Journals >Opto-Electronic Engineering
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2022
Volume: 49 Issue 11
7 Article(s)
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Research Articles
Label-free far-field subdiffraction imaging based on hyperbolic metamaterial
Xuesong Chen, Wenjuan Du, Zhilang Lou, and Dongliang Tang
Overview: The spatial resolution of traditional optical microscopy is limited by the diffraction limit λ/(2NA) (λ is the wavelength, NA is the numerical aperture of the objective lens of system), and the lateral resolution is about 200 nm~300 nm, which makes it difficult to achieve clear imaging for micro-nano structurOverview: The spatial resolution of traditional optical microscopy is limited by the diffraction limit λ/(2NA) (λ is the wavelength, NA is the numerical aperture of the objective lens of system), and the lateral resolution is about 200 nm~300 nm, which makes it difficult to achieve clear imaging for micro-nano structures or cell samples. In this paper, a label-free far-field super-resolution imaging method based on hyperbolic metamaterial is proposed. Super-resolution optical microscopy is an important technology due to the non-contact and non-destructive advantages. Currently, most of the super-resolution imaging methods rely on the fluorescent dyes, which limited their applications. The label-free far-field microscopy imaging method based on the frequency shift effect has been proposed and developed in recent years. However, its spatial resolution is limited by the refractive index of waveguide materials. Based on the characteristic of optical spatial spectrum band-pass filtering in hyperbolic metamaterials (HMM), a large-area uniform bulk plasmon polariton (BPP) field with high spatial frequency can be achieved by combining with nano-scale gratings. Due to the large wave vector of the BPP illumination, the high-frequency information of the object can be transferred to the passband in traditional imaging systems and participate in super-resolution imaging. Illuminated by a BPP field with 2.66k0 at the wavelength of 532 nm, a double-slits structure with a 100 nm-wide center-to-center distance has been resolved with a 0.85 numerical aperture standard objective based on this method. The lateral resolution is improved to λ/5.32. By further improving the transverse wave vector of BPP, it can be improved to λ/7.82. This design is label-free and conveniently integrated with traditional microscopes, which provides a visual super-resolution imaging method for applications in biomedicine, on-chip industry, material science, and other fields.Super-resolution optical microscopy is an important technology due to the non-contact and non-destructive advantages. Currently, most of the super-resolution imaging methods rely on fluorescent dyes, which limited their applications. The label-free far-field microscopy imaging method based on the frequency shift effect has been proposed and developed in recent years. However, its spatial resolution is limited by the refractive index of waveguide materials. Based on the characteristic of optical spatial spectrum band-pass filtering in hyperbolic metamaterials (HMM), a large-area uniform bulk plasmon polariton (BPP) field with high spatial frequency can be achieved by combining with nano-scale gratings. Due to the large wave vector of the BPP illumination, the high-frequency information of the object can be transferred to the passband in traditional imaging systems and participate in super-resolution imaging. Illuminated by a BPP field with 2.66 k0 at a wavelength of 532 nm, a double-slit structure with a 100 nm-wide center-to-center distance has been resolved with a 0.85 numerical aperture standard objective based on this method. The lateral resolution is improved to λ/5.32. By further improving the transverse wave vector of BPP, it can be improved toλ/7.82. This design is label-free and conveniently integrated with traditional microscopes, which provides a visual super-resolution imaging method for applications in biomedicine, on-chip industry, material science, and other fields..
Opto-Electronic Engineering
- Publication Date: Nov. 25, 2022
- Vol. 49, Issue 11, 220056 (2022)
Vortex field manipulation based on deformation mirror with continuous surface
Guangyun Xiong, Ao Tang, Bin Lan, and Feng Shen
Overview: In recent years, vortex beams have become the focus of research, and their orbital angular momentum makes them have many important applications, like optical communication, particle manipulation, and optical measurement. At the same time, researchers are paying attention to more abundant generation methods. IOverview: In recent years, vortex beams have become the focus of research, and their orbital angular momentum makes them have many important applications, like optical communication, particle manipulation, and optical measurement. At the same time, researchers are paying attention to more abundant generation methods. In previous studies, vortex beam generation methods are usually divided into two categories. The first category is the outcavity, such as spiral phase plate method, spatial light modulator method, mode conversion method, metasurface method, and corner array method, and the second category is the incavity, such as point-loss method, off-axis pumping method, and spatial light modulator method. However, these methods can not tolerate high power laser output and adjust topological charges flexibly. Therefore, how to generate a vortex beam that can tolerate high power laser output and adjust the topological charges flexibly is an important problem to be solved. Continuous surface deformation mirror is a key component of adaptive optical system. In the study of wavefront fitting for continuous surface deformation mirrors, there are usually two kinds of methods. The first type is model-free method, such as genetic algorithm, simulated annealing algorithm, stochastic parallel gradient descent (SPGD) algorithm, etc. These methods generally require many iterations and slow convergence, and it is difficult to change the topological charge flexibly. The second type is pattern method, such as Zernike mode method, Lukosz mode method, and enginmode method. This method first defines a set of complete orthogonal modes, calculates the mode coefficients, and completes the fitting of the target wavefront by linear superposition of each mode. Zernike mode is orthogonal in the circular domain, Lukosz mode is orthogonal in the circular domain derivative. However, usually the configuretion of deformation mirror is not circular domain. For example, the deformation mirror driver used in this paper is arranged in circular domain. In this case, the orthogonal basis needs to be rebuilt to use these two methods. The eigenmode of the deformed mirror is directly and precisely derived from the influence function of the deformed mirror drivers, so it can not only avoid the influence of fitting error, improve the fitting accuracy, but also adapt to the different configuration of the deformed mirror. Combined with the eigenmode method, continuous surface deformation mirror can fit all kinds of vortex beams with high precision and fast fitting speed, and can be applied to all kinds of deformation mirrors with different configurations. In this paper, the eigenmode method of continuous surface deformation mirror is used to simulate and analyze the fitting of the spiral wavefront of integer order with topological charge is ?5 to 5, fractional order, multi-fractional order, and superposition state with the absolute value of topological charge less than 5. Various vortex light fields are generated by dynamic manipulation. The results show that the continuous surface deformation mirror will have a good application prospect in the field of high-power vortex field manipulation.A complete orthogonal basis was constructed by using the eigen-mode method of continuous surface deformation mirror, and the voltage of each driver of the deformation mirror can be obtained according to the spiral wavefront information which needs to be manipulated. The spiral wavefront of integral order, fractional order, multi-fractional order, and superposition state with the absolute value of topological charge less than 5 was generated, and the dynamic manipulation of the vortex beam was realized. The results obtained were the same as those obtained by the ideal spiral wavefront. The ability of the continuous surface deformation mirror to fit the spiral wavefront was demonstrated and good results were obtained. This method has a good application prospect in the dynamic manipulation of high-power vortex laser..
Opto-Electronic Engineering
- Publication Date: Nov. 25, 2022
- Vol. 49, Issue 11, 220066 (2022)
Longitudinal super-resolution spherical multi-focus array based on column vector light modulation
Xiaolan Xia, Xianzhi Zeng, Shichao Song, Xiaowei Liu, and Yaoyu Cao
Overview: Featured by the capability of multi degree-of-freedom light-field manipulations while reserving high spatial resolution, multifocal laser arrays have been widely applied in femtosecond laser micro/nanofabrication, optical trapping, etc. However, for lens diffraction, the smaller momentum spread along the optiOverview: Featured by the capability of multi degree-of-freedom light-field manipulations while reserving high spatial resolution, multifocal laser arrays have been widely applied in femtosecond laser micro/nanofabrication, optical trapping, etc. However, for lens diffraction, the smaller momentum spread along the optical axis with respect to that in the transverse direction could introduce a larger position spread in real space, which in turn leads to lower axial resolution than the transverse resolution. The anisotropy of the focused laser beam, inherent regardless of paraxial or tight-focusing cases, has been a great hurdle for laser printing of functional microdevices with precise control on feature size and improved mechanical performances. To this end, in this research, a feasible method for generation of isotropic focused laser beam with quasi-spherical 3D point spread function (PSF) is developed based on vectorial light field modulation. We demonstrate that through simultaneous implementation of phase modulation and amplitude modulation, homogeneous multifocal array with quasi-spherical focal spots can be generated. Particularly, with the use of a well-designed annular mask, the suppression on the axial spread of field is accomplished via accurate control on the coherent superposition of the orthogonal radially polarized beam (RPB) and azimuthally polarized beam (APB) in the focal region since the depolarized axial component of the AP beam vanishes in vicinity of the gaussian focus even under tight focusing condition. Using the proposed method, isotropic 3D PSF with identical axial and transverse FWHM of 0.71λ is achieved. Meanwhile, based on iterative phase retrieval algorithm, phase-only holograms are designed and employed transforming the incident wavelet as the summation of sub-wavelets, yielding multiple converging sites in 3D space, thereby generating the multifocal array. We further present the synthesis of quasi-spherical multifocal array. A high uniformity up to 99% for a 10-by-10 multifocal array, in which the single focus elements share near-identical axial and transverse FWHM, being 0.76λ on average. The standard deviation of the axial and transverse FWHM of the multifocal array are evaluated be 0.005λ and 0.019λ, respectively, highlighting the features of high uniformity and isotropy. The reported strategy renders precise control on the axial feature size and is potential for the application in high-precision parallel laser printing technique.Featured by the capability of multi degree-of-freedom light-field manipulations while reserving high spatial resolution, multifocal laser arrays have been widely applied in femtosecond laser micro/nanofabrication, optical trapping, and so forth. Yet, due to the relatively lower axial resolution of single focuses within the array in comparison with the lateral resolution of their own, multifocal laser array has been refrained from isotropic 3D nanofabrication. Herein, we propose a feasible method for generation of axially super-resolved multifocal array with quasi-spherical focal spots. In particular, quasi-spherical multifocal array is optically synthesized via precise modulation on the coherent superposition of the orthogonal radially polarized beam (RPB) and azimuthally polarized beam (APB) states in the focal region based on annular amplitude modulation. We show theoretically the generation of quasi-spherical multifocal array with a high uniformity up to 99%. The average axial and lateral full-width-half maximum (FWHM) of the focal array are measured to be 0.76λ with the standard deviations in the axial and lateral directions being 0.005λ and 0.019λ, respectively. The presented strategy for synthesis of quasi-spherical multifocal array with high uniformity paves the way for high-precision laser fabrication of 3D micro/nano devices..
Opto-Electronic Engineering
- Publication Date: Nov. 25, 2022
- Vol. 49, Issue 11, 220109 (2022)
Light field regulation based on polarization holography
Shujun Zheng, Xiao Lin, Zhiyun Huang, Lu Huang, Yuanying Zhang, Yi Yang, and Xiaodi Tan
Overview: Polarization holography has important application prospects in the field of data storage and polarized light imaging due to its ability to record amplitude, phase, and polarization information. In addition, it also has the ability to regulate light fields, which can regulate special light fields with helical Overview: Polarization holography has important application prospects in the field of data storage and polarized light imaging due to its ability to record amplitude, phase, and polarization information. In addition, it also has the ability to regulate light fields, which can regulate special light fields with helical phase distribution and spatial polarization distribution. Such special light fields have broad application prospects in the fields of optical communication, particle manipulation, photon entanglement, etc. There is also a lot of researches focused on how to generate such beams, such as helical phase plates, mode conversion, spatial light modulators, etc. However, the traditional method requires the construction of a relatively large optical system, which limits its application in fields such as integrated optics. The introduction of the beam preparation method of polarization holography can reduce the volume of the optical system to a certain extent. At the same time, the use of polarization-sensitive materials with the ability to record multi-dimensional information greatly reduces the cost on the one hand. On the other hand, it is easy to operate during the preparation process, which is expected to be an ideal material for beam preparation to some extent. Based on the introduction of the principle of faithful reconstruction of any polarization state by polarization holography, this paper reviews the research progress of generating vector beams, scalar vortex beams, and vector vortex beams based on polarization holography in the past two years. Faithful reconstruction for any polarization state refers to under the incident into the polarization-sensitive material at 90 degrees interference angle between the signal and reference waves, the recording and reading waves are p-polarized and the reconstruction wave can be reconstructed correctly. Phenanthrenequinone-doped polymethyl methacrylate photopolymer (PQ/PMMA) is used as a recording material in the experiment. First, the single control ability of polarization holography in polarization and phase is demonstrated respectively, and then the ability of polarization holography to control both polarization and phase at the same time is further introduced. Based on the characteristics of polarization holography, the signal optical path is regulated, and the vector beam, scalar vortex beam, and vector vortex beam are generated by setting the initial azimuth angle of the rotating components and adjusting their relative rotational angular velocity under dynamic exposure. In the fabrication process, the desired beam can be generated by simply controlling the parameters of some devices. Finally, the ability and prospect of generating special light fields based on polarization holography are briefly summarized and discussed.Polarization holography has important application prospects in the field of data storage and polarized light imaging due to its ability to record amplitude, phase and polarization information. In addition, it also has the ability to regulate light fields, which can regulate special light fields with helical phase distribution and spatial polarization distribution. Such special light fields have broad application prospects in the fields of optical communication, particle manipulation, photon entanglement, etc. There is also a lot of research focused on how to generate such beams. The latest research progress in preparing vector beams, scalar vortex beams, and vector vortex beams by using polarization holography is introduced in this paper. The light field regulation method based on polarization holography has the advantages of a simple fabrication process, the small size of the optical system and low production cost, which provides a new idea for the manufacture of special light fields..
Opto-Electronic Engineering
- Publication Date: Nov. 25, 2022
- Vol. 49, Issue 11, 220114 (2022)
Research advances of partially coherent beams with novel coherence structures: engineering and applications
Yonglei Liu, Zhen Dong, Yahong Chen, and Yangjian Cai
Overview: Optical coherence, as a fundamental resource in all areas of optical physics, plays a vital role in understanding interference, propagation, scattering, imaging, light-matter interactions, and other fundamental characteristics from classical to quantum optical wave fields. The theory of optical coherence is tOverview: Optical coherence, as a fundamental resource in all areas of optical physics, plays a vital role in understanding interference, propagation, scattering, imaging, light-matter interactions, and other fundamental characteristics from classical to quantum optical wave fields. The theory of optical coherence is the most powerful tool to describe the statistical characters of random light beams (also named partially coherent beams). In the space-frequency domain, the spatial coherence property of a partially coherent light beam is characterized by a two-point spectral degree of coherence that is a normalized version of the cross-spectral density function. Nowadays, the degree of coherence has been viewed as a novel degree of freedom for the structured partially coherent light beams, which is akin to the deterministic properties, such as the amplitude, phase, and polarization of a fully coherent structured light beam. Due to the fundamental difference between the two-point degree of coherence of partially coherent light and the one-point deterministic features of fully coherent light, the partially coherent beams with customized spatial coherence have shown many unique properties and been found to be more advantageous in particular applications. By simply adjusting the spatial coherence width of the degree of coherence for a partially coherent beam can help reduce the turbulence-induced signal distortion in free-space optical communications and resist the speckle noise in optical imaging. Only recently, it has been found that not only the spatial coherence width but also the spatial coherence distribution of the degree of coherence can be customized, which has enabled a host of novel physical effects, including beam’s self-shaping, self-reconstruction, and self-focusing, and has aroused many important potential applications. In this paper, we review the fundamental theory and efficient experimental protocols for tailoring the spatial coherence structure of the degree of coherence for the partially coherent light beams. The differences and the advantages between the two strategies for producing the partially coherent beams with nonconventional spatial coherence structures are discussed. Meanwhile, we mainly focus on the applications of the spatial coherence structure engineering in coherence-based optical encryption, robust optical imaging, sub-Rayleigh imaging, robust far-field information transfer, and high-quality beam shaping. It is found that the spatial coherence structure engineering provides an efficient degree of freedom for the manipulation of structured light and paves the way for resisting the side effects induced by random fluctuations of complex media. We prospect that the spatial coherence engineering protocols can be extended to the temporal domain or even to the spatiotemporal domain and will find broader applications for light manipulations and light-matter interactions.Structured light has rich adjustable spatial degrees of freedom, including amplitude, phase, polarization, degree of coherence, etc. The modulation of these degrees of freedom has triggered a variety of novel physical effects and has found use in constructing new structured light beams and a large range of applications. Compared to the fully coherent light, partially coherent beams (PCBs) have advantages in resisting the speckle noise and the fluctuations of atmospheric turbulence. Recently, the PCBs with nonconventional coherence structures have been found to have important potential applications in atmospheric transmission, optical encryption and imaging, robust information transmission, and high-quality beam shaping. In this review, we summarize in detail the progress of the theoretical construction and experimental generation of PCBs with novel coherence structures. Meanwhile, we outline their robust propagation properties in complex media and important applications in optical encryption, imaging, robust information transfer, and beam shaping. It is found the modulation of spatial coherence structure of PCBs provides not only an efficient way to resist the random fluctuations of complex environments, but also a new degree of freedom to enrich the application scopes of structured light. Finally, the development trend and the further applications of the nonconventional coherence structure engineering are prospected..
Opto-Electronic Engineering
- Publication Date: Nov. 25, 2022
- Vol. 49, Issue 11, 220178 (2022)
Tamm-surface plasmon hybrid mode for improving sensing figure of merit
Xinran Wei, Yuzhang Liang, Yijin He, Yurui Fang, and Wei Peng
Overview: Surface plasmon resonance (SPR) sensing technology has attracted widespread attention due to its advantages of high sensitivity, label-free, and real-time dynamic monitoring. Traditional SPR sensing platform needs the use of a prism, and requires that the transverse magnetic (TM) polarized light incident at aOverview: Surface plasmon resonance (SPR) sensing technology has attracted widespread attention due to its advantages of high sensitivity, label-free, and real-time dynamic monitoring. Traditional SPR sensing platform needs the use of a prism, and requires that the transverse magnetic (TM) polarized light incident at a specific angle to satisfy the wave vector matching condition and excite the surface plasmon polariton (SPP) mode at the interface between the metal film and the external environment. Moreover, Tamm plasmon polariton (TPP), as a special plasmon boundary state mode, can be excited by using the boundary between the one-dimensional Bragg photonic crystal (PC) and the metal film and has broad application prospects in the fields of new optoelectronic devices. Compared with SPP, the excitation of TPP does not require wavevector compensation for incident light and can be achieved at any polarization. However, the enhanced electromagnetic field of the TPP mode is mainly localized inside the structure and cannot sense the changes in the external environment, which greatly limits its application in the field of biochemical sensing. To break through this limitation, researchers integrated the one-dimensional Bragg PC structures onto the traditional prism structures to achieve hybrid coupling of SPP mode and TPP mode by using the oblique incident light, which could improve the sensing performance of the SPR sensors. However, this kind of TPP-SPP strong coupling excitation also requires a bulky prism and a precise incident light angle control system, which is not conducive to the miniaturization and integrated application of the structure. Therefore, we propose a feasible design of a grating-coupled multilayer stack in this paper. The structure mainly consists of three parts: a nanometric gold film on the top layer, a one-dimensional Bragg PC in the middle, and a gold nanograting on the bottom. In this structure, the SPP and TPP resonance excitations on the upper and lower surfaces of the top nano-gold film are simultaneously achieved by utilizing the first-order transmitted light of the bottom nanograting. The coupling hybridization between the two modes greatly reduces the resonance bandwidth of the generated hybrid mode, resulting in a significant improvement in its sensing figure of merit. In addition, the coupling hybridization of the SPP and the TPP can be realized in a wide spectral range by changing the period of the nanograting and the thickness of the dielectric layers constituting the one-dimensional Bragg PC. Compared with the traditional prism TPP and SPP dual-mode coupling structure, the designed multilayer nanostructure can realize the resonance coupling of the two modes over broad wavelength ranges at the normal incidence. These results not only make it easier to further integrate and miniaturize the structure, but also have important significance for broadening the practical application of the surface plasmon resonance sensors.The hybrid coupling of Tamm plasmon polariton (TPP) and surface plasmon polariton (SPP) on the surface of a gold film based on the prism coupling has attracted extensive attention and has been widely investigated. However, the traditional excitation configuration has bulky optical elements and requires accurate control of the angle of incident light, which limits its integration and practical application. In order to simplify the excitation condition of the TPP-SPP hybrid mode, a feasible grating-coupled multilayer stack structure is proposed in this paper. The structure mainly consists of three parts: a nanometric thin gold film on the top layer, a one-dimensional Bragg photonic crystal in the middle, and a gold nanograting on the bottom. In this structure, the SPR and TPP resonance excitations on the upper and lower surfaces of the top gold film are simultaneously achieved by utilizing the first-order transmitted light of the bottom nanograting. The hybrid coupling between the two modes greatly reduces the resonance bandwidth of the generated mode, thereby significantly improving the sensing figure of merit of the generated mode. Additionally, the hybrid coupling of both SPP and TPP modes can be realized in a wide spectral range by altering the period of the nanograting and the thickness of the one-dimensional Bragg photonic crystal. Compared with the traditional prism-coupled TPP and SPP dual-mode coupling structures, the designed grating-coupled multilayer nanostructure can realize the resonant coupling of the two modes at the normal incidence without prism and limitation of incident angle. This not only facilitates the further integration and miniaturization of the structure, but also has important significance for broadening the practical application of surface plasmon resonance sensors..
Opto-Electronic Engineering
- Publication Date: Nov. 25, 2022
- Vol. 49, Issue 11, 220217 (2022)
Silicon-based super-resolution metalens with weak sidelobe
Kun Zhang, Zijie Ma, Yi Zhou, Gaofeng Liang, Zhongquan Wen, Zhihai Zhang, Zhengguo Shang, and Gang Chen
Overview: Optical super-resolution lenses have shown great potential in super-resolution microscopic systems and nano-fabrication systems. With the decrease of the focusing spot of the super-resolution lens, it is inevitable that large sidelobes and sidebands will be generated, which will lead to a limited field of vieOverview: Optical super-resolution lenses have shown great potential in super-resolution microscopic systems and nano-fabrication systems. With the decrease of the focusing spot of the super-resolution lens, it is inevitable that large sidelobes and sidebands will be generated, which will lead to a limited field of view and imaging artifacts. Therefore, when designing super-resolution optical devices, it is necessary to adopt a balanced strategy between focusing spot and side lobe according to the practical applications. Metasurface is a planar structure composed of nanoscale meta-atoms, which can flexibly regulate the amplitude, phase and polarization of the optical field, being beneficial to construct complex super-resolution optical fields. The PB phase meta-atom is comparatively easy to fabricate due to its simplicity. Using Finite-Difference Time-Domain (FDTD) solutions to optimize the size of the meta-atom, we can get a structure with high transmittance. By rotating the angle of the meta-atom, we can achieve linear phase control. The application of PB phase metasurface has been demonstrated in the field of super-resolution focusing devices with suppressed sidelobe. Based on the vector angular spectrum method and particle swarm optimization (PSO) algorithm, a super-resolution point focusing lens with a large numerical aperture and weak sidelobe is optimally designed with a 32-valued phase control at the wavelength of λ=632.8 nm. Based on the silicon-based PB phase metasurface, our metalens was fabricated by electron beam lithography and orthoplastic etching. The lens radius Rlens=57λ, focal length zf=20λ, corresponding to the numerical aperture of NA=0.944. The optical field distribution of the super-resolution metalens was measured experimentally by a large-numerical-aperture microscopy system. The results show that, at the focal plane, the FWHM of the focal spot is 0.45λ, which is less than the diffraction limit of 0.53λ (the diffraction limit is 0.5λ/NA), the side-lobe ratio SR is 0.07, and the depth of focus is 0.4λ. Our proposed metalens can achieve a small depth of focus, a weak sidelobe ratio, and super-resolution point focusing. Our proposed super-resolution metalens bears the potential to realize the miniaturization, lightweight, and integration of super-resolution optical devices or systems.Metasurface is a spatially varying ultrathin nanostructure that has been widely studied and used in optical super-resolution focusing, either in lenses or in systems. However, with the decrease of the focal spot size of the metalens, large sidelobes are inevitably generated, limiting the field of view and potential applications of the lens. In this paper, a method for producing super-resolution metalens with a large numerical aperture (NA=0.944) and weak sidelobe is presented. For a circularly polarized light with the wavelength of λ=632.8 nm, a super-resolution point-focusing with a weak sidelobe is realized based on PB phase regulation of silica-based metasurface. Experimental results show that the FWHM (full-width at half maximum) of our focusing spot is 0.45λ, which is less than the diffraction limit of 0.53λ (the diffraction limit is 0.5λ/NA), and the sidelobe ratio (SR) is 0.07. Our proposed super-resolution metalens bears the potential to realize the miniaturization, lightweight and integration of super-resolution optical devices or systems..
Opto-Electronic Engineering
- Publication Date: Nov. 25, 2022
- Vol. 49, Issue 11, 220258 (2022)
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