Modern Optics Research Articles

Reference-free in situ rapid regional calibration of phase-only spatial light modulators.

Spatial light modulators (SLMs) have become an indispensable element in modern optics for their versatile performance in many applications. Among various types of SLMs, such as digital micromirror devices (DMD), liquid crystal-based phase-only spatial light modulators (LC-SLMs), and deformable mirrors (DM), LC-SLMs are often the method of choice due to their high efficiency, precise phase modulation, and abundant number of effective pixels. In general, for research grade applications, an additional SLM calibration step is required due to fabrication imperfection resulting in non-flat liquid crystal panels and varying phase responses over the SLM area. Here, we demonstrate a straightforward approach for reference-free orthogonal calibration of an arbitrary number of SLM subregions which only requires the same measurement time as global calibration. The proposed method requires minimal optical elements and can be applied to any optical setup as is. As a benchmark performance test, we achieved a 2.2-fold enhancement in correction efficiency for wavefront shaping through scattering media utilizing the calibrated 2160 subregions of the SLM, in comparison with a single global look-up table (LUT).

Preface to the Proceedings of the 14th International Symposium on Modern Optics and Its Applications (ISMOA)

We are pleased to present the proceedings of the 14th International Symposium on Modern Optics and Its Applications (ISMOA), held from August 1 to August 4, 2023, at Institut Teknologi Bandung (ITB) in Bandung, Indonesia. The event was organized by the Indonesian Optical Society (InOS) in collaboration with Institut Teknologi Bandung, Universitas Padjadjaran and the National Research and Innovation Agency of Indonesia.This 14th instalment of a bi-annual meeting gathered scientists and researchers to discuss the latest developments in optics. ISMOA covered a range of topics, from nonlinear optics to quantum entanglement, with a focus on practical applications. An interesting aspect of ISMOA is the involvement of OPTICA Fellows, promoting interactions between speakers, students, and contributors. This inclusive approach aims to encourage collaboration among regional scientists and international speakers. The May-On Tjia Lecture, initiated in 2021 to honor the late Prof. May-On Tjia, continued to be a key feature in 2023. The lecture by Dr. K. Hendrik Kurniawan and Dr. Indra Karnadi focused on H-D Isotopic Analysis Using Laser-Induced Breakdown Spectroscopy, reflecting Prof. Tjia’s commitment to excellence and collaboration in optics and photonics.To broaden the reach of optics and photonics education, the Indonesian Optical Society organized the Summer Course on Modern Optics and Its Applications (SCoMOA), a free program that attracted over 250 participants both in-person and online. This initiative, in collaboration with local and international universities, set the stage for ISMOA, incorporating joint activities with Tutorial Lecture Sessions on the first day. The SCoMOA course materials are now open for public through UNESCO learning platform.ISMOA 2023 featured 84 presented papers, including contributions from 12 invited speakers. More than half of the 117 participants were students, emphasizing the symposium’s commitment to nurturing the next generation of optical scientists. This symposium marked a significant point in the ISMOA series, characterized by a record number of papers and active participation from students and researchers. Twenty-three of the presented papers have been selected and reviewed by international Board of Reviewers are presented in this proceeding. It is our hope that the findings presented in these papers may contribute to the advancement of knowledge and applications of optics and photonics.We express our gratitude to all participants, contributors, sponsors, and organizers for their contributions to the success of ISMOA 2023. The following proceedings capture the knowledge and collaborative spirit of this international gathering on modern optics and its applications.Editors, Alexander A.P. Iskandar Institut Teknologi Bandung, Indonesia Henri P. Uranus Universitas Pelita Harapan, IndonesiaChairs of the Organizing Committee Rachmat Hidayat Institut Teknologi Bandung, Indonesia F. Fitrilawati Universitas Padjadjaran, Indonesia Isnaeni National Research and Innovation Agency, IndonesiaList of International Scientific Program Committee, Organizing Committee, Board of Reviewers are available in this pdf.

Peer Review Declaration

14th International Symposium on Modern Optics and Its Applications (ISMOA) All papers published in this volume have been reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.Type of Review : Single AnonymousReview Criteria : One-round-review based on the quality, technical details, presentation and English Language of the manuscriptsConference submission management system : MorressierNumber of submissions received : 36Number of submissions sent for review : 35Number of submissions accepted : 16Acceptance Rate : 44.4%Number of reviews per paper : 2Total number of Reviewers : 23

Multi-fidelity machine learning for predicting bandgaps of nonlinear optical crystals.

Nonlinear optical (NLO) materials are of great importance in modern optics and industry because of their intrinsic capability of wavelength conversion. Bandgap is a key property of NLO crystals. In recent years, machine learning (ML) has become a powerful tool to predict the bandgaps of compounds before synthesis. However, the shortage of available experimental data of NLO crystals poses a significant challenge for the exploration of new NLO materials using ML. In this work, we proposed a new multi-fidelity ML approach based on the multilevel descriptors developed by us (Z.-Y. Zhang, X. Liu, L. Shen, L. Chen and W.-H. Fang, J. Phys. Chem. C, 2021, 125, 25175-25188) and the gradient boosting regression tree algorithm. The calculated and experimental bandgaps of NLO crystals were collected as the low- and high-fidelity labels, respectively. The experimental values were predicted based on chemical compositions of crystals without prior knowledge about crystal structures. The multi-fidelity ML model overcame the performance of single-fidelity predictor. Furthermore, it was observed that less accurate predictions on the low-fidelity label may result in more accurate prediction on the high-fidelity label, at least in the present case. Using the multi-fidelity ML model with the best performance in this work, the mean absolute error on the test set of experimental bandgaps was 0.293 eV, which is smaller than that using the single-fidelity model (0.355 eV). It is far from perfect but accurate enough as an effective computational tool in the first step to discover novel NLO materials.

Editorial of special issue on optics and photonics for the 40th anniversary of Institute of Modern Optics, Nankai University

Editorial of special issue on optics and photonics for the 40th anniversary of Institute of Modern Optics, Nankai University

Effect of Pr and Mn co-substitution on Structural and Optical Properties of Bismuth Ferrite

One of the most recent developments in the area of modern optics arises due to perovskite materials. The ABO3 perovskite materials like bismuth ferrite is an appealing alternative for various optical devices. Hence, in the present study, Praseodymium (Pr) and Manganese (Mn) co-substituted bismuth ferrite ceramics are prepared by the modified sol-gel method and the correlation between structural and optical properties with the variation in co-substitution concentration has been investigated. Rietveld refinement of X-ray diffraction patterns demonstrates a structural phase change in crystal symmetry from rhombohedral to orthorhombic phase with the increase in concentration for x ≥ 0.025. Lattice deformation in the co-substituted samples is confirmed by Fourier Transform Infrared (FTIR) and Raman spectra. UV–vis diffuse reflectance spectra confirm the strong absorption of light in the visible region. Furthermore, optical energy band gap decreases from 1.95 eV to 1.50 eV with increase in concentration from x = 0.000 to x = 0.100. The refractive index attains the maximum value i.e. 6.16 for x = 0.025 whereas it drops to minimum value of 4.06 for x = 0.100. This demonstrates that the structural modification in bismuth ferrite can be used to tune its optical parameters for the device applications.

Generic fabrication solution of freeform Fresnel optics using ultra-precision turning.

Freeform Fresnel optics represent an emerging category of modern optics that reproduces powerful optical functionalities while maintaining an ultra-compact volume. The existing ultra-precision machining (UPM) technique faces technical challenges in meeting the fabrication requirements for freeform Fresnel optics because of the absence of appropriate geometry definition and corresponding tool path planning strategy to overcome the extreme asymmetry and discontinuity. This study proposes a new scheme for ultra-precision machining using four axes (X, Y, Z, C) to fabricate freeform Fresnel optics, including a general geometry description for freeform Fresnel optics, the quasi-spiral tool path generation strategy to overcome the lack of rotary symmetry, and the adaptive tool pose manipulation method for avoiding tool interference. In addition, the tool edge compensation and the adaptive timestep determination are also introduced to enhance the performance and efficiency of the proposed scheme. The machining of two exemplary freeform Fresnel lenses is successfully demonstrated. Overall, this study introduces a comprehensive routine for the fabrication of freeform Fresnel optics and proposes the adaptive tool pose manipulation scheme, which has the potential for broader applications in the ultra-precision machining of complex or discontinuous surfaces.

Neural network assisted high-spatial-resolution polarimetry with non-interleaved chiral metasurfaces

Polarimetry plays an indispensable role in modern optics. Nevertheless, the current strategies generally suffer from bulky system volume or spatial multiplexing scheme, resulting in limited performances when dealing with inhomogeneous polarizations. Here, we propose a non-interleaved, interferometric method to analyze the polarizations based on a tri-channel chiral metasurface. A deep convolutional neural network is also incorporated to enable fast, robust and accurate polarimetry. Spatially uniform and nonuniform polarizations are both measured through the metasurface experimentally. Distinction between two semblable glasses is also demonstrated. Our strategy features the merits of compactness and high spatial resolution, and would inspire more intriguing design for detecting and sensing.

Tunable parity-time symmetry vortex laser from a phase change material-based microcavity

Traditional light sources cannot emit an electromagnetic (EM) field with an orbital angular momentum (OAM), limiting their applications in modern optics. The recent development of the OAM laser, mainly based on micro- and nanostructures, can satisfy the increasing requirements for on-chip photonics and information capacities. Nevertheless, the photonic structures have fixed parameters that prevent these OAM lasers from being dynamically tuned. Here, we propose tunable vortex lasing from a microring cavity integrated by a phase change material, Ge2Sb2Te5 (GST225). By modulating the complex refractive index to create an exceptional point (EP) to break the degeneracy of whispering gallery modes with opposite orientations, the microlaser working at the EP can impart an artificial angular momentum, thus emitting vortex beams with well-defined OAM. The grating scatter on the edge of the microring can provide efficient vertical radiation. The vortex laser wavelength from the GST225/InGaAsP dual-layered microring cavity can be dynamically tuned by switching the state of GST225 between amorphous and crystalline without changing the microring geometry. We construct an electric-thermal model to show the tuning range of operating wavelengths (EPs) from 1544.5 to 1565.9 nm in ~25 ns. Our study on high-speed tunable PT-symmetry vortex lasers facilitates the next generation of integrated optoelectronic devices for optical computing and communications in both classical and quantum regions.

Topologically crafted spatiotemporal vortices in acoustics

Vortices in fluids and gases have piqued the human interest for centuries. Development of classical-wave physics and quantum mechanics highlighted wave vortices characterized by phase singularities and topological charges. In particular, vortex beams have found numerous applications in modern optics and other areas. Recently, optical spatiotemporal vortex states exhibiting the phase singularity both in space and time have been described. Here, we report the topologically robust generation of acoustic spatiotemporal vortex pulses. We utilize an acoustic meta-grating with broken mirror symmetry which exhibits a topological phase transition with a pair of phase singularities with opposite topological charges emerging in the momentum-frequency domain. We show that these vortices are topologically robust against structural perturbations of the meta-grating and can be employed for the generation of spatiotemporal vortex pulses. Our work paves the way for studies and applications of spatiotemporal structured waves in acoustics and other wave systems.

Dynamical and topological properties of the spin angular momenta in general electromagnetic fields

Spin angular momenta play important roles in light–matter interactions, leading to the emergence of the spin Hall effect and topological quasiparticles in modern optics. The typical approach is to decompose the spins of plane electromagnetic waves into longitudinal and transverse components, yet this description is not easily transferable to more structured electromagnetic environments. Here, we developed a field theory to reveal the physical origin and topological properties of longitudinal and transverse spins for arbitrary electromagnetic waves (including water waves and acoustic waves) in both near-field and free space. For electromagnetic waves carrying intrinsic helicity, we observed the emergence of helicity-dependent transverse spin possessing helicity-dependent spin-momentum locking. To verify that the number of spin-momentum locking states coincides with the spin Chern number, we experimentally measured the three-dimensional spin angular momentum densities of Bloch-type optical skyrmions. Our findings yield valuable insight for constructing spin-based field theory and exploiting optical topological quasiparticle-based applications.

Advances in light transverse momenta and optical lateral forces

Harnessing linear and angular momenta of light is one of the cornerstones in modern optics and has found tremendous applications in optical circuits, particle manipulation, metrology, quantum information processing, etc. Emerging theoretical protocols and experimental explorations have created a surge of interest in light lateral momenta and forces, which are perpendicular to the light wave propagation direction. However, there is yet a lack of a comprehensive and holistic overview of transverse momenta (both linear and angular) as well as of optical lateral forces (OLFs). In this article, we first review the most recent transverse momenta including the transverse spin angular momentum, optical skyrmions, as well as lateral momenta from directional side scattering, spin–orbit interaction, and surface plasmon polaritons. Since optical forces result from the momentum exchange between light and matter, the transverse momentum consequently gives rise to intriguing OLFs, which is the second topic of this article. Additional non-trivial lateral forces that combine optics with other effects from thermodynamics, electricity, and microfluidics, are also discussed. It should be emphasized that these momenta and forces ubiquitously exist in a broad range of optical phenomena and have often been neglected due to their unpredicted underlying physics and shortage of experimental means, especially prior to the last decade.

Colossal Optical Anisotropy from Atomic-Scale Modulations.

Materials with large birefringence (Δn, where n is the refractive index) are sought after for polarization control (e.g., in wave plates, polarizing beam splitters, etc.), nonlinear optics, micromanipulation, and as a platform for unconventional light-matter coupling, such as hyperbolic phonon polaritons. Layered 2Dmaterials can feature some of the largest optical anisotropy; however, their use in most optical systems is limited because their optical axis is out of the plane of the layers and the layers are weakly attached. This work demonstrates that a bulk crystal with subtle periodic modulations in its structure-Sr9/8 TiS3 -is transparent and positive-uniaxial, with extraordinary index ne = 4.5 and ordinary index no = 2.4 in the mid- to far-infrared. The excess Sr, compared to stoichiometric SrTiS3 , results in the formation of TiS6 trigonal-prismatic units that break the chains of face-sharing TiS6 octahedra in SrTiS3 into periodic blocks of five TiS6 octahedral units. The additional electrons introduced by the excess Sr form highly oriented electron clouds, which selectively boost the extraordinary index ne and result in record birefringence (Δn > 2.1 with low loss). The connection between subtle structural modulations and large changes in refractive index suggests new categories of anisotropic materials and also tunable optical materials with large refractive-index modulation.

Charged biexciton polaritons sustaining strong nonlinearity in 2D semiconductor-based nanocavities

Controlling the interaction between light and matter at micro- and nano-scale can provide new opportunities for modern optics and optoelectronics. An archetypical example is polariton, a half-light-half-matter quasi particle inheriting simultaneously the robust coherence of light and the strong interaction of matter, which plays an important role in many exotic phenomena. Here, we open up a new kind of cooperative coupling between plasmon and different excitonic complexes in WS2-silver nanocavities, namely plasmon-exciton-trion-charged biexciton four coupling states. Thanks to the large Bohr radius of up to 5 nm, the charged biexciton polariton exhibits strong saturation nonlinearity, ~30 times higher than the neutral exciton polariton. Transient absorption dynamics further reveal the ultrafast many-body interaction nature, with a timescale of <100 fs. The demonstration of biexciton polariton here combines high nonlinearity, simple processing and strong scalability, permitting access for future energy-efficient optical switching and information processing.

Terahertz-infrared spectroscopy of Ge2Sb2Te5 films on sapphire: Evolution of broadband electrodynamic response upon phase transitions

Phase-change alloy Ge2Sb2Te5 (GST) forms a favorable material platform for modern optics, photonics, and electronics thanks to a pronounced increase in conductivity with thermally induced phase transitions from amorphous (a-GST) into cubic (c-GST) and then hexagonal (h-GST) crystalline states at the temperatures of ≃150 and ≃300°C, respectively. Nevertheless, the data on broadband electrodynamic response of distinct GST phases are still missing, which hamper the design and implementation of related devices and technologies. In this paper, a-, c-, and h-GST films on a sapphire substrate are studied using broadband dielectric spectroscopy. For all GST phases, complex dielectric permittivity is retrieved using Drude and Lorentz models in the frequency range of 0.06–50 THz or the wavelength range of ≃5000–6 μm. A contribution from the free charge-carriers conductivity and vibrational modes to the broadband response of an analyte is quantified. In this way, the Drude model allows for estimation of the static (direct current—DC) and dynamic (at 1.0 THz) conductivity values, caused by motions of free charges only, which are as high as σDC≃15 and 40 S/cm and σ1.0THz≃8.8 and 28.6 S/cm for the c- and h-GSTs, respectively. This overall agrees with the results of electrical measurements of GST conductivity using the four-point probe technique. The broadband electrodynamic response models obtained for the three GST phases are important for further research and developments of GST-based devices and technologies.

Nanoscale modeling of dynamically tunable planar optical absorbers utilizing InAs and InSb in metal-oxide-semiconductor–metal configurations

The attainment of dynamic tunability in spectrally selective optical absorption has been a longstanding objective in modern optics. Typically, Fabry–Perot resonators comprising metal and semiconductor thin films have been employed for spectrally selective light absorption. In such resonators, the resonance wavelength can be altered via structural modifications. The research has progressed further with the advent of specialized patterning of thin films and the utilization of metasurfaces. Nonetheless, achieving dynamic tuning of the absorption wavelength without altering the geometry of the thin film or without resorting to lithographic fabrication still poses a challenge. In this study, the incorporation of a metal-oxide-semiconductor (MOS) architecture into the Fabry–Perot nanocavity is shown to yield dynamic spectral tuning in a perfect narrowband light absorber within the visible range. Such spectral tuning is achieved using n-type-doped indium antimonide and n-type-doped indium arsenide as semiconductors in a MOS-type structure. These semiconductors offer significant tuning of their optical properties via electrically induced carrier accumulation. The planar structure of the absorber models presented facilitates simple thin-film fabrication. With judicious material selection and appropriate bias voltage, a spectral shift of 47 nm can be achieved within the visible range, thus producing a discernible color change.

Passive nonreciprocal transmission and optical bistability based on polarization-independent bound states in the continuum

Abstract Free-space nonreciprocal transmission is a crucial aspect of modern optics devices. The implementation of nonreciprocal optical devices through optical nonlinearity has been demonstrated. However, due to the weak nonlinearity of traditional materials, most self-biased nonreciprocal devices are heavily dependent on the high Q strong resonances. In general, these resonances are frequently polarization sensitive. In this work, we propose ultrathin optical metasurface embedding Kerr nonlinearities to achieve nonreciprocal transmission and optical bistability for free-space propagation based on symmetry-protected bound states in the continuum (BICs). Since the structure of the metasurface retains C4ν symmetry, the symmetry-protected BIC is polarization-independent. It is also shown that the nonreciprocal intensity range could be largely tuned by the structure parameters. The demonstrated devices merge the field of nonreciprocity with ultrathin metasurface technologies making this design an exciting prospect for an optical switch, routing, and isolator with optimal performance.

Topologically protected optical polarization singularities in four-dimensional space.

Optical singularities play a major role in modern optics and are frequently deployed in structured light, super-resolution microscopy, and holography. While phase singularities are uniquely defined as locations of undefined phase, polarization singularities studied thus far are either partial, i.e., bright points of well-defined polarization, or are unstable for small field perturbations. We demonstrate a complete, topologically protected polarization singularity; it is located in the four-dimensional space spanned by the three spatial dimensions and the wavelength and is created in the focus of a cascaded metasurface-lens system. The field Jacobian plays a key role in the design of such higher-dimensional singularities, which can be extended to multidimensional wave phenomena, and pave the way for unconventional applications in topological photonics and precision sensing.

Diffractive Theory Study of Twisted Light’s Evolution during Phase-Only OAM Manipulations

Twisted light, or orbital angular momentum (OAM) carrying beams or photons, is a pillar of structured photonics, a booming subfield of modern optics. The generation and transformation of twisted light, which lie with coupling topological charges into target light’s wavefunctions, are usually performed by phase-only OAM manipulations. The practical twisted lights, however, obtained by this method are actually noneigen modes of free space, leading to an evolution through the diffractive propagation. Here, we present a general theoretical frame for accurately describing this evolution. Based on the theory, the whole diffractive propagation history in a typical OAM-manipulation loop, converting Gaussian light into a twisted one and then reconverting back, is demonstrated via a set of exact analytical solutions. These results provide a powerful tool for analyzing the transverse profiles of twisted light through the diffractive evolution, as a guideline for studying the science of structured light, which would provide guidelines for research studies in nonlinear optics and high-dimensional quantum information technology based on OAM-degree of freedom.

Mid-infrared broadband metamaterial absorber based on van der Waals material

Van der Waals materials, such as α-phase molybdenum trioxide (α-MoO3), have promising prospects in modern optics technologies, such as nano-imaging, negative refraction, and infrared detection. Particularly, the natural hyperbolic properties of α-MoO3 make it an excellent candidate for perfect absorber. Here, we propose a design method for achieving broadband absorption based on van der Waals material (α-MoO3) in the mid-infrared band. The segmented cubic Hermite interpolation is used to generate various geometric structures. Numerical results show that the average spectral absorptance of the optimized structure is up to 0.993 in the wavelength range of 10.4–12.7 μm. The high absorption performance can be explained as the slow-light effect. The impact of incident angle on absorption performance is also investigated. Finally, we calculate the spectral absorptance of the proposed absorber when the crystal axes of α-MoO3 are rotated in the x-y plane. Our findings pave a novel path for designing broadband absorbers based on van der Waals materials, particularly in the mid-infrared band.