Phase Mismatch Research Articles

Tailoring the pulse characteristics of LiB3O5-based femtosecond optical parametric oscillators by temperature tuning.

We show that the phase mismatch in LiB3O5 (LBO) crystals is approximately proportional to the temperature deviation from the phase-matching temperature of crystals. Moreover, a fixed temperature deviation would result in approximately the same amount of phase mismatch over a large range of wavelengths. Based on this, we demonstrate that the pulse characteristics of LBO-based femtosecond optical parametric oscillators (OPOs) can be tailored by simply tuning the crystal temperature. Experimentally, at a temperature deviation of 10°C, nearly transform-limited optical pulses were obtained over a tuning range of 780-910 nm, and at a temperature deviation of -9°C, linearly chirped pulses with broadened spectra were obtained, which were de-chirped to be nearly transform-limited ones outside the cavity. The capability of generating femtosecond pulses with different pulse characteristics and at various wavelengths would benefit many applications, including spectroscopy and Raman microscopy.

Determination of the Sound Intensity Vector Field from Synchronized Sound Pressure Waveforms

Visualization of vector acoustic fields using sound intensity measurements is a very interesting field of acoustics and has numerous applications. Unfortunately, sound intensity measurement itself requires specialized measuring instruments (presure–presure (PP) or pressure–velocity (PU)-type probes). This article presents a simplified and low-cost method of sound intensity measurement based on sound pressure measurements made synchronously. This allows for the use of a single microphone and eliminates one of the main problems of the classical PP probe, which is the phase mismatch of two different microphones. The described method was used to visualize the vector acoustic field in front of an active loudspeaker. The results were compared qualitatively and quantitatively with measurements made with a commercial PU intensity probe. The results obtained showed that the proposed method has the same level of metrological accuracy.

Dynamically controllable two-color electromagnetically induced grating via spatially modulated inelastic two-wave mixing

A scheme for controlling two-color electromagnetically induced grating (TCEIG) in a coherently prepared cold atomic ensemble with a four-level inverted Y-type configuration is proposed via exploiting inelastic two-wave mixing process. By adding an intensity mask behind the auxiliary control field, the transmission functions of the incident probe field and the generated signal field are modulated periodically, thereby leading to the formation of TCEIG. Using experimentally achievable parameters, both the probe and signal fields with different frequencies can be simultaneously diffracted into high-order diffractions. It is found that the diffraction efficiencies of TCEIG, especially the first-order diffraction efficiency, can be significantly improved via adjusting the detunings of the probe and signal fields. Furthermore, it is also demonstrated that the diffraction of TCEIG can be manipulated via tuning the intensity and detuning of the control field. Finally, we investigate the influence the phase mismatch on the diffraction of TCEIG. It is shown that the diffraction pattern of the probe field is rather robust against the phase mismatch, while the diffraction intensities of the signal field are suppressed by the phase mismatch. Our scheme may provide a possibility for the all-optical control of optical switch and wavelength division multiplexing.

Generation of Tunable Three‐Photon Entanglement in Cubic Nonlinear Coupled Waveguides

AbstractThe generation of three‐photon states with spatial entanglement in cubic nonlinear coupled waveguides is theoretically investigated using third‐order spontaneous parametric down‐conversion and quantum walks. This approach involves independently pumping two coupled waveguides to generate a path‐encoded three‐photon Greenberger–Horne–Zeilinger (GHZ) state, which then evolves with complex spatial dynamics governed by coupling coefficients and phase mismatch. By appropriate parameter tuning, the generation of robust heralded Bell states is demonstrated, uniform states, and GHZ‐like states at the chip output. This work demonstrates an integrated source of three‐photon spatial entanglement on a simple chip, offering additional reconfigurability for advanced multiphoton quantum applications.

Iron-Induced Lipid Oxidation Alters Membrane Mechanics Favoring Permeabilization.

Ferroptosis is a form of regulated necrosis characterized by the iron-dependent accumulation of lipid peroxides in cell membranes. However, how lipid oxidation via iron-mediated Fenton reactions affects the biophysical properties of cellular membranes and how these changes contribute to the opening of plasma membrane pores are major questions in the field. Here, we characterized the dynamics of membrane alterations during lipid oxidation induced onsite by Fenton reactions in chemically defined in vitro model membrane systems. We find that lipid vesicle permeabilization kinetically correlates with the appearance of malondialdehyde (MDA), a product of lipid oxidation. Iron-induced lipid oxidation also alters the lateral organization of supported lipid bilayers (SLBs) with lipid phase coexistence in a time-dependent manner, reducing the lipid phase mismatch and the circularity of liquid ordered domains, which indicates a decrease in line tension at the phase boundaries. Further analysis of oxidized SLBs by force spectroscopy reveals a significant decrease in the average membrane breakthrough force upon oxidation, resulting from changes in lipid bilayer organization that make it more susceptible to permeabilization. Our findings suggest that lipid oxidation via iron-mediated Fenton-like reactions induces strong changes in membrane lipid interactions and mechanical properties leading to reduced line tension in the permeabilized state of the bilayer, which promotes membrane pore formation.

Numerical Investigation of Raman-Assisted Four-Wave Mixing in Tapered Fiber Raman Fiber Amplifier

The generation of unwanted higher-order Raman effects is the main factor restricting the power scaling of Raman fiber amplifiers (RFAs). This phenomenon arises from an interplay of physical processes, including stimulated Raman scattering (SRS), four-wave mixing (FWM), and the intricate temporal and spectral dynamics. Tapered fibers have demonstrated excellent nonlinear effects suppression characteristics due to the varying core diameter along the fiber, which is widely used in ytterbium-doped fiber lasers. In this paper, a comprehensive numerical investigation is conducted on the core-pumping tapered fiber RFAs considering Raman-assisted FWM. The higher-order Raman power in the tapered fiber is always kept at a low level, showing a weak Raman-assisted FWM effect. A numerical investigation is conducted to study the impact of the tapering ratio, the lengths of the thin part, tapered region, and thick part on the higher-order Raman threshold of RFAs. Furthermore, the impact of phase mismatch variations caused by changes in the seed wavelength, on the output signal power and nonlinear effects is analyzed. This paper presents, for the first time, a study on core-pumped RFAs using tapered fibers, providing a novel perspective on enhancing the power of RFAs.

Controller Area Network (CAN) Bus Transceiver with Authentication Support and Enhanced Rail Converters

This paper presents an advanced Controller Area Network (CAN) bus transceiver designed to enhance security using frame-level authentication with the concept of a nonphysical virtual auxiliary data channel. We describe the newly conceived transceiver security features and provide results concerning the design, implementation, fabrication and test of the transceiver to validate its functionality and robust operation in the presence of systemic error sources including Process, Voltage, and Temperature (PVT) variations. The virtual auxiliary channel integrates CAN frame authentication signatures into the primary data payload via phase modulation while also providing compatibility with existing CAN protocols, interoperability with non-enhanced systems and requiring no network or software modifications. Enhanced rail converters are designed to facilitate single-rail to dual-rail data conversion and vice versa, preserving phase information and minimizing phase errors across various nonideal effects such as frequency drift, Process, Voltage, and Temperature (PVT) variations, and cable phase mismatch. This ensures reliable data transmission and robust authentication in the presence of adversarial cyberattacks such as packet injection. The receiver recovers both the CAN frame data and the security signature, comparing the latter with an authorized signature to provide a real-time “GO/NO_GO” signal for verifying packet authenticity and without exceeding the CAN clock jitter specifications.

Nonlinear optical properties of some nanosized ammonium dihydrogen phosphate crystals incorporated in aluminum oxide nanopores

This study explores the nonlinear optical properties of aluminum oxide (Al2O3) matrices embedded in ammonium dihydrogen phosphate (ADP) nanocrystals using third-harmonic generation (THG) techniques. The successful integration of ADP crystallites within the nanopores of the Al2O3 matrix was confirmed using x-ray structural analysis and electron microscopy. The optical absorption characteristics were examined over a wide wavelength range, revealing that the reflection and transmission spectra were notably affected by pore size and surface scattering effects. THG measurements conducted with a high-intensity infrared laser demonstrated a pronounced third-order nonlinear response, whereas second-harmonic generation was not observed. The absence of SHG can be attributed to phase mismatch and inherent material properties, including centrosymmetry and surface roughness. The comparative and Reintjes models were used to calculate the third-order nonlinear optical susceptibilities. Among these, the Reintjes model provided the most accurate fit for the experimental data. This research underscores the considerable influence of nanopore size on THG efficiency, highlighting the importance of light scattering and phase-matching conditions. These findings contribute to a growing body of knowledge regarding nonlinear optical phenomena in nanocomposite materials and offer valuable insights for future applications in photonic devices. This comprehensive analysis highlights the potential of Al2O3 matrices with embedded ADP nanocrystals to advance the field of nonlinear optics in nanocomposite materials and offers insights for prospective applications in photonic devices.

An Improved Phase Noise Reduction in Millimeter-Wave FBMC Systems

The next generation mobile network needs to have a spectrum above the 30 GHz radio band. The 5G system is a promising technology for future communication systems. It has been used in Device-to-Device (D2D) communications, IoT, Machine type communications (MTC), and wireless backhaul. The 5G is expected to have speeds of hundreds of times and satisfy the requirements of larger traffic density, low latency, connective density, higher capacity & reliability, data rate, super high mobility, etc. It is expected to have applications such as HD video, virtual reality & augmented reality, online games, and cloud desktops. For this, Millimeter wave (Mmwave) has been used for fifth-generation mobile networks. The millimeter wave has a frequency range from 30 to 300 GHz. When the usage of frequency is above 60 GHz, the band will acquire RF impairments such as PAPR, Phase noise, non-linearity, and phase and quadrature timing mismatch (IQTM). This article shows the Phase noise reduction in MIMO FBMC systems using Extended Kalman filter techniques.

Vortex light bullets in rotating Quasi-Phase-Matched photonic crystals

We present a methodology for the generation of stable vortex light bullets (LBs) in rotating Quasi-Phase-Matched (QPM) photonic crystals with quadratic nonlinearity. The photonic crystal is designed with a checkerboard structure, which is feasible to realize by using contemporary technological advancements. Within this framework, square- and rhombus-shaped LBs are observed, both of which are constructed as four-peak vortex mode. The control parameters include the effective phase mismatch, power, rotating frequency, and the size of checkerboard cells. These parameters play key roles in determining the distribution and stability domains of vortex LBs. In contrast to the stable vortex solitons observed in two-dimensional (2D) quadratic systems, the LBs investigated in the 3D rotating system exhibit narrower stability domains within the system’s parameter space. The rotating frequency results in the transition of LBs from quadrupole to traditional vortex modes. Potential applications of this research lie in the field of optical communications and information processing.

Topological polarization beam splitter based on directional coupling between asymmetric valley photonic crystal waveguides.

Compared with symmetric directional couplers (DCs), asymmetric DCs constructed by two or over two different parallel waveguides offer a more flexible structure and allow for easier expansion of mode channels. In this Letter, we propose a kind of asymmetric topological DC based on two different valley photonic crystal waveguides (VPCWs). According to the coupled-mode theory, phase matching induces the complete coupling for the guide modes of two different VPCWs, whereas significant phase mismatching indicates no coupling occurs. Furthermore, the asymmetric topological DCs exhibit backscattering immunity and anti-disturbance robustness owing to the topological edge states (TESs), which greatly improve the performance of asymmetric DCs. We further design a new, to the best of our knowledge, kind of topological polarization beam splitter (TPBS) at the communication wavelength of 1550 nm by ensuring that the transverse electric mode satisfies the phase matching condition, while the transverse magnetic mode is phase-mismatched. The simulated results demonstrate that the proposed TPBS exhibits highly effective polarization separation and is robust against defects. This design holds significant potential for applications in optical communication systems.

Transceiver impairment robust and joint monitoring of PDL, DGD, and CD using frequency domain pilot tones for digital subcarrier multiplexing systems

Optical performance monitoring is vital for enabling dynamically reconfigurable optical networks. This paper introduces a monitoring scheme that is robust to transceiver impairments for coherent digital subcarrier multiplexing (DSCM) systems that simultaneously monitors polarization-dependent loss (PDL), differential group delay (DGD), and chromatic dispersion (CD). In the proposed scheme, a pair of frequency domain pilot tones (FPTs) are inserted into the X and Y polarizations of the transmitted dual-polarization signal. Both the signal and the FPTs endure identical channel impairments during fiber transmission. At the receiver side, the transmitted FPTs are extracted to monitor the channel impairments. We begin by establishing a simplified system model using a single frequency tone to analyze the effects of system impairments on the frequency domain pilots. Based on this model, CD, PDL, and DGD are jointly and accurately estimated. In addition, the influences of temporal, amplitude, and phase mismatches between in-phase (I) and quadrature (Q) components of transceivers on channel impairment monitoring are completely eliminated. This achieves a channel impairment monitoring scheme that is robust to transceiver impairments. Experimental verification shows that the proposed scheme can jointly and accurately estimate a wide range of CD, PDL, and DGD. Additionally, the proposed monitoring scheme demonstrates strong robustness against transceiver impairments, rapid polarization fluctuations, and amplified spontaneous emission (ASE) noise.

Generating first-order optical vortex beams by photonic crystal slabs.

Optical vortices, which are beams with helical wavefronts and spiral phase mismatches, have garnered considerable attention in various fields. In this study, we theoretically proposed and experimentally implemented a simple method for generating first-order optical vortices. To generate first-order vortex beams using the polarization field in the momentum space of photonic crystal slabs, topological half charges are required. We propose a method to divide the polarization vortex in the momentum space by breaking symmetry, which results in Dirac points or circularly polarized points. This approach enables the transformation of topological integer charges into topological half-integer charges, thereby facilitating the generation of first-order vortex beams. This approach extends the application of bound states in continuum and topological photonics.

Characterizing electric fields in semiconductor devices: effect of second-harmonic light interference.

Characterizing electric fields in semiconductor devices using electric field-induced second-harmonic generation (EFISHG) has opened new opportunities for an advanced device design. However, this new technique still has challenges due to the interference between background second-harmonic generation (SHG) and EFISHG generated light. We demonstrate that interference effects can effectively be eliminated during EFISHG measurements by focusing the laser from the transparent substrate side of a GaN PN diode, enabling straightforward quantitative electric field analysis, in contrast to PN junction interface side measurements. A model based on wave generation and propagation is proposed and highlights the incoherence between background SHG and EFISHG light. This incoherence may be attributed to the depth of focus of the incident laser and phase mismatch between incident and SHG light.

Ultra-broadband detection of coherent infrared pulses by sum-frequency generation spectroscopy in reflection geometry.

We have newly developed, to the best of our knowledge, a detection method for broadband infrared pulses based on sum-frequency generation spectroscopy in reflection geometry, which can avoid a restriction of the detection bandwidth originating from the phase mismatch that is inevitable for the upconversion in transmission geometry. Using a GaAs crystal, we successfully demonstrated the ultra-broadband detection of the infrared pulses generated from a two-color laser-induced air plasma filament in a region from 300 to 3300 cm-1. With the advantage of ultra-short infrared pulses, the present detection method holds promise for application to time-resolved, ultra-broadband vibrational spectroscopy.

Investigation of the role of yttrium sesquioxide nanoparticles on the properties of zinc oxide ceramics

In this work, zinc oxide (ZnO) ceramics were synthesized containing 0-5wt% of cubic yttrium sesquioxide (Y 2 O 3) nanoparticles with solid state sintering technique at 1150°C. The secondary phase of Y 2 O 3 did not enter into the crystalline zinc oxide. The Y 2 O 3 acts as an inhibitor of grain growth. The absorption of the free charge carriers by the Y 2 O 3 phase influences the infrared transmissions. The minimization of the phase mismatch while transferring the electric signal caused lower losses when Y 2 O 3 was added to the zinc oxide matrices. The presence of the cubic sesquioxide at the grain boundary contributes to the interfacial polarization at lower frequencies when an alternating field is applied to the ceramics. These properties are anticipated to show a wider range of physical, optical and dielectric properties of ZnO: Y ceramics for optoelectronic applications.

Dispersion mismatch correction for evident chromatic anomaly in low coherence interferometry.

The applications of ultrafast optics to biomedical microscopy have expanded rapidly in recent years, including interferometric techniques like optical coherence tomography and microscopy (OCT/OCM). The advances of ultra-high resolution OCT and the inclusion of OCT/OCM in multimodal systems combined with multiphoton microscopy have marked a transition from using pseudo-continuous broadband sources, such as superluminescent diodes, to ultrafast supercontinuum optical sources. We report anomalies in the dispersion profiles of low-coherence ultrafast pulses through long and non-identical arms of a Michelson interferometer that are well beyond group delay or third-order dispersions. This chromatic anomaly worsens the observed axial resolution and causes fringe artifacts in the reconstructed tomograms in OCT/OCM using traditional algorithms. We present DISpersion COmpensation Techniques for Evident Chromatic Anomalies (DISCOTECA) as a universal solution to address the problem of chromatic dispersion mismatch in interferometry, especially with ultrafast sources. First, we demonstrate the origin of these artifacts through the self-phase modulation of ultrafast pulses due to focusing elements in the beam path. Next, we present three solution paradigms for DISCOTECA: optical, optoelectronic, and computational, along with quantitative comparisons to traditional methods to highlight the improvements to the dynamic range and axial profile. We explain the piecewise reconstruction of the phase mismatch between the arms of the spectral-domain interferometer using a modified short-term Fourier transform algorithm inspired by spectroscopic OCT. Finally, we present a decision-making guide for evaluating the utility of DISCOTECA in interferometry and for the artifact-free reconstruction of OCT images using an ultrafast supercontinuum source for biomedical applications.

Wideband N-Path-Based Phased-Array Receiver With Gain and Phase Mismatch Calibration

Wideband N-Path-Based Phased-Array Receiver With Gain and Phase Mismatch Calibration

Hybrid Coupler Used as Tunable Phase Shifter Based on Varactor Diodes.

This paper describes the design of a hybrid coupler with a continuously variable output phase difference. This is achieved by using reconfigurable transmission lines with electrically tunable lengths controlled by two biasing voltages through varactor diodes placed across the coupler branches. The design of the coupler is based on the quadrature hybrid structure for the case where the output phase difference is 90° and on the asymmetric structure for the other cases. The proposed coupler can achieve a tunable output phase difference from 52° to 128°, while keeping a coupling coefficient of -3 dB (± 0.5 dB) over the entire desired frequency band. To validate the simulated results, a prototype working at 3.5 GHz was fabricated and tested. The measurement results show good correspondence with the simulation results, especially when the output phase difference is 90°, while a phase mismatch of less than 7° was observed for the other cases. The presented coupler would be a great asset for antenna feeding arrays, especially the Butler matrix.

Характеристики обнаружения когерентной системы при рассогласовании квадратурных каналов

Introduction – The operation of an adaptive coherent detection system is considered. The structure of a processing device is presented, containing a series-connected shaper of quadrature signal components that convert high-frequency input radio signals to video frequency, an adaptive multi-channel coherent storage device with threshold devices. Goal – To study the influence of amplitude and phase mismatches of quadrature channel parameters, which are inevitable in practice, on the operation of an adaptive coherent detection system. Formulation of the problem – Determine the spectral-correlation characteristics of the processed signals when the parameters of the quadrature channels are mismatched. Assess the influence of amplitude and phase deviations of the parameters of quadrature channels on the characteristics of a coherent detection system. Method – The complex variable method is used, in which the input high-frequency signals are represented at the video frequency by a pair of complex conjugate real components, shifted in phase by ninety degrees. Results – A model of the processed signal is presented at the video frequency, taking into account possible mismatches in the parameters of quadrature channels in practice. Expressions are obtained and graphs of the spectral density of the complex signal are plotted separately for the amplitude and phase mismatch of the quadrature channels. It is shown that the mismatch of quadrature channels leads to the appearance in the spectrum of the output signal of phase detectors of a component at a frequency that is the mirror frequency of the signal, which leads to an increase in the probability of false detection. The results of calculations of the probability of false detection of a signal depending on the deviation of the transmission coefficients of the quadrature channels and the phase mismatch of the reference voltages of the quadrature channels are presented. Conclusion – The significant influence of amplitude and phase mismatches of the parameters of quadrature channels on the spectral-correlation characteristics of the complex signal is shown. The mismatch of the parameters of the quadrature channels leads to deterioration in the detection characteristics of the coherent processing system. The research methodology used allows us to develop requirements for the quality of tuning quadrature channels.