Optical Modes Research Articles

Simultaneous measurement of multimode squeezing through multimode phase-sensitive amplification

Multimode squeezed light is an increasingly popular tool in photonic quantum technologies, including sensing, imaging, and computation. Meanwhile, the existing methods of its characterization are technically complicated, which reduces the level of squeezing, and mostly deal with a single mode at a time. Here, for the first time, to the best of our knowledge, we employ optical parametric amplification to characterize multiple squeezing eigenmodes simultaneously. We retrieve the shapes and squeezing degrees of all modes at once through direct detection followed by modal decomposition. This method is tolerant to inefficient detection and does not require a local oscillator. For a spectrally and spatially multimode squeezed vacuum, we characterize eight strongest spatial modes, obtaining squeezing and anti-squeezing values of up to −5.2 ± 0.2 dB and 8.6 ± 0.3 dB, respectively, despite the 50% detection loss. This work, being the first exploration of an optical parametric amplifier’s multimode capability for squeezing detection, paves the way for the real-time detection of multimode squeezing.

Design and Fabrication of Multi-Magnetron Microwave Oven for High-Temperature Applications

This article examines the design, manufacture, and performance of multi-magnetron ovens capable of reaching high temperatures. Firstly, an appropriate waveguide was simulated, and the production process was completed. Then, the proposed designs for multi-magnetron ovens were simulated, and appropriate dimensions were suggested. It was reported that the average power density (PD) value of the produced multi-magnetron oven was 0.37 mW/cm², which indicates its performance and efficiency. This value was found to be compliant with standards and safe for human use. The main objective of our study was to demonstrate that waveguides can reach high temperatures at the center of the oven without affecting each other. In this context, it was observed that the temperature created by magnetrons operating in single, double, triple, and quadruple modes gradually increased at the center of the oven. The simulation results supporting this showed that the S21 parameter was -177 dB. The design proposed and applied in our study was efficient, easy to produce, safe for human use, low cost, and usable in commercial and academic studies for reaching high temperatures. Overall, the multi-magnetron oven design proved to be a successful and practical solution for applications requiring high temperatures, showcasing its potential for both industrial and research purposes. The findings of this study contribute valuable insights into the development of advanced heating technologies, demonstrating significant improvements in efficiency and safety for high-temperature applications.

Normal Form Formulae of Turing–Turing Bifurcation for Partial Functional Differential Equations With Nonlinear Diffusion

ABSTRACTFor most systems, the appearance of Turing bifurcation means that it is possible to excite Turing–Turing bifurcation, thus inducing superimposed spatial patterns, multistable spatial patterns co‐existing, and others.It is undoubtedly of interest to qualitatively analyze the structures and stability of these spatially heterogeneous solutions generated by Turing–Turing bifurcation. Therefore, in this paper, with the aid of the center manifold theory and the normal form method, for general partial functional differential equations with nonlinear diffusion, the third‐order normal form is firstly derived. It is locally topologically equivalent to the primitive partial functional differential equations at the Turing–Turing bifurcation point. And then the explicit formulae for the coefficients in the normal form associated with three different spatial modes are presented. As an application, a predator–prey model with predator–taxis is considered. It is theoretically revealed that the system admits the coexistence of a pair of stable steady states with a single characteristic wavelength and the coexistence of four stable steady states with different single characteristic wavelengths. Further, the parameter regions in which these phenomena will arise are quantitatively given. It is illustrated that the self‐diffusion of prey and predator–taxis complement each other to promote the formation for the spatially homogeneous distributions of populations.

Time-domain analysis of mode competition in ZnO nanowire lasers in inhomogeneous environments

Zinc oxide (ZnO) nanowire lasers are increasingly integrated into complex optoelectronic devices as a source of coherent radiation. To enable the rational design of these devices, it is crucial to understand how both the nanowire resonator and its surrounding environment influence mode competition and the three-dimensional structure of lasing modes. Additionally, realistic models of the lasing process must account for transient gain dynamics. In order to investigate the impact of an inhomogeneous environment, composed of various materials and structures, on mode competition, we conducted Finite-Difference Time-Domain (FDTD) simulations of the dominant lasing modes in different ZnO nanowire laser configurations. Our model describes how key parameters such as nanowire diameter, length, and substrate choice affect the field distribution in the lasing regime. We show that metallic substrates support lasing in thin nanowires in two distinct coupling regimes. Furthermore, we show that metallic particles attached to the nanowire end facets as a result of established nanowire growth techniques significantly influence lasing threshold, field distribution and competition between counter-propagating modes. We show that attaching an aluminum particle at the end facet of a ZnO nanowire leads to a threshold reduction, a switching of the dominant lasing mode and a mono-directional power flow inside a large segment of the nanowire.

On-chip microresonator dispersion engineering via segmented sidewall modulation

Microresonator dispersion plays a crucial role in shaping the nonlinear dynamics of microcavity solitons. Here, we introduce and validate a method for dispersion engineering through modulating a portion of the inner edge of ring waveguides. We demonstrate that such partial modulation has a broadband effect on the dispersion profile, whereas modulation on the entire resonator’s inner circumference leads to mode splitting primarily affecting one optical mode. The impact of spatial modulation amplitude, period, and number of modulations on the mode splitting profile is also investigated. Through the integration of four modulated sections with different modulation amplitudes and periods, we achieve mode splitting across more than 50 modes over a spectral range exceeding 100 nm in silicon nitride resonators. These results highlight both the simplicity and efficacy of our method in achieving flatter dispersion profiles.

Real-time modal decomposition of fiber laser beams using a spatial mode multiplexer.

A novel, to the best of our knowledge, approach for the modal decomposition of a fiber laser beam is demonstrated using a spatial mode multiplexer. Since the modal decomposition is carried out optically, this approach is able to obtain the modal content at speeds up to the GHz level. In order to demonstrate such performance, we have applied this approach to the modal analysis of a Q-switched pulse generated in a multimode fiber with alternating intra-pulse mode content.

Hybrid Hermite-Laguerre-Gaussian vector modes.

Vector modes are well-defined field distributions with spatially varying polarization states, rendering them irreducible to the product of a single spatial mode and a single polarization state. Traditionally, the spatial degree of freedom of vector modes is constructed using two orthogonal modes from the same family. Here, we introduce a novel class of vector modes whose spatial degree of freedom is encoded by combining modes from both the Hermite- and Laguerre-Gaussian families, ensuring that the modes are shape-invariant upon propagation. This superposition is not arbitrary, and we provide a detailed explanation of the methodology employed to achieve it. This new class of vector modes, which we term hybrid Hermite-Laguerre-Gaussian (HHLG) vector modes, gives rise to subsets of modes exhibiting polarization dependence on propagation due to the difference in mode orders between the constituent modes, while remaining eigenmodes of free space. To the best of our knowledge, this is the first demonstration of vector modes composed of two scalar modes originating from different families.

On-demand spatial modes and vortex beams from a visible Pr:YLF orbital Poincaré laser with a hybrid pumping scheme.

The controlled visible spatial modes and vortex beams with tunable properties are highly sought after in cutting-edge applications, such as optical communication. In this study, by utilizing a hybrid pumping scheme, we demonstrate an ultra-compact, 607 nm orbital Poincaré laser based on a diode-pumped Pr:YLF laser. The system can generate various structured modes, including Laguerre-Gaussian (LG), Hermite-Gaussian (HG), and Hermite-Laguerre-Gaussian (HLG), all of which are mapped onto a first-order orbital Poincaré sphere. A numerical analysis of the coherent superposition of HG modes with varying phases is in complete agreement with the experimental results. The handedness of the generated vortex beam can be selectively controlled by precisely adjusting the angle of output coupler. In comparison to other schemes, the hybrid pumping scheme offers advantages of high precision and excellent tunability, enabling the emitting of high-order HG modes, LG modes, along with a wide range of spatial modes on the orbital Poincaré sphere. Our scheme can also be extended to different gain media, which could lead to the creation of structured beams with richer wavelength, offering a promising platform for innovative studies on multidimensional light-field control.

Establishing an animal model for post-inflammatory hyperpigmentation following fractional CO2 laser application.

Post-inflammatory hyperpigmentation (PIH) is a common cosmetic concern, often leading to significant psychological distress for the patients. With the widespread application of lasers including ablative fractional resurfacing (AFR) with a 10,600nm CO2 laser, PIH caused by lasers is becoming increasingly common. But due to the absence of an appropriate animal research model, our understanding of pathophysiological mechanisms and preventive strategies for PIH remains limited. This study aimed to establish an animal model to investigate PIH following AFR CO2 laser application, focusing on the dynamic changes in melanin, inflammatory cytokines, growth factors, and skin structures as PIH developed. We employed pigmented guinea pigs as our experimental subjects and conducted our research in two phases. In the first phase, we utilized three modes of AFR CO2 laser to identify which laser mode could induce PIH by monitoring dynamic melanin changes. In the second phase, the laser mode that most reliably induced PIH was applied to re-establish the PIH model. Pathophysiological changes during PIH progression were investigated through histopathological observations, real-time quantitative polymerase chain reaction, and two-photon microscopy. We successfully established a replicable animal model for PIH following AFR CO2 laser application. We observed a significant increase in inflammatory cytokines and growth factors within the skin tissue by the second week, with stable pigmentation becoming apparent by the third week. Our research provides a promising animal model for understanding and further investigating the mechanisms of PIH after laser procedures. V (animal study).

Topological bound states in the continuum in a non-Hermitian photonic system.

Topological insulators and bound states in the continuum represent two fascinating topics in the optical and photonic domain. The exploration of their interconnection and potential applications has emerged as a current research focus. Here, we investigated non-Hermitian photonics based on a parallel cascaded-resonator system, where both direct and indirect coupling between adjacent resonators can be independently manipulated. We observed the emergence of topological Fabry-Pérot bound states in the continuum in this non-Hermitian system, and theoretically validated its robustness. We also observed topological phase transitions and exceptional points in the same system. By elucidating the relationship between topological insulators and bound states in the continuum, this work will enable various applications that harness the advantages of bound states in the continuum, exceptional points, and topology. These applications may include optical delay and storage, highly robust optical devices, high-sensitivity sensing, and chiral mode switching.

Broadband negative refraction based on a pair of anti-parity-time structures

Abstract An anti-parity-time(A-PT) symmetric system, of which the refractive index satisfies n( - x) = - n*(x), can present intriguing scattering properties like continuous coherent perfect absorption(CPA) spectrum and laser spectrum, which are symmetric to each other in the parameter space. In this work, an acoustic parity-time(PT) symmetric system consisting of two A-PT symmetric structures is introduced to realize a broadband negative refraction. When the two A-PT symmetric structures are at their CPA mode and laser mode respectively, the PT symmetric system can display its unidirectional negative refraction property. As the two A-PT structures we design here have a broadband CPA and laser modes, the PT symmetric negative refraction system would be broadband. Besides, the exceptional point(EP) of the proposed PT-symmetric system corresponds to the CPA point and laser point of its two components, and it's unidirectionally transparent on broadband as well.

Bending behavior and influence parameter optimization of connection joints of disc-buckle type formwork support

In order to systematically study the bending behavior of the connection joints of the disc-buckle type formwork support, the accurate numerical model of the disc-buckle type connection joints was obtained through the experimental on the bending behavior of the connection joints of the disc-buckle type, and the bending moment-rotation curve of the joints was verified. The analysis of the failure mode and stress distribution of the joints reveals the importance of the bending behavior of each component. By establishing an accurate numerical model of the joint, the accuracy of the bending experiment of the joint was verified, and the parametric analysis of the influence factors such as the depth of the wedge insertion the disk-plate, the initial position of the wedge insertion the disk-plate, the thickness of the wedge, material constitutive of the wedge and the thickness of the disk-plate was carried out to grasp the influence of the relevant parameters on the bending behavior of the joint. The results shown that the connection joints of the disc-buckle type formwork support were a typical semi-rigid connection joints. The thickness of the disk-plate plays a decisive role in the joint bending capacity, and the optimum thickness of the disk-plate was 10 mm. The thickness of the wedge was proportional to the joint bending capacity, and the optimal thickness of the wedge was 7 mm. The drop depth of the wedge should not exceed 6 mm during the locking process and the most suitable yield strength of the wedge was set to 450–500 MPa.

Single-Defect Mode Lasing in a Non-Hermitian 1D Trivial SSH Lattice

Single-Defect Mode Lasing in a Non-Hermitian 1D Trivial SSH Lattice

Quantum dot distributed feedback laser grown on silicon with laterally coupled gratings

Abstract The direct epitaxy of quantum dot (QD) lasers on silicon was considered as holy grail of integrated silicon photonics. With demonstration of various InAs/GaAs QD lasers directly grown on silicon substrates, there are limited research carried on single longitudinal mode lasers on silicon. Here, to avoid any regrowth procedures, distributed feedback (DFB) QD lasers on silicon are fabricated with lateral coupled (LC) gratings via simplified fabrication process. The LC-DFB laser has a maximum laser power of 4.5 mW and threshold current of 80 mA under continuous-wave current mode at room temperature. Under injection current of 110 mA, the side mode suppression ratio (SMSR) reaches 50 dB at room temperature. The RIN of the laser is measured with value of -135dB/Hz with corresponding optical linewidth of 3.5 MHz.

Study on physical properties of Coronene oxide as a function of number of oxygen atoms and temperature by density functional theory

The electronic properties like (HOMO, LUMO levels and Energy gap), and spectroscopic properties (IR spectra) in addition to thermodynamics characteristics like (Gibbs free Energy, Enthalpy, Entropy, and Heat capacity) of Coronene C24 and reduced Coronene oxide C24Ox where x=1-5 is a number of oxygen atoms and different temperature from (298 – 398) K were studied. The methodology utilized in this study involved the application of Density Functional Theory (DFT) using the Hybrid functional B3LYP (Becke, 3-parameters, Lee –Yang-Parr) with 6-311G** basis sets. The band gap of Coronene (C24) 3.5 eV was calculated, while for reduced coronene oxide C24O - C24O5 has been varied from (1.68 to 0.89) eV due to broken symmetry and adding levels inside the energy gap. The IR intensity of C24O5 increases with increasing temperature between (298 and 398) K because of the number of excited atoms, the spectroscopic properties were compared with experimental results, in particular the Longitudinal Optical (LO) mode of vibration for graphene oxide 1582 cm-1 which agreed well. The Gibbs free energy and enthalpy decreased (in the negative sign) with an increased number of oxygen atoms and temperatures which means an exergonic reaction.

Long-term stable laser injection locking for quasi-CW applications

Generating high output powers while achieving narrow line single mode lasing are often mutual exclusive properties of commercial laser diodes. For this reason, efficient and scalable amplification of narrow line laser light is still a major driving point in modern laser system designs. Commonly, injection locking of high-power semiconductor laser diodes are used for this purpose. However, for many laser diodes it is very challenging to achieve stable operation of the injection locked state due to a complex interplay of non-linearities and thermal effects. Different approaches of active or passive stabilization usually require a large overhead of optical and electrical equipment and are not generally applicable. In our work we present an active, periodically applied stabilization scheme which is generally applicable, technically easy to implement and extremely cost-effective. It is based on the externally synchronized automatic acquisition of the optimal injection state. Central to our simple but powerful scheme is the management of thermalization effects during lock acquisition. By periodical relocking, spectrally pure amplified light is maintained in a quasi-CW manner over long timescales. We characterize the performance of our method for laser diodes amplifying 671 nm light and demonstrate the general applicability by confirming the method to work also for laser diodes at 401 nm, 461 nm and 689 nm. Our scheme enables the scaled operation of injection locks, even in cascaded setups, for the distributed amplification of single frequency laser light.

Towards a spectrally multiplexed quantum repeater

Extended quantum networks are based on quantum repeaters that often rely on the distribution of entanglement in an efficient and heralded fashion over multiple network nodes. Many repeater architectures require multiplexed sources of entangled photon pairs, multiplexed quantum memories, and photon detection that distinguishes between the multiplexed modes. Here we demonstrate the concurrent employment of (1) spectrally multiplexed cavity-enhanced spontaneous parametric down-conversion in a nonlinear crystal; (2) a virtually-imaged phased array that enables mapping of spectral modes onto distinct spatial modes for frequency-selective detection; and (3) a cryogenically-cooled Tm3+:LiNbO3 crystal that allows spectral filtering in an approach that anticipates its use as a spectrally-multiplexed quantum memory. Through coincidence measurements, we demonstrate quantum correlations between energy-correlated photon pairs and a strong reduction of the correlation strength between all other photons. This constitutes an important step towards a frequency-multiplexed quantum repeater.

Coordination-Defect-Driven Construction of Responsive Pure-MOF Microspheres for Switchable Mode-Dependent Anticounterfeiting Labels.

Luminescent metal-organic frameworks (MOFs) with exceptional dynamics and diverse active sites possess tremendous potential in information security and anticounterfeiting applications. However, traditional MOF systems are based on broadband spectral signals with spectrum overlap, which easily leads to low-resolution signal identification, compromising the overall security level. Here, we report the coordination-defect-induced amorphous pure-MOF microsphere with switchable whispering-gallery-mode (WGM) signals as a mode-dependent security platform. Amorphous MOF microspheres are prepared by a chlorine coordination-defect-driven growth strategy based on the aperiodic arrangement in coordinate networks. The as-prepared amorphous MOF microspheres with well-defined circular morphology display the typical WGM resonance with dimension-dependent character, permitting the creation of photonic barcodes with substantial encoding capacity. Furthermore, the amorphous MOF microspheres exhibit optical mode switching behavior due to reversible framework shrinkage, which enables the design of covert photonic barcodes as anticounterfeiting labels, finally demonstrating responsive coding property and enhanced information security. The results provide a novel strategy for exploring an MOF-based security platform for information encryption and optical anticounterfeiting.

Optical and Electrical Dual-Mode Detection of a Carcinogenic Substance Based on Synergy of Liquid Crystals and Ionic Liquids.

Visual, sensitive, and selective detection of carcinogenic substances is highly desired in portable health protection and practical medicine production. However, achieving this goal presents significant challenges with the traditional single-mode sensors reported so far, as they have limited sensing mechanisms and provide only a single output signal. Here, we report an effective optical and electrical dual-mode sensor for the visual, sensitive, and selective detection of N-nitrosodiethylamine (NDEA), a typical volatile carcinogenic substance, leveraging the synergy of ionic liquid-doped liquid crystals (IL-LC). The optical mode derived from LCs provides the sensor with a visual identification recognizable by the naked eye, while the electrical mode derived from ILs offers a quantitative detection capability. It is noteworthy that the synergistic effect of the IL and LC enhances the performance of both optical and electrical modes. Unique sensing mechanisms derived from the interaction between NDEA and IL-LC endow the sensor with excellent selectivity. As a proof of concept, a portable kit based on a dual-mode sensor has been developed for the real-time and on-site analysis of N-nitrosamine impurities in pharmaceuticals. This work provides valuable insights and a theoretical foundation for developing portable multimode chemical sensors.

Impact of non-Hermiticity and nonlinear interactions on disorder-induced localized modes

In non-Hermitian photonics, introducing gain and loss offers new degrees of freedom to control optical systems and a unique approach to explore fundamental concepts. Random lasers are a natural class of non-Hermitian open optical systems where spatial confinement, leakage, and non-orthogonality of the modes are further controlled by the degree of scattering. How Anderson localization is impacted by complex potentials, gain and loss and, more generally, nonlinearities has been the subject of numerous theoretical debates, without any conclusive experimental demonstration yet. Indeed, in systems where localized modes have sufficient spatial extension to be observed and investigated, their mutual interaction and coupling to the sample boundaries make it extremely difficult to isolate them spectrally and investigate them alone. Here, the degree of non-Hermiticity of an active scattering medium is controlled by shaping the pump. By imaging the intensity distribution of individual localized lasing modes, we demonstrate experimentally their insensitivity to local pumping; a signature that orthogonality is preserved between modes localized away from the system boundaries, as theoretically established. Demonstration of the one-to-one correspondence between lasing modes and localized states of the passive system opens the route to investigate the robustness of localized states in the presence of nonlinear gain and nonlinear modal interactions. Interestingly, gain saturation and mode competition for gain do not affect the spatial distribution of the modes, demonstrating their orthogonality in an otherwise strongly non-Hermitian system.