Optical Mode Field Research Articles

Study on the mechanism of laser-induced breakdown and damage performance of internal defects in transparent materials through local optical field modulation

This paper establishes a photothermal damage model for bubble impurities affecting laser optical field modulation based on Mie scattering theory and incorporates the effects of optical field modulation. This model elucidates the evolution mechanism of synergistic damage in fused silica, with simulation results validated through experimental verification. A novel characterization of optical breakdown due to bubble impurities is proposed, occurring on a millisecond timescale through the dynamic evolution of combustion waves. The model delineates the influence of bubble size and spacing on optical field distribution, temperature, stress distribution, and their evolutionary behaviors. The modulation of the optical field due to double bubble impurities creates a localized “hot spot,” resulting in a differential transverse contraction stress at the edges of the bubble impurities, thereby reducing the damage threshold of fused silica. The spacing of 1.1 λ represents the enhancement node for optical field modulation by double bubble impurities. Furthermore, localized oscillations in the optical field arise when the spacing between the double bubbles exceeds 1.1 λ, attributed to changes in the refractive index at the bubble defects and resonance oscillations generated by optical field modulation. This study not only enhances our understanding of the optical field modulation processes occurring at 1064 nm in the presence of bubble defects but also establishes a theoretical foundation for detecting internal defects at this wavelength without inducing surface damage.

Numerical investigation of steering synchronization dynamics of laterally coupled laser array with monolithically-integrated external cold cavity

This study numerically explores the synchronization dynamics of a one-dimension edge-emitting laser array monolithically-integrated with an external cold cavity comprehensively, aiming to achieve an in-phase mode optical field. By employing the optical feedback rate equation, the impact of mutual feedback coefficient and coupling coefficient on the synchronization process are investigated thoroughly. The proposed external cold cavity, designed according to the Talbot effect, could significantly diminish the reflectivity of front facet through separated electrode structure, therefore facilitating the phase-locking process. Consequently, the study uncovers the effective regime for establishing in-phase mode operation. Additionally, the numerical analysis also reveals the vivid synchronization dynamic from a chaotic state to partially-phase-locked, then completely-phase-locked, and ultimately periodic oscillation. Furthermore, the impact of practical fabrication tolerances on the synchronization process are explored as well. Based on the simulation results, our work could offer valuable insights for steering the on-chip optical field and developing novel laser arrays with high beam quality.

All-fiber tunable mode converter for a mini-two-arm Mach-Zehnder interferometer.

In this Letter, an all-fiber tunable mode converter for a mini-two-arm Mach-Zehnder interferometer (MTA-MZI) is proposed and realized for the first time to our knowledge. Employing an electric arc discharge technology, we couple a multi-mode fiber (MMF) and a single-mode fiber (SMF), resulting in an MZI characterized by centimeter-scale arms. The varied sensitivity of fiber modes to curvature makes the high-order modes of the MMF more prone to leakage when subjected to bending, leading to alterations in the output interference fringe pattern of the MZI. Through continuous monitoring of the interference fringes of the MZI, we effectively detect the mode properties within the MZI in real time. In addition, a verification experiment is conducted by introducing a peanut structure to excite further higher-order modes of light to enter the MZI in advance. Upon modifying the curvature of the MZI, these excited higher-order modes leak, causing the interference fringe pattern to revert to its initial state without a peanut structure. This experimental validation highlights the potential employment of the MTA-MZI as an all-fiber mode converter and paves the way for optical field mode conversion within an all-fiber framework.

Propagation properties of a partially coherent Laguerre–Gaussian beam with multiple off-axis vortex phases

In this paper, a new theoretical model of a partially coherent Laguerre–Gaussian (LG) beam carrying multiple off-axis vortex phases was established. The evolution properties of the focused intensity of the beam after passing through a thin lens were theoretically studied, and then the modulation effect of multiple off-axis vortex phases on the beam with multiring structured intensity was explored. The results indicate that the multiple off-axis vortex phases can reconstruct the multiring structured intensity within the LG beam, thus generating a structured intensity with multilobe and multiring patterns. What is more, the intensity distribution of the lobes between two adjacent rings is complementary, and its number is related to the number and topological charge of off-axis vortex phases. However, with a decrease in the coherence, such a multilobe and multiring structured intensity distribution disappears, gradually evolves into a polygonal flat-topped distribution, and finally degenerates into a quasi-Gaussian distribution. This work demonstrates the effective regulation of multiple off-axis vortex phases on a beam with a multiring structured intensity and indicates that regulating the multiple off-axis vortices provides an additional degree of freedom for optical field modulation, which will have potential applications in the fields of optical micromanipulation and optical information storage.

Terahertz reflective metasurfaces realize wavefront modulation of circular polarization channels

The emergence of many efficient optical field modulation methods and planar optical devices is attributed to the continuous research of geometric phase. Nevertheless, conjugate symmetry of the geometric phase limits the multiplexing of metasurfaces. To overcome this limitation, integrating the propagation phase and the geometric phase to achieve self-decouped metasurfaces can effectively double channel capacity. Herein, a more in-depth derivation of Jones matrices is conducted, leveraging two degrees of freedom offered by the propagation phase and the geometric phase. This approach enables complete modulation in circular polarization channels. By designing the phase difference between a fast axis and a slow axis, energy allocation between different channels can be controlled. It means independent complex amplitude modulation is achieved. On this basis, the geometric phase is introduced to realize tri-channel multiplexing metasurfaces. To verify the feasibility of this method, two metasurfaces are designed, including a bifocal metasurface with adjustable energy allocation and a tri-channel multiplexing metasurface. The proposed multifunctional metasurface offers new insights into wavefront multiplexing for communication systems.

Rigorous results on approach to thermal equilibrium, entanglement, and nonclassicality of an optical quantum field mode scattering from the elements of a non-equilibrium quantum reservoir

Rigorous derivations of the approach of individual elements of large isolated systems to a state of thermal equilibrium, starting from arbitrary initial states, are exceedingly rare. This is particularly true for quantum mechanical systems. We demonstrate here how, through a mechanism of repeated scattering, an approach to equilibrium of this type actually occurs in a specific quantum system, one that can be viewed as a natural quantum analog of several previously studied classical models. In particular, we consider an optical mode passing through a reservoir composed of a large number of sequentially-encountered modes of the same frequency, each of which it interacts with through a beam splitter. We then analyze the dependence of the asymptotic state of this mode on the assumed stationary common initial state σ of the reservoir modes and on the transmittance τ=cos⁡λ of the beam splitters. These results allow us to establish that at small λ such a mode will, starting from an arbitrary initial system state ρ, approach a state of thermal equilibrium even when the reservoir modes are not themselves initially thermalized. We show in addition that, when the initial states are pure, the asymptotic state of the optical mode is maximally entangled with the reservoir and exhibits less nonclassicality than the state of the reservoir modes.

Research on high precision time-frequency transmission under low available bandwidth based on free space optical communication with special beam

As a powerful supplement to the wireless communication, free space optical (FSO) communication has many advantages, but the high-precision time-frequency transmission based on FSO communication is limited by complex equipment factors, especially under the condition of limited communication bandwidth. In this paper, a high-precision frequency transfer system based on a tunable optical field is established. Theoretical analysis yields the detection probability and intensity distribution of Bessel beams. In experiments, Bessel beams generated through optical field modulation exhibit enhanced laser data communication capabilities, achieving high-precision frequency transfer at 2e-12@1s, 3.3e-14@1000s,. This research introduces a novel approach for designing and optimizing frequency transfer methods between smaller platforms in the future.

Entanglement and Squeezing of the Optical Field Modes in High Harmonic Generation.

Squeezed optical fields are a powerful resource for a variety of investigations in basic research and technology. However, the generation of intense squeezed light is challenging. Here, we show that intense squeezed light can be produced using strongly laser driven atoms and the so far unrelated process of high harmonic generation. We demonstrate that when the intensity of the driving field significantly depletes the ground state of the atoms, leading to dipole moment correlations, the quantum state of the driving field and the generated high harmonics are entangled and squeezed. Furthermore, we analyze how the resulting quadrature squeezing of the fundamental laser mode after the interaction can be controlled. The findings open the way for the generation of high intensity squeezed light states for a wide range of applications.

Compressed Hermite–Gaussian differential single-pixel imaging

Traditional single-pixel imaging (SPI) encounters challenges such as high sampling redundancy and poor imaging quality, constraining its widespread application. Despite a range of orthogonal modulation modes have been employed in structured illumination to enhance imaging performance, some encoding issues still persist in information sampling, impeding the further progression of SPI. We propose an SPI method based on orthogonal Hermite–Gaussian (HG) moments, achieving improved imaging reconstruction through differential modulation of HG basis patterns and linear weighting of acquired intensity. Both simulations and experiments confirm superior imaging quality and computation efficiency of proposed Hermite–Gaussian single-pixel imaging (HG-SI), especially at low-measurement levels. Moreover, we incorporate compressed sensing algorithms within the framework of HG-SI, integrating moments-based sampling strategies to optimize imaging capability under sparse measurements. Our research underscores the effectiveness of HG modulation in SPI reconstruction, enabling high-quality outcomes via compressed sampling. This advancement propels the investigation of optical field modulation modes within SPI and holds promise in offering a universal solution for weak-intensity and non-visible light microscopy.

Compact and efficient lossy mode resonant refractive index sensor for aqueous environment

A very short length high sensitivity, large figure of merit and very high resolution integrated-photonic refractometer for aqueous environment operating in visible region of wavelength is proposed. The sensor design depends on the periodic coupling of the guided dielectric optical waveguide mode field and the lossy mode field of the conducting indium-tin-oxide thin film. Various layer thicknesses can be optimized to provide power transfer to the lossy layer and lossy mode resonance, resulting in a strong guided mode power absorption in the lossy layer occurs. The sensor has been designed to operate in both the TE and TM polarizations with different optimized layer frthicknesses. The optimized thicknesses are different for TE and TM polarizations. The obtained numerical results show that a spectral sensitivity of 2200 nm/RIU/2645 nm/RIU for TE/TM mode could be achieved with a very high resolution. Also, the sensors can operate in power interrogation mode with a maximum sensitivity nearly 5 × 107 dB RIU−1.

Self‐Aligned Photonic Defect Microcavity Lasers with Site‐Controlled Quantum Dots

AbstractSelf‐assembled semiconductor quantum dots face challenges in terms of scalable device integration because of their random growth positions, originating from the Stranski–Krastanov growth mode. Even with existing site‐controlled growth techniques, for example, nanohole or buried stressor concepts, a further lithography and etching step with high spatial alignment requirements is necessary to accurately integrate quantum dots into the nanophotonic devices. Here, the fabrication and characterization of strain‐induced site‐controlled microcavities are reported, where site‐controlled quantum dots are positioned at the antinode of the optical mode field in a self‐aligned manner without the need of any further nano‐processing. It is shown that the cavity properties such as Q‐factor, mode volume, and mode splitting can be tailored by the geometry of the integrated buried stressor, with an opening <4 µm. The experimental results are complemented with theory calculations based on continuum elasticity. Lasing signatures, including super‐linear input‐output response and linewidth narrowing, are observed for a 3.6‐µm self‐aligned cavity with a Q‐factor of 18 000. Furthermore, the quasi‐planar site‐controlled cavities exhibit no detrimental thermal effects. This approach integrates seamlessly with the industrial‐matured manufacturing process and the buried‐stressor technique, paving the way for exceptional scalability and straightforward manufacturing of high‐β microlasers and bright quantum light sources.

Secondary-deposited elevated self-assembling nanosphere lithography: A powerful tool to achieve heterostructure metasurface

The heterostructure integration of nanostructures, which can involve higher freedom of degree by applying two or more materials into one integrated photonic or electromagnetic devices, attracted extensively increasing attention among the communities of electrons, photonics, materials science, and engineering. However, it is still a challenging topic to realize heterostructure integration with accurate micro–nano-scale geometry in a large area. Here, we propose the secondary-deposited elevated self-assembling nanosphere lithography for large-area heterostructure integration of plasmonic metasurface. As the proof of concept, an infrared metasurface composed of Au–Ag crescent pairs is realized in the practice. By adjusting the evaporation angle, crescent pairs with different morphologies can be freely machined without changing masks. Optical characterization and numerical results show that the heterostructure crescent-pair metasurface owns uniform and stable geometrical properties and flexible capability on infrared optical field modulation. Our work enriches the degree of freedom of nano-structure-based optical devices and paves the heterostructure integrated metasurface to potential industrial applications with large dimension, low cost, and fast production.

Electrically-switched differential microscopy based on computing liquid-crystal platforms

Abstract Detection of transparent phase specimens especially biological cells with desired contrasts is of great importance in visual display and medical diagnosis. Due to the pure-phase nature, conventional detection approaches may damage samples or require complex operations. Computing liquid crystal (LC) is a thin and flat optical element with excellent capability in optical field modulation, which gives a feasible way to this issue from the perspective of analog optical computing. We here propose and experimentally implement an electrically switched two-dimensional (2D) differential microscopy based on computing LC platforms. The Pancharatnam–Berry phase LC polarization grating induces light’s spin separation to promote the 2D differential operation. Using the electrically tunable LC plate as the system phase retardance provider, the detecting mode can be flexibly switched from bright-field images to edge-enhanced images with desired contrasts. Remarkably, owing to the wavelength-independent feature closely related to the geometric phases, our proposed scheme is demonstrated to be applicable to the multi-wavelength microscopy imaging. These results open avenues to form real-time all-optical image processing and may facilitate multifunctional differential microscopy.

Design and fabrication of indium tin oxide for high performance electro-optic modulators at the communication wavelength

In recent years, transparent conductive oxides(TCO) based electro-optic modulators has garnered significant attention due to its epsilon-near-zero(ENZ) effect to enhance the local optical field and produce a large refractive index change in the vicinity of ENZ wavelength, thereby enabling substantial optical field modulation at micrometer size. The modulators manipulate the light field by altering the carrier concentration in TCO through an electric field. Therefore, the modulator's performance is closely related to the TCO's material behavior. In this paper, the effect of carrier concentration and mobility of indium tin oxide(ITO) on the modulation efficiency, depth and bandwidth was analyzed and it is found that ITO with the carrier concentration near 1 × 1020 cm−3 and mobility as high as 80 cm2/Vs is beneficial to the electro-optic modulators with large modulation depth and bandwidth. Specifically, our research shows that the carrier concentration and mobility of ITO films can be tunned over a wide range from 2.2 × 1019cm−3 to 7.7 × 1020cm−3 and 7.2 cm2/Vs to 82.3 cm2/Vs respectively, by changing doping concentration, deposition conditions and annealing parameters. As a result, ITO film integrated on a 3.5-μm-long silicon waveguide with an MOS structure can achieves a high modulation bandwidth of over 40 GHz at the optical communication wavelength.

Study on the influence of local optical field amplification effect on laser-induced damage of fused silica materials

Fused silica is an important part of optical components in large laser systems. Due to the limitation of manufacturing process, impurities and defects in the optical element would greatly reduce the service life of the optical element, and significantly reduce the final output of the laser performance. Aiming at the modulation effect of the internal defect of the component on the internal optical field of the component, the theoretical, simulation and experimental research are carried out. The results show that in the double-bubble impurity coupling, under the same radius R, when the impurity spacing is 1 λ, the local optical field amplification has a maximum value. The effect is equivalent to single-bubble modulation with radius 2 R–3 R. There is an extreme point of the modulated optical field between the air and fused silica crossing line for bubble impurities of different radii. The optical field modulation of small radius impurities is distributed behind the bubble impurities, and the modulation effect of large radius impurities is the maximum when the spacing is 2 λ. The temperature distribution curve of the fused silica element modulated by bubble impurities is consistent with the optical field distribution curve, showing a trend of decreasing slope. The presence of bubble impurities will cause the surface combustion wave of the component to flash and accelerate, and the bubble impurities will increase the generation and expansion rate of the surface combustion wave. This study provides a basis for reducing the uneven distribution of laser energy during the interaction between laser and fused silica, improving the lifetime of the overall optical system, and experimental measurement and analysis.

Metasurfaces toward Optical Manipulation Technologies for Quantum Precision Measurement

AbstractMetasurface‐based optical field manipulation has significantly broadened the application range of micro‐optical components and integrated optics, gradually replacing bulky and complicated optical components. With the continuous development of micro and nano processing technology as well as computational analysis technology, metasurfaces have progressively shown their superior application prospects. After demonstrating tremendous results in classical optical applications, their application range has now extended to the field of quantum sensing. Due to their unique properties, such as small planar size, easy integration, flexible performance design, and tunable functionality, they have opened up a series of novel and rich applications for generating, manipulating, controlling, and detecting optical fields. In this paper, the basic principle and implementation of quantum measurement are presented and an overview of the design principles of metasurfaces, along with a summary of the latest advancements and potential applications of these surfaces in optical field modulation techniques for quantum precision measurement. Additionally, a thorough discussion and analysis of the challenges encountered by metasurfaces and their future development prospects is provided. Metasurfaces offer brand‐new opportunities for low‐cost, high‐performance, multifunctional miniaturized quantum sensors and are expected to play a significant role in the development of next‐generation quantum sensors.

Focusing property and optical field modulation of three-core fiber optical tweezers

This work develops a three-core fiber optical tweezers probe with a double cone angle and a tip microlens based on the Lorentz-Mie scattering theory. The primary parameters of the structural probe, such as the cone angle and the thickness of the microlens, are investigated and clarified by theoretical research, model construction, and simulation analysis. The best capture ability is at 44° of second-order cone angle. In order to create a focused light field, the microlens must be thicker than 8 μm. Under the probe framework, we investigated the primary purposes of various core optical powers. We designed a set of optical fiber tweezers control schemes to adjust the capture effect in real time, which enhances the control capability of optical fiber tweezers. We leverage the difference in input optical power between different cores. The focusing effect of the optical field can be changed, enabling real-time control of the captured item, by modifying the incidence angle and power. The power is inversely correlated with the movement of the capture position. The capture point moves 0.1 μm when the optical power is changed to 0.3 W/m.

Design of a Metasurface with Long Depth of Focus Using Superoscillation.

Longitudinal optical field modulation is very important for applications such as optical imaging, spectroscopy, and optical manipulation. It can achieve high-resolution imaging or manipulation of the target object, but it is also limited by its depth of focus. The depth of focus determines whether the target object can be clearly imaged or manipulated at different distances, so extending the depth of focus can improve the adaptability and flexibility of the system. However, how to extend the depth of focus is still a significant challenge. In this paper, we use a super-oscillation phase modulation optimization method to design a polarization-independent metalens with extended focal depth, taking the axial focal depth length as the optimization objective. The optimized metalens has a focal depth of 13.07 μm (about 22.3 λ), and in the whole focal depth range, the transverse full width at half maximum values are close to the Rayleigh diffraction limit, and the focusing efficiency is above 10%. The results of this paper provide a new idea for the design of a metalens with a long focal depth and may have application value in imaging, lithography, and detection.

Spatial Full Degree‐Of‐Freedom Scattered Optical Field Modulation

AbstractScattered optical field modulations can enable the function of traditional optical technologies, such as the dynamic holographic display, in a scattering environment. Nonetheless, only part of the degrees of freedom in the optical field can be effectively modulated so far. Here, this work proposes spatial full degree‐of‐freedom scattered optical field modulation (SF‐SOM) to impose a control on the amplitude, phase, and polarization of the optical field. To do so, this method independently modulates the complex amplitude of two orthogonally polarized components. It also contains a full degree‐of‐freedom vector transmission matrix model to describe the transformation from the incident field to the scattered field. Compared with the single degree‐of‐freedom modulation methods against the same scattering environment, SF‐SOM increases the contrast of focus by a factor of five. Furthermore, the experiments demonstrate a holographic display and orbital angular momentum control with SF‐SOM to show its ubiquitous utility in optics.

Electrically Sensitive Plasmonic Photonic Crystals for Dynamic Upconversion Manipulation

AbstractLocal optical field modulation using plasmonic materials or photonic crystals provides a powerful strategy for enhancing upconversion emission of lanthanide‐doped upconversion nanocrystals (UCNPs). However, it is restricted to static UC enhancement and the corresponding dynamic modulation of UC is yet to be reported, limiting its practical applications in information devices. Here, a dynamic UC modulation system is reported through electric stimulation by integrating UCNPs with electrically sensitive WO3−x plasmonic photonic crystals (PPCs). The tunable emission enhancement of UCNPs varying from five to 26 folds is achieved in WO3−x PPCs/UCNPs hybrids through external electric stimulation within +1.6 and −1.6 V. It stems from the reversible control of the photonic bandgaps and localized surface plasmon resonance of WO3−x PPCs, ascribed to the variation of refractive index and oxygen vacancy of WO3−x, induced by the reversible change of atomic ratio of W5+ to W6+ under different applied voltages. Moreover, the electrically triggered information encryption devices are developed, employing a programmable logic gate array based on WO3−x PPCs/UCNPs with the ability to convert information‐encrypted electrical signals into visible patterns. These observations offer a new attempt to manipulate the UC and will simulate the new applications in the display and optical storage devices.