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Arbitrarily shaped near field with arbitrary polarization is practical application requirements. Our previous work proposed combining the phase conjugation (PC) and planar tensor impedance modulated holographic metasurface (TIMHMS) for arbitrarily shaped near field with arbitrary polarization. This paper proposes to generate arbitrarily shaped near field with arbitrary polarization by cylindrical conformal TIMHMS based on PC and Blackman window function. For the first time to the knowledge of the authors, arbitrarily shaped near field with arbitrary polarization is generated by conformal TIMHMSs. As an example, two cylindrical conformal TIMHMSs are constructed at 30 GHz for rectangle-shaped near field: (LHCP, z = 100 mm) and (LP, z = 200 mm), where LHCP and LP are left hand circular and linear polarizations, respectively. Blackman window function is used to optimize the cylindrical conformal TIMHMS design for optimized field pattern efficiency and low sidelobe. The calculated, simulated, and measured results agree well, and validate the proposed design method for conformal TIMHMS. The designed conformal TIMHMSs have the advantages of high pattern efficiency 42.1%, flexibly shaped field patterns and polarizations, and low sidelobe (-15 dB). The design method does not need complicated calculations and can be used in the upcoming sixth-generation wireless networks with required shaped near field for Radio Frequency Identification, holographic imaging, biomedical applications, etc. [ABSTRACT FROM AUTHOR]

Stimulated Brillouin scattering is a well-known nonlinear optical interaction valued for applications including narrow-linewidth lasers, phase conjugation, sensing, and RF-signal processing such as delay lines and filters. While interaction strength and linewidth directly affect device performance, most strongly interacting Brillouin systems have linewidths of many MHz, limited by the high frequency of the participating acoustic waves. By engineering Forward Inter-Modal Brillouin interactions to access the Fundamental Acoustic Modes (FIM-FAM), strong Brillouin coupling can be extended over a wide frequency range, including lower frequencies that support significantly narrower linewidths. In this work, sub-MHz Brillouin linewidths as narrow as 110 kHz are observed in tapered optical fibers with homogeneous waists. Tight confinement of both the optical and acoustic waves yields Brillouin gains over a thousand times higher than traditional backward Brillouin scattering in standard fibers, and a long waist and low-loss transitions enable a Brillouin interaction strength nearly a hundred times greater than prior taper-based FIM-FAM demonstrations. A specific radius and comprehensive polarization control suppress background scattering by over 40 dB relative to the signal. A comprehensive theoretical model is developed accounting for the dynamical behavior of optical and acoustic waves, reproducing qualitative behavior for several experimental configurations. In addition, the dependence of homogeneity of the linewidth is investigated and reveals a route toward further linewidth reduction by controlling phase-matched frequency variations throughout the waist. Extending strongly coupled Brillouin interactions to ultranarrow linewidths with a recipe for fabrication, detailed characterization techniques, and a comprehensive theoretical treatment will benefit high-performance Brillouin-based photonic applications. [ABSTRACT FROM AUTHOR]

A theory of degenerate four‐wave mixing (DFWM) and phase conjugation is developed for metallic nanohybrids, which consist of an ensemble of interacting metallic nanoshells and noninteracting quantum dots (QDs). It is considered that three incident waves are applied to the metallic nanohybrid, and they produce a fourth output mixed wave. These waves induce dipoles in metallic nanoshells, generating surface plasmon polaritons, and interact with each other via the dipole–dipole interactions (DDI). In DFWM, the input and output waves travel in opposite directions, and this retroreflective nature is responsible for the phenomenon of phase conjugation. The analytical expressions for the input transmitted and output reflected wave intensities are calculated in the presence of the surface plasmon polaritons (SPPs) and the DDI polaritons. It is demonstrated that the phase conjugation, the phase coherent phenomena, and the intensities of both input transmitted and output reflected waves are enhanced due to SPPs and DDI polaritons. These findings indicate that the nanohybrid acts as a phase conjugate device and a phase coherent optical amplifier, which can be applied to fabricate optical nanoamplifiers, phase conjugate mirrors, and nanosensors by measuring the intensity of the output reflected wave. [ABSTRACT FROM AUTHOR]

Cucurbitacin B (CuB) is a natural triterpenoid with diverse pharmacological effects including potent anticancer activity. However, its oral bioavailability is hampered by limited metabolism in vivo. We characterized CuB's in vivo metabolism in rats to uncover bioactive metabolites retaining therapeutic potential, using a robust UHPLC-Q-TOF–MS/MS workflow. This workflow combined molecular networking, fragmentation filtering, and mass defect filtering to identify CuB metabolites in rat urine, plasma, and feces following oral administration. Thirteen metabolites were identified and seven were confirmed. Major phase I transformations involved hydrolysis, reduction, epoxidation, and amination. Phase II conjugation included cysteine, glutathione, glucuronide, and gluconic acid conjugates. Notably, one of the main metabolites formed was the cysteine conjugate CuB-Cys. CuB-Cys maintained similar in vitro antiproliferative activity to CuB on HepG2, MCF-7, and PANC-1 cancer cell lines. However, it demonstrated lower cytotoxicity towards non-cancerous L02 cells, highlighting improved therapeutic selectivity. Mechanistically, CuB-Cys induced greater apoptotic signaling in HepG2 cells than CuB via enhanced caspase activation and disrupted BAX-Bcl-2 balance. This represents the first systematic characterization of CuB's in vivo metabolic pathway. The identification and confirmation of CuB-Cys provide insight for drug development efforts aiming to maintain therapeutic efficacy while reducing toxicity, via metabolite-based approaches. Our findings shed light on strategies for improving CuB's clinical potential. [ABSTRACT FROM AUTHOR]

A new type of fully polarimetric retrodirective array (RDA) using a PON-type structure is proposed in this paper. The fully polarimetric property is the result of the proposed phase conjugation circuits, which perform phase conjugation processing on the x, y, and z polarization electric field components of the incident wave when combined with a tri-polarized antenna array. It enables the retrodirective array to receive and retransmit an arbitrary polarized incident wave. The measured results of the monostatic radar cross-section (RCS) show that the −5 dB beam width of the array was greater than 95° at 9.6 GHz for different polarized incident waves. Furthermore, the proposed RDA has better retrodirectivity performance on arbitrary polarized incident waves when using a wide-beam antenna, and if we further incorporate modulation and demodulation into the circuits, it has the potential to be applied to the wireless communications field. [ABSTRACT FROM AUTHOR]

A conjugation on a Hilbert space $ \mathcal {H} $ H means an antilinear bounded operator that the squares to the identity, which generalizes the traditional conjugation on complex Euclidean spaces. In this paper, with the help of normalized conjugation we introduce the notion of conjugate phase retrieval on general Hilbert spaces. We characterize frames that do conjugate phase retrieval; prove that every conjugate phase retrieval frame for $ \mathcal {H} $ H consisting of all real vectors has the complement property in $ \mathcal {H} $ H , and the converse is true if $ dim({\mathcal {H}})\leq ~2 $ dim (H) ≤ 2 ; and also prove that a small perturbation of conjugate phase retrieval frame still gives a conjugate phase retrieval frame if $ dim({\mathcal {H}}) \lt \infty $ dim (H) < ∞ , but it is false if $ dim({\mathcal H})=\infty $ dim (H) = ∞. [ABSTRACT FROM AUTHOR]

Quaternion algebra ℍ is a noncommutative associative algebra. In recent years, quaternionic Fourier analysis has received increasing attention due to its applications in signal analysis and image processing. This paper addresses conjugate phase retrieval problem in the quaternion Euclidean space ℍ M with M ≥ 2 . Write ℂ η = { ξ : ξ = ξ 0 + β ⁢ η , ξ 0 , β ∈ ℝ } for η ∈ { i , j , k } . We remark that not only ℂ η M -vectors cannot allow traditional conjugate phase retrieval in ℍ M , but also ℂ i M ∪ ℂ j M -complex vectors cannot allow phase retrieval in ℍ M . We are devoted to conjugate phase retrieval of ℂ i M ∪ ℂ j M -complex vectors in ℍ M , where "conjugate" is not the traditional conjugate. We introduce the notions of conjugation, maximal commutative subset and conjugate phase retrieval. Using the phase lifting techniques, we present some sufficient conditions on complex vectors allowing conjugate phase retrieval. And some examples are also provided to illustrate the generality of our theory. [ABSTRACT FROM AUTHOR]

In this paper, the impact of polarization mode dispersion (PMD) on system performance in coherent optical transmission assisted by optical phase conjugation (OPC) technique is numerically investigated for a 9-channel PM-4QAM system at 128Gbit/s. The OPC-aided transmission, amplified with lumped erbium doped fiber amplifier (EDFA), is a variation of the conventional dispersion-managed link, which is also called dispersion-inverted link. We demonstrate that introducing more OPCs along the link can partly suppress the PMD-induced impairments and thus improve the system performance significantly. Results of 960-km dispersion-managed transmission show that PMD effect will cause a performance penalty of 1.8 dB when using mid-link OPC (i.e., only 1-OPC), while this penalty will decrease to about 0.4 dB when employing 6-OPCs along the link. Comparing with conventional digital back-propagation (DBP) technique, a performance improvement of about 3.1 dB is observed with multi-OPCs when fiber PMD is equal to 0.1ps/ k m . [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate stable radio frequency (RF) transfer via metropolitan optical fiber link in the Beijing area. The phase variation of the RF signal is compensated by a phase conjugation method incorporating two high-performance phase-locked loops. The wavelength conversion module extends the transmission length to 200 km with only two parallel 50 km dark optical fibers available. We optimize the configuration of dispersion compensation and optical amplification due to the high loss (0.31 dB/km) of the optical fiber link. At the same time, comparative experiments verify the short-term instability limitation that arises from the group velocity dispersion of the optical fiber link. The measured standard Allan deviation of the 2.4 GHz RF transmission system with dispersion compensation is 4.5 × 10−14/1 and 2.6 × 10−17/20 000 s, which is superior to that of the reference rubidium clock. The short-term instability of the system is deteriorated to 2.5 × 10−13/1 s without dispersion compensation. [ABSTRACT FROM AUTHOR]

An all-optical crosstalk suppression scheme is desirable for wavelength and space division multiplexing optical networks by improving the performance of the corresponding nodes. We put forward a scheme comprising double-stage semiconductor optical amplifiers (SOAs) for wavelength-preserving crosstalk suppression. The wavelength position of the degenerate pump in the optical phase conjugation (OPC) is optimized for signal-to-crosstalk ratio (SXR) improvement. The crosstalk suppression performance of the double-stage SOA scheme for 20 Gb/s quadrature phase shift keying (QPSK) signals is investigated by means of simulations, including the input SXR range and the crosstalk wavelength deviation. For the case with identical-frequency crosstalk, the double-stage SOA scheme can achieve equivalent SXR improvement of 1.5 dB for an input SXR of 10 dB. Thus, the double-stage SOA scheme proposed here is more suitable for few-mode fiber systems and networks. [ABSTRACT FROM AUTHOR]

Stimulated Brillouin scattering (SBS) is an effective method for compensating wavefront aberrations in high-energy lasers due to its phase conjugation property. However, SBS phase conjugate mirrors (SBS-PCMs) under high-power pumping often suffer from significant spatial aberrations and decreased energy reflectivity, indicating instability in the nonlinear gain. Here, a nonlinear gain modulation method is proposed to realize the stable output. Experiments show that the energy reflectivity of SBS decreased due to the thermal effect in high-repetition-rate pumped SBS-PCMs. The nonlinear gain modulation was accomplished with simultaneous adaptation of radial and axial focusing parameters resulting in a higher SBS gain under short-focus conditions. The feasibility of the method was experimentally confirmed by obtaining SBS energy reflectivity stabilized at 60%, while the root mean squares of steady-state Stokes energy and pulse time delay enhanced to 1.97% and 1.81%, respectively, in an HT-230 medium. This scheme ensures stable and efficient SBS output under high-power pumping, which is of great significance for expanding the application of SBS-PCMs in high-repetition-rate laser systems. [ABSTRACT FROM AUTHOR]

The research on sound source identification in an infinite free sound field has been relatively in-depth, but there is relatively little research on sound source identification and localization in limited spaces, especially those with sound absorption and insulation materials. The identification and reconstruction of the acoustical steady propagation field radiated from a single frequency finite space are studied numerically using discrete elements based on the phase conjugation method by FEM. Two different kinds of array forms of phase conjugation arrays are studied for sound source localization such as the planar array and the linear array. In addition, the influences of the existence of sound-absorbing material on the wall on the focusing properties are also discussed. The numerical results show that: The phase conjugation method can completely achieve the identification and location of the acoustical source finite space no matter using the planar array form or the linear array according to FEM. The linear array form can obtain the subwavelength focusing with fewer elements. The optimal distance between the array and the sound source is 0.5 λ and 2 λ to get the best reconstruction results. The smaller the absorption coefficient, the more to meet the multi-path phase compensation principle, the better reconstruction of the sound source. [ABSTRACT FROM AUTHOR]

Optical communication systems introduced paradigm shift in the forte of data transmission at higher speeds and over longer distances where, on contrary electrical transmission systems failed due to higher amplitude degradation, interferences and lower bandwidths. However, pulse width increase (PWI) in the optical fiber limits the overall distance reach and also introduces more bit errors which needs to addressed. So far, pulse width shortening fibers (PFs) and fiber Bragg grating (FG) used individually in most of the reported studies, however pulse width shortening (PWS) took either high cost (in PFs) or lower PWS efficiency (PWSE) (in FG). Therefore, in this research manuscript, we made emphasis on the combined PWS effects of diverse techniques such as optical phase conjugation (OC), FG and PFs in ultra-dense wavelength division multiplexing (WDM) system. Total link length of 400 km has been covered in 128 channels ultra dense wavelength division multiplexing (UDWDM) system at 10 Gbps by incorporating diverse combined organized placements of FG, OC and PFs such as FG-PF, OC-PF and FG-PF-OC. Results revealed that economical and maximum PWSE arrangement for proposed system is FG-PF-OC. [ABSTRACT FROM AUTHOR]

Optical phase conjugation (OPC) is a nonlinear technique used for counteracting wavefront distortions, with applications ranging from imaging to beam focusing. Here, we present a diffractive wavefront processor to approximate all-optical phase conjugation. Leveraging deep learning, a set of diffractive layers was optimized to all-optically process an arbitrary phase-aberrated input field, producing an output field with a phase distribution that is the conjugate of the input wave. We experimentally validated this wavefront processor by 3D-fabricating diffractive layers and performing OPC on phase distortions never seen during training. Employing terahertz radiation, our diffractive processor successfully performed OPC through a shallow volume that axially spans tens of wavelengths. We also created a diffractive phase-conjugate mirror by combining deep learning-optimized diffractive layers with a standard mirror. Given its compact, passive and multi-wavelength nature, this diffractive wavefront processor can be used for various applications, e.g., turbidity suppression and aberration correction across different spectral bands. The authors present a diffractive optical processor that approximates optical phase conjugation operation without any digital computing. This compact and all-optical wavefront processor can be used for various applications, including turbidity suppression and aberration correction. [ABSTRACT FROM AUTHOR]

This paper describes the recent advances in device designs and optical transmission applications of semiconductor optical amplifiers (SOA). The device advances described are quantum-dot-based SOA and photonic-integrated circuits using SOA. The use of nonlinear properties of SOAs in high-speed optical transmission is discussed. [ABSTRACT FROM AUTHOR]

Structured light with multiple degrees of freedom has inspired many advanced applications, and its nonlinear control plays an important role in the interactions between light and matter. Stimulated Brillouin scattering (SBS) based on light–sound coupling can be used to realize wavefront‐reversal nonlinear reflection of ordinary light; consequently, it is used to correct wavefront aberrations in high‐power laser systems. However, high‐fidelity wavefront reversal of structured light with orbital angular momentum and high‐reflectivity single‐end SBS of weak incident waves remain challenging. Here, the authors propose a cross‐pump focused SBS scheme that enables wavefront reversal with high fidelity, low threshold, and high reflectivity for arbitrary structured light. The authors demonstrate the capability of this approach to perform conformal and enhanced SBS reflections with a fidelity of >95% and reflectivity of >100%. Compared with the conventional focused SBS configuration, the SBS threshold is reduced by more than ten times, and wavefront reversal of weakly structured light is realized. This proof‐of‐principle study provides a high‐performance SBS platform with potential implications for high‐power structured lasers, high signal‐to‐noise‐ratio microscopy imaging, and the development of nonlinear optics with structured light. [ABSTRACT FROM AUTHOR]

Noise pollution is the most serious environmental pollution, which seriously affects people's normal life and physical and mental health, as well as normal production work. Therefore, noise control is necessary, but before noise control, the first thing to do is to identify the location of the noise source, and the noise control work is meaningless when the noise cannot be identified. Flat plate structures are a fundamental part of complex ship structures, and their vibration, noise, and their interrelationships when excited by the outside world are receiving increasing attention. The core of the research in this paper is the identification of the sound source of the vibrating plate. A method combining phase conjugation with interior boundary element method is developed for the identification of the pressure and normal velocity distribution of a vibrating plate. An interior problem is formed by enclosing the phase conjugation array plane and the plate surface. The pressures at the array elements are phase-conjugated as the specified pressure boundary condition. The impedance relationship between the surface pressure and the surface normal velocity of the plate is utilized as a specified impedance boundary condition. The interior boundary element method is applied to solve the interior problem. The identification of the surface pressure and normal velocity distribution is studied numerically. The numerical results show that with the array located in the near field the proposed method achieves subwavelength focusing to identify the surface pressure and normal velocity distribution and clearly shows the response shapes. [ABSTRACT FROM AUTHOR]

In the discretely amplified transmission systems with erbium-doped fiber amplifiers, the system performance of nonlinearity-compensated optical transmission based on pre-dispersed spectral inversion (PSI) is investigated numerically. We find that PSI offers more significant performance improvement in dispersion-managed (DM) links than that in non-dispersion-managed (noDM) links. On the other hand, the DM link is more sensitive to the span offset from the center of the transmission link than noDM link. The performance difference between DM and noDM links is 1 dB if the span offset equals four spans in 20 × 90 km nonlinear transmission. Furthermore, we show that for the dispersion-managed transmission, in order to obtain the best system performance, the amount of pre-dispersion of the PSI, should be optimized over different dispersion maps. [ABSTRACT FROM AUTHOR]

The intrinsic noise of different transformers in the same substation belongs to the same type of noise, which is strongly coherent and difficult to separate, greatly increasing the cost of substation noise assessment and treatment. To solve the problem, the present paper proposes a noise separation technique using the phase conjugation method to separate the intrinsic noise signals of different transformers: firstly, the reconstruction of sound source information is realized by the phase conjugation method based on the measurement and emission of a line array; secondly, the intrinsic noise signals of the sound source are obtained by the equivalent point source method. The error of the separation technique is analyzed by point source simulation, and the optimal arrangement form of the microphone line array is studied. A validation experiment in a semi-anechoic chamber is also carried out, and the results prove that the error of separation technique is less than 2dBA, which is the error tolerance of engineering applications. Finally, a noise separation test of three transformers is performed in a substation using the proposed technique. The results show that the proposed technique is able to realize the intrinsic noise separation of each transformer in the substation, which is of positive significance for substation noise assessment and management. [ABSTRACT FROM AUTHOR]

Abstract The authors analyse the influence of reference sphere on the test accuracy of Ritchey–Common method during testing of flat mirror surface. A simulation model is established to simulate the influence of different radii of curvature of reference sphere on system wavefront. Then, the difference between the flat mirror surface result with reference sphere surface error to the actual flat mirror surface is examined by this model. The test accuracy of flat mirror result can be effectively improved by eliminating the influence of the surface error of reference sphere. When the surface accuracy of the reference sphere is better than 0.01 λ, the influence on RMS test accuracy is within 0.01 λ. R–C test path is built to test a 100 mm‐diameter flat mirror surface, and its results are compared with those of the flat mirror surface without surface error of reference sphere and with the test result of the interferometer. When the surface accuracy of the actual used area of reference sphere is better than 0.01 λ, the effect on flat mirror RMS accuracy is within 0.01 λ. The RMS test accuracy can reach 0.01 λ, when the surface error of reference sphere is retained. The experiment verifies the correctness of the simulation results and guarantees the improvement in the test accuracy of R–C method.

In order to break through the diffraction limit of traditional sound sources, an idea of far-field super-resolution imaging based on acoustic superlens is proposed, that is, acoustic super-lens is used to transmit near-field sound field information to the far-field, and far-field super-resolution imaging is realized by combining phase conjugate algorithm. In this paper, the sound source localization effect of the two-dimensional honeycomb acoustic superlens of water/mercury material is systematically studied, and the sub-wavelength imaging with a resolution of 0.22λ is obtained by simulating the point sound source imaging through numerical simulation, and the imaging principle of the refractive index n = –1 configuration is explained by combining the imaging principle of flat lens imaging and the law of refraction. A multi-lens was designed for far-field localization of point sound sources, and sub-wavelength imaging with a resolution of 0.19 λ was obtained. [ABSTRACT FROM AUTHOR]

The authors analyse the influence of reference sphere on the test accuracy of Ritchey–Common method during testing of flat mirror surface. A simulation model is established to simulate the influence of different radii of curvature of reference sphere on system wavefront. Then, the difference between the flat mirror surface result with reference sphere surface error to the actual flat mirror surface is examined by this model. The test accuracy of flat mirror result can be effectively improved by eliminating the influence of the surface error of reference sphere. When the surface accuracy of the reference sphere is better than 0.01 λ, the influence on RMS test accuracy is within 0.01 λ. R–C test path is built to test a 100 mm‐diameter flat mirror surface, and its results are compared with those of the flat mirror surface without surface error of reference sphere and with the test result of the interferometer. When the surface accuracy of the actual used area of reference sphere is better than 0.01 λ, the effect on flat mirror RMS accuracy is within 0.01 λ. The RMS test accuracy can reach 0.01 λ, when the surface error of reference sphere is retained. The experiment verifies the correctness of the simulation results and guarantees the improvement in the test accuracy of R–C method. [ABSTRACT FROM AUTHOR]

The stimulated Brillouin scattering phase conjugation mirror (SBS-PCM) based on liquid media is widely used in high-power laser systems due to its robust thermal load capacity, high energy conversion efficiency and improved beam quality. Nevertheless, with an increase in the pump repetition rate, thermally-induced blooming and optical breakdown can emerge, leading to distortions in the Stokes beam. In this study, we delved into the thermal effects in liquid SBS-PCMs employing hydrodynamic analysis, establishing a relationship between beam profile distortion and the thermal convection field. We calculated the temperature and convection velocity distribution based on the pump light parameters and recorded the corresponding beam profiles. The intensities of the beam profiles were modulated in alignment with the convection directions, reaching a velocity peak of 2.85 mm/s at a pump pulse repetition rate of 250 Hz. The residual sum of squares (RSS) was employed to quantify the extent of beam profile distortion relative to a Gaussian distribution. The RSS escalated to 7.8, in contrast to 0.7 of the pump light at a pump pulse repetition rate of 500 Hz. By suppressing thermal convection using a high-viscosity medium, we effectively mitigated beam distortion. The RSS was reduced to 0.7 at a pump pulse repetition rate of 500 Hz, coinciding with a twentyfold increase in viscosity, thereby enhancing the beam quality. By integrating hydrodynamic analysis, we elucidated and mitigated distortion with targeted solutions. Our research offers an interdisciplinary perspective on studying thermal effects and contributes to the application of SBS-PCMs in high-repetition-rate laser systems by unveiling the mechanism of photothermal effects. [ABSTRACT FROM AUTHOR]

Significance: In nonballistic regime, optical scattering impedes high-resolution imaging through/inside complex media, such as milky liquid, fog, multimode fiber, and biological tissues, where confocal and multiphoton modalities fail. The significant tissue inhomogeneity-induced distortions need to be overcome and a technique referred as optical wavefront shaping (WFS), first proposed in 2007, has been becoming a promising solution, allowing for flexible and powerful light control. Understanding the principle and development of WFS may inspire exciting innovations for effective optical manipulation, imaging, stimulation, and therapy at depths in tissue or tissue-like complex media. Aim: We aim to provide insights about what limits the WFS towards biomedical applications, and how recent efforts advance the performance of WFS among different trade-offs. Approach: By differentiating the two implementation directions in the field, i.e., precompensation WFS and optical phase conjugation (OPC), improvement strategies are summarized and discussed. Results: For biomedical applications, improving the speed of WFS is most essential in both directions, and a system-compatible wavefront modulator driven by fast apparatus is desired. In addition to that, algorithm efficiency and adaptability to perturbations/noise is of concern in precompensation WFS, while for OPC significant improvements rely heavily on integrating physical mechanisms and delicate system design for faster response and higher energy gain. Conclusions: Substantial improvements in WFS implementations, from the aspects of physics, engineering, and computing, have inspired many novel and exciting optical applications that used to be optically inaccessible. It is envisioned that continuous efforts in the field can further advance WFS towards biomedical applications and guide our vision into deep biological tissues. [ABSTRACT FROM AUTHOR]

Three different stimulated Brillouin scattering (SBS) configurations in perfluorooctane were experimentally compared to achieve the ultimate compression of ~1.1 ns pulses from a commercially available Nd:YAG mini-laser. These schemes contained either a focusing lens and a plane feedback mirror, a spherical mirror, or variable pulse splitting to provide self-seeding of the SBS. In the optimal configuration with a focusing lens and return mirror, 93 ps pulses with an energy of 9.5 mJ were achieved at the output of the double-pass phase-conjugated Nd:YAG amplifier. The resulting diffraction-free, high-quality beams with M2~1.2 and excellent pointing stability are of practical interest for scientific, medical, and industrial applications. [ABSTRACT FROM AUTHOR]

Ensuring operational reliability in machinery requires accurate fault detection. While time-domain vibration pulsation signals are intuitive for pattern recognition and feature extraction, downsampling can reduce analytical complexity, but may result in low-precision data, affecting fault detection performance. To address this, we propose time–frequency feature fusion, combining information from both the time and frequency domains for fault detection. Our approach transforms vibrational pulse data into instantaneous revolutions per minute (RPM) and employs statistical analysis for the time-domain features. For the frequency-domain features, we use the combined method of empirical mode decomposition and independent component analysis (EMD-ICA), along with the Wigner bispectrum method to capture the nonlinear characteristics and phase conjugation. Using a deep neural network (DNN), we classify the anomaly states, demonstrating the effectiveness and versatility of our approach in detecting anomalies and improving diagnostic precision. Compared to using time or frequency features alone, our time–frequency feature fusion model achieves higher accuracy, with 100% accuracy at lower downsampling rates and 96.3% accuracy at a downsampling rate of 100×. [ABSTRACT FROM AUTHOR]

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To improve the reconstruction accuracy in the fringe projection profilometry (FPP), a bidimensional empirical mode decomposition and principal component analysis (BEMD&PCA) algorithm are proposed to directly acquire the object phase from fundamental-frequency component which includes the carrier phase and object phase. BEMD is employed to remove the zero frequency to reduce the spectrum overlapping. A reduced-size spectrum is adopted to limit the size of the spectrum for principal component analysis. PCA is used to decompose the phase into several principal components and extract the carrier phase from the first dominant component, and the object phase can be acquired by multiplying with the carrier phase conjugation. The experiment and analysis results illustrate that the proposed method has the merit of less error distribution and single-frame acquisition. [ABSTRACT FROM AUTHOR]

The degradation of three antibiotics (sulfamethoxazole, trimethoprim, and ofloxacin) and one synthetic hormone (17 α-ethinylestradiol) was investigated in three in-vitro biotransformation models (i.e., pure enzymes, hairy root, and Trichoderma asperellum cultures) for anticipating the relevance of the formation of transformation products (TPs) in constructed wetlands (CWs) bioaugmented with T. asperellum fungus. The identification of TPs was carried out employing high-resolution mass spectrometry, using databases, or by interpreting MS/MS spectra. An enzymatic reaction with β-glucosidase was also used to confirm the presence of glycosyl-conjugates. The results showed synergies in the transformation mechanisms between these three models. Phase II conjugation reactions and overall glycosylation reactions predominated in hairy root cultures, while phase I metabolization reactions (e.g., hydroxylation and N-dealkylation) predominated in T. asperellum cultures. Following their accumulation/degradation kinetic profiles helped in determining the most relevant TPs. Identified TPs contributed to the overall residual antimicrobial activity because phase I metabolites can be more reactive and glucose-conjugated TPs can be transformed back into parent compounds. Similar to other biological treatments, the formation of TPs in CWs is of concern and deserves to be investigated with simple in vitro models to avoid the complexity of field-scale studies. This paper brings new findings on the emerging pollutants metabolic pathways established between T. asperellum and model plants, including extracellular enzymes. [ABSTRACT FROM AUTHOR]

Transcranial focused ultrasound stimulation is a promising therapeutic modality for human brain disorders because of its noninvasiveness, long penetration depth, and versatile spatial control capability through beamforming and beam steering. However, the skull presents a major hurdle for successful applications of ultrasound stimulation. Specifically, skull-induced focal aberration limits the capability for accurate and versatile targeting of brain subregions. In addition, there lacks a fully functional preclinical neuromodulation system suitable to conduct behavioral studies. Here, we report a miniature ultrasound system for neuromodulation applications that is capable of highly accurate multiregion targeting based on acoustic holography. Our work includes the design and implementation of an acoustic lens for targeting brain regions with compensation for skull aberration through time-reversal recording and a phase conjugation mirror. Moreover, we utilize MEMS and 3D-printing technology to implement a 0.75-g lightweight neuromodulation system and present in vivo characterization of the packaged system in freely moving mice. This preclinical system is capable of accurately targeting the desired individual or multitude of brain regions, which will enable versatile and explorative behavior studies using ultrasound neuromodulation to facilitate widespread clinical adoption. [ABSTRACT FROM AUTHOR]

An optimized design for a broadband Raman optical amplifier in standard single-mode fiber covering the C and L bands is presented, to be used in combination with wideband optical phase conjugation (OPC) nonlinearity compensation. The use of two Raman pumps and fiber Bragg grating reflectors at different wavelengths for the transmitted (C band) and conjugated (L band) WDM channels is proposed to extend bandwidth beyond the limits imposed by single-wavelength pumping, for a total 10 THz. Optimization of pump and reflector wavelength, as well as pump powers, allows us to achieve low asymmetry across the whole transmission band for optimal nonlinearity compensation. System performance is simulated to estimate OSNR, gain flatness and nonlinear Kerr distortion. [ABSTRACT FROM AUTHOR]

• Controlling the vector light field through scattering media was developed based on digital optical phase conjugation technique. • Feasibility of vector superposition of multiple phase conjugate beams was verified experimentally. • Digital holography is used for speckle field recording and analysis of superposed phase conjugated beams. • The simultaneous loading and modulation of four conjugate phase maps are achieved by split-screen multiplexing of dual SLMs. Vector modulation of the light field through scattering media holds significant scientific and application value in areas such as optical imaging, optical communications, nonlinear optics, and biomedicine. Digital optical phase conjugation (DOPC), grounded in the time reversal principle, has been extensively investigated for wavefront shaping in scattering media. Nonetheless, reports on vector modulation of phase conjugate beams via DOPC remain scarce. In this study, we propose a vector DOPC to recover and modulate the polarization state of the phase conjugate beams based on vector decomposition and superimposition of light field. First, pre-set two orthogonal polarization basis probe beams to pass through a multimode fiber and use digital holography to record the phase distribution of their orthogonal polarization components in the speckle field. Then, perform polarization-preserving phase conjugation and vector superposition of both components simultaneously. By altering the phase difference and amplitude ratio between the two, vector modulation of the synthesized phase conjugate beam can be achieved. Theoretical analysis aligns well with experimental results, demonstrating a positive impact on understanding the physical properties of scattering media and expanding the applications of the DOPC technique. [ABSTRACT FROM AUTHOR]

• The use of fused silica as an all-solid-state SBS-PCM significantly improves the beam quality factor from 1.23 to 1.085 times the diffraction limit. • The SBS-PCM system achieved a maximum output energy of 672 mJ from an input energy of 75.2 mJ, demonstrating a substantial magnification of approximately 9 times. • The SBS-PCM effectively mitigates unfavorable diffraction patterns induced by the hard-edge aperture, leading to a more uniform beam profile. • The coefficient of determination (R 2) of the beam profile improved by 2.18% compared to that of the high-reflection mirror. Beam quality is critical for laser applications in both scientific and industrial fields. Stimulated Brillouin scattering phase conjugate mirror (SBS-PCM) serves as an effective beam cleanup scheme due to its phase conjugation properties. In this work, a SBS-PCM using fused silica was constructed and employed in a double-pass amplifier setup. With an input energy of 75.2 mJ, the system achieved a maximum magnification of approximately 9 times, resulting in an output energy of 672 mJ. Comparative analysis with a high-reflection mirror revealed that the SBS-PCM effectively mitigated unfavorable diffraction patterns induced by the hard-edge aperture in the near-field pattern, improving the beam quality factor from 1.23 to 1.085 times the diffraction limit. Additionally, the coefficient of determination (R 2) of the beam profile improved by 2.18 % compared to that of the high-reflection mirror. These results indicate that the free-space all-solid-state SBS-PCM can provide a promising approach to improving beam quality for high-power laser systems. [ABSTRACT FROM AUTHOR]

Due to their ability to boost transmission rate and reach by compensating for Kerr nonlinearity-induced distortions, optical compensation techniques are interesting for broadband wavelength division multiplexing. This is due to the fact that these techniques have been shown to increase transmission rate. Yet, in the majority of instances, they call for more devices to be integrated into the network. This can be challenging for systems that are already in place, and it can be even more challenging for transmissions that are not repeated. The linear and nonlinear compensation system for the Dense Wave Division Multiplexing (DWDM) transmission system has been created and researched in this work. Along the optical link, a new method known as optical phase conjugation (OPC) is used as part of the process of improving the performance of communication systems. This method is used to improve the performance of 896 Gb/s sixteen channels dual polarization signalling of 50 GHz channel spacing over 800 km with three scenarios that use mid and multiple OPC. The results of the simulation indicate that multiple OPC with backward Raman amplifier method on the received signal is effective for nonlinearity compensation when compared with the mid OPC module in terms of enhanced Q-factor improvement, BER performance, EVM, and maximum transmission link length.

The propagation of a linearly polarized transverse sound wave in a semiconductor layer with a certain crystallographic structure with a sufficiently high concentration of conduction electrons is considered. The semiconductor layer is located in a spatially uniform magnetic field directed perpendicular to the plane of incidence of the sound wave and modulated with the sound frequency. The relationship between the plasma subsystem and acoustic oscillations in the layer is achieved due to the internal piezoelectric field. It is shown that propagation of a sound beam under these conditions is accompanied by a counterpropagating sound wave with a conjugated wave front. The conversion coefficient of direct and phase-conjugated waves is found. [ABSTRACT FROM AUTHOR]

Nonsteroidal anti‐inflammatory drugs represent one of the most popularly used classes of drugs. However, their long‐term administration is associated with various side effects including gastrointestinal ulceration. One of the major reasons of NSAIDs ulcerogenicity is direct damage of the epithelial lining cells by the acidic moieties present in many drugs. Another drawback for this acidic group is its rapid metabolism and clearance through Phase II conjugation. Three series of thiophene and thienopyrimidine derivatives were designed and synthesized as nonacidic anti‐inflammatory agents. In vivo testing of their analgesic activity indicated that compounds 2b and 7a‐d showed higher PI values than that of the positive control drugs, indomethacin and celecoxib. The latter compounds 2b and 7a‐d were subjected to further anti‐inflammatory activity testing where they showed comparable percentage edema inhibition to that of indomethacin and celecoxib. Compounds 2b, 7a, 7c, and 7d inhibited PGE2 synthesis by 61.10%–74.54% (71.47% for indomethacin, and 80.11% for celecoxib). The same compounds inhibited the expression of rat mPGES‐1 and cPGES3 by 74%–83% (77% for indomethacin, and 82% for celecoxib) and 48%–70% (62% for indomethacin, and 70% for celecoxib), respectively. The stability of the most active compound 2b in Nonenzymatic gastrointestinal fluids and in human plasma was tested. Additionally, studying the metabolic stability of compound 2b in S9 rat liver fraction showed that it displayed a slow in vitro clearance with half‐life time 1.5‐fold longer than indomethacin. The metabolites of 2b were predicted via UPLC‐MS/MS. In silico ADMET profiling study was also included. [ABSTRACT FROM AUTHOR]

A dispersion map was proposed to improve the compensation effect of a distorted WDM (wavelength division multiplexed) channel in a dispersion-managed link coupled with optical phase conjugation. The dispersion map is an origin-symmetric structure around the optical phase conjugator in the middle of the transmission path. In addition, the dispersion map has a form in which a constant dispersion accumulation pattern is repeated regularly. Through simulation, we confirmed that the application of the origin-symmetric dispersion map with a repetitively shaped configuration was more effective in compensating for the distorted WDM channel than in the dispersion-managed link with a conventional dispersion map. In addition, we confirmed that the compensation effect could be increased when the cumulative dispersion distribution of the origin-symmetric distribution map had a positive value in the first half section and a negative value in the second half section. Further, we observed that as the number of repeated dispersion accumulation patterns increased, the residual dispersion per span should also be increased. [ABSTRACT FROM AUTHOR]

Scattering-medium-based optical image encryption provides an intrinsically tamper-resistant physical key. In this paper, we utilize a scattering medium with ideal optical properties as the physical key. The plaintext is transformed into four noise-like holograms with the help of the four-step phase-shifting digital holography. Low-frequency components of the four holograms are extracted and combined into a new image by the lifting wavelet transform (LWT). Then the combined image is scrambled by the nonlinear 3D chaos-based cyclic shift. In decryption, the digital optical phase conjugation (DOPC) technique is utilized to extract plaintext. Numerical simulations prove the feasibility of the proposed method, and the security analysis shows that our method can resist different attacks. [ABSTRACT FROM AUTHOR]

We propose a spatial mode compensation method using progressive phase conjugation (PPC) to establish a dynamic control technology for mode distribution in multi-mode fiber (MMF). PPC is a phase conjugate generation technology that can be far away from the signal source and does not require an additional reference beam. We confirm the basic operation of the proposed scheme by considering the coupling efficiency between the compensated spatial mode component and incident mode. We quantitatively evaluate the mode recovery from the mixed state of LP11, LP22, LP02, and LP31 to LP01, the fundamental mode. Using a random optical diffuser to uniformly scatter the intensity distribution of the signal beam, high compensation performance can be obtained because the influence of the mode intensity distribution is reduced. [ABSTRACT FROM AUTHOR]

The weakness of the dispersion-managed link, which is combined with optical phase conjugation to compensate for optical signal distortion caused by chromatic dispersion and the nonlinear Kerr effect of the standard single mode fiber is, its limited structural flexibility. We propose a dispersion map that can simultaneously compensate for the distorted wavelength division multiplexed signal while increasing the configurational flexibility. Each residual dispersion per span (RDPS) in the former half of the proposed link is randomly determined, and in the latter half, the arrangement order of RDPS is the same as or inverted in the former half. We confirm that the dispersion maps in which the RDPS distribution pattern in the latter half is opposite to the arrangement order in the former half are more effective in compensation, and the compensation effect is better than in the dispersion map of the conventional scheme. The notable result of this study is that the flexibility can be increased by randomly arranging RDPS in the former half, and compensation improvement can be achieved by inversing the order of RDPS arrangement of the former half in the latter half, which makes the dispersion profile of each half link roughly symmetric with respect to the midway optical phase conjugator. [ABSTRACT FROM AUTHOR]

In this paper, we investigate various designs of distributed Raman amplifier (DRA) to extend amplification bandwidth in mid-link optical phase conjugation (OPC) systems and compare bands 191–197 THz and 192–198 THz giving a total bandwidth of 6 THz using a single wavelength pump. We demonstrate the use of highly reflective fiber Bragg grating (FBG) to minimize gain variation across a WDM grid by optimizing forward and backward pump powers as well as the wavelength of FBGs for original and conjugated channels. Finally, we also simulate OSNR and Kerr nonlinear reduction as a product of signals asymmetry and nonlinear phase shift (NPS) for all channels. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surfaces (RISs) are gaining huge momentum in the field of wireless communications due to the paradigm shift that they bring. Indeed, they allow making any environment electromagnetically smart and dynamically reconfigurable for more efficient and greener wireless communications. As physicists, we proposed to use electronically tunable metasurfaces to shape the electromagnetic waves carrying our wireless communications in reflection almost ten years ago, inspired by some works that we and colleagues did in the field of wave control in complex media. In this article, we review the seminal works that led us to propose this concept, starting from the original one that is time reversal. Then, we propose a physicist’s point of view of RISs using a comparison with phase conjugation. Finally, we highlight what we think are their limitations, relying on both our knowledge of wave control and our study of them over a decade. [ABSTRACT FROM AUTHOR]