensors have enhanced their accuracy and efficiency by integrating technologies, such as nanomaterials, hydrogels, and machine learning; particularly, the use of graphene and plasmonic nanostructures has improved detection sensitivity and enabled simultaneous monitoring of multiple biomarkers. Additionally, the development of implantable and wearable sensors has made long-term and noninvasive monitoring possible. Despite significant advancements, limitations such as biocompatibility, standardization of diagnostic methods, and scalability for widespread use in clinical settings remain. However, the combination of FOBs with artificial intelligence and microfluidics has opened new horizons for personalized medicine and the management of neurological diseases. These technologies have the potential to become key tools in the early diagnosis and effective monitoring of neurodegenerative diseases. This narrative review synthesizes recent advancements in FOB technology for neurological biomarker detection, highlighting interdisciplinary innovations and future clinical translation pathways.
Coherent optical communication systems are essential for modern high-speed data transmission. However, these systems face challenges related to high cost and complexity, especially in short-reach coherent optical communication systems. To address these issues, we present a low-resolution coherent optical communication system with low-complexity adaptive equalizer. The system's performance is evaluated in a 5 km 28 GBaud 16 QAM transmission scenario. The simulation results indicate that error-feedback noise shaping (EFNS) is highly effective in suppressing digital-to-analog converter (DAC) quantization noise, thereby reducing resolution demands on the DAC. Furthermore, the adaptive equalizer, based on a Stokes-domain depolarization scheme (SS-AEQ), achieves a 45% reduction in the complexity of the equalization algorithm. Compared with the 8-bit resolution DAC and the traditional 2 × 2 MIMO AEQ scheme, the system, employing 4-bit DAC for low-resolution transmission, achieves low-complexity equalization while maintaining comparable transmission performance.
The TiO2-doped V2O5/FTO nanocomposite thin films were prepared on the FTO substrates by sol-gel method and post-annealing process, and the MSM structural devices based on the prepared films were fabricated by sputtering, photolithography and etching techniques. SEM, XRD, and XPS were respectively used to study the morphology, structure and composition of the film, and the electrical and optical regulations of the device were measured by using spectrophotometry and semiconductor parameter analyzer. In the temperature range of 20–360 °C, the maximum modulation amplitude of the TiO2-doped V2O5/FTO film in the 400–1600 nm band was 18.282% and the modulation of the V2O5/FTO film was increased by 9.663% after TiO2-doping. The resistance of the FTO/V2O5-TiO2/FTO device reduced by 3–4 orders of magnitude by comparing with the FTO/V2O5/FTO device. The FTO/V2O5-TiO2/FTO device underwent semiconductor-metal state transition (SMT) around 259.91 °C. Under the applied voltage of 0–5 V, the maximum transmittance variations could reach 8.821%, 7.174% and 11.540% in 400–1600 nm band at the temperature of 20 °C, 40 °C and 80 °C, respectively. The outstanding optical and electrical regulation properties and the favorable cycling stability make the nanocomposite film expected to be applied in the field of optoelectronic devices.
The demand for structured light with a reconfigurable spatial and polarization distribution has been increasing across a wide range of fundamental and advanced photonics applications, including microscopy, imaging, sensing, communications, and quantum information processing. Nevertheless, the unique challenge in manipulating light structure after optical fiber transmission is the necessity to dynamically address the inherent unknown fiber transmission matrix, which can be affected by factors like variations in the fiber stress and inter-modal coupling. In this study, we demonstrated that the beam structure at the fiber end including its spatial and polarization distribution can be precisely and adaptively reconfigured by a programmable silicon photonic processor, without prior knowledge of the optical fiber systems and their changes in the transmission matrices. Our demonstrated photonic chip can generate and control the full set of spatial and polarization modes or their superposition in a two-mode few-mode optical fiber. High-quality beam structures can be obtained in experiments. In addition, efficient generation is achieved by our proposed chip-to-fiber emitter while using a complementary metal-oxide-semiconductor compatible fabrication technology. Our findings present a scalable pathway towards achieving a portable and reliable system capable of achieving precise control, efficient emission, and adaptive reconfiguration for structured light in optical fibers.
Data center interconnections are cost-sensitive. We propose and demonstrate a cost-effective C-band intensity modulation direct detection (IM/DD) transmitter for extended range (ER) inter-datacenter interconnects utilizing only a 2-bit digital-to-analog converter (DAC). Tomlinson-Harashima precoding (THP) is used in transmitter DSP to compensate for dispersion-induced impairments. Due to the uniform distribution of signal levels after THP encoding, a high-resolution DAC is required to generate electrical signals. The hardware cost of the transmitter can be significantly reduced by compressing the physical number of bits (PNOB) of the DAC to 2 bits. We quantize the signal to 4 levels and utilize up-sampling and noise shaping to greatly reduce the in-band quantization noise. The in-band signal to noise ratio (SNR) can be increased to 23 dB. We experimentally demonstrate a cost-effective 40-Gbaud probabilistic shaping PAM-4 C-band IM/DD transmission over 50-km utilizing only a 2-bit DAC in the transmitter without any optical dispersion compensation. The performance of the proposed scheme is proximate to the common case of using an 8-bit DAC. It has a BER gap of about 2 × 10<sup>−3</sup> only when the received optical power (ROP) is higher than −6 dBm.
Artem I. Kashapov, Leonid L. Doskolovich, Evgeni A. Bezus
et al.
We theoretically demonstrate the possibility of generating a spatiotemporal optical vortex (STOV) beam in a dielectric slab waveguide. The STOV is generated upon reflection of a spatiotemporal optical pulse from an integrated metal-dielectric structure consisting of metal strips "buried" in the waveguide. For describing the interaction of the incident pulse with the integrated structure, we derive its "vectorial" spatiotemporal transfer function (TF) describing the transformation of the electromagnetic field components of the incident pulse. We show that if the TF of the structure corresponds to the TF of a spatiotemporal differentiator with a $π/2$ phase difference between the terms describing temporal and spatial differentiation, then the envelope of the reflected pulse will contain an STOV in all nonzero components of the electromagnetic field. The obtained theoretical results are in good agreement with the results of rigorous numerical simulation of the STOV generation using a three-strip metal-dielectric integrated structure. We believe that the presented results pave the way for the research and application of STOV beams in the on-chip geometry.
Agostino Di Francescantonio, Attilio Zilli, Davide Rocco
et al.
All-optical modulation yields the promise of high-speed information processing. In this frame, metasurfaces are rapidly gaining traction as ultrathin multifunctional platforms for light management. Among the featured functionalities, they enable light wavefront manipulation and, more recently, demonstrated the ability to perform light-by-light manipulation through nonlinear optical processes. Here, by employing a nonlinear periodic metasurface, we demonstrate all-optical routing of telecom photons upconverted to the visible range. This is achieved via the interference between two frequency-degenerate upconversion processes, namely third-harmonic and sum-frequency generation, stemming from the interaction of a pump pulse with its frequency-doubled replica. By tuning the relative phase and polarization between these two pump beams, and concurrently engineering the nonlinear emission of the individual elements of the metasurfaces (meta-atoms) along with its pitch, we route the upconverted signal among the diffraction orders of the metasurface with a modulation efficiency up to 90%. Thanks to the phase control and the ultrafast dynamics of the underlying nonlinear processes, free-space all-optical routing could be potentially performed at rates close to the employed optical frequencies divided by the quality factor of the optical resonances at play. Our approach adds a further twist to optical interferometry, which is a key-enabling technique in a wide range of applications, such as homodyne detection, radar interferometry, LiDAR technology, gravitational waves detection, and molecular photometry. In particular, the nonlinear character of light upconversion combined with phase sensitivity is extremely appealing for enhanced imaging and biosensing.
Recent experimental work has demonstrated the potential to combine the merits of diffractive and on-chip photonic information processing devices in a single chip by making use of planar (or slab) waveguides. Researchers have adapted key results of 3D Fourier optics to 2D, by analogy, but rigorous derivations in planar contexts have been lacking. Here, such arguments are developed to show that diffraction formulas familiar from 3D can be adapted to 2D under certain mild conditions on the operating speeds of the devices in question. Equivalents to the Rayleigh-Sommerfeld diffraction (RS) formulas in 2D are provided and a Radiation Condition of validity proved. The equivalence of the first 2D RS formula with an angular spectrum formulation is demonstrated. Finally Fresnel approximations are derived starting from the RS formulation and that of the angular spectrum. In addition to serving those working with slab waveguides, this letter provides analytical tools to researchers in any field where 2D diffraction is encountered, including the study of surface plasmon polaritons, surface waves, 3D diffraction with line-sources or corresponding symmetries, and the optical, acoustic and crystallographic properties of 2D materials.
Abstract Achievement of high photoluminescence quantum efficiency and thermal stability is challenging for near-infrared (NIR)-emitting phosphors. Here, we designed a “kill two birds with one stone” strategy to simultaneously improve quantum efficiency and thermal stability of the NIR-emitting Ca3Y2-2x (ZnZr) x Ge3O12:Cr garnet system by chemical unit cosubstitution, and revealed universal structure-property relationship and the luminescence optimization mechanism. The cosubstitution of [Zn2+–Zr4+] for [Y3+–Y3+] played a critical role as reductant to promote the valence transformation from Cr4+ to Cr3+, resulting from the reconstruction of octahedral sites for Cr3+. The introduction of [Zn2+–Zr4+] unit also contributed to a rigid crystal structure. These two aspects together realized the high internal quantum efficiency of 96% and excellent thermal stability of 89%@423 K. Moreover, information encryption with “burning after reading” was achieved based on different chemical resistance of the phosphors to acid. The developed NIR-emitting phosphor-converted light-emitting diode demonstrated promising applications in bio-tissue imaging and night vision. This work provides a new perspective for developing high-performance NIR-emitting phosphor materials.
Motonobu Tomoda, Akihisa Kubota, Osamu Matsuda
et al.
We present a picosecond optoacoustic technique for mapping both the longitudinal sound velocity v and the refractive index n in solids by automated measurement at multiple probe incidence angles in time-domain Brillouin scattering. Using a fused silica sample with a deposited titanium film as an optoacoustic transducer, we map v and n in the depth direction. Applications include the imaging of sound velocity and refractive index distributions in three dimensions in inhomogeneous samples such as biological cells.
Achieving a broadband nonreciprocal device without gain and any external bias is very challenging and highly desirable for modern photonic technologies and quantum networks. Here, we theoretically propose a passive and bias-free all-optical isolator for a femtosecond laser pulse by exploiting a new mechanism of unidirectional self-induced transparency, obtained with a nonlinear medium followed by a normal absorbing medium at one side. The transmission contrast between the forward and backward directions can reach ~14.3 dB for a 2π5 fs laser pulse, implying isolation of a signal with an ultrabroad bandwidth of 200 THz. The 20 dB bandwidth is about 57 nm, already comparable with a magneto-optical isolator. This cavity-free optical isolator may pave the way to integrated nonmagnetic isolation of ultrashort laser pulses.
EditorialAdaptive optics (AO), a technique originally introduced by astronomers to correct for optical distortions when looking at distant stars, now benefits the entire optics and photonics society. Prof. Martin Booth, who leads his research lab at the University of Oxford where he started his career, was one of the first people to take advantage of AO for microscopy. Since then, he has been continuously promoting the wide application of AO in all aspects of biological research and material science. As one of the few people who has witnessed the growth of AO in various communities, Prof. Martin Booth talks about their major differences, as well as their current challenges and future development. He discusses how AO can benefit emerging areas and the key challenges that may be faced. Prof. Martin Booth has also been making continuous efforts in removing the barriers of AO so that it can be promoted towards the wider community. Finally, he shares his experience from actively taking up different roles in education and in various societies and provides valuable advice to all early career researchers on the wisdom of being successful in their future careers. It is an honour for us to invite Prof. Martin Booth on this issue, and to learn from his inspirations, enthusiasm, and dedication.
The carrier-envelope phase (CEP) plays an increasingly important role in precise frequency comb spectroscopy, all-optical atomic clocks, quantum science and technology, astronomy, space-borne-metrology, and strong-field science. Hitherto, it has been essentially assumed that CEP is strictly a temporal phenomenon. Here we introduce an approach for space-time calculation of the CEP in the spatially defined region of interest. We find a significant variation of CEP in the focal volume of refracting focusing elements and accurately calculate its value. We discuss the implications and importance of this finding. Our method is particularly suitable for application to complex, real-world, optical systems thereby making it especially useful to applications in research labs as well as in the engineering of innovative designs that rely on the CEP.
In this work, magneto-optical properties of a dichroic cholesteric liquid-crystal layer are theoretically investigated at large values of the magneto-optical parameter. Features of all solutions of the dispersion equation are studied in detail. Peculiarities of the reflection, transmission, absorption spectra and the influence of dielectric boundaries on them are investigated. Specific properties of the localization of light and magnetically induced transparency in dichroic cholesteric liquid crystals are considered. The study of the light localization features showed that the presence of an external magnetic field, as well as the presence of dielectric boundaries, led to the appearance of oscillations in the dependence of the intensity of the layer-confined energy on the coordinate of the axis directed along the cholesteric axis. A strong influence of the refractive index of isotropic half-spaces adjacent to a dichroic cholesteric liquid crystal layer on the optics of the layer under consideration is shown. In particular, magnetically induced transparency and diffraction transmission appear only at certain intervals of the refractive index of isotropic half-spaces.